14 CFR Part 36 — Noise Standards: Aircraft Type and Airworthiness Certification

14 CFR Ch. I (1–1–25 Edition) Pt. 36 alternative program has been FAA ap- Subparts L–N [ Reserved ] proved.’’ Subpart O—Documentation, Operating [Amdt. 35–5, 45 FR 60182, Sept. 11, 1980, as Limitations and Information amended by Amdt. 35–6, 54 FR 34330, Aug. 18, 1989] 36.1501 Procedures, noise levels and other information.

36.1581 Manuals, markings, and placards.

PART 36—NOISE STANDARDS: AIR- 36.1583 Noncomplying agricultural and fire CRAFT TYPE AND AIRWORTHI- fighting airplanes.

NESS CERTIFICATION A PPENDIX A TO P ART 36—A IRCRAFT N OISE M EASUREMENT AND E VALUATION U NDER Subpart A—General § 36.101 APPENDIX B TO P ART 36—N OISE L EVELS FOR Sec.

T RANSPORT C ATEGORY AND J ET A IR - 36.1 Applicability and definitions.

PLANES U NDER § 36.103 36.2 Requirements as of date of application.

A PPENDIXES C–E TO P ART 36 [R ESERVED ] 36.3 Compatibility with airworthiness re- A PPENDIX F TO P ART 36—F LYOVER N OISE R E - quirements.

QUIREMENTS FOR P ROPELLER -D RIVEN 36.5 Limitation of part.

S MALL A IRPLANE AND P ROPELLER -D RIVEN , 36.6 Incorporations by reference.

COMMUTER C ATEGORY A IRPLANE C ERTIFI - 36.7 Acoustical change: Transport category CATION T ESTS P RIOR TO DECEMBER 22, 1988 large airplanes and jet airplanes.

A PPENDIX G TO P ART 36—T AKEOFF N OISE R E - 36.9 Acoustical change: Propeller-driven QUIREMENTS FOR P ROPELLER -D RIVEN small airplanes and propeller-driven S MALL A IRPLANE AND P ROPELLER -D RIVEN , commuter category airplanes.

COMMUTER C ATEGORY A IRPLANE C ERTIFI - 36.11 Acoustical change: Helicopters.

CATION T ESTS ON OR A FTER D ECEMBER 22, 36.13 Acoustical change: Tiltrotor aircraft.

A PPENDIX H TO P ART 36—N OISE R EQUIRE - Subpart B—Transport Category Large MENTS FOR H ELICOPTERS U NDER S UBPART Airplanes and Jet Airplanes H A PPENDIX I TO P ART 36 [R ESERVED ] 36.101 Noise measurement and evaluation.

A PPENDIX J TO P ART 36—A LTERNATIVE N OISE 36.103 Noise limits.

C ERTIFICATION P ROCEDURE F OR H ELI - 36.105 Flight Manual Statement of Chapter COPTERS U NDER S UBPART H H AVING A 4 equivalency.

M AXIMUM C ERTIFICATED T AKEOFF W EIGHT 36.106 Flight Manual statement of Chapter O F N OT M ORE T HAN 7,000 POUNDS 14 noise level equivalency.

A PPENDIX K TO P ART 36—N OISE R EQUIRE - MENTS FOR T ILTROTORS U NDER S UBPART K Subpart C [ Reserved ] A UTHORITY : 42 U.S.C. 4321 et seq.; 49 U.S.C.

Subpart D—Noise Limits for Supersonic 106(g), 40113, 44701–44702, 44704, 44715; sec. 305, Transport Category Airplanes Pub. L. 96–193, 94 Stat. 50, 57; E.O. 11514, 35 FR 4247, 3 CFR, 1966–1970 Comp., p. 902.

36.301 Noise limits: Concorde.

S OURCE : Docket No. 9337, 34 FR 18364, Nov.

18, 1969, unless otherwise noted.

Subpart E [ Reserved ] Subpart F—Propeller Driven Small Airplanes Subpart A—General and Propeller-Driven, Commuter Cat- egory Airplanes § 36.1 Applicability and definitions.

(a) This part prescribes noise stand- 36.501 Noise limits.

ards for the issue of the following cer- Subpart G [ Reserved ] tificates: (1) Type certificates, and changes to Subpart H—Helicopters those certificates, and standard air- worthiness certificates, for subsonic 36.801 Noise measurement.

transport category large airplanes, and 36.803 Noise evaluation and calculation.

36.805 Noise limits. for subsonic jet airplanes regardless of category.

Subparts I–J [ Reserved ] (2) Type certificates and changes to those certificates, standard airworthi- Subpart K—Tiltrotors ness certificates, and restricted cat- egory airworthiness certificates, for 36.1101 Noise measurement and evaluation.

36.1103 Noise limits. propeller-driven, small airplanes, and Federal Aviation Administration, DOT § 36.1 for propeller-driven, commuter cat- (ii) December 31, 1974, for airplanes egory airplanes except those airplanes with maximum weights greater than that are designed for ‘‘agricultural air- 75,000 pounds and that are powered by craft operations’’ (as defined in § 137.3 Pratt & Whitney Turbo Wasp JT3D se- of this chapter, as effective on January ries engines; and 1, 1966) or for dispersing fire fighting (iii) December 31, 1974, for airplanes materials to which § 36.1583 of this part with maximum weights of 75,000 pounds does not apply.

and less.

(3) A type certificate and changes to (2) The provisions of this part in ef- that certificate, and standard air- fect on October 13, 1977, including the worthiness certificates, for Concorde stage 2 noise limits, for Concorde air- airplanes.

planes that have not had flight time (4) Type certificates, and changes to before January 1, 1980.

those certificates, for helicopters ex- (e) Each person who applies for the cept those helicopters that are des- original issue of a standard airworthi- ignated exclusively for ‘‘agricultural ness certificate under § 21.183, or for the aircraft operations’’ (as defined in original issue of a restricted category § 137.3 of this chapter, as effective on airworthiness certificate under § 21.185, January 1, 1966), for dispensing fire for propeller-driven, commuter cat- fighting materials, or for carrying ex- egory airplanes for a propeller driven ternal loads (as defined in § 133.1(b) of small airplane that has not had any this chapter, as effective on December flight time before January 1, 1980, must 20, 1976).

show compliance with the applicable (5) Type certificates, changes to provisions of this part.

those certificates, and standard air- (f) For the purpose of showing com- worthiness certificates, for tiltrotors.

pliance with this part for transport (b) Each person who applies under category large airplanes and jet air- Part 21 of this chapter for a type of air- planes regardless of category, the fol- worthiness certificate specified in this lowing terms have the following mean- part must show compliance with the ings: applicable requirements of this part, in (1) A ‘‘Stage 1 noise level’’ means a addition to the applicable airworthi- flyover, lateral or approach noise level ness requirements of this chapter.

greater than the Stage 2 noise limits (c) Each person who applies under prescribed in section B36.5(b) of appen- Part 21 of this chapter for approval of dix B of this part.

an acoustical change described in (2) A ‘‘Stage 1 airplane’’ means an § 21.93(b) of this chapter must show that airplane that has not been shown under the aircraft complies with the applica- this part to comply with the flyover, ble provisions of §§ 36.7, 36.9, 36.11 or lateral, and approach noise levels re- 36.13 of this part in addition to the ap- quired for Stage 2 or Stage 3 airplanes.

plicable airworthiness requirements of (3) A ‘‘Stage 2 noise level’’ means a this chapter.

noise level at or below the Stage 2 (d) Each person who applies for the noise limits prescribed in section original issue of a standard airworthi- B36.5(b) of appendix B of this part but ness certificate for a transport cat- higher than the Stage 3 noise limits egory large airplane or for a jet air- prescribed in section B36.5(c) of appen- plane under § 21.183 must, regardless of dix B of this part.

date of application, show compliance (4) A ‘‘Stage 2 airplane’’ means an with the following provisions of this airplane that has been shown under part (including appendix B): this part to comply with Stage 2 noise (1) The provisions of this part in ef- levels prescribed in section B36.5(b) of fect on December 1, 1969, for subsonic appendix B of this part (including use airplanes that have not had any flight of the applicable tradeoff provisions time before— specified in section B36.6) and that does (i) December 1, 1973, for airplanes not comply with the requirements for a with maximum weights greater than Stage 3 airplane.

75,000 pounds, except for airplanes that are powered by Pratt & Whitney Turbo (5) A ‘‘Stage 3 noise level’’ means a Wasp JT3D series engines; noise level at or below the Stage 3 14 CFR Ch. I (1–1–25 Edition) § 36.1 noise limits prescribed in section in the primary, normal, transport, and B36.5(c) of appendix B of this part. restricted categories, the following (6) A ‘‘Stage 3 airplane’’ means an terms have the specified meanings: airplane that has been shown under (1) Stage 1 noise level means a takeoff, this part to comply with Stage 3 noise flyover, or approach noise level greater levels prescribed in section B36.5(c) of than the Stage 2 noise limits pre- appendix B of this part (including use scribed in section H36.305 of appendix H of the applicable tradeoff provisions of this part, or a flyover noise level specified in section B36.6). greater than the Stage 2 noise limits (7) A ‘‘subsonic airplane’’ means an prescribed in section J36.305 of appen- airplane for which the maximum oper- dix J of this part.

ating limit speed, M , does not exceed (2) Stage 1 helicopter means a heli- mo a Mach number of 1. copter that has not been shown under (8) A ‘‘supersonic airplane’’ means an this part to comply with the takeoff, airplane for which the maximum oper- flyover, and approach noise levels re- ating limit speed, M , exceeds a Mach quired for Stage 2 helicopters as pre- mo number of 1. scribed in section H36.305 of appendix H (9) A ‘‘Stage 4 noise level’’ means a of this part, or a helicopter that has noise level at or below the Stage 4 not been shown under this part to com- noise limit prescribed in section ply with the flyover noise level re- B36.5(d) of appendix B of this part. quired for Stage 2 helicopters as pre- (10) A ‘‘Stage 4 airplane’’ means an scribed in section J36.305 of appendix J airplane that has been shown under of this part.

this part not to exceed the Stage 4 (3) Stage 2 noise level means a takeoff, noise limit prescribed in section flyover, or approach noise level at or B36.5(d) of appendix B of this part. below the Stage 2 noise limits pre- (11) A ‘‘Chapter 4 noise level’’ means scribed in section H36.305 of appendix H a noise level at or below the maximum of this part, or a flyover noise level at noise level prescribed in Chapter 4, or below the Stage 2 limit prescribed in Paragraph 4.4, Maximum Noise Levels, section J36.305 of appendix J of this of the International Civil Aviation Or- part.

ganization (ICAO) Annex 16, Volume I, (4) Stage 2 helicopter means a heli- Amendment 7, effective March 21, 2002. copter that has been shown under this [Incorporated by reference, see § 36.6]. part to comply with Stage 2 noise lim- (12) A ‘‘Stage 5 noise level’’ means a its (including applicable tradeoffs) pre- noise level at or below the Stage 5 scribed in section H36.305 of appendix H noise limit prescribed in section of this part, or a helicopter that has B36.5(e) of appendix B to this part. been shown under this part to comply (13) A ‘‘Stage 5 airplane’’ means an with the Stage 2 noise limit prescribed airplane that has been shown under in section J36.305 of appendix J of this this part not to exceed the Stage 5 part.

noise limit prescribed in section (5) A ‘‘Stage 3 noise level’’ means a B36.5(e) of appendix B to this part. takeoff, flyover, or approach noise (14) A ‘‘Chapter 14 noise level’’ means level at or below the Stage 3 noise lim- a noise level at or below the Chapter 14 its prescribed in section H36.305 of ap- maximum noise level prescribed in pendix H of this part, or a flyover noise Chapter 14 of the ICAO Annex 16, Vol- level at or below the Stage 3 noise ume 1, Seventh Edition, Amendment limit prescribed in section J36.305 of 11–B (Incorporated by reference, see appendix J of this part.

§ 36.6). (6) A ‘‘Stage 3 helicopter’’ means a (g) For the purpose of showing com- helicopter that has been shown under pliance with this part for transport this part to comply with the Stage 3 category large airplanes and jet air- noise limits (including applicable planes regardless of category, each air- tradeoffs) prescribed in section H36.305 plane may not be identified as com- of appendix H of this part, or a heli- plying with more than one stage or copter that has been shown under this configuration simultaneously. part to comply with the Stage 3 noise (h) For the purpose of showing com- limit prescribed in section J36.305 of pliance with this part, for helicopters appendix J of this part.

Federal Aviation Administration, DOT § 36.2 (7) Maximum normal operating RPM Nacelle angle is defined as the angle means the highest rotor speed cor- between the rotor shaft centerline and responding to the airworthiness limit the longitudinal axis of the aircraft fu- selage.

imposed by the manufacturer and ap- Tiltrotor means a class of aircraft ca- proved by the FAA. Where a tolerance pable of vertical take-off and landing, on the highest rotor speed is specified, within the powered-lift category, with the maximum normal operating rotor rotors mounted at or near the wing tips speed is the highest rotor speed for that vary in pitch from near vertical to which that tolerance is given. If the near horizontal configuration relative rotor speed is automatically linked to the wing and fuselage.

with flight condition, the maximum Vertical takeoff and landing (VTOL) normal operating rotor speed cor- mode means the aircraft state or con- responding with the reference flight figuration having the rotors orientated condition must be used during the with the axis of rotation in a vertical noise certification procedure. If rotor manner ( i.e. , nacelle angle of approxi- speed can be changed by pilot action, mately 90 degrees) for vertical takeoff the highest normal operating rotor and landing operations.

speed specified in the flight manual V is defined as the maximum au- CON limitation section for reference condi- thorized speed for any nacelle angle in tions must be used during the noise VTOL/Conversion mode.

certification procedure.

VTOL/Conversion mode is all approved (i) For the purpose of showing com- nacelle positions where the design op- pliance with this part for tiltrotors, erating rotor speed is used for hover the following terms have the specified operations.

meanings: VTOL mode RPM means highest range Airplane mode means a configuration of RPM that occur for takeoff, ap- with nacelles on the down stops (axis proach, hover, and conversion condi- aligned horizontally) and rotor speed tions.

set to cruise revolutions per minute [Doc. No. 13243, Amdt. 36–4, 40 FR 1034, Jan.

(RPM).

6, 1975] Airplane mode RPM means the lower E DITORIAL N OTE : For F EDERAL R EGISTER ci- range of rotor rotational speed in RPM tations affecting § 36.1, see the List of CFR defined for the airplane mode cruise Sections Affected, which appears in the flight condition.

Finding Aids section of the printed volume Fixed operation points mean des- and at www.govinfo.gov.

ignated nacelle angle positions selected for airworthiness reference. These are § 36.2 Requirements as of date of ap- plication.

default positions used to refer to nor- mal nacelle positioning operation of (a) Section 21.17 of this chapter not- the aircraft. The nacelle angle is con- withstanding, each person who applies trolled by a self-centering switch.

for a type certificate for an aircraft When the nacelle angle is 0 degrees covered by this part, must show that (airplane mode) and the pilot moves the aircraft meets the applicable re- the nacelle switch upwards, the na- quirements of this part that are effec- celles are programmed to automati- tive on the date of application for that cally turn to the first default position type certificate. When the time inter- (for example, 60 degrees) where they val between the date of application for will stop. A second upward move of the the type certificate and the issuance of switch will tilt the nacelle to the sec- the type certificate exceeds 5 years, the ond default position (for example, 75 applicant must show that the aircraft degrees). Above the last default posi- meets the applicable requirements of tion, the nacelle angle can be set to this part that were effective on a date, any angle up to approximately 95 de- to be selected by the applicant, not grees by moving the switch in the up or earlier than 5 years before the issue of down direction. The number and posi- the type certificate.

tion of the fixed operation points may (b) Section 21.101(a) of this chapter vary on different tiltrotor configura- notwithstanding, each person who ap- tions. plies for an acoustical change to a type

14 CFR Ch. I (1–1–25 Edition) § 36.3 design specified in § 21.93(b) of this these noise levels are or should be ac- chapter must show compliance with ceptable or unacceptable for operation the applicable requirements of this at, into, or out of, any airport.

part that are effective on the date of [Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as application for the change in type de- amended by Docket FAA–2015–3782, Amdt. 36– sign. When the time interval between 31, 82 FR 46129, Oct. 4, 2017] the date of application for the change in type design and the issuance of the § 36.6 Incorporation by reference.

amended or supplemental type certifi- (a) Certain material is incorporated cate exceeds 5 years, the applicant by reference into this part with the ap- must show that the aircraft meets the proval of the Director of the Federal applicable requirements of this part Register under 5 U.S.C. 552(a) and 1 that were effective on a date, to be se- CFR part 51. All approved material is lected by the applicant, not earlier available for inspection at the loca- than 5 years before the issue of the tions in this paragraph (a) and may be amended or supplemental type certifi- obtained from the sources detailed in cate.

paragraphs (a)(1) through (12) of this (c) If an applicant elects to comply section.

with a standard in this part that was (1) The U.S. Department of Transpor- effective after the filing of the applica- tation, Docket Operations, West Build- tion for a type certificate or change to ing Ground Floor, Room W12–140, 1200 a type design, the election: New Jersey Avenue SE., Washington, (1) Must be approved by the FAA; DC 20590.

(2) Must include standards adopted (2) Federal Aviation Administration between the date of application and the New England Regional Headquarters, date of the election; 12 New England Executive Park, Bur- (3) May include other standards lington, MA 01801.

adopted after the standard elected by the applicant as determined by the (3) Federal Aviation Administration FAA. Eastern Region Headquarters, Federal Building, John F. Kennedy Inter- [Amdt. 36–54, 67 FR 45211, July 8, 2002; Amdt.

national Airport, Jamaica, NY 11430.

36–24, 67 FR 63195, Oct. 10, 2002] (4) Federal Aviation Administration § 36.3 Compatibility with airworthi- Southern Region Headquarters, 1701 ness requirements.

Columbia Avenue, College Park, GA 30337.

It must be shown that the aircraft (5) Federal Aviation Administration meets the airworthiness regulations Great Lakes Region Headquarters, constituting the type certification O’Hare Lake Office Center, 2300 East basis of the aircraft under all condi- tions in which compliance with this Devon Avenue, Des Plaines, IL 60018.

part is shown, and that all procedures (6) Federal Aviation Administration used in complying with this part, and Central Region Headquarters, Federal all procedures and information for the Building, 601 East 12th Street, Kansas flight crew developed under this part, City, MO 64106.

are consistent with the airworthiness (7) Federal Aviation Administration regulations constituting the type cer- Southwest Region Headquarters, 2601 tification basis of the aircraft.

Meacham Boulevard, Fort Worth, TX 76137.

[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as (8) Federal Aviation Administration amended by Amdt. 36–14, 53 FR 3540, Feb. 5, 1988] Northwest Mountain Region Head- quarters, 1601 Lind Avenue SW, § 36.5 Limitation of part.

Renton, WA 98055.

Pursuant to 49 U.S.C. 44715, the noise (9) Federal Aviation Administration levels in this part have been deter- Western Pacific Region Headquarters, mined to be as low as is economically 15000 Aviation Boulevard, Hawthorne, reasonable, technologically prac- CA 92007.

ticable, and appropriate to the type of (10) Federal Aviation Administration aircraft to which they apply. No deter- Alaskan Region Headquarters, 222 West mination is made, under this part, that 7th Avenue, #14, Anchorage, AK 99513.

Federal Aviation Administration, DOT § 36.7 (11) Federal Aviation Administration Laboratory Standard Microphones by European Office Headquarters, 15 Rue the Reciprocity Technique, edition 1.0, de la Loi, Third Floor, B–1040, Brussels, 1995 (IEC 61094–3) IBR approved for ap- Belgium. pendix A to part 36.

(12) The National Archives and (6) Publication No. 61094–4, Measure- Records Administration (NARA). For ment Microphones—Part 4: Specifica- information on the availability of this tions for Working Standard Micro- information at NARA, call 202–741–6030 phones, edition 1.0, 1995, (IEC 61094–4) or go to http://www.archives.gov/fed- IBR approved for appendix A to part 36.

eral _ register/code _ of _ federal _ regulations/ (7) Publication No. 61260, ibr _ locations.html. Electroacoustics-Octave-Band and (b) International Civil Aviation Orga- Fractional-Octave-Band Filters, edi- nization (ICAO), Document Sales Unit, tion 1.0, 1995, (IEC 61260), IBR approved 999 University Street, Montreal, Que- for appendix A to part 36.

(8) Publication No, 60942, bec, H3C 5H7, Canada. http:// Electroacoustics-Sound Calibrators, www.icao.int/publications/Pages/de- edition 2.0, 1997, (IEC 60942) IBR ap- fault.aspx .

proved for appendix A to part 36.

(1) International Standards and Rec- (d) Society of Automotive Engineers, ommended Practices, Annex 16 to the Inc. (SAE), 400 Commonwealth Drive, Convention on International Civil Warrentown, PA 15096, http:// Aviation, Environmental Protection, www.sae.org/pubs/.

Volume I, Aircraft Noise, Third Edi- (1) ARP 866A, Standard Values at At- tion, July 1993, Amendment 7 effective mospheric Absorption as a Function of March 21, 2002, IBR approved for Temperature and Humidity for use in § 36.1(f), and appendices A and B to part Evaluating Aircraft Flyover Noise, 36.

March 15, 1975, IBR approved for appen- (2) International Standards and Rec- dix H to part 36.

ommended Practices, Annex 16 to the (2) [Reserved] Convention on International Civil Aviation, Environmental Protection, [Doc. No. FAA–2015–3782, Amdt. No. 36–31, 82 Volume I, Aircraft Noise, Seventh Edi- FR 46129, Oct. 4, 2017] tion, July 2014, Amendment 11–B, appli- § 36.7 Acoustical change: Transport cable January 1, 2015, IBR approved for category large airplanes and jet air- § 36.1(f) and appendices A and B to part planes.

36.

(c) International Electrotechnical (a) Applicability. This section applies Commission (IEC) 3 Rue de Varembe, to all transport category large air- Case Postale 131, 1211 Geneva 20, Swit- planes and jet airplanes for which an zerland, http://www.iec.ch/standardsdev/ acoustical change approval is applied publications/?ref=menu. for under § 21.93(b) of this chapter.

(1) Publication No. 179, Precision (b) General requirements. Except as Level Sound Meters, (IEC 179) 1973, IBR otherwise specifically provided, for approved for appendix F to part 36. each airplane covered by this section, (2) Publication No. 561, Electro- the acoustical change approval require- acoustical Measuring Equipment for ments are as follows: Aircraft Noise Certification, first edi- (1) In showing compliance, noise lev- tion, 1976, (IEC 561), IBR approved for els must be measured and evaluated in appendices G and J to part 36. accordance with the applicable proce- (3) Publication No. 651, Sound Level dures and conditions prescribed in Ap- Meters, first edition, 1979, (IEC 651), pendix A of this part.

IBR approved for appendices G and J to (2) Compliance with the noise limits part 36. prescribed in section B36.5 of appendix (4) Publication No. 804, Integrating- B must be shown in accordance with averaging Sound Level Meters, first the applicable provisions of sections edition, 1985, (IEC 804), IBR approved B36.7 and B36.8 of appendix B of this for appendix J to part 36. part.

(5) Publication No. 61094–3, Measure- (c) Stage 1 airplanes. For each Stage 1 ment Microphones—Part 3: Primary airplane prior to the change in type de- Method for Free-Field Calibration of sign, in addition to the provisions of 14 CFR Ch. I (1–1–25 Edition) § 36.7 paragraph (b) of this section, the fol- (i) The airplane may not be a Stage 1 lowing apply: airplane after the change in type de- sign; and (1) If an airplane is a Stage 1 airplane prior to the change in type design, it (ii) During the flyover and lateral may not, after the change in type de- noise tests conducted before the change sign, exceed the noise levels created in type design, the quietest airworthi- prior to the change in type design. The ness approved configuration available tradeoff provisions of section B36.6 of for the highest approved takeoff weight must be used.

appendix B of this part may not be used to increase the Stage 1 noise lev- (e) Stage 3 airplanes. If an airplane is els, unless the aircraft qualifies as a a Stage 3 airplane prior to the change Stage 2 airplane. in type design, the following apply, in addition to the provisions of paragraph (2) In addition, for an airplane for (b) of this section: which application is made after Sep- (1) If compliance with Stage 3 noise tember 17, 1971— levels is not required before the change (i) There may be no reduction in in type design, the airplane must— power or thrust below the highest air- worthiness approved power or thrust, (i) Be a Stage 2 airplane after the during the tests conducted before and change in type design and compliance after the change in type design; and must be shown under the provisions of paragraph (d)(1) or (d)(2) of this sec- (ii) During the flyover and lateral tion, as appropriate; or noise tests conducted before the change in type design, the quietest airworthi- (ii) Remain a Stage 3 airplane after ness approved configuration available the change in type design. Compliance for the highest approved takeoff weight must be shown under the provisions of must be used. paragraph (e)(2) of this section.

(d) Stage 2 airplanes. If an airplane is (2) If compliance with Stage 3 noise a Stage 2 airplane prior to the change levels is required before the change in in type design, the following apply, in type design, the airplane must be a addition to the provisions of paragraph Stage 3 airplane after the change in (b) of this section: type design.

(1) Airplanes with high bypass ratio jet (3) Applications on or after [August engines. For an airplane that has jet 14, 1989.] The airplane must remain a engines with a bypass ratio of 2 or Stage 3 airplane after the change in more before a change in type design— type design.

(4) If an airplane is a Stage 3 airplane (i) The airplane, after the change in prior to a change in type design, and type design, may not exceed either (A) becomes a Stage 4 after the change in each Stage 3 noise limit by more than type design, the airplane must remain 3 EPNdB, or (B) each Stage 2 noise a Stage 4 airplane.

limit, whichever is lower: (ii) The tradeoff provisions of section (5) If an airplane is a Stage 3 airplane B36.6 of appendix B of this part may be prior to a change in type design, and used in determining compliance under becomes a Stage 5 airplane after the this paragraph with respect to the change in type design, the airplane Stage 2 noise limit or to the Stage 3 must remain a Stage 5 airplane.

plus 3 EPNdB noise limits, as applica- (f) Stage 4 airplanes. (1) If an airplane ble; and is a Stage 4 airplane prior to a change (iii) During the flyover and lateral in type design, the airplane must re- noise test conducted before the change main a Stage 4 airplane after the in type design, the quietest airworthi- change in type design.

ness approved configuration available (2) If an airplane is a Stage 4 airplane for the highest approved takeoff weight prior to a change in type design, and must be used. becomes a Stage 5 airplane after the change in type design, the airplane (2) Airplanes that do not have high by- must remain a Stage 5 airplane.

pass ratio jet engines. For an airplane that does not have jet engines with a (g) Stage 5 airplanes. If an airplane is bypass ratio of 2 or more before a a Stage 5 airplane prior to a change in change in type design— type design, the airplane must remain Federal Aviation Administration, DOT § 36.11 a Stage 5 airplane after the change in (a) General requirements. Except as type design. otherwise provided, for helicopters cov- ered by this section, the acoustical [Amdt. 36–7, 42 FR 12371, Mar. 3, 1977; Amdt.

change approval requirements are as 36–8, 43 FR 8730, Mar. 2, 1978; Amdt. 36–10, 43 follows: FR 28420, June 29, 1978; Amdt. 36–12, 46 FR 33464, June 29, 1981; Amdt. 36–15, 53 FR 16366, (1) In showing compliance with the May 6, 1988; 53 FR 18950, May 25, 1988; Amdt.

requirements of appendix H of this 36–17, 54 FR 21042, May 15, 1989; Amdt. 36–54, part, noise levels must be measured, 67 FR 45212, July 8, 2002; Amdt. 36–26, 70 FR evaluated, and calculated in accord- 38749, July 5, 2005; FAA Doc. No. FAA–2015– ance with the applicable procedures 3782, Amdt. No. 36–31, 82 FR 46130, Oct. 4, and conditions prescribed in parts B 2017] and C of appendix H of this part. For helicopters having a maximum certifi- § 36.9 Acoustical change: Propeller- driven small airplanes and pro- cated takeoff weight of not more than peller-driven commuter category 7,000 pounds that alternatively dem- airplanes.

onstrate compliance under appendix J For propeller-driven small airplanes of this part, the flyover noise level pre- in the primary, normal, utility, acro- scribed in appendix J of this part must batic, transport, and restricted cat- be measured, evaluated, and calculated egories and for propeller-driven, com- in accordance with the applicable pro- muter category airplanes for which an cedures and conditions prescribed in acoustical change approval is applied parts B and C of appendix J of this for under § 21.93(b) of this chapter after part.

January 1, 1975, the following apply: (2) Compliance with the noise limits (a) If the airplane was type certifi- prescribed in section H36.305 of appen- cated under this part prior to a change dix H of this part must be shown in ac- in type design, it may not subsequently cordance with the applicable provisions exceed the noise limits specified in of part D of appendix H of this part.

§ 36.501 of this part.

For those helicopters that demonstrate (b) If the airplane was not type cer- compliance with the requirements of tificated under this part prior to a appendix J of this part, compliance change in type design, it may not ex- with the noise levels prescribed in sec- ceed the higher of the two following tion J36.305 of appendix J of this part values: must be shown in accordance with the (1) The noise limit specified in § 36.501 applicable provisions of part D of ap- of this part, or pendix J of this part.

(2) The noise level created prior to (b) Stage 1 helicopters. Except as pro- the change in type design, measured vided in § 36.805(c), for each Stage 1 hel- and corrected as prescribed in § 36.501 of icopter prior to a change in type de- this part.

sign, the helicopter noise levels may not, after a change in type design, ex- [Amdt. 36–16, 53 FR 47400, Nov. 22, 1988; 53 FR 50157, Dec. 13, 1988; Amdt. 36–19, 57 FR 41369, ceed the noise levels specified in sec- Sept. 9, 1992] tion H36.305(a)(1) of appendix H of this part where the demonstration of com- § 36.11 Acoustical change: Helicopters.

pliance is under appendix H of this This section applies to all helicopters part. The tradeoff provisions under sec- in the primary, normal, transport, and tion H36.305(b) of appendix H of this restricted categories for which an part may not be used to increase any acoustical change approval is applied Stage 1 noise level beyond these limits.

for under § 21.93(b) of this chapter on or If an applicant chooses to demonstrate after March 6, 1986. Compliance with compliance under appendix J of this the requirements of this section must part, for each Stage 1 helicopter prior be demonstrated under appendix H of to a change in type design, the heli- this part, or, for helicopters having a copter noise levels may not, after a maximum certificated takeoff weight change in type design, exceed the Stage of not more than 7,000 pounds, compli- 2 noise levels specified in section ance with this section may be dem- J36.305(a) of appendix J of this part.

onstrated under appendix J of this (c) Stage 2 helicopters. For each heli- part. copter that is Stage 2 prior to a change 14 CFR Ch. I (1–1–25 Edition) § 36.13 in type design, after a change in type § 36.103 Noise limits.

design the helicopter must either: (a) For subsonic transport category (1) Remain a Stage 2 helicopter; or large airplanes and subsonic jet air- (2) Comply with Stage 3 requirements planes compliance with this section and remain a Stage 3 helicopter there- must be shown with noise levels meas- after. ured and evaluated as prescribed in ap- pendix A of this part, and dem- (d) Stage 3 helicopters. For a heli- onstrated at the measuring points, and copter that is a Stage 3 helicopter prior in accordance with the test procedures to a change in type design, the heli- under section B36.8 (or an approved copter must remain a Stage 3 heli- equivalent procedure), stated under ap- copter after a change in type design.

pendix B of this part.

[Doc. No. 26910, 57 FR 42854, Sept. 16, 1992, as (b) Type certification applications amended by Amdt. 36–25, 69 FR 31234, June 2, between November 5, 1975 and Decem- 2004; Amdt. 36–30, 79 FR 12044, Mar. 4, 2014] ber 31, 2005. If application is made on or after November 5, 1975, and before Jan- § 36.13 Acoustical change: Tiltrotor uary 1, 2006, it must be shown that the aircraft.

noise levels of the airplane are no The following requirements apply to greater than the Stage 3 noise limit tiltrotors in any category for which an prescribed in section B36.5(c) of appen- acoustical change approval is applied dix B of this part.

for under § 21.93(b) of this chapter on or (c) Type certification applications between January 1, 2006, and the date after March 11, 2013: specified in paragraph (d) or (e) of this (a) In showing compliance with Ap- section, as applicable for airplane pendix K of this part, noise levels must weight. If application is made on or be measured, evaluated, and calculated after January 1, 2006, and before the in accordance with the applicable pro- date specified in paragraph (d) or (e) of cedures and conditions prescribed in this section (as applicable for airplane Appendix K of this part.

weight), it must be shown that the (b) Compliance with the noise limits noise levels of the airplane are no prescribed in section K4 (Noise Limits) greater than the Stage 4 noise limit of Appendix K of this part must be prescribed in section B36.5(d) of appen- shown in accordance with the applica- dix B of this part. If an applicant chose ble provisions of sections K2 (Noise to voluntarily certificate an airplane Evaluation Measure), K3 (Noise Meas- to Stage 4 prior to January 2006, then urement Reference Points), K6 (Noise the requirements of § 36.7(f) apply to Certification Reference Procedures), that airplane.

and K7 (Test Procedures) of Appendix K (d) For airplanes with a maximum of this part. certificated takeoff weight of 121,254 (c) After a change in type design, pounds (55,000 kg) or more, type certifi- cation applications on or after Decem- tiltrotor noise levels may not exceed ber 31, 2017. If application is made on or the limits specified in § 36.1103.

after December 31, 2017, it must be [Amdt. 36–29, 78 FR 1139, Jan. 8, 2013] shown that the noise levels of the air- plane are no greater than the Stage 5 Subpart B—Transport Category noise limit prescribed in section B36.5(e) of appendix B of this part.

Large Airplanes and Jet Airplanes Prior to December 31, 2017, an appli- § 36.101 Noise measurement and eval- cant may seek voluntary certification uation.

to Stage 5. If Stage 5 certification is chosen, the requirements of § 36.7(g) For transport category large air- will apply.

planes and jet airplanes, the noise gen- (e) For airplanes with a maximum erated by the airplane must be meas- certificated take-off weight of less ured and evaluated under appendix A of than 121,254 pounds (55,000 kg), type this part or under an approved equiva- certification applications on or after lent procedure.

December 31, 2020. If application is [Amdt. 36–54, 67 FR 45212, July 8, 2002] made on or after December 31, 2020, it Federal Aviation Administration, DOT § 36.501 must be shown that the noise levels of FAA to be equivalent to the Chapter 14 the airplane are no greater than the noise levels required by the Inter- Stage 5 noise limit prescribed in sec- national Civil Aviation Organization tion B36.5(e) of appendix B of this part. (ICAO) in Annex 16, Volume 1, Aircraft Prior to December 31, 2020, an appli- Noise, Seventh Edition, July 2014, cant may seek voluntary certification Amendment 11–B, applicable January 1, to Stage 5. If Stage 5 certification is 2015.’’ chosen, the requirements of § 36.7(g) [FAA Doc. No. FAA–2015–3782, Amdt. No. 36– will apply.

31, 82 FR 46129, Oct. 4, 2017] [Amdt. 36–54, 67 FR 45212, July 8, 2002, as amended by Amdt. 36–26, 70 FR 38749, July 5, Subpart C [ Reserved ] 2005; FAA Doc. No. FAA–2015–3782, Amdt. No.

36–31, 82 FR 46130, Oct. 4, 2017] Subpart D—Noise Limits for Super- § 36.105 Flight Manual Statement of sonic Transport Category Air- Chapter 4 equivalency.

planes For each airplane that meets the re- § 36.301 Noise limits: Concorde.

quirements for Stage 4 certification, the Airplane Flight Manual or oper- (a) General. For the Concorde air- ations manual must include the fol- plane, compliance with this subpart lowing statement: ‘‘The following noise must be shown with noise levels meas- levels comply with part 36, Appendix B, ured and evaluated as prescribed in Stage 4 maximum noise level require- Subpart B of this part, and dem- ments and were obtained by analysis of onstrated at the measuring points pre- approved data from noise tests con- scribed in appendix B of this part.

ducted under the provisions of part 36, (b) Noise limits. It must be shown, in Amendment 36 (insert part 36 amend- accordance with the provisions of this ment to which the airplane was certifi- part in effect on October 13, 1977, that cated). The noise measurement and the noise levels of the airplane are re- evaluation procedures used to obtain duced to the lowest levels that are eco- these noise levels are considered by the nomically reasonable, technologically FAA to be equivalent to the Chapter 4 practicable, and appropriate for the noise level required by the Inter- Concorde type design.

national Civil Aviation Organization [Amdt. 36–10, 43 FR 28420, June 29, 1978, as (ICAO) in Annex 16, Volume I, Appen- amended by Amdt. 36–54, 67 FR 45212, July 8, dix 2, Amendment 7, effective March 21, 2002] 2002.’’.

[Amdt. 36–26, 70 FR 38749, July 5, 2005; 70 FR Subpart E [ Reserved ] 41610, July 20, 2005; FAA Doc. No. FAA–2015– 3782, Amdt. No. 36–31, 82 FR 46129, Oct. 4, Subpart F—Propeller Driven Small 2017] Airplanes and Propeller-Driv- § 36.106 Flight Manual statement of en, Commuter Category Air- Chapter 14 noise level equivalency.

planes For each airplane that meets the re- § 36.501 Noise limits.

quirements for Stage 5 certification, the Airplane Flight Manual or oper- (a) Compliance with this subpart ations manual must include the fol- must be shown for— lowing statement: ‘‘The following noise (1) Propeller driven small airplanes levels comply with part 36, appendix B, for which application for the issuance Stage 5 maximum noise level require- of a new, amended, or supplemental ments and were obtained by analysis of type certificate in the normal, utility, approved data from noise tests con- acrobatic, transport, or restricted cat- ducted under the provisions of part 36, egory is made on or after October 10, Amendment [insert part 36 amendment 1973; and propeller-driven, commuter number to which the airplane was cer- category airplanes for which applica- tificated]. The noise measurement and tion for the issuance of a type certifi- evaluation procedures used to obtain cate in the commuter category is made these noise levels are considered by the on or after January 15, 1987.

14 CFR Ch. I (1–1–25 Edition) § 36.801 (2) Propeller driven small airplanes Subpart G [ Reserved ] and propeller-driven, commuter cat- egory airplanes for which application is Subpart H—Helicopters made for the original issuance of a standard airworthiness certificate or S OURCE : Amdt. 36–14, 53 FR 3540, Feb. 5, restricted category airworthiness cer- 1988; 53 FR 7728, Mar. 10, 1988, unless other- tificate, and that have not had any wise noted.

flight time before January 1, 1980 (re- gardless of date of application).

§ 36.801 Noise measurement.

(3) Airplanes in the primary cat- For primary, normal, transport, or egory: restricted category helicopters for (i) Except as provided in paragraph which certification is sought under ap- (a)(3)(ii) of this section, for an airplane pendix H of this part, the noise gen- for which application for a type certifi- erated by the helicopter must be meas- cate in the primary category is made, ured at the noise measuring points and and that was not previously certifi- under the test conditions prescribed in cated under appendix F of this part, part B of appendix H of this part, or compliance with appendix G of this under an FAA-approved equivalent pro- part must be shown.

cedure. For those primary, normal, (ii) For an airplane in the normal, transport, and restricted category heli- utility or acrobatic category that (A) copters having a maximum certificated has a type certificate issued under this takeoff weight of not more than 7,000 chapter, (B) has a standard airworthi- pounds for which compliance with ap- ness certificate issued under this chap- pendix J of this part is demonstrated, ter, (C) has not undergone an acous- the noise generated by the helicopter tical change from its type design, (D) must be measured at the noise meas- has not previously been certificated uring point and under the test condi- under appendix F or G of this part, and tions prescribed in part B of appendix J (E) for which application for conver- of this part, or an FAA-approved equiv- sion to the primary category is made, alent procedure.

no further showing of compliance with [Doc. No. 26910, 57 FR 42854, Sept. 16, 1992, as this part is required.

amended by Amdt. 36–25, 69 FR 31234, June 2, (b) For aircraft covered by this sub- 2004] part for which certification tests are completed before December 22, 1988, § 36.803 Noise evaluation and calcula- compliance must be shown with noise tion.

levels as measured and prescribed in The noise measurement data required Parts B and C of appendix F, or under under § 36.801 and obtained under ap- approved equivalent procedures. It pendix H of this part must be corrected must be shown that the noise level of to the reference conditions contained the airplane is no greater than the ap- in part A of appendix H of this part, plicable limit set in Part D of appendix and evaluated under the procedures of F.

part C of appendix H of this part, or an (c) For aircraft covered by this sub- FAA-approved equivalent procedure.

part for which certification tests are The noise measurement data required not completed before December 22, 1988, under § 36.801 and obtained under ap- compliance must be shown with noise pendix J of this part must be corrected levels as measured and prescribed in to the reference conditions contained Parts B and C of appendix G, or under in part A of appendix J of this part, and approved equivalent procedures. It evaluated under the procedures of part must be shown that the noise level of C of appendix J of this part, or an FAA- the airplane is no greater than the ap- approved equivalent procedure.

plicable limits set in Part D of appen- dix G. [Doc. No. 26910, 57 FR 42854, Sept. 16, 1992] [Doc. No. 13243, 40 FR 1034, Jan. 6, 1975, as § 36.805 Noise limits.

amended by Amdt. 36–13, 52 FR 1836, Jan. 15, (a) Compliance with the noise levels 1987; Amdt. 36–16, 53 FR 47400, Nov. 22, 1988; Amdt. 36–19, 57 FR 41369, Sept. 9, 1992] prescribed under part D of appendix H Federal Aviation Administration, DOT § 36.1103 of this part, or under part D of appen- (1) Except as provided in paragraph dix J of this part, must be shown for (d)(2) of this section, for a helicopter helicopters for which application for for which application for a type certifi- issuance of a type certificate in the cate in the primary category is made, primary, normal, transport, or re- and that was not previously certifi- cated under appendix H of this part, stricted category is made on or after compliance with appendix H of this March 6, 1986.

part must be shown.

(b) For helicopters covered by this (2) For a helicopter that: section, except as provided in para- (i) Has a normal or transport type graph (c) or (d)(2) of this section, it certificate issued under this chapter, must be shown either: (ii) Has a standard airworthiness cer- (1) When an application for issuance tificate issued under this chapter, of a type certificate in the primary, normal, transport, or restricted cat- (iii) Has not undergone an acoustical egory is made on and after March 6, change from its type design, 1986 and before May 5, 2014, that the (iv) Has not previously been certifi- noise levels of the helicopter are no cated under appendix H of this part, greater than the Stage 2 noise limits and prescribed in either section H36.305 of (v) For which application for conver- appendix H of this part or section sion to the primary category is made, J36.305 of appendix J of this part, as ap- no further showing of compliance with plicable; or this part is required.

(2) When an application for issuance [Doc. No. 26910, 57 FR 42855, Sept. 16, 1992, as of a type certificate in the primary, amended by Amdt. 36–30, 79 FR 12045, Mar. 4, normal, transport, or restricted cat- 2014] egory is made on or after May 5, 2014, that the noise levels of the helicopter Subparts I–J [ Reserved ] are no greater than the Stage 3 noise limits prescribed in either section Subpart K—Tiltrotors H36.305 of appendix H of this part, or section J36.305 of appendix J of this part, as applicable.

S OURCE : 78 FR 1139, Jan. 8, 2013, unless oth- erwise noted.

(c) For helicopters for which applica- tion for issuance of an original type § 36.1101 Noise measurement and eval- certificate in the primary, normal, uation.

transport, or restricted category is made on or after March 6, 1986, and For tiltrotors, the noise generated must be measured and evaluated under which the FAA finds to be the first Appendix K of this part, or under an civil version of a helicopter that was approved equivalent procedure.

designed and constructed for, and ac- cepted for operational use by, an § 36.1103 Noise limits.

Armed Force of the United States or the U.S. Coast Guard on or before (a) Compliance with the maximum March 6, 1986, it must be shown that noise levels prescribed in Appendix K the noise levels of the helicopter are no of this part must be shown for a greater than the noise limits for a tiltrotor for which the application for change in type design as specified in the issuance of a type certificate is section H36.305(a)(1)(ii) of appendix H of made on or after March 11, 2013.

this part for compliance demonstrated (b) To demonstrate compliance with under appendix H of this part, or as this part, noise levels may not exceed specified in section J36.305 of appendix the noise limits listed in Appendix K, J of this part for compliance dem- Section K4, Noise Limits of this part.

onstrated under appendix J of this Appendix K of this part (or an approved part. Subsequent civil versions of any equivalent procedure) must also be such helicopter must meet the Stage 2 used to evaluate and demonstrate com- requirements.

pliance with the approved test proce- (d) Helicopters in the primary cat- dures, and at the applicable noise egory: measurement points.

14 CFR Ch. I (1–1–25 Edition) § 36.1501 this part, along with the maximum Subparts L–N [ Reserved ] takeoff weight and configuration.

(3) For rotorcraft, the noise level in- Subpart O—Documentation, Op- formation must be one value for each erating Limitations and Infor- takeoff, flyover, and approach as de- mation fined and required by appendix H of this part, or one value for flyover as § 36.1501 Procedures, noise levels and defined and required by appendix J of other information.

this part, at the maximum takeoff weight and configuration.

(a) All procedures, weights, configu- (b) If supplemental operational noise rations, and other information or data level information is included in the ap- employed for obtaining the certified proved portion of the Airplane Flight noise levels prescribed by this part, in- Manual, it must be segregated, identi- cluding equivalent procedures used for fied as information in addition to the flight, testing, and analysis, must be certificated noise levels, and clearly developed and approved. Noise levels distinguished from the information re- achieved during type certification quired under § 36.1581(a).

must be included in the approved air- (c) The following statement must be plane (rotorcraft) flight manual.

furnished near the listed noise levels: (b) Where supplemental test data are approved for modification or extension No determination has been made by the Fed- of an existing flight data base, such as eral Aviation Administration that the noise levels of this aircraft are or should be ac- acoustic data from engine static tests ceptable or unacceptable for operation at, used in the certification of acoustical into, or out of, any airport.

changes, the test procedures, physical configuration, and other information (d) For transport category large air- and procedures that are employed for planes and jet airplanes, for which the obtaining the supplemental data must weight used in meeting the takeoff or be developed and approved. landing noise requirements of this part is less than the maximum weight es- [Amdt. 36–15, 53 FR 16366, May 6, 1988] tablished under the applicable air- worthiness requirements, those lesser § 36.1581 Manuals, markings, and plac- weights must be furnished, as oper- ards.

ating limitations in the operating limi- (a) If an Airplane Flight Manual or tations section of the Airplane Flight Rotorcraft Flight Manual is approved, Manual. Further, the maximum takeoff the approved portion of the Airplane weight must not exceed the takeoff Flight Manual or Rotorcraft Flight weight that is most critical from a Manual must contain the following in- takeoff noise standpoint.

formation, in addition to that specified (e) For propeller driven small air- under § 36.1583 of this part. If an Air- planes and for propeller-driven, com- plane Flight Manual or Rotorcraft muter category airplanes for which the Flight Manual is not approved, the pro- weight used in meeting the flyover cedures and information must be fur- noise requirements of this part is less nished in any combination of approved than the maximum weight by an manual material, markings, and plac- amount exceeding the amount of fuel ards.

needed to conduct the test, that lesser (1) For transport category large air- weight must be furnished, as an oper- planes and jet airplanes, the noise level ating limitation, in the operating limi- information must be one value for each tations section of an approved Airplane flyover, lateral, and approach as de- Flight Manual, in approved manual fined and required by appendix B of material, or on an approved placard.

this part, along with the maximum (f) For primary, normal, transport, takeoff weight, maximum landing and restricted category helicopters, if weight, and configuration.

the weight used in meeting the takeoff, (2) For propeller driven small air- flyover, or approach noise require- planes, the noise level information ments of appendix H of this part, or the must be one value for takeoff as de- weight used in meeting the flyover fined and required by appendix G of noise requirement of appendix J of this

Federal Aviation Administration, DOT Pt. 36, App. A

part, is less than the certificated max- A PPENDIX A TO P ART 36—A IRCRAFT imum takeoff weight established under N OISE M EASUREMENT AND E VALUA - either § 27.25(a) or § 29.25(a) of this chap- TION UNDER § 36.101 ter, that lesser weight must be fur- Sec.

nished as an operating limitation in A36.1 Introduction.

the operating limitations section of the A36.2 Noise Certification Test and Measurement Rotorcraft Flight Manual, in FAA-ap- Conditions.

proved manual material, or on an FAA- A36.3 Measurement of Airplane Noise Received approved placard.

on the Ground.

(g) Except as provided in paragraphs A36.4 Calculations of Effective Perceived Noise Level From Measured Data.

(d), (e), and (f) of this section, no oper- A36.5 Reporting of Data to the FAA.

ating limitations are furnished under A36.6 Nomenclature: Symbols and Units.

this part.

A36.7 Sound Attenuation in Air.

A36.8 [Reserved] [Doc. No. 13243, 40 FR 1035, Jan. 6, 1975] A36.9 Adjustment of Airplane Flight Test Re- E DITORIAL N OTE : For F EDERAL R EGISTER ci- sults.

tations affecting § 36.1581, see the List of CFR Section A36.1 Introduction Sections Affected, which appears in the Finding Aids section of the printed volume A36.1.1 This appendix prescribes the condi- and at www.govinfo.gov.

tions under which airplane noise certifi- cation tests must be conducted and states § 36.1583 Noncomplying agricultural the measurement procedures that must be and fire fighting airplanes.

used to measure airplane noise. The proce- dures that must be used to determine the (a) This section applies to propeller- noise evaluation quantity designated as ef- driven, small airplanes that— fective perceived noise level, EPNL, under (1) Are designed for ‘‘agricultural air- §§ 36.101 and 36.803 are also stated.

craft operations’’ (as defined in § 137.3 A36.1.2 The instructions and procedures of this chapter, effective on January 1, given are intended to ensure uniformity dur- 1966) or for dispensing fire fighting ma- ing compliance tests and to permit compari- son between tests of various types of air- terials; and planes conducted in various geographical lo- (2) Have not been shown to comply cations.

with the noise levels prescribed under A36.1.3 A complete list of symbols and appendix F of this part— units, the mathematical formulation of per- (i) For which application is made for ceived noisiness, a procedure for determining the original issue of a standard air- atmospheric attenuation of sound, and de- worthiness certificate and that do not tailed procedures for correcting noise levels from non-reference to reference conditions have any flight time before January 1, are included in this appendix.

1980; or A36.1.4 For Stage 4 airplanes, an acceptable (ii) For which application is made for alternative for noise measurement and eval- an acoustical change approval, for air- uation is Appendix 2 to ICAO Annex 16, Vol- planes which have a standard air- ume I, Amendment 7 (incorporated by ref- worthiness certificate after the change erence, see § 36.6).

in the type design, and that do not A36.1.5 For Stage 5 airplanes, an acceptable have any flight time in the changed alternative for noise measurement and eval- uation is Appendix 2 to ICAO Annex 16, Vol- configuration before January 1, 1980.

ume 1, Amendment 11–B (incorporated by (b) For airplanes covered by this sec- reference, see § 36.6).

tion an operating limitation reading as follows must be furnished in the man- Section A36.2 Noise Certification Test and ner prescribed in § 36.1581: Measurement Conditions A36.2.1 General.

Noise abatement: This airplane has not A36.2.1.1 This section prescribes the condi- been shown to comply with the noise limits tions under which noise certification must in FAR Part 36 and must be operated in ac- be conducted and the measurement proce- cordance with the noise operating limitation dures that must be used.

prescribed under FAR § 91.815.

N OTE : Many noise certifications involve [Amdt. 36–11, 45 FR 67066, Oct. 9, 1980. Redes- only minor changes to the airplane type de- ignated by Amdt. 36–14, 53 FR 3540, Feb. 5, sign. The resulting changes in noise can 1988; Amdt. 36–18, 54 FR 34330, Aug. 18, 1989] often be established reliably without resort- ing to a complete test as outlined in this ap- pendix. For this reason, the FAA permits the

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

use of approved equivalent procedures. There to compute equivalent weighted sound at- are also equivalent procedures that may be tenuations in each one-third octave band; used in full certification tests, in the inter- the FAA will determine whether a sufficient est of reducing costs and providing reliable number of layered sections have been used.

results. Guidance material on the use of For each measurement, where multiple equivalent procedures in the noise certifi- layering is not required, equivalent sound at- cation of subsonic jet and propeller-driven tenuations in each one-third octave band large airplanes is provided in the current ad- must be determined by averaging the atmos- visory circular for this part.

pheric absorption coefficients for each such A36.2.2 Test environment. band at 33 ft (10 m) above ground level, and A36.2.2.1 Locations for measuring noise at the flight level of the airplane at the time from an airplane in flight must be sur- of PNLTM, for each measurement; rounded by relatively flat terrain having no (e) Average wind velocity 33 ft (10 m) above excessive sound absorption characteristics ground may not exceed 12 knots and the such as might be caused by thick, matted, or crosswind velocity for the airplane may not tall grass, shrubs, or wooded areas. No ob- exceed 7 knots. The average wind velocity structions that significantly influence the must be determined using a 30-second aver- sound field from the airplane must exist aging period spanning the 10 dB-down time within a conical space above the point on the interval. Maximum wind velocity 33 ft (10 m) ground vertically below the microphone, the above ground is not to exceed 15 knots and cone being defined by an axis normal to the the crosswind velocity is not to exceed 10 ground and by a half-angle 80 ° from this axis.

knots during the 10 dB-down time interval; OTE : Those people carrying out the meas- N (f) No anomalous meteorological or wind urements could themselves constitute such conditions that would significantly affect obstruction.

the measured noise levels when the noise is A36.2.2.2 The tests must be carried out recorded at the measuring points specified under the following atmospheric conditions.

by the FAA; and (a) No precipitation; (g) Meteorological measurements must be (b) Ambient air temperature not above 95 obtained within 30 minutes of each noise test ° F (35 ° C) and not below 14 ° F ( ¥ 10 ° C), and measurement; meteorological data must be relative humidity not above 95% and not interpolated to actual times of each noise below 20% over the whole noise path between measurement.

a point 33 ft (10 m) above the ground and the A36.2.2.3 When a multiple layering calcula- airplane; tion is required by section A36.2.2.2(c) or N OTE : Care should be taken to ensure that A36.2.2.2(d) the atmosphere between the air- the noise measuring, airplane flight path plane and 33 ft (10 m) above the ground must tracking, and meteorological instrumenta- be divided into layers of equal depth. The tion are also operated within their specific depth of the layers must be set to not more environmental limitations.

than the depth of the narrowest layer across (c) Relative humidity and ambient tem- which the variation in the atmospheric ab- perature over the whole noise path between sorption coefficient of the 3150 Hz one-third a point 33 ft (10 m) above the ground and the octave band is not greater than ± 1.6 dB/1000 airplane such that the sound attenuation in ft ( ± 0.5 dB/100m), with a minimum layer the one-third octave band centered on 8 kHz depth of 100 ft (30 m). This requirement must will not be more than 12 dB/100 m unless: be met for the propagation path at PNLTM.

(1) The dew point and dry bulb tempera- The mean of the values of the atmospheric tures are measured with a device which is ac- absorption coefficients at the top and bot- curate to ± 0.9 ° F ( ± 0.5 ° C) and used to obtain tom of each layer may be used to charac- relative humidity; in addition layered sec- terize the absorption properties of each tions of the atmosphere are used as described layer.

in section A36.2.2.3 to compute equivalent A36.2.2.4 The airport control tower or an- weighted sound attenuations in each one- other facility must be aproved by the FAA third octave band; or for use as the central location at which (2) The peak noy values at the time of measurements of atmospheric parameters PNLT, after adjustment to reference condi- are representative of those conditions exist- tions, occur at frequencies less than or equal ing over the geographical area in which noise to 400 Hz.; measurements are made.

(d) If the atmospheric absorption coeffi- A36.2.3 Flight path measurement.

cients vary over the PNLTM sound propaga- tion path by more than ± 1.6 dB/1000 ft ( ± 0.5 A36.2.3.1 The airplane height and lateral dB/100m) in the 3150Hz one-third octave band position relative to the flight track must be from the value of the absorption coefficient determined by a method independent of nor- derived from the meteorological measure- mal flight instrumentation such as radar ment obtained at 33 ft (10 m) above the sur- tracking, theodolite triangulation, or photo- face, ‘‘layered’’ sections of the atmosphere graphic scaling techniques, to be approved must be used as described in section A36.2.2.3 by the FAA.

Federal Aviation Administration, DOT Pt. 36, App. A

A36.2.3.2 The airplane position along the dence angle, the quotient of the root mean flight path must be related to the noise re- square voltage at the output of a microphone corded at the noise measurement locations system and the root mean square sound pres- by means of synchronizing signals over a dis- sure that would exist at the position of the tance sufficient to assure adequate data dur- microphone in its absence.

ing the period that the noise is within 10 dB A36.3.1.6 Free-field sensitivity level of a micro- of the maximum value of PNLT.

phone system means, in decibels, twenty A36.2.3.3 Position and performance data re- times the logarithm to the base ten of the quired to make the adjustments referred to ratio of the free-field sensitivity of a micro- in section A36.9 of this appendix must be phone system and the reference sensitivity automatically recorded at an approved sam- of one volt per Pascal.

pling rate. Measuring equipment must be ap- N OTE : The free-field sensitivity level of a proved by the FAA.

microphone system may be determined by subtracting the sound pressure level (in deci- Section A36.3 Measurement of Airplane Noise bels re 20 μ Pa) of the sound incident on the Received on the Ground microphone from the voltage level (in deci- A36.3.1 Definitions.

bels re 1 V) at the output of the microphone For the purposes of section A36.3 the fol- system, and adding 93.98 dB to the result.

lowing definitions apply: A36.3.1.7 Time-average band sound pressure A36.3.1.1 Measurement system means the level means in decibels, ten times the loga- combination of instruments used for the rithm to the base ten, of the ratio of the measurement of sound pressure levels, in- time mean square of the instantaneous cluding a sound calibrator, windscreen, sound pressure during a stated time interval microphone system, signal recording and and in a specified one-third octave band, to conditioning devices, and one-third octave the square of the reference sound pressure of band analysis system.

20 μ Pa.

N OTE : Practical installations may include A36.3.1.8 Level range means, in decibels, an a number of microphone systems, the out- operating range determined by the setting of puts from which are recorded simultaneously the controls that are provided in a measure- by a multi-channel recording/analysis device ment system for the recording and one-third via signal conditioners, as appropriate. For octave band analysis of a sound pressure sig- the purpose of this section, each complete nal. The upper boundary associated with any measurement channel is considered to be a particular level range must be rounded to measurement system to which the require- the nearest decibel.

ments apply accordingly.

A36.3.1.9 Calibration sound pressure level A36.3.1.2 Microphone system means the com- means, in decibels, the sound pressure level ponents of the measurement system which produced, under reference environmental produce an electrical output signal in re- conditions, in the cavity of the coupler of sponse to a sound pressure input signal, and the sound calibrator that is used to deter- which generally include a microphone, a pre- mine the overall acoustical sensitivity of a amplifier, extension cables, and other de- measurement system.

vices as necessary.

A36.3.1.10 Reference level range means, in A36.3.1.3 Sound incidence angle means in de- decibels, the level range for determining the grees, an angle between the principal axis of acoustical sensitivity of the measurement the microphone, as defined in IEC 61094–3 and system and containing the calibration sound IEC 61094–4, as amended and a line from the pressure level.

sound source to the center of the diaphragm A36.3.1.11 Calibration check frequency of the microphone (incorporated by ref- means, in hertz, the nominal frequency of erence, see § 36.6).

the sinusoidal sound pressure signal pro- N OTE : When the sound incidence angle is duced by the sound calibrator.

0 ° , the sound is said to be received at the A36.3.1.12 Level difference means, in deci- microphone at ‘‘normal (perpendicular) inci- bels, for any nominal one-third octave dence;’’ when the sound incidence angle is midband frequency, the output signal level 90 ° , the sound is said to be received at ‘‘graz- measured on any level range minus the level ing incidence.’’ of the corresponding electrical input signal.

A36.3.1.13 Reference level difference means, A36.3.1.4 Reference direction means, in de- in decibels, for a stated frequency, the level grees, the direction of sound incidence speci- fied by the manufacturer of the microphone, difference measured on a level range for an relative to a sound incidence angle of 0 ° , for electrical input signal corresponding to the which the free-field sensitivity level of the calibration sound pressure level, adjusted as microphone system is within specified toler- appropriate, for the level range.

ance limits. A36.3.1.14 Level non-linearity means, in deci- A36.3.1.5 Free-field sensitivity of a micro- bels, the level difference measured on any phone system means, in volts per Pascal, for level range, at a stated one-third octave a sinusoidal plane progressive sound wave of nominal midband frequency, minus the cor- specified frequency, at a specified sound inci- responding reference level difference, all

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

input and output signals being relative to at any frequency less than 12.5 kHz. The the same reference quantity. sampling rate must be at least 28 kHz. An A36.3.1.15 Linear operating range means, in anti-aliasing filter must be included before decibels, for a stated level range and fre- the digitization process.

quency, the range of levels of steady sinus- A36.3.4 Windscreen.

oidal electrical signals applied to the input A36.3.4.1 In the absence of wind and for si- of the entire measurement system, exclusive nusoidal sounds at grazing incidence, the in- of the microphone but including the micro- sertion loss caused by the windscreen of a phone preamplifier and any other signal-con- stated type installed around the microphone ditioning elements that are considered to be must not exceed ± 1.5 dB at nominal one-third part of the microphone system, extending octave midband frequencies from 50 Hz to 10 from a lower to an upper boundary, over kHz inclusive.

which the level non-linearity is within speci- A36.3.5 Microphone system.

fied tolerance limits.

A36.3.5.1 The microphone system must N OTE : Microphone extension cables as con- meet the specifications in sections A36.3.5.2 figured in the field need not be included for to A36.3.5.4. Various microphone systems the linear operating range determination.

may be approved by the FAA on the basis of A36.3.1.16 Windscreen insertion loss means, demonstrated equivalent overall in decibels, at a stated nominal one-third oc- electroacoustical performance. Where two or tave midband frequency, and for a stated more microphone systems of the same type sound incidence angle on the inserted micro- are used, demonstration that at least one phone, the indicated sound pressure level system conforms to the specifications in full without the windscreen installed around the is sufficient to demonstrate conformance.

microphone minus the sound pressure level N OTE : An applicant must still calibrate with the windscreen installed.

and check each system as required in section A36.3.2 Reference environmental conditions.

A36.3.9.

A36.3.2.1 The reference environmental con- ditions for specifying the performance of a A36.3.5.2 The microphone must be mounted measurement system are: with the sensing element 4 ft (1.2 m) above (a) Air temperature 73.4 ° F (23 ° C); the local ground surface and must be ori- (b) Static air pressure 101.325 kPa; and ented for grazing incidence, i.e. , with the (c) Relative humidity 50%.

sensing element substantially in the plane A36.3.3. General.

defined by the predicted reference flight path of the aircraft and the measuring station.

N OTE : Measurements of aircraft noise that The microphone mounting arrangement are made using instruments that conform to must minimize the interference of the sup- the specifications of this section will yield one-third octave band sound pressure levels ports with the sound to be measured. Figure as a function of time. These one-third octave A36–1 illustrates sound incidence angles on a band levels are to be used for the calculation microphone.

of effective perceived noise level as described A36.3.5.3 The free-field sensitivity level of in section A36.4. the microphone and preamplifier in the ref- erence direction, at frequencies over at least A36.3.3.1 The measurement system must the range of one-third-octave nominal consist of equipment approved by the FAA midband frequencies from 50 Hz to 5 kHz in- and equivalent to the following: clusive, must be within ± 1.0 dB of that at the (a) A windscreen (See A36.3.4.); calibration check frequency, and within ± 2.0 (b) A microphone system (See A36.3.5): dB for nominal midband frequencies of 6.3 (c) A recording and reproducing system to kHz, 8 kHz and 10 kHz.

store the measured aircraft noise signals for A36.3.5.4 For sinusoidal sound waves at subsequent analysis (see A36.3.6); (d) A one-third octave band analysis sys- each one-third octave nominal midband fre- tem (see A36.3.7); and quency over the range from 50 Hz to 10 kHz (e) Calibration systems to maintain the inclusive, the free-field sensitivity levels of acoustical sensitivity of the above systems the microphone system at sound incidence within specified tolerance limits (see angles of 30 ° , 60 ° , 90 ° , 120 ° and 150 ° , must not A36.3.8). differ from the free-field sensitivity level at A36.3.3.2. For any component of the meas- a sound incidence angle of 0 ° (‘‘normal inci- urement system that converts an analog sig- dence’’) by more than the values shown in nal to digital form, such conversion must be Table A36–1. The free-field sensitivity level performed so that the levels of any possible differences at sound incidence angles be- aliases or artifacts of the digitization proc- tween any two adjacent sound incidence an- ess will be less than the upper boundary of gles in Table A36–1 must not exceed the tol- the linear operating range by at least 50 dB erance limit for the greater angle.

Federal Aviation Administration, DOT Pt. 36, App. A

A36.3.6 Recording and reproducing systems. over the range of nominal one-third octave midband frequencies from 800 Hz to 10 kHz A36.3.6.1 A recording and reproducing sys- inclusive, the electrical gain provided by the tem, such as a digital or analog magnetic pre-emphasis network must not exceed 20 dB tape recorder, a computer-based system or relative to the gain at 800 Hz.

other permanent data storage device, must A36.3.6.3 For steady sinusoidal electrical be used to store sound pressure signals for signals applied to the input of the entire subsequent analysis. The sound produced by measurement system including all parts of the aircraft must be recorded in such a way the microphone system except the micro- that a record of the complete acoustical sig- nal is retained. The recording and reproduc- phone at a selected signal level within 5 dB ing systems must meet the specifications in of that corresponding to the calibration sections A36.3.6.2 to A36.3.6.9 at the recording sound pressure level on the reference level speeds and/or data sampling rates used for range, the time-average signal level indi- the noise certification tests. Conformance cated by the readout device at any one-third must be demonstrated for the frequency octave nominal midband frequency from 50 Hz to 10 kHz inclusive must be within ± 1.5 dB bandwidths and recording channels selected of that at the calibration check frequency.

for the tests.

The frequency response of a measurement A36.3.6.2 The recording and reproducing system, which includes components that systems must be calibrated as described in convert analog signals to digital form, must section A36.3.9.

be within ± 0.3 dB of the response at 10 kHz (a) For aircraft noise signals for which the over the frequency range from 10 kHz to 11.2 high frequency spectral levels decrease rap- kHz.

idly with increasing frequency, appropriate pre-emphasis and complementary de-empha- N OTE : Microphone extension cables as con- sis networks may be included in the meas- figured in the field need not be included for urement system. If pre-emphasis is included, the frequency response determination. This

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

allowance does not eliminate the require- A36.3.7.2 The output of the analysis system ment of including microphone extension ca- must consist of one-third octave band sound bles when performing the pink noise record- pressure levels as a function of time, ob- ing in section A36.3.9.5. tained by processing the noise signals (pref- erably recorded) through an analysis system A36.3.6.4 For analog tape recordings, the with the following characteristics: amplitude fluctuations of a 1 kHz sinusoidal (a) A set of 24 one-third octave band filters, signal recorded within 5 dB of the level cor- or their equivalent, having nominal midband responding to the calibration sound pressure frequencies from 50 Hz to 10 kHz inclusive; level must not vary by more than ± 0.5 dB (b) Response and averaging properties in throughout any reel of the type of magnetic which, in principle, the output from any one- tape used. Conformance to this requirement third octave filter band is squared, averaged must be demonstrated using a device that and displayed or stored as time-averaged has time-averaging properties equivalent to sound pressure levels; those of the spectrum analyzer.

(c) The interval between successive sound A36.3.6.5 For all appropriate level ranges pressure level samples must be 500 ms ± 5 mil- and for steady sinusoidal electrical signals liseconds(ms) for spectral analysis with or applied to the input of the measurement sys- without slow time-weighting, as defined in tem, including all parts of the microphone section A36.3.7.4; system except the microphone, at one-third- (d) For those analysis systems that do not octave nominal midband frequencies of 50 process the sound pressure signals during the Hz, 1 kHz and 10 kHz, and the calibration period of time required for readout and/or re- check frequency, if it is not one of these fre- setting of the analyzer, the loss of data must quencies, the level non-linearity must not not exceed a duration of 5 ms; and exceed ± 0.5 dB for a linear operating range of (e) The analysis system must operate in at least 50 dB below the upper boundary of real time from 50 Hz through at least 12 kHz the level range.

inclusive. This requirement applies to all op- N OTE 1: Level linearity of measurement erating channels of a multi-channel spectral system components may be tested according analysis system.

to the methods described in IEC 61265 as A36.3.7.3 The minimum standard for the amended.

one-third octave band analysis system is the N OTE 2: Microphone extension cables con- class 2 electrical performance requirements figured in the field need not be included for of IEC 61260 as amended, over the range of the level linearity determination.

one-third octave nominal midband fre- A36.3.6.6 On the reference level range, the quencies from 50 Hz through 10 kHz inclusive level corresonding to the calibration sound (incorporated by reference, see § 36.6).

pressure level must be at least 5 dB, but no N OTE : IEC 61260 specifies procedures for more than 30 dB less than the upper bound- testing of one-third octave band analysis ary of the level range.

systems for relative attenuation, anti- A36.3.6.7 The linear operating ranges on ad- aliasing filters, real time operation, level jacent level ranges must overlap by at least linearity, and filter integrated response (ef- 50 dB minus the change in attenuation intro- fective bandwidth).

duced by a change in the level range con- A36.3.7.4 When slow time averaging is per- trols.

formed in the analyzer, the response of the N OTE : It is possible for a measurement sys- one-third octave band analysis system to a tem to have level range controls that permit sudden onset or interruption of a constant attenuation changes of either 10 dB or 1 dB, sinusoidal signal at the respective one-third for example. With 10 dB steps, the minimum octave nominal midband frequency, must be overlap required would be 40 dB, and with 1 measured at sampling instants 0.5, 1, 1.5 and dB steps the minimum overlap would be 49 2 seconds(s) after the onset and 0.5 and 1s dB.

after interruption. The rising response must A36.3.6.8 An overload indicator must be in- be ¥ 4 ± 1 dB at 0.5s, ¥ 1.75 ± 0.75 dB at 1s, ¥ 1 cluded in the recording and reproducing sys- ± 0.5 dB at 1.5s and ¥ 0.5 ± 0.5 dB at 2s relative tems so that an overload indication will to the steady-state level. The falling re- occur during an overload condition on any sponse must be such that the sum of the out- relevant level range. put signal levels, relative to the initial A36.3.6.9 Attenuators included in the meas- steady-state level, and the corresponding ris- urement system to permit range changes ing response reading is ¥ 6.5 ± 1 dB, at both 0.5 must operate in known intervals of decibel and 1s. At subsequent times the sum of the steps. rising and falling responses must be ¥ 7.5 dB A36.3.7 Analysis systems. or less. This equates to an exponential aver- A36.3.7.1 The analysis system must con- aging process (slow time-weighting) with a form to the specifications in sections nominal 1s time constant ( i.e., 2s averaging A36.3.7.2 to A36.3.7.7 for the frequency time).

bandwidths, channel configurations and gain A36.3.7.5 When the one-third octave band settings used for analysis. sound pressure levels are determined from

Federal Aviation Administration, DOT Pt. 36, App. A

the output of the analyzer without slow sound pressure level at a known frequency.

time-weighting, slow time-weighting must The minimum standard for the sound cali- be simulated in the subsequent processing. brator is the class 1L requirements of IEC Simulated slow time-weighted sound pres- 60942 as amended (incorporated by reference, sure levels can be obtained using a contin- see § 36.6).

A36.3.9 Calibration and checking of system.

uous exponential averaging process by the following equation: A36.3.9.1 Calibration and checking of the 0.1 Ls[i, ( k ¥ 1 ) ] measurement system and its constituent L (i,k) = 10 log [(0.60653) 10 + s 0.1 L ( i, k ) components must be carried out to the satis- (0.39347) 10 ] faction of the FAA by the methods specified where L (i,k) is the simulated slow time- s in sections A36.3.9.2 through A36.3.9.10. The weighted sound pressure level and L(i,k) calibration adjustments, including those for is the as-measured 0.5s time average environmental effects on sound calibrator sound pressure level determined from the output level, must be reported to the FAA output of the analyzer for the k-th in- and applied to the measured one-third-oc- stant of time and i-th one-third octave tave sound pressure levels determined from band. For k = 1, the slow time-weighted the output of the analyzer. Data collected sound pressure L [i, (k ¥ 1 = 0)] on the s during an overload indication are invalid and right hand side should be set to 0 dB. An may not be used. If the overload condition approximation of the continuous expo- occurred during recording, the associated nential averaging is represented by the test data are invalid, whereas if the overload following equation for a four sample occurred during analysis, the analysis must averaging process for k ≥ 4: be repeated with reduced sensitivity to ¥ 0.1 L[i, ( k 3 ) ] 0.1 (i,k) = 10 log [(0.13) 10 + (0.21) 10 L s eliminate the overload.

¥ ¥ L[i, ( k 2 ) ] 0.1 L[i, ( k 1 ) ] 0.1 L[i, + (0.27) 10 + (0.39) 10 A36.3.9.2 The free-field frequency response k] ] of the microphone system may be deter- where L (i, k) is the simulated slow time- mined by use of an electrostatic actuator in s weighted sound pressure level and L (i, k) combination with manufacturer’s data or by is the as measured 0.5s time average tests in an anechoic free-field facility. The sound pressure level determined from the correction for frequency response must be output of the analyzer for the k-th in- determined within 90 days of each test series.

stant of time and the i-th one-third oc- The correction for non-uniform frequency re- tave band. sponse of the microphone system must be re- The sum of the weighting factors is 1.0 in ported to the FAA and applied to the meas- the two equations. Sound pressure levels cal- ured one-third octave band sound pressure culated by means of either equation are valid levels determined from the output of the an- for the sixth and subsequent 0.5s data sam- alyzer.

ples, or for times greater than 2.5s after ini- A36.3.9.3 When the angles of incidence of tiation of data analysis. sound emitted from the aircraft are within ± 30 ° of grazing incidence at the microphone N OTE : The coefficients in the two equa- (see Figure A36–1), a single set of free-field tions were calculated for use in determining corrections based on grazing incidence is equivalent slow time-weighted sound pres- considered sufficient for correction of direc- sure levels from samples of 0.5s time average tional response effects. For other cases, the sound pressure levels. The equations do not angle of incidence for each 0.5 second sample work with data samples where the averaging must be determined and applied for the cor- time differs from 0.5s.

rection of incidence effects.

A36.3.7.6 The instant in time by which a A36.3.9.4 For analog magnetic tape record- slow time-weighted sound pressure level is ers, each reel of magnetic tape must carry at characterized must be 0.75s earlier than the least 30 seconds of pink random or pseudo- actual readout time.

random noise at its beginning and end. Data N OTE : The definition of this instant in obtained from analog tape-recorded signals time is needed to correlate the recorded will be accepted as reliable only if level dif- noise with the aircraft position when the ferences in the 10 kHz one-third-octave-band noise was emitted and takes into account are not more than 0.75 dB for the signals re- the averaging period of the slow time- corded at the beginning and end.

weighting. For each 0.5 second data record A36.3.9.5 The frequency response of the en- this instant in time may also be identified as tire measurement system while deployed in 1.25 seconds after the start of the associated the field during the test series, exclusive of 2 second averaging period.

the microphone, must be determined at a A36.3.7.7 The resolution of the sound pres- level within 5 dB of the level corresponding sure levels, both displayed and stored, must to the calibration sound pressure level on be 0.1 dB or finer. the level range used during the tests for each A36.3.8 Calibration systems. one-third octave nominal midband frequency A36.3.8.1 The acoustical sensitivity of the from 50 Hz to 10 kHz inclusive, utilizing pink measurement system must be determined random or pseudo-random noise. Within six using a sound calibrator generating a known months of each test series the output of the

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

noise generator must be determined by a tion A36.3.9.3. The interval between angles method traceable to the U.S. National Insti- tested must not exceed 30 degrees. For a tute of Standards and Technology or to an windscreen that is undamaged and equivalent national standards laboratory as uncontaminated, the insertion loss may be determined by the FAA. Changes in the rel- taken from manufacturer’s data. Alter- ative output from the previous calibration at natively, within six months of each test se- each one-third octave band may not exceed ries the insertion loss of the windscreen may 0.2 dB. The correction for frequency response be determined by a method traceable to the must be reported to the FAA and applied to U.S. National Institute of Standards and the measured one-third octave sound pres- Technology or an equivalent national stand- sure levels determined from the output of ards laboratory as determined by the FAA.

the analyzer.

Changes in the insertion loss from the pre- A36.3.9.6 The performance of switched at- vious calibration at each one-third-octave tenuators in the equipment used during frequency band must not exceed 0.4 dB. The noise certification measurements and cali- correction for the free-field insertion loss of bration must be checked within six months the windscreen must be reported to the FAA of each test series to ensure that the max- and applied to the measured one-third octave imum error does not exceed 0.1 dB.

sound pressure levels determined from the A36.3.9.7 The sound pressure level produced output of the analyzer.

in the cavity of the coupler of the sound cali- A36.3.10 Adjustments for ambient noise.

brator must be calculated for the test envi- A36.3.10.1 Ambient noise, including both an ronmental conditions using the manufactur- acoustical background and electrical noise of er’s supplied information on the influence of the measurement system, must be recorded atmospheric air pressure and temperature.

for at least 10 seconds at the measurement This sound pressure level is used to establish points with the system gain set at the levels the acoustical sensitivity of the measure- used for the aircraft noise measurements.

ment system. Within six months of each test Ambient noise must be representative of the series the output of the sound calibrator acoustical background that exists during the must be determined by a method traceable flyover test run. The recorded aircraft noise to the U.S. National Institute of Standards data is acceptable only if the ambient noise and Technology or to an equivalent national levels, when analyzed in the same way, and standards laboratory as determined by the quoted in PNL (see A36.4.1.3 (a)), are at least FAA. Changes in output from the previous 20 dB below the maximum PNL of the air- calibration must not exceed 0.2 dB.

craft.

A36.3.9.8 Sufficient sound pressure level A36.3.10.2 Aircraft sound pressure levels calibrations must be made during each test within the 10 dB-down points (see A36.4.5.1) day to ensure that the acoustical sensitivity must exceed the mean ambient noise levels of the measurement system is known at the determined in section A36.3.10.1 by at least 3 prevailing environmental conditions cor- dB in each one-third octave band, or must be responding with each test series. The dif- adjusted using a method approved by the ference between the acoustical sensitivity FAA; one method is described in the current levels recorded immediately before and im- advisory circular for this part.

mediately after each test series on each day may not exceed 0.5 dB. The 0.5 dB limit ap- Section A36.4 Calculation of Effective Perceived plies after any atmospheric pressure correc- Noise Level From Measured Data tions have been determined for the cali- brator output level. The arithmetic mean of A36.4.1 General.

the before and after measurements must be A36.4.1.1 The basic element for noise cer- used to represent the acoustical sensitivity tification criteria is the noise evaluation level of the measurement system for that measure known as effective perceived noise test series. The calibration corrections must level, EPNL, in units of EPNdB, which is a be reported to the FAA and applied to the single number evaluator of the subjective ef- measured one-third octave band sound pres- fects of airplane noise on human beings.

sure levels determined from the output of EPNL consists of instantaneous perceived the analyzer. noise level, PNL, corrected for spectral A36.3.9.9 Each recording medium, such as a irregularities, and for duration. The spectral reel, cartridge, cassette, or diskette, must irregularity correction, called ‘‘tone correc- carry a sound pressure level calibration of at tion factor’’, is made at each time increment least 10 seconds duration at its beginning for only the maximum tone.

and end. A36.4.1.2 Three basic physical properties of A36.3.9.10 The free-field insertion loss of sound pressure must be measured: level, fre- the windscreen for each one-third octave quency distribution, and time variation. To nominal midband frequency from 50 Hz to 10 determine EPNL, the instantaneous sound kHz inclusive must be determined with si- pressure level in each of the 24 one-third oc- nusoidal sound signals at the incidence an- tave bands is required for each 0.5 second in- gles determined to be applicable for correc- crement of time during the airplane noise tion of directional response effects per sec- measurement.

Federal Aviation Administration, DOT Pt. 36, App. A

A36.4.1.3 The calculation procedure that N OTE : PNL(k) is plotted in the current ad- uses physical measurements of noise to de- visory circular for this part.

rive the EPNL evaluation measure of subjec- A36.4.3 Correction for spectral irregularities.

tive response consists of the following five A36.4.3.1 Noise having pronounced spectral steps: irregularities (for example, the maximum (a) The 24 one-third octave bands of sound discrete frequency components or tones) pressure level are converted to perceived must be adjusted by the correction factor noisiness (noy) using the method described C(k) calculated as follows: in section A36.4.2.1 (a). The noy values are (a) Step 1: After applying the corrections combined and then converted to instanta- specified under section A36.3.9, start with the neous perceived noise levels, PNL(k).

sound pressure level in the 80 Hz one-third (b) A tone correction factor C(k) is cal- octave band (band number 3), calculate the culated for each spectrum to account for the changes in sound pressure level (or ‘‘slopes’’) subjective response to the presence of spec- in the remainder of the one-third octave tral irregularities.

bands as follows: (c) The tone correction factor is added to s (3, k ) = no value the perceived noise level to obtain tone-cor- s(4, k ) = SPL(4, k ) ¥ SPL(3, k ) rected perceived noise levels PNLT(k), at • each one-half second increment: • s( i,k ) = SPL( i,k ) ¥ SPL( i ¥ 1, k ) PNLT(k) = PNL(k) + C(k) • The instantaneous values of tone-corrected • perceived noise level are derived and the s(24, k ) = SPL(24, k ) ¥ SPL(23, k ) maximum value, PNLTM, is determined.

(b) Step 2: Encircle the value of the slope, (d) A duration correction factor, D, is com- s(i, k), where the absolute value of the puted by integration under the curve of tone- change in slope is greater than five; that is corrected perceived noise level versus time.

where: (e) Effective perceived noise level, EPNL, is determined by the algebraic sum of the | D s ( i,k ) | = | s ( i,k ) ¥ s ( i ¥ 1, k ) | >5 maximum tone-corrected perceived noise (c) Step 3: level and the duration correction factor: (1) If the encircled value of the slope s(i, k) is positive and algebraically greater than the EPNL = PNLTM + D slope s(i ¥ 1, k) encircle SPL(i, k).

A36.4.2 Perceived noise level.

(2) If the encircled value of the slope s(i, k) A36.4.2.1 Instantaneous perceived noise lev- is zero or negative and the slope s(i ¥ 1, k) is els, PNL(k), must be calculated from instan- positive, encircle SPL(i ¥ 1, k).

taneous one-third octave band sound pres- (3) For all other cases, no sound pressure sure levels, SPL(i, k) as follows: level value is to be encircled.

(a) Step 1: For each one-third octave band (d) Step 4: Compute new adjusted sound from 50 through 10,000 Hz, convert SPL(i, k) pressure levels SPL ′ (i, k) as follows: to perceived noisiness n(i, k), by using the (1) For non-encircled sound pressure levels, mathematical formulation of the noy table set the new sound pressure levels equal to given in section A36.4.7.

the original sound pressure levels, SPL ′ (i, k) (b) Step 2: Combine the perceived noisiness = SPL(i, k).

values, n(i, k), determined in step 1 by using (2) For encircled sound pressure levels in the following formula: bands 1 through 23 inclusive, set the new sound pressure level equal to the arithmetic

⎧ ⎫

⎡ ⎤ average of the preceding and following sound

⎪ ⎪

N (k) n (k) + n (i, k) = 0 15 . ( ) n k pressure levels as shown below:

⎢ ⎥ − ⎨ ⎬ ∑

⎪ ⎪

SPL ′ ( i,k ) = ⁄2[SPL( i ¥ 1, k ) + SPL( i + 1, k )]

⎣ ⎦ = 1 i

⎩ ⎭

(3) If the sound pressure level in the high- est frequency band (i = 24) is encircled, set

( , ) = + 0 85 0 15 . ( ) . n k n i k

the new sound pressure level in that band

∑

equal to: = 1 i SPL ′ (24, k ) = SPL(23, k ) + s (23, k ) where n(k) is the largest of the 24 values of n(i, k) and N(k) is the total perceived (e) Step 5: Recompute new slope s ′ (i, k), in- noisiness. cluding one for an imaginary 25th band, as (c) Step 3: Convert the total perceived follows: noisiness, N(k), determined in Step 2 into s ′ (3, k ) = s ′ (4, k ) perceived noise level, PNL(k), using the fol- s ′ (4, k ) = SPL ′ (4, k ) ¥ SPL ′ (3, k ) lowing formula: • • s ′ ( i,k ) = SPL ′ ( i,k ) ¥ SPL ′ ( i ¥ 1, k )

PNL (k) = 40.0 + log N (k)

•

log 2

•

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

s ′ (24, k ) = SPL ′ (24, k ) ¥ SPL ′ (23, k ) • s ′ (25, k ) = s ′ (24, k ) • ¯ SPL ′ (24, k ) = SPL ′ (23,k) + s (23,k) (f) Step 6: For i, from 3 through 23, com- pute the arithmetic average of the three ad- (h) Setp 8: Calculate the differences, F jacent slopes as follows: (i,k), between the original sound pressure s ¯ ( i,k ) = ⁄ 3 [ s ′ ( i,k ) + s ′ ( i + 1, k ) + s ′ ( i + 2, k )] level and the final background sound pres- sure level as follows: (g) Step 7: Compute final one-third octave- F ( i,k ) = SPL( i,k )-SPL ′ ( i,k ) band sound pressure levels, SPL ′ (i,k), by be- ginning with band number 3 and proceeding and note only values equal to or greater than to band number 24 as follows: 1.5.

SPL ′ (3, k ) = SPL(3,k) (i) Step 9: For each of the relevant one- ¯ SPL ′ (4, k ) = SPL ′ (3,k) + s (3, k ) third octave bands (3 through 24), determine • tone correction factors from the sound pres- • sure level differences F (i, k) and Table A36– ¯ SPL ′ ( i,k ) = SPL ′ (i ¥ 1,k) + s (i ¥ 1,k) 2.

Federal Aviation Administration, DOT Pt. 36, App. A

(j) Step 10: Designate the largest of the rection factor is suspected to result from tone correction factors, determined in Step something other than (or in addition to) an 9, as C(k). (An example of the tone correction actual tone (or any spectral irregularity procedure is given in the current advisory other than airplane noise), an additional circular for this part). Tone-corrected per- analysis may be made using a filter with a ceived noise levels PNLT(k) must be deter- bandwidth narrower than one-third of an oc- mined by adding the C(k) values to cor- tave. If the narrow band analysis corrobo- responding PNL(k) values, that is: rates these suspicions, then a revised value PNLT( k ) = PNL( k ) + C ( k ) for the background sound pressure level For any i-th one-third octave band, at any k- th increment of time, for which the tone cor-

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

SPL ′ (i,k), may be determined from the nar- recorded fully in a single one-third octave row band analysis and used to compute a re- band.

vised tone correction factor for that par- A36.4.4 Maximum tone-corrected perceived ticular one-third octave band. Other methods noise level of rejecting spurious tone corrections may be A36.4.4.1 The maximum tone-corrected per- approved. ceived noise level, PNLTM, must be the max- imum calculated value of the tone-corrected A36.4.3.2 The tone correction procedure perceived noise level PNLT(k). It must be will underestimate EPNL if an important calculated using the procedure of section tone is of a frequency such that it is re- A36.4.3. To obtain a satisfactory noise time corded in two adjacent one-third octave history, measurements must be made at 0.5 bands. An applicant must demonstrate that second time intervals.

either: (a) No important tones are recorded in two N OTE 1: Figure A36–2 is an example of a fly- adjacent one-third octave bands; or over noise time history where the maximum (b) That if an important tone has occurred, value is clearly indicated.

the tone correction has been adjusted to the N OTE 2: In the absence of a tone correction value it would have had if the tone had been factor, PNLTM would equal PNLM.

A36.4.4.2 After the value of PNLTM is ob- average value of C(k) for the five consecutive tained, the frequency band for the largest time intervals, the average value of C(k) tone correction factor is identified for the must be used to compute a new value for two preceding and two succeeding 500 ms PNLTM.

data samples. This is performed in order to A36.4.5 Duration correction.

identity the possibility of tone suppression A36.4.5.1 The duration correction factor D at PNLTM by one-third octave band sharing determined by the integration technique is of that tone. If the value of the tone correc- defined by the expression: tion factor C(k) for PNLTM is less than the

Federal Aviation Administration, DOT Pt. 36, App. A

2 t ( )

⎡ ⎤

PNLT 1

⎛ ⎞

⎢ ⎥

D log antilog = − 10 dt PNLTM

∫

⎝ ⎠

T 10 ⎢ ⎥

t 1 ( )

⎣ ⎦

where T is a normalizing time constant, A36.4.5.2 Since PNLT is calculated from PNLTM is the maximum value of PNLT, measured values of sound pressure level t(1) is the first point of time after which (SPL), there is no obvious equation for PNLT becomes greater than PNLTM–10, PNLT as a function of time. Consequently, and t(2) is the point of time after which the equation is to be rewritten with a sum- PNLT remains constantly less than mation sign instead of an integral sign as PNLTM–10. follows: d/ t Δ

⎡ ⎤

1 ( ) PNLT k

⎛ ⎞

D 10 log t.antilog PNLTM = Δ

⎢ ⎥ − ∑

⎝ ⎠

T 10

⎣ ⎦ = k 0

where D t is the length of the equal incre- (b) A shorter time interval with approved ments of time for which PNLT(k) is cal- limits and constants.

A36.4.5.4 The following values for T and D t culated and d is the time interval to the must be used in calculating D in the equa- nearest 0.5s during which PNLT(k) re- tion given in section A36.4.5.2: mains greater or equal to PNLTM–10.

A36.4.5.3 To obtain a satisfactory history of T = 10 s, and D t = 0.5s (or the approved sampling time in- the perceived noise level use one of the fol- terval).

lowing: (a) Half-Second time intervals for D t; or Using these values, the equation for D be- comes: 2d

⎡ ⎤

PNLT k ( )

D = 10 log antilog PNLTM − 13

∑ ⎢ ⎥ −

k = ⎣ ⎦ 0

where d is the duration time defined by the where PNLTM and D are calculated using points corresponding to the values the procedures given in sections A36.4.2, A36.4.3, A36.4.4. and A36.4.5.

PNLTM–10.

A36.4.7 Mathematical formulation of noy ta- A36.4.5.5 If in using the procedures given in bles.

section A36.4.5.2, the limits of PNLTM–10 fall A36.4.7.1 The relationship between sound between the calculated PNLT(k) values (the pressure level (SPL) and the logarithm of usual case), the PNLT(k) values defining the perceived noisiness is illustrated in Figure limits of the duration interval must be cho- A36–3 and Table A36–3.

sen from the PNLT(k) values closest to A36.4.7.2 The bases of the mathematical PNLTM–10. For those cases with more than formulation are: one peak value of PNLT(k), the applicable (a) The slopes (M(b), M(c), M(d) and M(e)) limits must be chosen to yield the largest of the straight lines; possible value for the duration time.

(b) The intercepts (SPL(b) and SPL(c)) of A36.4.6 Effective perceived noise level. the lines on the SPL axis; and (c) The coordinates of the discontinuities, The total subjective effect of an airplane SPL(a) and log n(a); SPL(d) and log n = ¥ 1.0; noise event, designated effective perceived and SPL(e) and log n = log (0.3).

noise level, EPNL, is equal to the algebraic A36.4.7.3 Calculate noy values using the sum of the maximum value of the tone-cor- following equations: rected perceived noise level, PNLTM, and (a) the duration correction D. That is: SPL ≥ SPL (a) EPNL = PNLTM + D n = antilog { (c)[SPL ¥ SPL(c)] }

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

(b) (d) SPL(d) ≤ SPL <SPL(e) SPL(b) ≤ SPL <SPL(a) n = 0.1 antilog { M(d)[SPL ¥ SPL(d)] } n = antilog { M(b)[SPL ¥ SPL(b)] } A36.4.7.4 Table A36–3 lists the values of the (c) constants necessary to calculate perceived SPL(e) ≤ SPL <SPL(b) noisiness as a function of sound pressure n = 0.3 antilog { M(e)[SPL ¥ SPL(e)] } level.

Federal Aviation Administration, DOT Pt. 36, App. A

Section A36.5 Reporting of Data to the FAA A36.5.2.1 The applicant must present meas- ured and corrected sound pressure levels in A36.5.1 General.

one-third octave band levels that are ob- A36.5.1.1 Data representing physical meas- tained with equipment conforming to the urements and data used to make corrections standards described in section A36.3 of this to physical measurements must be recorded appendix.

in an approved permanent form and ap- A36.5.2.2 The applicant must report the pended to the record.

make and model of equipment used for meas- A36.5.1.2 All corrections must be reported urement and analysis of all acoustic per- to and approved by the FAA, including cor- formance and meteorological data.

rections to measurements for equipment re- A36.5.2.3 The applicant must report the fol- sponse deviations.

lowing atmospheric environmental data, as A36.5.1.3 Applicants may be required to measured immediately before, after, or dur- submit estimates of the individual errors in- ing each test at the observation points pre- herent in each of the operations employed in scribed in section A36.2 of this appendix.

obtaining the final data.

(a) Air temperature and relative humidity; A36.5.2 Data reporting.

(b) Maximum, minimum and average wind An applicant is required to submit a noise velocities; and certification compliance report that includes the following. (c) Atmospheric pressure.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

A36.5.2.4 The applicant must report condi- urement. The calculation must be performed tions of local topography, ground cover, and by: events that might interfere with sound re- (a) Computing the arithmetic average for cordings.

each flight phase using the values from each A36.5.2.5 The applicant must report the fol- microphone point; and lowing: (b) Computing the overall arithmetic aver- (a) Type, model and serial numbers (if any) age for each reference condition (flyover, lat- of airplane, engine(s), or propeller(s) (as ap- eral or approach) using the values in para- plicable); graph (a) of this section and the related 90 (b) Gross dimensions of airplane and loca- percent confidence limits.

tion of engines; A36.5.4.2 For each of the three certification (c) Airplane gross weight for each test run and center of gravity range for each series of measuring points, the minimum sample size test runs; is six. The sample size must be large enough (d) Airplane configuration such as flap, air- to establish statistically for each of the brakes and landing gear positions for each three average noise certification levels a 90 test run; percent confidence limit not exceeding ± 1.5 (e) Whether auxiliary power units (APU), EPNdB. No test result may be omitted from when fitted, are operating for each test run; the averaging process unless approved by the (f) Status of pneumatic engine bleeds and FAA.

engine power take-offs for each test run; NOTE : Permitted methods for calculating (g) Indicated airspeed in knots or kilo- the 90 percent confidence interval are shown meters per hour for each test run; in the current advisory circular for this part.

(h) Engine performance data: (1) For jet airplanes: engine performance in A36.5.4.3 The average EPNL figures ob- terms of net thrust, engine pressure ratios, tained by the process described in section jet exhaust temperatures and fan or com- A36.5.4.1 must be those by which the noise pressor shaft rotational speeds as determined performance of the airplane is assessed from airplane instruments and manufactur- against the noise certification criteria.

er’s data for each test run; (2) For propeller-driven airplanes: engine Section A36.6 Nomenclature: Symbols and Units performance in terms of brake horsepower and residual thrust; or equivalent shaft Symbol Unit Meaning horsepower; or engine torque and propeller rotational speed; as determined from air- antilog .......... ..................... Antilogarithm to the base 10.

plane instruments and manufacturer’s data C(k) .............. dB ................ Tone correction factor. The factor to be added to for each test run; PNL(k) to account for the (i) Airplane flight path and ground speed presence of spectral irreg- during each test run; and ularities such as tones at (j) The applicant must report whether the the k-th increment of time.

airplane has any modifications or non-stand- d ................... s .................. Duration time. The time inter- ard equipment likely to affect the noise val between the limits of characteristics of the airplane. The FAA t(1) and t(2) to the nearest must approve any such modifications or non- 0.5 second.

standard equipment. D .................. dB ................ Duration correction. The fac- tor to be added to PNLTM A36.5.3 Reporting of noise certification ref- to account for the duration erence conditions.

of the noise.

A36.5.3.1 Airplane position and perform- EPNL ........... EPNdB ........ Effective perceived noise ance data and the noise measurements must level. The value of PNL ad- be corrected to the noise certification ref- justed for both spectral erence conditions specified in the relevant irregularities and duration of sections of appendix B of this part. The ap- the noise. (The unit EPNdB plicant must report these conditions, includ- is used instead of the unit dB).

ing reference parameters, procedures and EPNL .......... EPNdB ........ Effective perceived noise configurations. r level adjusted for reference A36.5.4 Validity of results.

conditions.

A36.5.4.1 Three average reference EPNL f(i) ................ Hz ................ Frequency. The geometrical values and their 90 percent confidence limits mean frequency for the i-th must be produced from the test results and one-third octave band.

reported, each such value being the arith- metical average of the adjusted acoustical measurements for all valid test runs at each measurement point (flyover, lateral, or ap- proach). If more than one acoustic measure- ment system is used at any single measure- ment location, the resulting data for each test run must be averaged as a single meas-

Federal Aviation Administration, DOT Pt. 36, App. A

Symbol Unit Meaning Symbol Unit Meaning F (i, k) .......... dB ................ Delta-dB. The difference be- PNL(k) ......... PNdB ........... The perceived noise level cal- tween the original sound culated from the 24 values pressure level and the final of SPL (i, k), at the k-th in- background sound pressure crement of time. (The unit level in the i-th one-third PNdB is used instead of octave band at the k-th in- the unit dB).

terval of time. In this case, PNLM ........... PNdB ........... Maximum perceived noise background sound pressure level. The maximum value level means the broadband of PNL(k). (The unit PNdB noise level that would be is used instead of the unit present in the one-third oc- dB).

tave band in the absence of PNLT ........... TPNdB ......... Tone-corrected perceived the tone.

noise level. The value of h ................... dB ................ dB-down. The value to be PNL adjusted for the spec- subtracted from PNLTM tral irregularities that occur that defines the duration of at any instant of time. (The the noise.

unit TPNdB is used instead H .................. Percent ........ Relative humidity. The ambi- of the unit dB).

ent atmospheric relative hu- PNLT(k) ....... TPNdB ......... The tone-corrected perceived midity.

noise level that occurs at i .................... ..................... Frequency band index. The the k-th increment of time.

numerical indicator that de- PNLT(k) is obtained by ad- notes any one of the 24 justing the value of PNL(k) one-third octave bands with for the spectral irregularities geometrical mean fre- that occur at the k-th incre- quencies from 50 to 10,000 ment of time. (The unit Hz. TPNdB is used instead of the unit dB).

k ................... ..................... Time increment index. The numerical indicator that de- PNLTM ........ TPNdB ......... Maximum tone-corrected per- notes the number of equal ceived noise level. The time increments that have maximum value of PNLT(k).

elapsed from a reference (The unit TPNdB is used in- zero. stead of the unit dB).

Log ............... ..................... Logarithm to the base 10. PNLT .......... TPNdB ......... Tone-corrected perceived r noise level adjusted for ref- log n(a) ........ ..................... Noy discontinuity coordinate.

erence conditions.

The log n value of the inter- section point of the straight s (i, k) .......... dB ................ Slope of sound pressure lines representing the vari- level. The change in level ation of SPL with log n. between adjacent one-third octave band sound pres- M(b), M(c), ..................... Noy inverse slope. The recip- sure levels at the i-th band etc. rocals of the slopes of for the k-th instant of time.

straight lines representing the variation of SPL with D s (i, k) ........ dB ................ Change in slope of sound log n. pressure level.

n ................... noy .............. The perceived noisiness at s ′ (i, k) ......... dB ................ Adjusted slope of sound pres- any instant of time that oc- sure level. The change in curs in a specified fre- level between adjacent ad- quency range. justed one-third octave band sound pressure levels n(i,k) ............. noy .............. The perceived noisiness at at the i-th band for the k-th the k-th instant of time that instant of time.

occurs in the i-th one-third ¯ octave band. s (i, k) .......... dB ................ Average slope of sound pres- n(k) .............. noy .............. Maximum perceived noisi- sure level.

ness. The maximum value SPL .............. dB re ........... Sound pressure level. The of all of the 24 values of 20 μ Pa sound pressure level that n(i) that occurs at the k-th occurs in a specified fre- instant of time. quency range at any instant of time.

N(k) .............. noy .............. Total perceived noisiness.

The total perceived noisi- SPL(a) ......... dB re ........... Noy discontinuity coordinate.

ness at the k-th instant of 20 μ Pa The SPL value of the inter- time calculated from the 24- section point of the straight instantaneous values of n lines representing the vari- (i, k). ation of SPL with log n.

p(b), p(c), etc ..................... Noy slope. The slopes of SPL(b) ......... dB re ........... Noy intercept. The intercepts straight lines representing SPL (c) 20 μ Pa on the SPL-axis of the the variation of SPL with straight lines representing log n. the variation of SPL with log n.

PNL .............. PNdB ........... The perceived noise level at any instant of time. (The SPL (i, k) ..... dB re ........... The sound pressure level at unit PNdB is used instead 20 μ Pa the k-th instant of time that of the unit dB). occurs in the i-th one-third octave band.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

Symbol Unit Meaning Symbol Unit Meaning SPL ′ (i, k) .... dB re ........... Adjusted sound pressure h ................. Degrees ....... Reference approach angle.

r 20 μ Pa level. The first approxima- q ................... Degrees ....... Noise angle (relative to flight tion to background sound path). The angle between pressure level in the i-th the flight path and noise one-third octave band for path. It is identical for both the k-th instant of time. measured and corrected SPL(i) ........... dB re ........... Maximum sound pressure flight paths.

20 μ Pa level. The sound pressure y .................. Degrees ....... Noise angle (relative to level that occurs in the i-th ground). The angle be- one-third octave band of tween the noise path and the spectrum for PNLTM. the ground. It is identical for SPL(i) .......... dB re ........... Corrected maximum sound both measured and cor- r 20 μ Pa pressure level. The sound rected flight paths.

pressure level that occurs μ .................. ..................... Engine noise emission pa- in the i-th one-third octave rameter.

band of the spectrum for μ r .................. ..................... Reference engine noise emis- PNLTM corrected for at- sion parameter.

D ................. EPNdB ........ PNLT correction. The correc- mospheric sound absorp- 1 tion to be added to the tion.

EPNL calculated from SPL ′ (i, k) .... dB re ........... Final background sound pres- measured data to account 20 μ Pa sure level. The second and for noise level changes due final approximation to back- to differences in atmos- ground sound pressure pheric absorption and noise level in the i-th one-third path length between ref- octave band for the k-th in- erence and test conditions.

stant of time.

D ................. EPNdB ........ Adjustment to duration correc- t .................... s .................. Elapsed time. The length of 2 tion. The adjustment to be time measured from a ref- made to the EPNL cal- erence zero.

t(1), t(2) ........ s .................. Time limit. The beginning and culated from measured end, respectively, of the data to account for noise noise time history defined level changes due to the by h. noise duration between ref- D t ................. s .................. Time increment. The equal in- erence and test conditions.

crements of time for which D ................. EPNdB ........ Source noise adjustment. The PNL(k) and PNLT(k) are adjustment to be made to calculated. the EPNL calculated from T .................. s .................. Normalizing time constant. measured data to account The length of time used as for noise level changes due a reference in the integra- to differences between ref- tion method for computing erence and test engine op- duration corrections, where erating conditions.

T = 10s.

t( ° F) ( ° C) ...... ° F, ° C .......... Temperature. The ambient air Section A36.7 Sound Attenuation in Air temperature.

a (i) ............... dB/1000ft db/ Test atmospheric absorption.

A36.7.1 The atmospheric attenuation of 100m. The atmospheric attenu- sound must be determined in accordance ation of sound that occurs with the procedure presented in section in the i-th one-third octave A36.7.2.

band at the measured air A36.7.2 The relationship between sound at- temperature and relative tenuation, frequency, temperature, and hu- humidity.

a (i) .............. dB/1000ft db/ Reference atmospheric ab- o midity is expressed by the following equa- 100m. sorption. The atmospheric tions.

attenuation of sound that A36.7.2(a) For calculations using the occurs in the i-th one-third English System of Units: octave band at a reference air temperature and relative − 4 humidity. θ 2.05log × − f / .33 . 1000 6 10 1 45325

( )+

0 [ ]

A ................. Degrees ....... First constant climb angle

1 α (i) 10 =

(Gear up, speed of at least V + 10 kt (V + 19 km/h), − 3 2 2 θ log × − f . . 4 6833 10 2 4215

( ) +

0 [ ]

takeoff thrust).

η δ + 10

( ) ×

A ................. Degrees ....... Second constant climb angle (Gear up, speed of at least and V + 10 kt (V + 19 km/h), 2 2 after cut-back).

− 2 θ − + × 1 97274664 2 288074 10 log H . .

d ................... Degrees ....... Thrust cutback angles. The ( )

δ = 10

e angles defining the points

f 0

on the takeoff flight path at ( )

which thrust reduction is started and ended respec- − − 5 2 7 3 θ θ − × + × 9 589 10 3 0 10 . .

( )

tively.

× 10

h .................. Degrees ....... Approach angle.

Federal Aviation Administration, DOT Pt. 36, App. A

where q is the temperature in ° F; and H is the relative humidity, expressed as a h ( d ) is listed in Table A36–4 and f in Table percentage.

A36–5; a (i) is the attenuation coefficient in dB/1000 A36.7.2(b) For calculations using the Inter- ft; national System of Units (SI): − 3 θ log × − 2 05 1000 1 1394 10 1 916984 . / . . f

0 ( )+

[ ]

α i ( ) = 10

− 3 θ × − 8 42994 10 2 755624 log . . f

0 ( )+

[ ]

η δ + × 10 ( )

and a (i) is the attenuation coefficient in dB/100 m; 2 − q is the temperature in ° C; and θ 1 3 179768 10 log .328924 . H − + ×

1010 ( )

δ = 10

H is the relative humidity, expressed as a

f

percentage.

A36.7.3 The values listed in table A36–4 are 4 2 6 3 − − θ θ 2 173716 10 1 7496 10 . . − × + ×

( )

to be used when calculating the equations

10 ×

listed in section A36.7.2. A term of quadratic where interpolation is to be used where necessary.

h ( d ) is listed in Table A36–4 and f in Table Section A36.8 [Reserved] A36–5;

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

Section A36.9 Adjustment of Airplane Flight methods described in sections A36.9.3 and Test Results. A36.9.4 for differences in the following: (a) Attenuation of the noise along its path A36.9.1 When certification test conditions as affected by ‘‘inverse square’’ and atmos- are not identical to reference conditions, ap- pheric attenuation propriate adjustments must be made to the (b) Duration of the noise as affected by the measured noise data using the methods de- distance and the speed of the airplane rel- scribed in this section.

ative to the measuring point A36.9.1.1 Adjustments to the measured noise values must be made using one of the

Federal Aviation Administration, DOT Pt. 36, App. A

(c) Source noise emitted by the engine as (a) The airplane begins the takeoff roll at affected by the differences between test and point A, lifts off at point B and begins its reference engine operating conditions first climb at a constant angle at point C.

(d) Airplane/engine source noise as affected Where thrust or power (as appropriate) cut- by differences between test and reference back is used, it is started at point D and airspeeds. In addition to the effect on dura- completed at point E. From here, the air- tion, the effects of airspeed on component plane begins a second climb at a constant noise sources must be accounted for as fol- angle up to point F, the end of the noise cer- lows: for conventional airplane configura- tification takeoff flight path.

tions, when differences between test and ref- (b) Position K is the takeoff noise meas- erence airspeeds exceed 15 knots (28 km/h) uring station and AK 1 is the distance from true airspeed, test data and/or analysis ap- start of roll to the flyover measuring point.

proved by the FAA must be used to quantify Position K is the lateral noise measuring the effects of the airspeed adjustment on re- station, which is located on a line parallel sulting certification noise levels.

to, and the specified distance from, the run- A36.9.1.2 The ‘‘integrated’’ method of ad- way center line where the noise level during justment, described in section A36.9.4, must takeoff is greatest.

be used on takeoff or approach under the fol- (c) The distance AF is the distance over lowing conditions: which the airplane position is measured and (a) When the amount of the adjustment synchronized with the noise measurements, (using the ‘‘simplified’’ method) is greater as required by section A36.2.3.2 of this part.

than 8 dB on flyover, or 4 dB on approach; or (b) When the resulting final EPNL value on A36.9.2.2 Approach Profile.

flyover or approach (using the simplified N OTE : Figure A36–5 illustrates a typical ap- method) is within 1 dB of the limiting noise proach profile.

levels as prescribed in section B36.5 of this (a) The airplane begins its noise certifi- part.

cation approach flight path at point G and A36.9.2 Flight profiles.

touches down on the runway at point J, at a As described below, flight profiles for both distance OJ from the runway threshold.

test and reference conditions are defined by their geometry relative to the ground, to- (b) Position K 3 is the approach noise meas- gether with the associated airplane speed uring station and K O is the distance from relative to the ground, and the associated the approach noise measurement point to engine control parameter(s) used for deter- the runway threshold.

mining the noise emission of the airplane.

(c) The distance GI is the distance over A36.9.2.1 Takeoff Profile.

which the airplane position is measured and N OTE : Figure A36–4 illustrates a typical synchronized with the noise measurements, takeoff profile. as required by section A36.2.3.2 of this part.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

The airplane reference point for approach differences between measured and reference measurements is the instrument landing sys- conditions at the moment of PNLTM.

tem (ILS) antenna. If no ILS antenna is in- A36.9.3.2 Adjustments to PNL and PNLT.

stalled an alternative reference point must (a) The portions of the test flight path and be approved by the FAA.

the reference flight path described below, A36.9.3 Simplified method of adjustment.

and illustrated in Figure A36–6, include the A36.9.3.1 General. As described below, the noise time history that is relevant to the simplified adjustment method consists of ap- calculation of flyover and approach EPNL.

plying adjustments (to the EPNL, which is In figure A36–6: calculated from the measured data) for the

Federal Aviation Administration, DOT Pt. 36, App. A

(1) XY represents the portion of the meas- (2) Q represents the airplane’s position on ured flight path that includes the noise time the measured flight path at which the noise was emitted and observed as PNLTM at the history relevant to the calculation of flyover noise measuring station K. Q is the cor- and approach EPNL; X Y represents the cor- r r r responding position on the reference flight responding portion of the reference flight path, and K the reference measuring station.

r path.

QK and Q K are, respectively, the measured r r and reference noise propagation paths, Q noise measuring station K. Q is the cor- r r being determined from the assumption that responding position on the reference flight QK and Q K form the same angle q with their path, and K the reference measuring station.

r r r respective flight paths. QK and Q K are, respectively, the measured r r (b) The portions of the test flight path and and reference noise propagation paths. In the reference flight path described in para- this case K is only specified as being on a r graph (b)(1) and (2), and illustrated in Figure particular Lateral line; K and Q are there- r r A36–7(a) and (b), include the noise time his- fore determined from the assumptions that tory that is relevant to the calculation of QK and Q K : r r lateral EPNL.

(i) Form the same angle q with their re- (1) In figure A36–7(a), XY represents the spective flight paths; and portion of the measured flight path that in- (ii) Form the same angle y with the cludes the noise time history that is relevant ground.

to the calculation of lateral EPNL; in figure A36–7(b), X Y represents the corresponding N OTE : For the lateral noise measurement, r r portion of the reference flight path. sound propagation is affected not only by in- (2) Q represents the airplane position on verse square and atmospheric attenuation, the measured flight path at which the noise but also by ground absorption and reflection was emitted and observed as PNLTM at the effects which depend mainly on the angle y .

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

A36.9.3.2.1 The one-third octave band levels determined under section A36.7 of this appen- SPL(i) comprising PNL (the PNL at the mo- dix; (2) The term 0.001 a (i) (QK ¥ Q K ) is the ad- ment of PNLTM observed at K) must be ad- 0 r r justment for the effect of the change in the justed to reference levels SPL(i) as follows: r noise path length on the sound attenuation; A36.9.3.2.1(a) For calculations using the (3) The term 20 log(QK/Q K ) is the adjust- r r English System of Units: ment for the effect of the change in the noise SPL( i ) = SPL( i ) + 0.001[ a ( i ) ¥ a ( i ) ]QK r 0 path length due to the ‘‘inverse square’’ law; + 0.001 a ( i ) (QK ¥ Q K ) 0 r r (4) QK and Q K are measured in feet and r r + 20log(QK/Q K ) r r a (i) and a (i) are expressed in dB/1000 ft.

A36.9.3.2.1(b) For calculations using the In this expression, International System of Units: (1) The term 0.001[ a ( i ) ¥ a ( i ) ]QK is the ad- SPL(i) = SPL(i) + 0.01[ a (i) ¥ a (i) ]QK justment for the effect of the change in r 0 + 0.01 a (i) (QK ¥ Q K ) sound attenuation coefficient, and a (i) and 0 r r + 20 log(QK/Q K ) r r a (i) 0 are the coefficients for the test and ref- erence atmospheric conditions respectively, In this expression,

Federal Aviation Administration, DOT Pt. 36, App. A

(1) The term 0.01[ a (i) ¥ a (i) ]QK is the ad- A36.9.3.3.1 Whenever the measured flight justment for the effect of the change in paths and/or the ground velocities of the test sound attenuation coefficient, and a (i) and conditions differ from the reference flight a (i) are the coefficients for the test and ref- paths and/or the ground velocities of the ref- erence atmospheric conditions respectively, erence conditions, duration adjustments determined under section A36.7 of this appen- must be applied to the EPNL values cal- dix; culated from the measured data. The adjust- (2) The term 0.01 a (i) (QK ¥ Q K ) is the ad- 0 r r ments must be calculated as described below.

justment for the effect of the change in the A36.9.3.3.2 For the flight path shown in Fig- noise path length on the sound attenuation; ure A36–6, the adjustment term is calculated (3) The term 20 log(QK/Q K ) is the adjust- r r as follows: ment for the effect of the change in the noise D 2 = ¥ 7.5 log(QK/Q r K r ) + 10 log(V/V r ) path length due to the inverse square law; (4) QK and Q K are measured in meters and (a) Add D arithmetically to the EPNL cal- r r 2 a (i) and a (i) are expressed in dB/100 m. culated from the measured data.

A36.9.3.2.1.1 PNLT Correction.

A36.9.3.4 Source noise adjustments.

(a) Convert the corrected values, SPL(i) , r A36.9.3.4.1 To account for differences be- to PNLT ; r tween the parameters affecting engine noise (b) Calculate the correction term D 1 using as measured in the certification flight tests, the following equation: and those calculated or specified in the ref- D = PNLT ¥ PNLTM 1 r erence conditions, the source noise adjust- ment must be calculated and applied. The A36.9.3.2.1.2 Add D arithmetically to the adjustment is determined from the manufac- EPNL calculated from the measured data.

turer’s data approved by the FAA. Typical A36.9.3.2.2 If, during a test flight, several data used for this adjustment are illustrated peak values of PNLT that are within 2 dB of in Figure A36–8 that shows a curve of EPNL PNLTM are observed, the procedure defined versus the engine control parameter μ , with in section A36.9.3.2.1 must be applied at each peak, and the adjustment term, calculated the EPNL data being corrected to all the according to section A36.9.3.2.1, must be other relevant reference conditions (airplane added to each peak to give corresponding ad- mass, speed and altitude, air temperature) justed peak values of PNLT. If these peak and for the difference in noise between the values exceed the value at the moment of test engine and the average engine (as de- PNLTM, the maximum value of such exceed- fined in section B36.7(b)(7)). A sufficient ance must be added as a further adjustment number of data points over a range of values to the EPNL calculated from the measured of μ is required to calculate the source noise r data. adjustments for lateral, flyover and ap- A36.9.3.3 Adjustments to duration correction. proach noise measurements.

A36.9.3.4.2 Calculate adjustment term D by to the parameter μ from the EPNL value cor- subtracting the EPNL value corresponding responding to the parameter μ . Add D r 3

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

arithmetically to the EPNL value calculated measured at these two points (see Figure from the measured data. A36–9(a)); A36.9.3.5 Symmetry adjustments.

(b) If the condition described in paragraph A36.9.3.5.1 A symmetry adjustment to each (a) of this section is not met, then it is as- lateral noise value (determined at the sec- sumed that the variation of noise with the tion B36.4(b) measurement points), is to be altitude of the airplane is the same on both made as follows: sides; there is a constant difference between (a) If the symmetrical measurement point the lines of noise versus altitude on both is opposite the point where the highest noise sides (see figure A36–9(b)). The certification level is obtained on the main lateral meas- noise level is the maximum value of the urement line, the certification noise level is mean between these lines.

the arithmetic mean of the noise levels A36.9.4 Integrated method of adjustment way. The main principles are described in A36.9.4.1 General. As described in this sec- sections A36.9.4.2 through A36.9.4.4.1.

A36.9.4.2 PNLT computations.

tion, the integrated adjustment method con- (a) The portions of the test flight path and sists of recomputing under reference condi- the reference flight path described in para- tions points on the PNLT time history cor- graph (a)(1) and (2), and illustrated in Figure responding to measured points obtained dur- A36–10, include the noise time history that is ing the tests, and computing EPNL directly relevant to the calculation of flyover and ap- for the new time history obtained in this proach EPNL. In figure A36–10:

Federal Aviation Administration, DOT Pt. 36, App. A

(1) XY represents the portion of the meas- graph (b)(1) and (2), and illustrated in Figure ured flight path that includes the noise time A36–11(a) and (b), include the noise time his- history relevant to the calculation of flyover tory that is relevant to the calculation of and approach EPNL; X Y represents the cor- r r lateral EPNL.

responding reference flight path.

(1) In figure A36–11(a) XY represents the (2) The points Q , Q , Q represent airplane 0 1 n portion of the measured flight path that in- positions on the measured flight path at cludes the noise time history that is relevant time t , t and t respectively. Point Q is the 0 1 n 1 to the calculation of lateral EPNL; in figure point at which the noise was emitted and ob- A36–11(b), X r Y r represents the corresponding served as one-third octave values SPL(i) at portion of the reference flight path.

the noise measuring station K at time t .

(2) The points Q , Q and Q represent air- 0 1 n Point Q represents the corresponding posi- r1 plane positions on the measured flight path tion on the reference flight path for noise ob- at time t 0 , t 1 and t n respectively. Point Q 1 is served as SPL(i) r1 at the reference measuring at time t . Q K and Q K are re- the point at which the noise was emitted and station K r r1 1 r1 r spectively the measured and reference noise observed as one-third octave values SPL(i) propagation paths, which in each case form at the noise measuring station K at time t .

the angle q with their respective flight 1 The point Q represents the corresponding r1 paths. Q and Q are similarly the points on r0 rn position on the reference flight path for the reference flight path corresponding to Q noise observed as SPL(i) at the measuring r1 and Q on the measured flight path. Q and Q n 0 n station K at time t . Q K and Q K are re- r r1 1 r1 r are chosen so that between Q and Q all r0 rn spectively the measured and reference noise values of PNLT (computed as described in r propagation paths. Q and Q are similarly r0 rn paragraphs A36.9.4.2.2 and A36.9.4.2.3) within the points on the reference flight path cor- 10 dB of the peak value are included.

responding to Q and Q on the measured 0 n (b) The portions of the test flight path and flight path.

the reference flight path described in para-

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. A

Q and Q are chosen to that between Q A36.9.4.2.3) within 10 dB of the peak value are 0 n ro and Q all values of PNLT (computed as de- included. In this case K is only specified as rn r r scribed in paragraphs A36.9.4.2.2 and

Federal Aviation Administration, DOT Pt. 36, App. A

being on a particular lateral line. The posi- A36.9.4.4.1 A source noise adjustment, D , tion of K and Q are determined from the must be determined using the methods of r r1 following requirements.

section A36.9.3.4 of this appendix.

(i) Q 1 K and Q r1 K r form the same angle q 1 with their respective flight paths; and A36.9.5 F LIGHT P ATH I DENTIFICATION P OSITIONS (ii) The differences between the angles and must be minimized using a method, ap- r1 Position Description proved by the FAA. The differences between the angles are minimized since, for geometri- A ........... Start of Takeoff roll.

B ........... Lift-off.

cal reasons, it is generally not possible to C .......... Start of first constant climb.

choose K so that the condition described in r D .......... Start of thrust reduction.

paragraph A36.9.4.2(b)(2)(i) is met while at E ........... Start of second constant climb.

the same time keeping 1 and r1 equal.

F ........... End of noise certification Takeoff flight path.

N OTE : For the lateral noise measurement, G .......... Start of noise certification Approach flight path.

sound propagation is affected not only by H .......... Position on Approach path directly above noise ‘‘inverse square’’ and atmospheric attenu- measuring station.

ation, but also by ground absorption and re- I ............ Start of level-off.

flection effects which depend mainly on the J ........... Touchdown.

angle.

K ........... Noise measurement point.

A36.9.4.2.1 In paragraphs A36.9.4.2(a)(2) and K .......... Reference measurement point.

r (b)(2) the time t r1 is later (for Q r1 K r >Q 1 K) K ......... Flyover noise measurement point.

by two separate amounts: than t 1 K ......... Lateral noise measurement point.

(1) The time taken for the airplane to trav- K 3 ......... Approach noise measurement point.

el the distance Q Q at a speed V less the r1 r0 r M .......... End of noise certification Takeoff flight track.

time taken for it to travel Q Q at V; 1 0 O .......... Threshold of Approach end of runway.

(2) The time taken for sound to travel the P ........... Start of noise certification Approach flight track.

distance Q K –Q K.

r1 r 1 Q .......... Position on measured Takeoff flight path cor- responding to apparent PNLTM at station K See N OTE : For the flight paths described in section A36.9.3.2.

paragraphs A36.9.4.2(a) and (b), the use of Q r ......... Position on corrected Takeoff flight path cor- thrust or power cut-back will result in test responding to PNLTM at station K. See section and reference flight paths at full thrust or A36.9.3.2.

power and at cut-back thrust or power.

V ........... Airplane test speed.

Where the transient region between these V .......... Airplane reference speed.

r thrust or power levels affects the final re- sult, an interpolation must be made between them by an approved method such as that A36.9.6 F LIGHT P ATH D ISTANCES given in the current advisory circular for Distance Unit Meaning this part.

A36.9.4.2.2 The measured values of SPL(i) AB ........ Feet (meters) Length of takeoff roll. The distance must be adjusted to the reference values along the runway between the SPL(i) to account for the differences be- r1 start of takeoff roll and lift off.

tween measured and reference noise path AK ........ Feet (meters) Takeoff measurement distance.

lengths and between measured and reference The distance from the start of roll to the takeoff noise measure- atmospheric conditions, using the methods ment station along the extended of section A36.9.3.2.1 of this appendix. A cor- center line of the runway.

responding value of PNL must be computed r1 AM ....... Feet (meters) Takeoff flight track distance. The according to the method in section A36.4.2.

distance from the start of roll to Values of PNL must be computed for times r the takeoff flight track position t through t .

0 n along the extended center line of A36.9.4.2.3 For each value of PNL r1 , a tone the runway after which the posi- correction factor C 1 must be determined by tion of the airplane need no longer be recorded.

analyzing the reference values SPL(i) r using QK ....... Feet (meters) Measured noise path. The distance the methods of section A36.4.3 of this appen- from the measured airplane po- dix, and added to PNL r1 to yield PNLT r1 .

sition Q to station K.

Using the process described in this para- Q r K r ..... Feet (meters) Reference noise path. The dis- graph, values of PNLT r must be computed for tance from the reference air- times t 0 through t n .

plane position Q r to station K r .

A36.9.4.3 Duration correction.

K H ...... Feet (meters) Airplane approach height. The A36.9.4.3.1 The values of PNLT cor- r height of the airplane above the responding to those of PNLT at each one- approach measuring station.

half second interval must be plotted against OK ...... Feet (meters) Approach measurement distance.

time (PNLT at time t ). The duration cor- The distance from the runway r1 r1 threshold to the approach meas- rection must then be determined using the urement station along the ex- method of section A36.4.5.1 of this appendix, tended center line of the runway.

to yield EPNL .

r A36.9.4.4 Source Noise Adjustment.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. B

(a) Lateral full-power reference noise A36.9.6 F LIGHT P ATH D ISTANCES—Continued measurement point: Distance Unit Meaning (1) For jet airplanes: The point on a line parallel to and 1,476 feet (450 m) from the OP ....... Feet (meters) Approach flight track distance. The runway centerline, or extended centerline, distance from the runway thresh- where the noise level after lift-off is at a old to the approach flight track maximum during takeoff. For the purpose of position along the extended cen- showing compliance with Stage 1 or Stage 2 ter line of the runway after which noise limits for an airplane powered by more the position of the airplane need no longer be recorded. than three jet engines, the distance from the runway centerline must be 0.35 nautical miles (648 m). For jet airplanes, when ap- [Amdt. 36–54, 67 FR 45212, July 8, 2002; Amdt.

proved by the FAA, the maximum lateral 36–24, 67 FR 63195, 63196, Oct. 10, 2002; 68 FR noise at takeoff thrust may be assumed to 1512, Jan. 10, 2003; Amdt. 36–26, 70 FR 38749, occur at the point (or its approved equiva- July 5, 2005; FAA Doc. No. FAA–2015–3782, lent) along the extended centerline of the Amdt. No. 36–31, 82 FR 46131, Oct. 4, 2017] runway where the airplane reaches 985 feet (300 meters) altitude above ground level. A A PPENDIX B TO P ART 36—N OISE L EVELS height of 1427 feet (435 meters) may be as- FOR T RANSPORT C ATEGORY AND J ET sumed for Stage 1 or Stage 2 four engine air- A IRPLANES U NDER § 36.103 planes. The altitude of the airplane as it passes the noise measurement points must Sec.

be within + 328 to ¥ 164 feet (+100 to ¥ 50 me- ters) of the target altitude. For airplanes B36.1 Noise Measurement and Evaluation.

powered by other than jet engines, the alti- B36.2 Noise Evaluation Metric.

tude for maximum lateral noise must be de- B36.3 Reference Noise Measurement Points.

termined experimentally.

B36.4 Test Noise Measurement Points.

(2) For propeller-driven airplanes: The B36.5 Maximum Noise Levels.

point on the extended centerline of the run- B36.6 Trade-Offs.

way above which the airplane, at full takeoff B36.7 Noise Certification Reference Procedures power, reaches a height of 2,133 feet (650 me- and Conditions.

ters). For tests conducted before August 7, B36.8 Noise Certification Test Procedures.

2002, an applicant may use the measurement point specified in section B36.3(a)(1) as an al- Section B36.1 Noise measurement and evaluation ternative.

(a) The procedures of Appendix A of this (b) Flyover reference noise measurement part, or approved equivalent procedures, point: The point on the extended centerline must be used to determine noise levels of an of the runway that is 21,325 feet (6,500 m) airplane. These noise levels must be used to from the start of the takeoff roll; show compliance with the requirements of (c) Approach reference noise measurement this appendix. point: The point on the extended centerline of the runway that is 6,562 feet (2,000 m) from (b) For Stage 4 airplanes, an acceptable al- the runway threshold. On level ground, this ternative to paragraph (a) of this section for corresponds to a position that is 394 feet (120 noise measurement and evaluation is Appen- m) vertically below the 3 ° descent path, dix 2 to ICAO Annex 16, Volume I, Amend- which originates at a point on the runway ment 7 (Incorporated by reference, see § 36.6).

984 feet (300 m) beyond the threshold.

(c) For Stage 5 airplanes, an acceptable al- ternative to paragraph (a) of this section for Section B36.4 Test noise measurement points.

noise measurement and evaluation is Appen- dix 2 to ICAO Annex 16, Volume 1, Amend- (a) If the test noise measurement points ment 11–B (Incorporated by reference, see are not located at the reference noise meas- urement points, any corrections for the dif- § 36.6).

ference in position are to be made using the Section B36.2 Noise Evaluation Metric same adjustment procedures as for the dif- ferences between test and reference flight The noise evaluation metric is the effec- paths.

tive perceived noise level expressed in (b) The applicant must use a sufficient EPNdB, as calculated using the procedures of number of lateral test noise measurement appendix A of this part.

points to demonstrate to the FAA that the maximum noise level on the appropriate lat- Section B36.3 Reference Noise Measurement eral line has been determined. For jet air- Points planes, simultaneous measurements must be When tested using the procedures of this made at one test noise measurement point at part, except as provided in section B36.6, an its symmetrical point on the other side of airplane may not exceed the noise levels the runway. Propeller-driven airplanes have specified in section B36.5 at the following an inherent asymmetry in lateral noise.

points on level terrain: Therefore, simultaneous measurements must

Federal Aviation Administration, DOT Pt. 36, App. B

be made at each and every test noise meas- EPNdB for a maximum weight of 77,200 urement point at its symmetrical position pounds or less.

on the opposite side of the runway. The (d) For any Stage 4 airplane, the flyover, measurement points are considered to be lateral, and approach maximum noise levels symmetrical if they are longitudinally with- are prescribed in Chapter 4, Paragraph 4.4, in 33 feet ( ± 10 meters) of each other. Maximum Noise Levels, and Chapter 3, Para- graph 3.4, Maximum Noise Levels, of the Section B36.5 Maximum Noise Levels International Civil Aviation Organization (ICAO) Annex 16, Environmental Protection, Except as provided in section B36.6 of this Volume I, Aircraft Noise, Third Edition, appendix, maximum noise levels, when deter- July 1993, Amendment 7, effective March 21, mined in accordance with the noise evalua- 2002. [Incorporated by reference, see § 36.6].

tion methods of appendix A of this part, may (e) For any Stage 5 airplane, the flyover, not exceed the following: lateral, and approach maximum noise levels (a) For acoustical changes to Stage 1 air- are prescribed in Chapter 14, Paragraph 14.4, planes, regardless of the number of engines, Maximum Noise Levels of ICAO Annex 16, the noise levels prescribed under § 36.7(c) of Volume I, Amendment 11–B (Incorporated by this part.

reference, see § 36.6).

(b) For any Stage 2 airplane regardless of the number of engines: Section B36.6 Trade-Offs (1) Flyover: 108 EPNdB for maximum Except when prohibited by sections weight of 600,000 pounds or more; for each 36.7(c)(1) and 36.7(d)(1)(ii), if the maximum halving of maximum weight (from 600,000 noise levels are exceeded at any one or two pounds), reduce the limit by 5 EPNdB; the measurement points, the following condi- limit is 93 EPNdB for a maximum weight of tions must be met: 75,000 pounds or less.

(a) The sum of the exceedance(s) may not (2) Lateral and approach: 108 EPNdB for be greater than 3 EPNdB; maximum weight of 600,000 pounds or more; (b) Any exceedance at any single point for each halving of maximum weight (from may not be greater than 2 EPNdB, and 600,000 pounds), reduce the limit by 2 EPNdB; (c) Any exceedance(s) must be offset by a the limit is 102 EPNdB for a maximum corresponding amount at another point or weight of 75,000 pounds or less.

points.

(c) For any Stage 3 airplane: (1) Flyover.

Section B36.7 Noise Certification Reference (i) For airplanes with more than 3 engines: Procedures and Conditions 106 EPNdB for maximum weight of 850,000 pounds or more; for each halving of max- (a) General conditions: imum weight (from 850,000 pounds), reduce (1) All reference procedures must meet the the limit by 4 EPNdB; the limit is 89 EPNdB requirements of section 36.3 of this part.

for a maximum weight of 44,673 pounds or (2) Calculations of airplane performance less; and flight path must be made using the ref- (ii) For airplanes with 3 engines: 104 erence procedures and must be approved by EPNdB for maximum weight of 850,000 the FAA.

pounds or more; for each halving of max- (3) Applicants must use the takeoff and ap- imum weight (from 850,000 pounds), reduce proach reference procedures prescribed in the limit by 4 EPNdB; the limit is 89 EPNdB paragraphs (b) and (c) of this section.

for a maximum weight of 63,177 pounds or (4) [Reserved] less; and (5) The reference procedures must be deter- (iii) For airplanes with fewer than 3 en- mined for the following reference conditions.

gines: 101 EPNdB for maximum weight of The reference atmosphere is homogeneous in 850,000 pounds or more; for each halving of terms of temperature and relative humidity maximum weight (from 850,000 pounds), re- when used for the calculation of atmospheric duce the limit by 4 EPNdB; the limit is 89 absorption coefficients.

EPNdB for a maximum weight of 106,250 (i) Sea level atmospheric pressure of 2116 pounds or less. pounds per square foot (psf) (1013.25 hPa); (2) Lateral, regardless of the number of en- (ii) Ambient sea-level air temperature of 77 gines: 103 EPNdB for maximum weight of ° F (25 ° C, i.e. , ISA + 10 ° C); 882,000 pounds or more; for each halving of (iii) Relative humidity of 70 per cent; maximum weight (from 882,000 pounds), re- (iv) Zero wind.

duce the limit by 2.56 EPNdB; the limit is 94 (v) In defining the reference takeoff flight EPNdB for a maximum weight of 77,200 path(s) for the takeoff and lateral noise pounds or less. measurements, the runway gradient is zero.

(3) Approach, regardless of the number of (b) Takeoff reference procedure: engines: 105 EPNdB for maximum weight of The takeoff reference flight path is to be 617,300 pounds or more; for each halving of calculated using the following: maximum weight (from 617,300 pounds), re- (1) Average engine takeoff thrust or power duce the limit by 2.33 EPNdB; the limit is 98 must be used from the start of takeoff to the

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. B

point where at least the following height gravity position, and the status of the air- above runway level is reached. The takeoff plane systems that can affect airplane per- thrust/power used must be the maximum formance or noise. Examples include, the po- available for normal operations given in the sition of lift augmentation devices, whether performance section of the airplane flight the APU is operating, and whether air bleeds manual under the reference atmospheric and engine power take-offs are operating; conditions given in section B36.7(a)(5).

(6) The weight of the airplane at the brake (i) For Stage 1 airplanes and for Stage 2 release must be the maximum takeoff weight airplanes that do not have jet engines with a at which the noise certification is requested, bypass ratio of 2 or more, the following which may result in an operating limitation apply: as specified in § 36.1581(d); and (A): For airplanes with more than three jet (7) The average engine is defined as the av- engines—700 feet (214 meters).

erage of all the certification compliant en- (B): For all other airplanes—1,000 feet (305 gines used during the airplane flight tests, meters).

up to and during certification, when oper- (ii) For Stage 2 airplanes that have jet en- ating within the limitations and according gines with a bypass ratio of 2 or more and for to the procedures given in the Flight Man- Stage 3 airplanes, the following apply: ual. This will determine the relationship of (A): For airplanes with more than three en- thrust/power to control parameters (e.g., N gines—689 feet (210 meters).

or EPR). Noise measurements made during (B): For airplanes with three engines—853 certification tests must be corrected using feet (260 meters).

this relationship.

(C): For airplanes with fewer than three (c) Approach reference procedure: engines—984 feet (300 meters).

The approach reference flight path must be (2) Upon reaching the height specified in calculated using the following: paragraph (b)(1) of this section, airplane (1) The airplane is stabilized and following thrust or power must not be reduced below a 3 ° glide path; that required to maintain either of the fol- (2) For subsonic airplanes, a steady ap- lowing, whichever is greater: proach speed of V + 10 kts (V + 19 km/h) ref ref (i) A climb gradient of 4 per cent; or with thrust and power stabilized must be es- (ii) In the case of multi-engine airplanes, tablished and maintained over the approach level flight with one engine inoperative.

measuring point. V is the reference landing ref (3) For the purpose of determining the lat- speed, which is defined as the speed of the eral noise level, the reference flight path airplane, in a specified landing configura- must be calculated using full takeoff power tion, at the point where it descends through throughout the test run without a reduction the landing screen height in the determina- in thrust or power. For tests conducted be- tion of the landing distance for manual land- fore August 7, 2002, a single reference flight ings. For Concorde airplanes, a steady ap- path that includes thrust cutback in accord- proach speed that is either the landing ref- ance with paragraph (b)(2) of this section, is erence speed + 10 knots or the speed used in an acceptable alternative in determining the establishing the approved landing distance lateral noise level.

under the airworthiness regulations consti- (4) The takeoff reference speed is the all- tuting the type certification basis of the air- engine operating takeoff climb speed se- plane, whichever speed is greater. This speed lected by the applicant for use in normal op- must be established and maintained over the eration; this speed must be at least V2 + 10kt approach measuring point.

(V2 + 19km/h) but may not be greater than (3) The constant approach configuration V2 + 20kt (V2 + 37km/h). This speed must be used in the airworthiness certification tests, attained as soon as practicable after lift-off but with the landing gear down, must be and be maintained throughout the takeoff maintained throughout the approach ref- noise certification test. For Concorde air- erence procedure; planes, the test day speeds and the acoustic day reference speed are the minimum ap- (4) The weight of the airplane at touch- proved value of V2 + 35 knots, or the all-en- down must be the maximum landing weight gines-operating speed at 35 feet, whichever permitted in the approach configuration de- speed is greater as determined under the reg- fined in paragraph (c)(3) of this section at ulations constituting the type certification which noise certification is requested, except basis of the airplane; this reference speed as provided in § 36.1581(d) of this part; and may not exceed 250 knots. For all airplanes, (5) The most critical configuration must be noise values measured at the test day speeds used; this configuration is defined as that must be corrected to the acoustic day ref- which produces the highest noise level with erence speed. normal deployment of aerodynamic control (5) The takeoff configuration selected by surfaces including lift and drag producing the applicant must be maintained constantly devices, at the weight at which certification throughout the takeoff reference procedure, is requested. This configuration includes all except that the landing gear may be re- those items listed in section A36.5.2.5 of ap- tracted. Configuration means the center of pendix A of this part that contribute to the

Federal Aviation Administration, DOT Pt. 36, App. F

noisiest continuous state at the maximum A PPENDIXES C–E TO P ART 36 [R ESERVED ] landing weight in normal operation.

APPENDIX F TO P ART 36—F LYOVER Section B36.8 Noise Certification Test N OISE R EQUIREMENTS FOR P RO - Procedures PELLER -D RIVEN S MALL A IRPLANE (a) All test procedures must be approved by AND P ROPELLER -D RIVEN , C OMMUTER the FAA.

C ATEGORY A IRPLANE C ERTIFICATION (b) The test procedures and noise measure- T ESTS P RIOR TO D ECEMBER 22, 1988 ments must be conducted and processed in PART A — GENERAL an approved manner to yield the noise eval- uation metric EPNL, in units of EPNdB, as Sec.

described in appendix A of this part.

F36.1 Scope.

(c) Acoustic data must be adjusted to the PART B — NOISE MEASUREMENT reference conditions specified in this appen- dix using the methods described in appendix F36.101 General test conditions.

A of this part. Adjustments for speed and F36.103 Acoustical measurement system.

thrust must be made as described in section F36.105 Sensing, recording, and reproducing A36.9 of this part.

equipment.

(d) If the airplane’s weight during the test F36.107 Noise measurement procedures.

is different from the weight at which noise F36.109 Data recording, reporting, and ap- certification is requested, the required EPNL proval.

adjustment may not exceed 2 EPNdB for F36.111 Flight procedures.

each takeoff and 1 EPNdB for each approach.

PART C — DATA CORRECTION Data approved by the FAA must be used to determine the variation of EPNL with F36.201 Correction of data.

weight for both takeoff and approach test F36.203 Validity of results.

conditions. The necessary EPNL adjustment PART D — NOISE LIMITS for variations in approach flight path from the reference flight path must not exceed 2 F36.301 Aircraft noise limits.

EPNdB.

(e) For approach, a steady glide path angle PART A — GENERAL of 3 ° ± 0.5 ° is acceptable.

Section F36.1 Scope. This appendix pre- (f) If equivalent test procedures different scribes noise level limits and procedures for from the reference procedures are used, the measuring and correcting noise data for the test procedures and all methods for adjusting propeller driven small airplanes specified in the results to the reference procedures must §§ 36.1 and 36.501(b).

be approved by the FAA. The adjustments may not exceed 16 EPNdB on takeoff and 8 PART B — NOISE MEASUREMENT EPNdB on approach. If the adjustment is Sec. F36.101 General test conditions.

more than 8 EPNdB on takeoff, or more than 4 EPNdB on approach, the resulting numbers (a) The test area must be relatively flat must be more than 2 EPNdB below the limit terrain having no excessive sound absorption noise levels specified in section B36.5.

characteristics such as those caused by (g) During takeoff, lateral, and approach thick, matted, or tall grass, by shrubs, or by tests, the airplane variation in instanta- wooded areas. No obstructions which signifi- neous indicated airspeed must be maintained cantly influence the sound field from the air- within ± 3% of the average airspeed between plane may exist within a conical space above the 10 dB-down points. This airspeed is deter- the measurement position, the cone being mined by the pilot’s airspeed indicator. How- defined by an axis normal to the ground and ever, if the instantaneous indicated airspeed by a half-angle 75 degrees from this axis.

exceeds ± 3 kt ( ± 5.5 km/h) of the average air- (b) The tests must be carried out under the speed over the 10 dB-down points, and is de- following conditions: termined by the FAA representative on the (1) There may be no precipitation.

flight deck to be due to atmospheric turbu- (2) Relative humidity may not be higher lence, then the flight so affected must be re- than 90 percent or lower than 30 percent.

jected for noise certification purposes. (3) Ambient temperature may not be above 86 degrees F. or below 41 degrees F. at 33 ′ N OTE : Guidance material on the use of above ground. If the measurement site is equivalent procedures is provided in the cur- within 1 n.m. of an airport thermometer the rent advisory circular for this part.

airport reported temperature may be used.

[Amdt. 36–54, 67 FR 45235, July 8, 2002; Amdt. (4) Reported wind may not be above 10 36–24, 67 FR 63196, Oct. 10, 2002; 68 FR 1512, knots at 33 ′ above ground. If wind velocities Jan. 10, 2003; Amdt. 36–26, 70 FR 38749, July 5, of more than 4 knots are reported, the flight 2005; FAA Doc. No. FAA–2015–3782, Amdt. No. direction must be aligned to within ± 15 de- 36–31, 82 FR 46131, Oct. 4, 2017] grees of wind direction and flights with tail

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. F

wind and head wind must be made in equal designated ‘‘slow,’’ as defined in IEC Publi- numbers. If the measurement site is within 1 cation No. 179, dated 1973. The output signal n.m. of an airport anemometer, the airport from the filter must be fed to a rectifying reported wind may be used. circuit with square law rectification, inte- (5) There may be no temperature inversion grated with time constants for charge and or anomalous wind conditions that would discharge of about 1 second or 800 milli- significantly alter the noise level of the air- seconds.

plane when the noise is recorded at the re- (f) The equipment must be acoustically quired measuring point. calibrated using facilities for acoustic (6) The flight test procedures, measuring freefield calibration and if analysis of the equipment, and noise measurement proce- tape recording is requested by the Adminis- dures must be approved by the FAA.

trator, the analysis equipment shall be elec- (7) Sound pressure level data for noise eval- tronically calibrated by a method approved uation purposes must be obtained with by the FAA.

acoustical equipment that complies with (g) A windscreen must be employed with section F36.103 of this appendix.

microphone during all measurements of air- craft noise when the wind speed is in excess Sec. F36.103 Acoustical measurement system.

of 6 knots.

The acoustical measurement system must consist of approved equipment equivalent to Sec. F36.107 Noise measurement procedures.

the following: (a) The microphones must be oriented in a (a) A microphone system with frequency known direction so that the maximum sound response compatible with measurement and received arrives as nearly as possible in the analysis system accuracy as prescribed in direction for which the microphones are cali- section F36.105 of this appendix.

brated. The microphone sensing elements (b) Tripods or similar microphone mount- must be approximately 4 ′ above ground.

ings that minimize interference with the (b) Immediately prior to and after each sound being measured.

(c) Recording and reproducing equipment test; a recorded acoustic calibration of the characteristics, frequency response, and dy- system must be made in the field with an namic range compatible with the response acoustic calibrator for the two purposes of and accuracy requirements of section F36.105 checking system sensitivity and providing of this appendix. an acoustic reference level for the analysis (d) Acoustic calibrators using sine wave or of the sound level data.

(c) The ambient noise, including both broadband noise of known sound pressure acoustical background and electrical noise of level. If broadband noise is used, the signal the measurement systems, must be recorded must be described in terms of its average and and determined in the test area with the sys- maximum root-mean-square (rms) value for tem gain set at levels that will be used for nonoverload signal level.

aircraft noise measurements. If aircraft Sec. F36.105 Sensing, recording, and sound pressure levels do not exceed the back- reproducing equipment.

ground sound pressure levels by at least 10 dB(A), approved corrections for the contribu- (a) The noise produced by the airplane tion of background sound pressure level to must be recorded. A magnetic tape recorder the observed sound pressure level must be is acceptable.

applied.

(b) The characteristics of the system must comply with the recommendations in IEC 179 Sec. F36.109 Data recording, reporting, and (incorporated by reference, see § 36.6).

approval.

(c) The response of the complete system to a sensibly plane progressive sinusoidal wave (a) Data representing physical measure- of constant amplitude must lie within the ments or corrections to measured data must tolerance limits specified in IEC Publication be recorded in permanent form and appended No. 179, dated 1973, over the frequency range to the record except that corrections to 45 to 11,200 Hz. measurements for normal equipment re- (d) If limitations of the dynamic range of sponse deviations need not be reported. All the equipment make it necessary, high fre- other corrections must be approved. Esti- quency pre-emphasis must be added to the mates must be made of the individual errors recording channel with the converse de-em- inherent in each of the operations employed phasis on playback. The pre-emphasis must in obtaining the final data.

be applied such that the instantaneous re- (b) Measured and corrected sound pressure corded sound pressure level of the noise sig- levels obtained with equipment conforming nal between 800 and 11,200 Hz does not vary to the specifications described in section more than 20 dB between the maximum and F36.105 of this appendix must be reported.

minimum one-third octave bands. (c) The type of equipment used for meas- (e) If requested by the Administrator, the urement and analysis of all acoustic, air- recorded noise signal must be read through plane performance, and meteorological data an ‘‘A’’ filter with dynamic characteristics must be reported.

Federal Aviation Administration, DOT Pt. 36, App. F

(d) The following atmospheric data, meas- must include at least six level flights over ured immediately before, after, or during the measuring station at a height of 1,000 ′ each test at the observation points pre- ± 30 ′ and ± 10 degrees from the zenith when scribed in section F36.101 of this appendix passing overhead.

must be reported: (b) Each test over flight must be con- (1) Air temperature and relative humidity. ducted: (2) Maximum, minimum, and average wind (1) At not less than the highest power in velocities. the normal operating range provided in an (e) Comments on local topography, ground Airplane Flight Manual, or in any combina- cover, and events that might interfere with tion of approved manual material, approved sound recordings must be reported. placard, or approved instrument markings; (f) The following airplane information and must be reported: (2) At stabilized speed with propellers syn- (1) Type, model and serial numbers (if any) chronized and with the airplane in cruise of airplanes, engines, and propellers.

configuration, except that if the speed at the (2) Any modifications or nonstandard power setting prescribed in this paragraph equipment likely to affect the noise charac- would exceed the maximum speed authorized teristics of the airplane.

in level flight, accelerated flight is accept- (3) Maximum certificated takeoff weights.

able.

(4) Airspeed in knots for each overflight of the measuring point. PART C — DATA CORRECTION (5) Engine performance in terms of revolu- Sec. F36.201 Correction of data.

tions per minute and other relevant param- eters for each overflight.

(a) Noise data obtained when the tempera- (6) Aircraft height in feet determined by a ture is outside the range of 68 degrees F. ± 9 calibrated altimeter in the aircraft, ap- degrees F., or the relative humidity is below proved photographic techniques, or approved 40 percent, must be corrected to 77 degrees F.

tracking facilities.

and 70 percent relative humidity by a meth- (g) Aircraft speed and position and engine od approved by the FAA.

performance parameters must be recorded at (b) The performance correction prescribed an approved sampling rate sufficient to en- in paragraph (c) of this section must be used.

sure compliance with the test procedures and It must be determined by the method de- conditions of this appendix.

scribed in this appendix, and must be added algebraically to the measured value. It is Sec. F36.111 Flight procedures.

limited to 5dB(A).

(a) Tests to demonstrate compliance with (c) The performance correction must be the noise level requirements of this appendix computed by using the following formula:

⎧ ⎫

R C /

⎪ ⎪

Δ dB D = − − + 60 20 11 430 50 log ( ,

⎨ ⎬

10 50

V

⎪ ⎪

y

⎩ ⎭

Where: (b) The samples must be large enough to establish statistically a 90 pecent confidence D = Takeoff distance to 50 feet at maximum limit not to exceed ± 1.5 dB(A). No test result certificated takeoff weight.

may be omitted from the averaging process, R/C = Certificated best rate of climb (fpm).

unless omission is approved by the FAA.

V y = Speed for best rate of climb in the same units as rate of climb.

PART D — NOISE LIMITS (d) When takeoff distance to 50 ′ is not list- Sec. F36.301 Aircraft noise limits.

ed as approved performance information, the figures of 2000 for single-engine airplanes and (a) Compliance with this section must be 1600 ′ for multi-engine airplanes must be used.

shown with noise data measured and cor- rected as prescribed in Parts B and C of this Sec. F36.203 Validity of results.

appendix.

(a) The test results must produce an aver- (b) For airplanes for which application for age dB(A) and its 90 percent confidence lim- a type certificate is made on or after October its, the noise level being the arithmetic av- 10, 1973, the noise level must not exceed 68 erage of the corrected acoustical measure- dB(A) up to and including aircraft weights of ments for all valid test runs over the meas- 1,320 pounds (600 kg.). For weights greater uring point. than 1,320 pounds up to and including 3,630

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. G

pounds (1.650 kg.) the limit increases at the PART A — GENERAL rate of 1 dB/165 pounds (1 dB/75 kg.) to 82 Section G36.1 Scope. This appendix pre- dB(A) at 3,630 pounds, after which it is con- scribes limiting noise levels and procedures stant at 82 dB(A). However, airplanes pro- for measuring noise and adjusting these data duced under type certificates covered by this to standard conditions, for propeller driven paragraph must also meet paragraph (d) of small airplanes and propeller-driven, com- this section for the original issuance of muter category airplanes specified in §§ 36.1 standard airworthiness certificates or re- and 36.501(c).

stricted category airworthiness certificates if those airplanes have not had flight time PART B — NOISE MEASUREMENT before the date specified in that paragraph.

Sec. G36.101 General Test Conditions.

(c) For airplanes for which application for a type certificate is made on or after Janu- (a) The test area must be relatively flat ary 1, 1975, the noise levels may not exceed terrain having no excessive sound absorption the noise limit curve prescribed in paragraph characteristics such as those caused by (b) of this section, except that 80 dB(A) may thick, matted, or tall grass, by shrubs, or by not be exceeded.

wooded areas. No obstructions which signifi- (d) For airplanes for which application is cantly influence the sound field from the air- made for a standard airworthiness certificate plane may exist within a conical space above or for a restricted category airworthiness the measurement position, the cone being certificate, and that have not had any flight defined by an axis normal to the ground and time before January 1, 1980, the require- by a half-angle 75 degrees from the normal ments of paragraph (c) of this section apply, ground axis.

regardless of date of application, to the (b) The tests must be carried out under the original issuance of the certificate for that following conditions: airplane.

(1) No precipitation; (2) Ambient air temperature between 36 [Doc. No. 13243, 40 FR 1035, Jan. 6, 1975; 40 FR and 95 degrees F (2.2 and 35 degrees C); 6347, Feb. 11, 1975, as amended by Amdt. 36– (3) Relative humidity between 20 percent 6, 41 FR 56064, Dec. 23, 1976; Amdt. 36-6, 42 FR and 95 percent, inclusively; 4113, Jan. 24, 1977; Amdt. 36–9, 43 FR 8754, (4) Wind speed may not exceed 10 knots (19 Mar. 2, 1978; Amdt. 36–13, 52 FR 1836, Jan. 15, km/h) and cross wind may not exceed 5 knots 1987; Amdt. 36–16, 53 FR 47400, Nov. 22, 1988; (9 km/h), using a 30-second average; FAA Doc. No. FAA–2015–3782, Amdt. No. 36– (5) No temperature inversion or anomalous 31, 82 FR 46131, Oct. 4, 2017] wind condition that would significantly alter the noise level of the airplane when the nose A PPENDIX G TO P ART 36—T AKEOFF is recorded at the required measuring point, N OISE R EQUIREMENTS FOR P RO - and PELLER -D RIVEN S MALL A IRPLANE (6) The meteorological measurements must AND P ROPELLER -D RIVEN, C OMMUTER be made between 4 ft. (1.2 m) and 33 ft. (10 m) C ATEGORY A IRPLANE C ERTIFICATION above ground level. If the measurement site is within 1 n.m. of an airport meteorological T ESTS ON OR A FTER D ECEMBER 22, station, measurements from that station may be used.

PART A — GENERAL (c) The flight test procedures, measuring equipment, and noise measurement proce- Sec.

dures must be approved by the FAA.

G36.1 Scope.

(d) Sound pressure level data for noise evaluation purposes must be obtained with PART B — NOISE MEASUREMENT acoustical equipment that complies with section G36.103 of this appendix.

G36.101 General Test Conditions.

G36.103 Acoustical measurement system.

Sec. G36.103 Acoustical Measurement System.

G36.105 Sensing, recording, and reproducing The acoustical measurement system must equipment.

consist of approved equipment with the fol- G36.107 Noise measurement procedures.

lowing characteristics: (a) A microphone sys- G36.109 Data recording, reporting, and ap- tem with frequency response compatible proval.

with measurement and analysis system accu- G36.111 Flight procedures.

racy as prescribed in section G36.105 of this PART C — DATA CORRECTIONS appendix.

(b) Tripods or similar microphone mount- G36.201 Corrections to Test Results.

ings that minimize interference with the G36.203 Validity of results.

sound being measured.

(c) Recording and reproducing equipment PART D — NOISE LIMITS characteristics, frequency response, and dy- G36.301 Aircraft Noise Limits. namic range compatible with the response

Federal Aviation Administration, DOT Pt. 36, App. G

and accuracy requirements of section G36.105 ground surface with no cavities below the of this appendix. plate. The microphone must be located (d) Acoustic calibrators using sine wave or three-quarters of the distance from the cen- broadband noise of known sound pressure ter to the back edge of the plate along a ra- level. If broadband noise is used, the signal dius normal to the line of flight of the test must be described in terms of its average and airplane.

(b) Immediately prior to and after each maximum root-mean-square (rms) value for test, a recorded acoustic calibration of the non-overload signal level.

system must be made in the field with an Sec. G36.105 Sensing, Recording, and acoustic calibrator for the purposes of Reproducing Equipment.

checking system sensitivity and providing an acoustic reference level for the analysis (a) The noise produced by the airplane of the sound level data. If a tape recorder or must be recorded. A magnetic tape recorder, graphic level recorder is used, the frequency graphic level recorder, or sound level meter response of the electrical system must be de- is acceptable when approved by the regional termined at a level within 10 dB of the full- certificating authority.

scale reading used during the test, utilizing (b) The characteristics of the complete sys- pink or pseudorandom noise.

tem must comply with the requirements in (c) The ambient noise, including both IEC 651 and IEC 561 (incorporated by ref- acoustic background and electrical systems erence, see § 36.6). Sound level meters must noise, must be recorded and determined in comply with the requirements for Type 1 the test area with the system gain set at lev- sound level meters as specified in IEC 651.

els which will be used for aircraft noise (c) The response of the complete system to measurements. If aircraft sound pressure lev- a sensibly plane progressive sinusoidal wave els do not exceed the background sound pres- of constant amplitude must be within the sure levels by at least 10 dB(A), a takeoff tolerance limits specified in IEC 651, over the measurement point nearer to the start of the frequency range 45 to 11,200 Hz.

takeoff roll must be used and the results (d) If equipment dynamic range limitations must be adjusted to the reference measure- make it necessary, high frequency pre-em- ment point by an approved method.

phasis must be added to the recording chan- nel with the converse de-emphasis on play- Sec. G36.109 Data Recording, Reporting, and back. The pre-emphasis must be applied such Approval.

that the instantaneous recorded sound pres- (a) Data representing physical measure- sure level of the noise signal between 800 and ments and adjustments to measured data 11,200 Hz does not vary more than 20 dB be- must be recorded in permanent form and ap- tween the maximum and minimum one-third pended to the record, except that corrections octave bands.

to measurements for normal equipment re- (e) The output noise signal must be read sponse deviations need not be reported. All through an ‘‘A’’ filter with dynamic charac- other adjustments must be approved. Esti- teristics designated ‘‘slow’’ as defined in IEC mates must be made of the individual errors 651. A graphic recorder, sound level meter, or inherent in each of the operations employed digital equipment may be used.

in obtaining the final data.

(f) The equipment must be acoustically (b) Measured and corrected sound pressure calibrated using facilities for acoustic free- levels obtained with equipment conforming field calibration and if analysis of the tape to the specifications in section G36.105 of recording is requested by the Administrator, this appendix must be reported.

the analysis equipment shall be electroni- (c) The type of equipment used for meas- cally calibrated by a method approved by the urement and analysis of all acoustical, air- FAA. Calibrations shall be performed, as ap- plane performance, and meteorological data propriate, in accordance with paragraphs must be reported.

A36.3.8 and A36.3.9 of appendix A of this part.

(d) The following atmospheric data, meas- (g) A windscreen must be employed with ured immediately before, after, or during the microphone during all measurements of each test at the observation points pre- aircraft noise when the wind speed is in ex- scribed in section G36.101 of this appendix cess of 5 knots (9 km/hr).

must be reported: (1) Ambient temperature and relative hu- Sec. G36.107 Noise Measurement Procedures.

midity.

(a) The microphone must be a pressure (2) Maximum and average wind speeds and type, 12.7 mm in diameter, with a protective directions for each run.

grid, mounted in an inverted position such (e) Comments on local topography, ground that the microphone diaphragm is 7 mm cover, and events that might interfere with above and parallel to a white-painted metal sound recordings must be reported.

circular plate. This white-painted metal (f) The aircraft position relative to the plate shall be 40 cm in diameter and at least takeoff reference flight path must be deter- 2.5 mm thick. The plate shall be placed hori- mined by an approved method independent of zontally and flush with the surrounding normal flight instrumentation, such as radar

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. G

tracking, theodolite triangulation, or photo- (ii) A constant takeoff configuration se- graphic scaling techniques. lected by the applicant must be maintained (g) The following airplane information through this segment.

must be reported: (iii) The maximum weight of the airplane (1) Type, model, and serial numbers (if any) at brake-release must be the maximum for of airplanes, engines, and propellers; which noise certification is requested.

(2) Any modifications or nonstandard (iv) The length of this first segment must equipment likely to affect the noise charac- correspond to the airworthiness approved teristics of the airplane; value for a takeoff on a level paved runway (3) Maximum certificated takeoff weight; (or the corresponding value for seaplanes).

(4) For each test flight, airspeed and ambi- (2) Second segment.

ent temperature at the flyover altitude over (i) The beginning of the second segment the measuring site determined by properly corresponds to the end of the first segment.

calibrated instruments; (ii) The airplane must be in the climb con- (5) For each test flight, engine perform- figuration with landing gear up, if retract- ance parameters, such as manifold pressure able, and flap setting corresponding to nor- or power, propeller speed (rpm) and other rel- mal climb position throughout this second evant parameters. Each parameter must be segment.

determined by properly calibrated instru- (iii) The airplane speed must be the speed ments. For instance, propeller RPM must be for the best rate of climb (V ).

y validated by an independent device accurate (iv) For airplanes equipped with fixed pitch to within ± 1 percent, when the airplane is propellers, takeoff power must be main- equipped with a mechanical tachometer.

tained throughout the second segment. For (6) Airspeed, position, and performance airplanes equipped with variable pitch or data necessary to make the corrections re- constant speed propellers, takeoff power and quired in section G36.201 of this appendix rpm must be maintained throughout the sec- must be recorded by an approved method ond segment. If airworthiness limitations do when the airplane is directly over the meas- not allow the application of takeoff power uring site.

and rpm up to the reference point, then take- Sec. G36.111 Flight Procedures. off power and rpm must be maintained for as long as is permitted by such limitations; (a) The noise measurement point is on the thereafter, maximum continuous power and extended centerline of the runway at a dis- rpm must be maintained. Maximum time al- tance of 8200 ft (2500 m) from the start of lowed at takeoff power under the airworthi- takeoff roll. The aircraft must pass over the ness standards must be used in the second measurement point within ± 10 degrees from segment. The reference height must be cal- the vertical and within 20% of the reference culated assuming climb gradients appro- altitude. The flight test program shall be ini- priate to each power setting used.

tiated at the maximum approved takeoff weight and the weight shall be adjusted back PART C — DATA CORRECTIONS to this maximum weight after each hour of flight time. Each flight test must be con- Sec. G36.201 Corrections to Test Results.

ducted at the speed for the best rate of climb (a) These corrections account for the ef- (V y ) ± 5 knots ( ± 9 km/hour) indicated airspeed.

fects of: All test, measurement, and data correction (1) Differences in atmospheric absorption procedures must be approved by the FAA.

of sound between meteorological test condi- (b) The takeoff reference flight path must tions and reference conditions.

be calculated for the following atmospheric (2) Differences in the noise path length be- conditions: tween the actual airplane flight path and the (1) Sea level atmospheric pressure of 1013.25 reference flight path.

mb (013.25 hPa); (3) The change in the helical tip Mach (2) Ambient air temperature of 59 ° F (15 number between test and reference condi- ° C); tions.

(3) Relative humidity of 70 percent; and (4) The change in the engine power between (4) Zero wind.

(c) The takeoff reference flight path must test and reference conditions.

be calculated assuming the following two (b) Atmospheric absorption correction is segments: required for noise data obtained when the (1) First segment. test conditions are outside those specified in (i) Takeoff power must be used from the Figure G1. Noise data outside the applicable brake release point to the point at which the range must be corrected to 59 F and 70 per- height of 50 ft (15m) above the runway is cent relative humidity by an FAA approved reached. method.

Federal Aviation Administration, DOT Pt. 36, App. G

(c) No corrections for helical tip Mach Values of Atmospheric Absorption as a number variation need to be made if the pro- function of Temperature and Humidity peller helical tip Mach number is: for use in Evaluating Aircraft Flyover (1) At or below 0.70 and the test helical tip Noise’’ as incorporated by reference Mach number is within 0.014 of the reference under § 36.6.

helical tip Mach number.

(2) Measured sound levels in decibels must (2) Above 0.70 and at or below 0.80 and the be corrected for height by algebraically add- test helical tip Mach number is within 0.007 ing an increment equal to Delta (1). When of the reference helical tip Mach number.

test day conditions are within those speci- (3) Above 0.80 and the test helical tip Mach fied in figure G1: number is within 0.005 of the reference hel- Delta (1) = 22 log (H /H ) T R ical tip Mach number. For mechanical ta- where H is the height of the test aircraft T chometers, if the helical tip Mach number is when directly over the noise measure- above 0.8 and the test helical tip Mach num- ment point and H is the reference R ber is within 0.008 of the reference helical tip height.

Mach number.

When test day conditions are outside those (d) When the test conditions are outside specified in figure G1: those specified, corrections must be applied Delta (1) = 20 log (H /H ) T R by an approved procedure or by the following (3) Measured sound levels in decibels must simplified procedure: (1) Measured sound levels must be cor- be corrected for helical tip Mach number by rected from test day meteorological condi- algebraically adding an increment equal to: tions to reference conditions by adding an Delta (2) = k log (M /M ) R T increment equal to where M and M are the test and reference T R Delta (M) = (H a —0.7 H )/1000 T R helical tip Mach numbers, respectively.

where H is the height in feet under test con- The constant ‘‘k’’ is equal to the slope of T ditions, H is the height in feet under ref- the line obtained for measured values of R erence conditions when the aircraft is di- the sound level in dB(A) versus helical rectly over the noise measurement point tip Mach number. The value of k may be and a is the rate of absorption for the determined from approved data. A nomi- test day conditions at 500 Hz as specified nal value of k = 150 may be used when M T in SAE ARP 866A, entitled ‘‘Standard is smaller than M . No correction may be R

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. G

made using the nominal value of k when PART D — NOISE LIMITS M is larger than M . The reference hel- T R Sec. G36.301 Aircraft noise limits.

ical tip Mach number M R is the Mach number corresponding to the reference (a) Compliance with this section must be conditions (RPM, airspeed, temperature) shown with noise data measured and cor- above the measurement point.

rected as prescribed in Parts B and C of this (4) Measured sound levels in decibels must appendix.

(b) For single-engine airplanes for which be corrected for engine power by algebra- the original type certification application is ically adding an increment equal to received before February 3, 2006 and multi- Delta (3) = K log (P /P ) 3 R T engine airplanes, the noise level must not ex- and P are the test and reference where P R T ceed 76 dB(A) up to and including aircraft engine powers respectively obtained from weights of 1,320 pounds (600 kg). For aircraft the manifold pressure/torque gauges and weights greater than 1,320 pounds, the limit engine rpm. The value of K shall be de- 3 increases from that point with the logarithm termined from approved data from the of airplane weight at the rate of 9.83 dB (A) test airplane. In the absence of flight per doubling of weight, until the limit of 88 test data and at the discretion of the Ad- dB (A) is reached, after which the limit is constant up to and including 19,000 pounds ministrator, a value of K 3 = 17 may be (8,618 kg). Figure G2 shows noise level limits used.

vs airplane weight.

Sec. G36.203 Validity of Results. (c) For single-engine airplanes for which the original type certification application is (a) The measuring point must be overflown received on or after February 3, 2006, the at least six times. The test results must noise level must not exceed 70dB(A) for air- produce an average noise level (L ) value Amax craft having a maximum certificated takeoff within a 90 percent confidence limit. The av- weight of 1,257 pounds (570 kg) or less. For erage noise level is the arithmetic average of aircraft weights greater than 1,257 pounds, the corrected acoustical measurements for the noise limit increases from that point all valid test runs over the measuring point.

with the logarithm of airplane weight at the (b) The samples must be large enough to rate of 10.75dB(A) per doubling of weight, establish statistically a 90 percent con- until the limit of 85dB(A) is reached, after fidence limit not exceeding ± 1.5 dB(A). No which the limit is constant up to and includ- test results may be omitted from the aver- ing 19,000 pounds (8,618 kg). Figure G2 depicts aging process unless omission is approved by noise level limits for airplane weights for the FAA. single-engine airplanes.

Federal Aviation Administration, DOT Pt. 36, App. H

(Secs. 313(a), 603, and 611(b), Federal Aviation (c) The noise limits for which compliance Act of 1958 as amended (49 U.S.C. 1354(a), must be shown under § 36.805.

1423, and 1431(b)); sec. 6(c), Department of Section H36.3 Reference Test Conditions.

Transportation Act (49 U.S.C. 1655 (c)); Title I, National Environmental Policy Act of 1969 (a) Meteorological conditions. Aircraft posi- (42 U.S.C. 4321 et seq. ); E. O. 11514, March 5, tion, performance data and noise measure- 1970 and 14 CFR 11.45).

ments must be corrected to the following noise certification reference atmospheric [Amdt. 36–16, 53 FR 47400, Nov. 22, 1988; 53 FR conditions which shall be assumed to exist 50157, Dec. 13, 1988, as amended by Amdt. 36– from the surface to the aircraft altitude: 22, 64 FR 55602, Oct. 13, 1999; Amdt. 36–54, 67 (1) Sea level pressure of 2,116 psf (1,013.25 FR 45236, July 8, 2002; Amdt. 36–27, 70 FR hPa).

45504, Aug. 5, 2005; Amdt. 36–28, 71 FR 532, (2) Ambient temperature of 77 degrees F (25 Jan. 4, 2006; FAA Doc. No. FAA–2015–3782, degrees C).

Amdt. No. 36–31, 82 FR 46131, Oct. 4, 2017] (3) Relative humidity of 70 percent.

(4) Zero wind.

A PPENDIX H TO P ART 36—N OISE R E- (b) Reference test site. The reference test QUIREMENTS F OR H ELICOPTERS site is flat and without line-of-sight obstruc- U NDER S UBPART H tions across the flight path that encom- passes the 10 dB down points.

PART A — REFERENCE CONDITIONS (c) Takeoff reference profile. (1) Figure H1 il- Sec.

lustrates a typical takeoff profile, including H36.1 General. reference conditions.

(2) The reference flight path is defined as a H36.3 Reference Test Conditions.

straight line segment inclined from the H36.5 Symbols and Units.

starting point (1,640 feet (500 meters) from PART B — NOISE MEASUREMENT UNDER § 36.801 the center microphone location and 65 feet (20 meters) above ground level) at a constant H36.101 Noise certification test and measurement climb angle b defined by the certificated best conditions.

rate of climb and V for minimum engine y H36.103 Takeoff test conditions.

performance. The constant climb angle b is H36.105 Flyover test conditions.

derived from the manufacturer’s data (ap- H36.107 Approach test conditions.

proved by the FAA) to define the flight pro- H36.109 Measurement of helicopter noise re- file for the reference conditions. The con- ceived on the ground.

stant climb angle b is drawn through C and r H36.111 Reporting and correcting measured continues, crossing over station A, to the po- data.

sition corresponding to the end of the type H36.113 Atmospheric attenuation of sound.

certification takeoff path represented by po- sition I .

r PART C — NOISE EVALUATION AND CALCULATION (d) Level flyover reference profile. The begin- UNDER § 36.803 ning of the level flyover reference profile is H36.201 Noise evaluation in EPNdB. represented by helicopter position D (Figure r H36.203 Calculation of noise levels. H2). The helicopter approaches position D in r H36.205 Detailed data correction procedures. level flight 492 feet above ground level as measured at Station A. Reference airspeed PART D — NOISE LIMITS UNDER § 36.805 must be either 0.9V ; 0.9V ; 0.45V + 65 kts H NE H (0.45V + 120km/h); or 0.45V + 65kts (0.45V H NE NE H36.301 Noise measurement, evaluation, and cal- + 120 km/h), whichever of the four speeds is culation.

least. The helicopter crosses directly over- H36.303 [Reserved] head station A in level flight and proceeds to H36.305 Noise levels.

position J .

r (e) For noise certification purposes, V is H PART A — REFERENCE CONDITIONS defined as the airspeed in level flight ob- Section H36.1 General. This appendix pre- tained using the minimum specified engine scribes noise requirements for helicopters torque corresponding to maximum contin- specified under § 36.1, including: uous power available for sea level pressure of (a) The conditions under which helicopter 2,116 psf (1,013.25 hPa) at 77 ° F (25 ° C) ambient noise certification tests under Part H must conditions at the relevant maximum certifi- be conducted and the measurement proce- cated weight. The value of V is the never- NE dures that must be used under § 36.801 to exceed airspeed. The values of V and V H NE measure helicopter noise during each test; that are used for noise certification must be (b) The procedures which must be used listed in the approved Rotorcraft Flight under § 36.803 to correct the measured data to Manual.

the reference conditions and to calculate the (f) Approach reference profile. (1) Figure H3 noise evaluation quantity designated as Ef- illustrates approach profile, including ref- fective Perceived Noise Level (EPNL); and erence conditions.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

(i) The beginning of the approach profile is F LIGHT P ROFILE I DENTIFICATION —P OSITIONS — represented by helicopter position E. The po- Continued sition of the helicopter is recorded for a suf- ficient distance (EK) to ensure recording of Posi- Description tion the entire interval during which the meas- ured helicopter noise level is within 10 dB of M ... Position on reference flyover flight path corresponding r Maximum Tone Corrected Perceived Noise to PNLTM of station A.

Level (PNLTM). The reference flight path, N ..... Position on measured approach flight path cor- E K represents a stable flight condition in responding to PNLTM at station A.

r r N .... Position on reference approach flight path cor- terms of torque, rpm, indicated airspeed, and r responding to PNLTM at station A.

rate of descent resulting in a 6 ° approach S ..... Sideline noise measuring station (note: a subscript angle.

denotes the aircraft orientation relative to the direc- (ii) The test approach profile is defined by tion of flight).

the approach angle h passing directly over the station A at a height of AH, to position K, which terminates the approach noise cer- F LIGHT P ROFILE D ISTANCES tification profile. The test approach angle h Dis- must be between 5.5 ° and 6.5 ° .

Unit Meaning tance (2) The helicopter approaches position H along a constant 6 ° approach slope through- AF ..... Feet Takeoff Height. The vertical distance be- out the 10 dB down time period. The heli- tween helicopter and station A.

AG ..... Feet Flyover Height. The vertical distance be- copter crosses position E and proceeds along tween the helicopter and station A.

the approach slope crossing over station A AH ..... Feet Approach Height. The vertical distance be- until it reaches position K.

tween the helicopter and station A.

AL ..... Feet Measured Takeoff Noise Path. The distance Section H36.5 Symbols and units. The fol- from station A to the measured helicopter lowing symbols and units as used in this ap- position L.

pendix for helicopter noise certification have AL .... Feet Reference Takeoff Noise Path. The distance r the following meanings.

from station A to the reference helicopter position L .

r F LIGHT P ROFILE IDENTIFICATION —P OSITIONS AM .... Feet Measured Flyover Noise Path. The distance from station A to the measured helicopter Posi- position M.

Description tion AM ... Feet Reference Flyover Noise Path. The distance r from station A to helicopter position M on r A ..... Location of the noise measuring point at the flight- the reference flyover flight path.

track noise measuring station vertically below the AN ..... Feet Measured Approach Noise Path. The dis- reference (takeoff, flyover, or approach) flight path.

tance from station A to the measured heli- C ..... Start of noise certification takeoff flight path.

copter noise position N.

C .... Start of noise certification reference takeoff flight path.

r AN .... Feet Reference Approach Noise Path. The dis- r D ..... Start of noise certification flyover flight path.

tance from station A to the reference heli- D .... Start of noise certification reference flyover path.

r copter position N .

r E ..... Start of noise certification approach flight path.

CI ...... Feet Takeoff Flight Path Distance. The distance E r .... Start of noise certification reference approach flight from position C at which the helicopter es- path.

tablishes a constant climb angle on the F ..... Position on takeoff flight path directly above noise takeoff flight path passing over station A measuring station A.

and continuing to position I at which the F r .... Position on reference takeoff path directly above position of the helicopter need no longer noise measuring Station A.

be recorded.

G ..... Position on flyover flight path directly above noise DJ ..... Feet Flyover Flight Path Distance. The distance measuring station A.

from position D at which the helicopter is G r .... Position on reference flyover path directly above established on the flyover flight path pass- noise measuring Station A.

ing over station A and continuing to posi- H ..... Position on approach flight path directly above noise tion J at which the position of the heli- measuring station A.

copter need no longer be recorded.

H r .... Position on reference path directly above noise meas- EK ..... Feet Approach Flight Path Distance. The distance uring Station A.

from position E at which the helicopter es- I ...... End of noise type certification takeoff flight path.

tablishes a constant angle on the approach I r ..... End of noise type certification reference takeoff flight flight path passing over station A and con- path.

tinuing to position K at which the position J ...... End of noise type certification flyover flight path.

of the helicopter need no longer be re- J r ..... End of noise type certification reference flyover flight corded.

path.

K ..... End of noise certification approach type flight path.

PART B — NOISE MEASUREMENT UNDER § 36.801 K r .... End of noise type certification reference approach flight path.

Section H36.101 Noise certification test and L ..... Position on measured takeoff flight path cor- measurement conditions.

responding to PNLTM at station A.

L r .... Position on reference takeoff flight path corresponding (a) General. This section prescribes the con- to PNLTM of station A.

ditions under which aircraft noise certifi- M .... Position on measured flyover flight path cor- cation tests must be conducted and the responding to PNLTM of station A.

Federal Aviation Administration, DOT Pt. 36, App. H

measurement procedures that must be used (ii) Each test weight must be between + 5 to measure helicopter noise during each test. percent and ¥ 10 percent of the maximum (b) Test site requirements. (1) Tests to show certification weight.

compliance with established helicopter noise (c) Weather restrictions. The tests must be certification levels must consist of a series conducted under the following atmospheric conditions: of takeoffs, level flyovers, and approaches (1) No rain or other precipitation.

during which measurement must be taken at (2) Ambient air temperature between 14 ° F noise measuring stations located at the and 95 ° F ( ¥ 10 ° C and 35 ° C), inclusively, at measuring points prescribed in this section.

a point 33 feet (10 meters) above the ground (2) Each takeoff test, flyover test, and ap- at the noise measuring station and at the proach test includes simultaneous measure- aircraft. The temperature and relative hu- ments at the flight-track noise measuring midity measured at a point 33 feet (10 me- station vertically below the reference flight ters) above the ground at the noise meas- path and at two sideline noise measuring uring station must be used to adjust for stations, one on each side of the reference propagation path absorption.

flight track 492 feet (150m) from, and on a (3) Relative humidity and ambient tem- line perpendicular to, the flight track of the perature at a point 33 feet (10 meters) above noise measuring station.

the ground at the noise measuring station (3) The difference between the elevation of and at the aircraft, is such that the sound at- either sideline noise measuring station may tenuation in the one-third octave band cen- not differ from the flight-track noise meas- tered at 8 kHz is not greater than 12 dB/100 uring station by more than 20 feet.

meters and the relative humidity is between (4) Each noise measuring station must be 20 percent and 95 percent, inclusively.

surrounded by terrain having no excessive (4) Wind velocity as measured at 10 meters sound absorption characteristics, such as above ground does not exceed 10 knots (19 might be caused by thick, matted, or tall km/h) and the crosswind component does not grass, shrubs, or wooded areas.

exceed 5 knots (9 km/h). The wind shall be (5) During the period when the takeoff, fly- determined using a continuous thirty-second over, or approach noise/time record indicates averaging period spanning the 10dB down the noise measurement is within 10 dB of time interval.

PNLTM, no obstruction that significantly (5) No anomalous meteorological condi- influences the sound field from the aircraft tions (including turbulence) that will signifi- may exist— cantly affect the noise level of the aircraft (i) For any flight-track or sideline noise when the noise is recorded at each noise measuring station, within a conical space measuring station.

above the measuring position (the point on (6) The wind velocity, temperature, and the ground vertically below the microphone), relative humidity measurements required the cone being defined by an axis normal to under the appendix must be measured in the the ground and by half-angle 80 ° from this vicinity of noise measuring stations 10 me- axis; and ters above the ground. The location of the (ii) For any sideline noise measuring sta- meteorological measurements must be ap- tion, above the line of sight between the proved by the FAA as representative of those microphone and the helicopter.

atmospheric conditions existing near the (6) If a takeoff or flyover test series is con- surface over the geographical area which air- ducted at weights other than the maximum craft noise measurements are made. In some takeoff weight for which noise certification cases, a fixed meteorological station (such as is requested, the following additional re- those found at airports or other facilities) quirements apply: may meet this requirement.

(i) At least one takeoff test and one flyover (7) Temperature and relative humidity test must be conducted at, or above, the measurements must be obtained within 30 maximum certification weight.

minutes of each noise test.

(ii) Each test weight must be within + 5 (d) Aircraft testing procedures. (1) The air- percent or ¥ 10 percent of the maximum cer- craft testing procedures and noise measure- tification weight.

ments must be conducted and processed in a (7) Each approach test must be conducted manner that yields the noise evaluation with the aircraft stabilized and following a measure designated as Effective Perceived 6.0 degree ± 0.5 degree approach angle and Noise Level (EPNL) in units of EPNdB, as must meet the requirements of section prescribed in Appendix A of this part.

H36.107 of this part. (2) The helicopter height and lateral posi- (8) If an approach test series is conducted tion relative to the reference flight track at weights other than the maximum landing (which passes through the flight track noise weight for which certification is requested, measuring station) must be determined the following additional requirements apply: using an FAA-approved method. The equip- (i) At least one approach test must be con- ment used to make the determination must ducted at a weight at, or above, the max- be independent of normal flight instrumen- imum landing weight. tation. Applicable independent systems are

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

radar tracking, theodolite triangulation, Section H36.105 Flyover test conditions.

laser trajectography, photo scaling, or dif- (a) This section, in addition to the applica- ferential global positioning system.

ble requirements of sections H36.101 and (3) The helicopter position along the flight H36.205(c) of this appendix, applies to all fly- path must be related to the noise recorded at over noise tests conducted under this appen- the noise measuring stations by means of dix to show compliance with Part 36.

synchronized signals recorded at an approved (b) A test series consists of at least six sampling rate. The helicopter position must flights. The number of level flights made be recorded relative to the reference flight with a headwind component must be equal to track during the entire time interval in the number of level flights made with a tail- which the recorded signal is within 10 dB of wind component with simultaneous measure- PNLTM. Measuring and sampling equipment ments at all three noise measuring sta- must be approved by the FAA before testing.

tions— (4) Aircraft performance data sufficient to (1) In level flight cruise configuration; make the corrections required under section (2) At a height of 492 feet ± 30 feet (150 ± 9 H36.205 of this appendix must be recorded at meters) above the ground level at the flight- an FAA-approved sampling rate using FAA- track noise measuring station; and approved equipment.

(3) The helicopter must fly within ± 10 ° or ± 65 feet ( ± 20 meters), whichever is greater, Section H36.103 Takeoff test conditions.

from the vertical above the reference track (a) This section, in addition to the applica- throughout the 10 dB-down time interval.

ble requirements of sections H36.101 and (c) Each flyover noise test must be con- H36.205(b) of this appendix, applies to all ducted— takeoff noise tests conducted under this ap- (1) At a speed of 0.9V H ; 0.9V NE ; 0.45V H + 65 pendix to show compliance with Part 36.

kts (0.45V H + 120 km/h); or 0.45V NE + 65 kts (b) A test series must consist of at least six (0.45V NE + 120 km/h), whichever speed is least, flights over the flight-track noise measuring to be maintained throughout the measured station (with simultaneous measurements at portion of the flyover; all three noise measuring stations) as fol- (2) At average rotor speed, which must not lows: vary from the maximum normal operating ± 5 knots or the (1) An airspeed of either V y rotor RPM by more than ± 1.0 percent during lowest approved speed ± 5 knots for the climb the 10 dB-down time interval.

after takeoff, whichever speed is greater, (3) With the power stabilized during the pe- must be established and maintained through- riod when the measured helicopter noise out the 10 dB-down time interval.

level is within 10 dB of PNLTM.

(2) The horizontal portion of each test (d) The airspeed shall not vary from the flight must be conducted at an altitude of 65 reference airspeed by more than ± 5 knots (9 feet (20 meters) above the ground level at the km/hr).

flight-track noise measuring station.

(3) Upon reaching a point 1,640 feet (500 me- Section H36.107 Approach test conditions.

ters) from the noise measuring station, the (a) This section, in addition to the require- helicopter must be stabilized at the max- ments of sections H36.101 and H36.205(d) of imum takeoff power that corresponds to this appendix, applies to all approach tests minimum installed engine(s) specification conducted under this appendix to show com- power available for the reference ambient pliance with Part 36.

conditions or gearbox torque limit, which- (b) A test series must consist of at least six ever is lower.

flights over the flight-track noise measuring (4) The helicopter must be maintained throughout the 10 dB-down time interval at station (with simultaneous measurements at the best rate of climb speed V ± 5 knots, or the three noise measuring stations)— y (1) On an approach slope of 6 ° ± 0.5 ° ; the lowest approved speed for climb after (2) At a height of 394 ± 33 feet (120 ± 10 me- takeoff, whichever is greater, for an ambient ters) temperature of 25 ° C at sea level.

(3) The helicopter must fly within ± 10 ° or (5) The average rotor speed must not vary ± 65 feet ( ± 20 meters) lateral deviation toler- from the maximum normal operating rotor ance, whichever is greater, from the vertical RPM by more than ± 1.0 percent during the 10 above the reference track throughout the 10 dB-down time interval.

(6) The helicopter must stay within ± 10 ° or dB-down time interval; ± 65 feet ( ± 20 meters), whichever is greater, (4) At stabilized airspeed equal to the cer- from the vertical above the reference track tificated best rate of climb V , or the lowest y throughout the 10dB-down time interval. approved speed for approach, whichever is (7) A constant takeoff configuration se- greater, with power stabilized during the ap- lected by the applicant must be maintained proach and over the flight path reference throughout the takeoff reference procedure point, and continued to a normal touchdown; with the landing gear position consistent and with the airworthiness certification tests for (5) At average rotor speed, which may not establishing best rate-of-climb speed, V . vary from the maximum normal operating y

Federal Aviation Administration, DOT Pt. 36, App. H

rotor RPM by more than ± 1.0 percent during trajectography, or photographic scaling the 10 dB-down time interval; and techniques.

(6) The constant approach configuration (6) Aircraft speed, and position, and engine used in airworthiness certification tests, performance parameters must be recorded at with the landing gear extended, must be an approved sampling rate sufficient to cor- rect to the noise certification reference test maintained throughout the approach ref- conditions prescribed in section H36.3 of this erence procedure.

appendix. Lateral position relative to the (c) The airspeed shall not vary from the reference flight-track must be reported.

reference airspeed by more than ± 5 knots ( ± 9 (c) Data corrections. (1) Aircraft position, km/hr).

performance data and noise measurement Section H36.109 Measurement of Helicopter must be corrected to the noise certification Noise Received on the Ground.

reference conditions as prescribed in sections H36.3 and H36.205 of this appendix.

The measurement system and the measure- (2) The measured flight path must be cor- ment, calibration and general analysis pro- rected by an amount equal to the difference cedures to be used are provided in Appendix between the applicant’s predicted flight path A, section A36.3 of this part.

for the certification reference conditions and the measured flight path at the test condi- Section H36.111 Reporting and correcting tions. Necessary corrections relating to heli- measured data.

copter flight path or performance may be de- (a) General. Data representing physical rived from FAA-approved data for the dif- measurements, and corrections to measured ference between measured and reference con- data, including corrections to measurements ditions, together with appropriate allow- for equipment response deviations, must be ances for sound attenuation with distance.

recorded in permanent form and appended to The Effective Perceived Noise Level (EPNL) the record. Each correction must be reported correction may not exceed 2.0 EPNdB except and is subject to FAA approval. An estimate for takeoff flight condition, where the cor- must be made of each individual error inher- rection may not exceed 4.0 EPNdB, of which ent in each of the operations employed in ob- the arithmetic sum of D (described in sec- taining the final data.

tion H36.205(f)(1)) and the term ¥ 7.5 log (AL/ (b) Data reporting. (1) Measured and cor- AL r ) from D 2 term (described in section rected sound pressure levels must be pre- H36.205(g)(1)(i)) may not exceed 2.0 EPNdB, sented in one-third octave band levels ob- for any combination of the following: tained with equipment conforming to the (i) The helicopter not passing vertically standards prescribed in section H36.109 of above the measuring station.

this appendix.

(ii) Any difference between the reference (2) The type of equipment used for meas- flight track and the actual test flight track; urement and analysis of all acoustic, aircraft and performance, and meteorological data must (iii) Detailed correction requirements pre- be reported.

scribed in section H36.205 of this appendix.

(3) The atmospheric environmental data (3) Helicopter sound pressure levels within required to demonstrate compliance with the 10 dB-down time interval must exceed this appendix, measured throughout the test the mean background sound pressure levels period, must be reported. determined under section B36.3.9.11 by at (4) Conditions of local topography, ground least 3 dB in each one-third octave band, or cover, or events which may interfere with must be corrected under an FAA-approved sound recording must be reported. method.

(5) The following aircraft information (d) Validity of results. (1) The test results must be reported: must produce three average EPNL values (i) Type, model, and serial numbers, if any, within the 90 percent confidence limits, each of aircraft engines and rotors. value consisting of the arithmetic average of (ii) Gross dimensions of aircraft and loca- the corrected noise measurements for all tion of engines. valid test runs at the takeoff, level flyovers, (iii) Aircraft gross weight for each test and approach conditions. The 90 percent con- run. fidence limit applies separately to takeoff, (iv) Aircraft configuration, including land- flyover, and approach.

ing gear positions. (2) The minimum sample size acceptable (v) Airspeed in knots. for each takeoff, approach, and flyover cer- (vi) Helicopter engine performance as de- tification measurements is six. The number termined from aircraft instruments and of samples must be large enough to establish manufacturer’s data. statistically for each of the three average (vii) Aircraft flight path, above ground noise certification levels a 90 percent con- level in feet, determined by an FAA approved fidence limit which does not exceed ± 1.5 method which is independent of normal EPNdB. No test result may be omitted from flight instrumentation, such as radar track- the averaging process, unless otherwise spec- ing, theodolite triangulation, laser ified by the FAA.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

(3) To comply with this appendix, a min- this section, the procedures in appendix A of imum of six takeoffs, six approaches, and six Part 36 must be used for computing EPNL.

level flyovers is required. To be counted to- appendix A includes requirements governing ward this requirement, each flight event determination of noise values, including cal- must be validly recorded at all three noise culations of: measuring stations.

(1) Perceived noise levels; (4) The approved values of V and V used H y (2) Corrections for spectral irregularities; in calculating test and reference conditions (3) Tone corrections; and flight profiles must be reported along (4) Duration corrections; with measured and corrected sound pressure (5) Effective perceived noise levels; and levels.

(6) Mathematical formulation of noy ta- bles.

Section H36.113 Atmospheric attenuation of (b) Notwithstanding the provisions of sec- sound.

tion A36.4.3.1(a), for helicopter noise certifi- (a) The values of the one-third octave band cation, corrections for spectral irregularities spectra measured during helicopter noise shall start with the corrected sound pressure certification tests under this appendix must level in the 50 Hz one-third octave band.

conform, or be corrected, to the reference conditions prescribed in section H36.3(a).

Section H36.203 Calculation of noise levels.

Each correction must account for any dif- (a) To demonstrate compliance with the ferences in the atmospheric attenuation of noise level limits of section H36.305, the sound between the test-day conditions and noise values measured simultaneously at the the reference-day conditions along the sound three noise measuring points must be propagation path between the aircraft and arithmetically averaged to obtain a single the microphone. Unless the meteorological EPNdB value for each flight.

conditions are within the test window pre- (b) The calculated noise level for each scribed in this appendix, the test data are noise test series, i.e. , takeoff, flyover, or ap- not acceptable.

proach must be the numerical average of at (b) Attenuation rates. The procedure for de- least six separate flight EPNdB values. The termining the atmospheric attenuation rates 90 percent confidence limit for all valid test of sound with distance for each one-third oc- runs under section H36.111(d) of this appendix tave bands must be determined in accord- applies separately to the EPNdB values for ance with SAE ARP 866A (Incorporated by reference, see § 36.6). The atmospheric at- each noise test series.

tenuation equations are provided in both the Section H36.205 Detailed data correction International and English systems of units procedures.

in section A36.7 of appendix A to this part.

(c) Correction for atmospheric attenuation. (1) (a) General. If the test conditions do not EPNL values calculated for measured data conform to those prescribed as noise certifi- must be corrected whenever— cation reference conditions under section (i) The ambient atmospheric conditions of H36.305 of this appendix, the following cor- temperature and relative humidity do not rection procedure shall apply: conform to the reference conditions, 77 ° F (1) If there is any difference between meas- and 70%, respectively, or ured test and reference conditions, an appro- (ii) The measured flight paths do not con- priate correction must be made to the EPNL form to the reference flight paths.

calculated from the measured noise data.

(iii) The temperature and relative humid- Conditions that can result in a different ity measured at 33 feet (10 meters) above the value include: ground must be used to adjust for propaga- (i) Atmospheric absorption of sound under tion path absorption.

measured test conditions that are different (2) The mean attenuation rate over the from the reference test conditions; or complete sound propagation path from the (ii) Measured flight path that is different aircraft to the microphone must be com- from the reference flight path.

puted for each one-third octave band from 50 (2) The following correction procedures Hz to 10,000 Hz. These rates must be used in may produce one or more possible correction computing the corrections required in sec- values which must be added algebraically to tion H36.111(d) of this appendix.

the calculated EPNL to bring it to reference PART C — NOISE EVALUATION AND CALCULATION conditions: UNDER § 36.803 (i) The flight profiles must be determined for both reference and test conditions. The Section H36.201 Noise Evaluation in EPNdB.

procedures require noise and flight path re- (a) Effective Perceived Noise Level cording with a synchronized time signal (EPNL), in units of effective perceived noise from which the test profile can be delin- decibels (EPNdB), shall be used for evalu- eated, including the aircraft position for ating noise level values under § 36.803 of this which PNLTM is observed at the noise meas- part. Except as provided in paragraph (b) of uring station. For takeoff, the flight profile

Federal Aviation Administration, DOT Pt. 36, App. H

corrected to reference conditions may be de- rection factor. Effective perceived noise rived from FAA approved manufacturer’s level, EPNL, is determined by the algebraic data. sum of the maximum tone corrected per- (ii) The sound propagation paths to the ceived noise level (PNLTM) and the duration microphone from the aircraft position cor- correction factor.

responding to PNLTM must be determined (iv) For aircraft flyover, alternative source for both the test and reference profiles. The noise corrections require FAA approval and SPL values in the spectrum of PNLTM must must be determined and adjusted to account then be corrected for the effects of— for noise level changes caused by the dif- (A) Change in atmospheric sound absorp- ferences between measured test conditions tion; and reference conditions.

(B) Atmospheric sound absorption on the (b) Takeoff profiles. (1) Figure H1 illustrates linear difference between the two sound path a typical takeoff profile, including reference lengths; and conditions.

(C) Inverse square law on the difference in (i) The reference takeoff flight path is de- sound propagation path length. The cor- scribed in section H36.3(c).

rected values of SPL must then be converted (ii) The test parameters are functions of to a reference condition PNLTM value from the helicopter’s performance and weight and which PNLTM must be subtracted. The re- the atmospheric conditions of temperature, sulting difference represents the correction pressure, wind velocity and direction.

which must be added algebraically to the (2) For the actual takeoff, the helicopter EPNL calculated from the measured data. approaches position C in level flight at 65 (iii) As observed at the noise measuring feet (20 meters) above ground level at the station, the measured PNLTM distance is flight track noise measuring station and at different from the reference PNLTM distance either V ± 5 knots or the lowest approved y and therefore the ratio must be calculated speed for the climb after takeoff, whichever and used to determine a noise duration cor- speed is greater.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

(3) Figure H1 illustrates the significant ge- from which PNLTM is observed at station A, ometrical relationships influencing sound and L is the corresponding position on the r propagation. Position L represents the heli- reference sound propagation path. Propaga- copter location on the measured takeoff path tion paths AL and AL both form the same r

Federal Aviation Administration, DOT Pt. 36, App. H

angle q (theta) relative to their respective mined using the procedures in section flight paths. H36.3(d). The number of level flights made (c) Level flyover profiles. (1) The noise type with a headwind component must be equal to certification level flyover profile is shown in the number of level flights made with a tail- Figure H2. Airspeed must be stabilized with- wind component.

in ± 5 knots of the reference airspeed deter-

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

(2) Figure H2 illustrates comparative fly- corded for a distance (DJ) sufficient to en- over profiles when test conditions do not sure recording of the entire interval during conform to prescribed reference conditions. which the measured helicopter noise level is The position of the helicopter shall be re-

Federal Aviation Administration, DOT Pt. 36, App. H

within 10 dB of PNLTM, as required. The fly- (d) Approach profiles. (1) Figure H3 illus- over profile is defined by the height AG trates a typical approach profile, including which is a function of the operating condi- reference conditions.

tions controlled by the pilot. Position M rep- (2) The helicopter approaches position H resents the helicopter location on the meas- along a 6 ° ( ± 0.5 ° ) average approach slope ured flyover flight path for which PNLTM is throughout the 10dB-down time interval. De- is the cor- observed at station A, and M r viation from the 6 ° average approach slope responding position on the reference flight must be approved by the FAA before testing.

path.

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

(3) Figure H3 illustrates portions of the The measured approach path is represented measured and reference approach flight by segment EK with an approach allowable paths including the significant geometrical angle q . Reference positions, E and K , define r r relationships influencing sound propagation. an idealized reference approach angle of 6 ° .

Federal Aviation Administration, DOT Pt. 36, App. H

Position N represents the helicopter location coefficients for the test and reference atmos- on the measured approach flight path for pheric conditions, respectively, for the i -th which PNLTM is observed at measuring sta- one-third octave band, and AL is the meas- tion A, and N is the corresponding position ured takeoff sound propagation path. The r on the reference approach flight path. The conversion factor constant, C , is 0.001 for measured and reference noise propagation English System of Units and is 0.01 for Inter- national System of Units. The second correc- paths are AN and AN , respectively, both of r tion term adjusts for the effects of atmos- which form the same angle, q , cor- APP pheric attenuation due to the difference in responding to PNLTM relative to their ap- the sound propagation path length where AL proach flight paths. r is the Reference takeoff sound propagation (e) Correction of noise at source during level path. The third correction term, known as flyover. (1) For level overflight, if any com- the ‘‘inverse square’’ law, adjusts for the ef- bination of the following three factors, air- fect of the difference in the sound propaga- speed deviations from reference, rotor speed tion path lengths.

deviations from reference, and temperature (ii) Step 2. The corrected values of the deviations from reference, results in a noise SPL( i ) are then converted to reference con- r correlating parameter whose value deviates dition PNLT and a correction term cal- from the reference value of this parameter, culated as follows: then source noise adjustments must be de- termined from the manufacturer’s data that D = PNLT ¥ PNLTM is approved by the FAA.

which represents the correction to be added (2) Off-reference tip Mach number adjust- algebraically to the EPNL calculated from ments must be based upon a sensitivity the measured data.

curve of PNLTM versus advancing blade tip (2) Level flyover flight path. (i) The proce- Mach number, deduced from overflights per- dure described in paragraph (f)(1) of this sec- formed at different airspeeds surrounding tion for takeoff paths is also used for the the reference airspeed. If the test aircraft is level flyover paths, with the values of SPL( i ) r unable to attain the reference value, then an relating to the flyover sound propagation extrapolation of the sensitivity curve is per- paths shown in Figure H2 as follows: mitted if data cover at least a range of 0.03 SPL( i ) = SPL( i ) + C [ a ( i ) ¥ a ( i ) ]AM + C a ( i ) r o o Mach units. The advancing blade tip Mach (AM ¥ AM ) + 20 log (AM/AM ) r r number must be computed using true air- where the lines AM and AM r are the meas- speed, onboard outside air temperature, and ured and reference level flyover sound propa- rotor speed. A separate PNLTM versus ad- gation paths, respectively.

vancing blade tip Mach number function (ii) The remainder of the procedure is the must be derived for each of the three certifi- same for the flyover condition as that pre- cation microphone locations, i.e. , centerline, scribed in the paragraph (f)(1)(ii) of this sec- sideline left, and sideline right. Sideline left tion regarding takeoff flight path.

and right are defined relative to the direc- (3) Approach flight path. (i) The procedure tion of flight for each run. PNLTM adjust- described in paragraph (f)(1) of this section ments are to be applied to each microphone for takeoff paths is also used for the ap- datum using the appropriate PNLTM func- proach paths, with the values of SPL( i ) re- r tion.

lating to the approach sound propagation (f) PNLT corrections. If the measured ambi- paths shown in Figure H3 as follows: ent atmospheric conditions of temperature SPL( i ) = SPL( i ) + C [ a ( i ) ¥ a ( i ) ]AN + C a ( i ) and relative humidity differ from those pre- r o o (AN ¥ AN ) + 20 log (AN/AN ) scribed as reference conditions under this ap- r r pendix (77 degrees F and 70 percent, respec- where the lines AN and AN are the measured r tively), corrections to the EPNL values must and reference approach sound propagation be calculated from the measured data under paths, respectively.

paragraph (a) of this section as follows: (ii) The remainder of the procedure is the (1) Takeoff flight path. For the takeoff same for the approach condition as that pre- flight path shown in Figure H1, the spectrum scribed in the paragraph (f)(1)(ii) of this sec- of PNLTM observed at station A for the air- tion regarding takeoff flight path.

craft at position L is decomposed into its in- (4) Sideline microphones. (i) The procedure dividual SPL( i ) values. prescribed in paragraph (f)(1) of this section (i) Step 1. A set of corrected values are for takeoff paths is also used for the propa- then computed as follows: gation to the sideline locations, with the val- ues of SPL( i ) relating as follows to the r SPL( i ) = SPL( i ) + C [ a ( i ) ¥ a ( i ) ]AL + C a ( i ) r o o measured sideline sound propagation path (AL ¥ AL ) + 20 log (AL/AL ) r r shown in Figure H3 as follows: where SPL( i ) and SPL( i ) are the measured r SPL( i ) = SPL( i ) + C [ a ( i ) ¥ a ( i ) ]SX + C a ( i ) r o o and corrected sound pressure levels, respec- (SX ¥ SX ) + 20 log (SX/SX ) r r tively, in the i -th one-third octave band. The first correction term adjusts for the effect of where S is the sideline measuring station change in atmospheric sound absorption and, based upon the flight condition, the hel- where a ( i ) and a ( i ) are the sound attenuation icopter positions, X and X , correspond to: o r

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. H

X = L, and X = L for takeoff tern, variable from one helicopter type to r r X = M, and X = M for flyover another, the propagation angle q shall be the r r X = N, and X r = N r for approach same for test and reference flight paths. The elevation angle y shall not be constrained (ii) The remainder of the procedure is the but must be determined and reported. The same for the sideline paths as that pre- certification authority shall specify the ac- scribed in the paragraph (f)(1)(ii) of this sec- ceptable limitations on y . Corrections to tion regarding takeoff flight paths.

data obtained when these limits are exceeded (g) Duration corrections. (1) If the measured shall be applied using FAA approved proce- takeoff and approach flight paths do not con- dures.

form to those prescribed as the corrected and reference flight paths, respectively, under PART D — NOISE LIMITS UNDER § 36.805 section A36.5(d)(2) it will be necessary to apply duration corrections to the EPNL val- Section H36.301 Noise measurement, evaluation, ues calculated from the measured data. Such and calculation.

corrections must be calculated as follows: Compliance with this part of this appendix (i) Takeoff flight path. For the takeoff path must be shown with noise levels measured, shown in Figure H1, the correction term is evaluated, and calculated as prescribed calculated using the formula— under Parts B and C of this appendix.

D = ¥ 7.5 log (AL/AL ) + 10 log (V/V ) 2 r r Section H36.303 [Reserved] which represents the correction that must be added algebraically to the EPNL calculated Section H36.305 Noise levels.

from the measured data. The lengths AL and AL r are the measured and reference takeoff (a) Limits. For compliance with this appen- distances from the noise measuring station dix, the applicant must show by flight test A to the measured and the reference takeoff that the calculated noise levels of the heli- paths, respectively. A negative sign indicates copter, at the measuring points described in that, for the particular case of a duration section H36.305(a) of this appendix, do not ex- correction, the EPNL calculated from the ceed the following, (with appropriate inter- measured data must be reduced if the meas- polation between weights): ured takeoff path is at greater altitude than (1) Stage 1 noise limits for acoustical the reference takeoff path. changes for helicopters are as follows: (ii) Level flyover flight paths. For the level (i) For takeoff, flyover, and approach cal- flyover flight path, the correction term is culated noise levels, the noise levels of each calculated using the formula— Stage 1 helicopter that exceed the Stage 2 noise limits plus 2 EPNdB may not, after a D = ¥ 7.5 log (AM/AM ) + 10 log (V/V ) 2 r r change in type design, exceed the noise lev- where AM is the measured flyover distance els created prior to the change in type de- from the noise measuring station A to the sign.

measured flyover path, and AM is the ref- r (ii) For takeoff, flyover, and approach cal- erence distance from station A to the ref- culated noise levels, the noise levels of each erence flyover path.

Stage 1 helicopter that do not exceed the (iii) Approach flight path. For the approach Stage 2 noise limits plus 2 EPNdB may not, path shown in Figure H3, the correction after the change in type design, exceed the term is calculated using the formula— Stage 2 noise limits plus 2 EPNdB.

D = ¥ 7.5 log (AN/AN ) + 10 log (V/V ) 2 r r (2) Stage 2 noise limits are as follows: where AN is the measured approach distance (i) For takeoff calculated noise levels —109 from the noise measuring station A to the EPNdB for maximum takeoff weights of measured approach path, and AN is the ref- 176,370 pounds (80,000 kg) or more, reduced by r erence distance from station A to the ref- 3.01 EPNdB per halving of the weight down erence approach path. to 89 EPNdB, after which the limit is con- (iv) Sideline microphones. For the sideline stant.

flight path, the correction term is calculated (ii) For flyover calculated noise levels —108 using the formula— EPNdB for maximum weights of 176,370 pounds (80,000 kg) or more, reduced by 3.01 = ¥ 7.5 log (SX/SX ) + 10 log (V/V ) D 2 r r EPNdB per halving of the weight down to 88 where S is the sideline measuring station EPNdB, after which the limit is constant.

and based upon the flight condition, the heli- (iii) For approach calculated noise levels —110 copter positions, X and X , correspond to: r EPNdB for maximum weights of 176,370 X = L, and X = L for takeoff r r pounds (80,000 kg) or more, reduced by 3.01 X = M, and X = M for flyover r r EPNdB per halving of the weight down to 90 X = N, and X = N for approach r r EPNdB, after which the limit is constant.

(2) The adjustment procedure described in (3) Stage 3 noise limits are as follows: this section shall apply to the sideline (i) For takeoff—For a helicopter having a microphones in the take-off, overflight, and maximum certificated takeoff weight of approach cases. Although the noise emission 176,370 pounds (80,000 kg) or more, the noise is strongly dependent on the directivity pat- limit is 106 EPNdB, which decreases linearly

Federal Aviation Administration, DOT Pt. 36, App. J

with the logarithm of the helicopter weight J36.109 Measurement of helicopter noise received (mass) at a rate of 3.0 EPNdB per halving of on the ground.

the weight (mass) down to 86 EPNdB, after J36.111 Reporting requirements.

which the limit is constant. J36.113 [Reserved] (ii) For flyover—For a helicopter having a PART C — NOISE EVALUATION AND CALCULATION maximum certificated takeoff weight of UNDER § 36.803 176,370 pounds (80,000 kg) or more, the noise limit is 104 EPNdB, which decreases linearly J36.201 Noise evaluation in SEL.

with the logarithm of the helicopter weight J36.203 Calculation of noise levels.

(mass) at a rate of 3.0 EPNdB per halving of J36.205 Detailed data correction procedures.

the weight (mass) down to 84 EPNdB, after PART D — NOISE LIMITS PROCEDURE UNDER which the limit is constant.

(iii) For approach—For a helicopter having § 36.805 a maximum certificated takeoff weight of J36.301 Noise measurement, evaluation, and cal- 176,370 pounds (80,000 kg) or more, the noise culation.

limit is 109 EPNdB, which decreases linearly J36.303 [Reserved] with the logarithm of the helicopter weight J36.305 Noise limits.

(mass) at a rate of 3.0 EPNdB per halving of the weight (mass) down to 89 EPNdB, after PART A — REFERENCE CONDITIONS which the limit is constant.

Section J36.1 General.

(b) Tradeoffs. Except to the extent limited under § 36.11(b) of this part, the noise limits This appendix prescribes the alternative prescribed in paragraph (a) of this section noise certification requirements identified may be exceeded by one or two of the take- under § 36.1 of this part and subpart H of this off, flyover, or approach calculated noise lev- part for helicopters in the primary, normal, els determined under section H36.203 of this transport, and restricted categories having appendix if maximum certificated takeoff weight of not (1) The sum of the exceedances is not more than 7,000 pounds including: greater than 4 EPNdB; (a) The conditions under which an alter- (2) No exceedance is greater than 3 EPNdB; native noise certification test under subpart and H of this part must be conducted and the al- (3) The exceedances are completely offset ternative measurement procedure that must by reduction in the other required calculated be used under § 36.801 of this part to measure noise levels.

the helicopter noise during the test; [Amdt. 36–14, 53 FR 3541, Feb. 5, 1988; 53 FR (b) The alternative procedures which must 4099, Feb. 11, 1988; 53 FR 7728, Mar. 10, 1988, as be used under § 36.803 of this part to correct amended by Amdt. 36–54, 67 FR 45237, July 8, the measured data to the reference condi- 2002; Amdt. 36–25, 69 FR 31234, June 2, 2004; tions and to calculate the noise evaluation Amdt. 36–25, 69 FR 41573, July 9, 2004; Amdt. quantity designated as Sound Exposure 36–30, 79 FR 12045, Mar. 4, 2014; FAA Doc. No. Level (SEL); and FAA–2015–3782, Amdt. No. 36–31, 82 FR 46131, (c) The noise limits for which compliance Oct. 4, 2017] must be shown under § 36.805 of this part.

Section J36.3 Reference Test Conditions.

A PPENDIX I TO P ART 36 [R ESERVED ] (a) Meteorological conditions. The following A PPENDIX J TO P ART 36—A LTERNATIVE are the noise certification reference atmos- N OISE C ERTIFICATION P ROCEDURE pheric conditions which shall be assumed to FOR H ELICOPTERS U NDER S UBPART H exist from the surface to the helicopter alti- tude: H AVING A M AXIMUM C ERTIFICATED (1) Sea level pressure of 2116 pounds per T AKEOFF W EIGHT OF N OT M ORE square foot (76 centimeters mercury); T HAN 7,000 P OUNDS (2) Ambient temperature of 77 degrees Fahrenheit (25 degrees Celsius); PART A — REFERENCE CONDITIONS (3) Relative humidity of 70 percent; and Sec.

(4) Zero wind.

J36.1 General.

(b) Reference test site. The reference test J36.3 Reference Test Conditions.

site is flat and without line-of-sight obstruc- J36.5 [Reserved] tions across the flight path that encom- passes the 10 dB down points of the A-weight- PART B — NOISE MEASUREMENT PROCEDURE ed time history.

UNDER § 36.801 (c) Level flyover reference profile. The ref- erence flyover profile is a level flight, 492 J36.101 Noise certification test and measurement feet (150 meters) above ground level as meas- conditions.

J36.103 [Reserved] ured at the noise measuring station. The ref- J36.105 Flyover test conditions. erence flyover profile has a linear flight J36.107 [Reserved] track and passes directly over the noise

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. J

monitoring station. Airspeed is stabilized at (3) Wind velocity that does not exceed 10 0.9V ; 0.9V ; 0.45V + 65 kts (120 km/h); or knots (19 km/h) and a crosswind component H NE H 0.45V + 65 kts (120 km/h), whichever of the that does not exceed 5 knots (9 km/h). The NE four airspeeds is least, and maintained wind shall be determined using a continuous throughout the measured portion of the fly- averaging process of no greater than 30 sec- over. Rotor speed is stabilized at the max- onds; imum normal operating RPM throughout the (4) Measurements of ambient temperature, 10 dB-down time interval. relative humidity, wind speed, and wind di- is rection must be made between 4 feet (1.2 me- (1) For noise certification purposes, V H ters) and 33 feet (10 meters) above the defined as the airspeed in level flight ob- ground. Unless otherwise approved by the tained using the minimum specification en- FAA, ambient temperature and relative hu- gine power corresponding to maximum con- midity must be measured at the same height tinuous power available for sea level pres- above the ground.

sure of 2,116 psf (1,013.25 hPa) at 77 ° F (25 ° C) ambient conditions at the relevant max- (5) No anomalous wind conditions (includ- imum certificated weight. The value of V H ing turbulence) or other anomalous meteoro- used for noise certification must be and V NE logical conditions that will significantly af- included in the Flight Manual. fect the noise level of the helicopter when (2) V is the never-exceed airspeed. the noise is recorded at the noise measuring NE (d) The weight of the helicopter shall be station; and the maximum takeoff weight at which noise (6) If the measurement site is within 6560 certification is requested. feet (2,000 meters) of a fixed meteorological station (such as those found at airports or Section J36.5 [Reserved] other facilities) the weather measurements reported for temperature, relative humidity P ART B—N OISE M EASUREMENT P ROCEDURE and wind velocity may be used, if approved U NDER § 36.801 by the FAA.

(d) Helicopter testing procedures. (1) The hel- Section J36.101 Noise certification test and icopter testing procedures and noise meas- measurement conditions.

urements must be conducted and processed (a) General. This section prescribes the con- in a manner which yields the noise evalua- ditions under which helicopter noise certifi- tion measure designated Sound Exposure cation tests must be conducted and the Level (SEL) as defined in section J36.109(b) measurement procedures that must be used of this appendix.

to measure helicopter noise during each test.

(2) The helicopter height relative to the (b) Test site requirements. (1) The noise noise measurement point sufficient to make measuring station must be surrounded by corrections required under section J36.205 of terrain having no excessive sound absorption this appendix must be determined by an characteristics, such as might be caused by FAA-approved method that is independent of thick, matted, or tall grass, shrubs, or wood- normal flight instrumentation, such as radar ed areas.

tracking, theodolite triangulation, laser (2) During the period when the flyover trajectography, or photographic scaling noise measurement is within 10 dB of the techniques.

maximum A-weighted sound level, no ob- (3) If an applicant demonstrates that the struction that significantly influences the design characteristics of the helicopter sound field from the helicopter may exist would prevent flight from being conducted in within a conical space above the noise meas- accordance with the reference test condi- uring position (the point on the ground tions prescribed under section J36.3 of this vertically below the microphone), the cone is appendix, then with FAA approval, the ref- defined by an axis normal to the ground and erence test conditions used under this appen- by half-angle 80 degrees from this axis. dix may vary from the standard reference (c) Weather restrictions. The test must be test conditions, but only to the extent de- conducted under the following atmospheric manded by those design characteristics conditions: which make compliance with the reference test conditions impossible.

(1) No rain or other precipitation; (2) Ambient air temperature between 36 de- Section J36.103 [Reserved] grees and 95 degrees Fahrenheit (2 degrees and 35 degrees Celsius), inclusively, and rel- Section J36.105 Flyover test conditions.

ative humidity between 20 percent and 95 percent inclusively, except that testing may (a) This section prescribes the flight test not take place where combinations of tem- conditions and allowable random deviations perature and relative humidity result in a for flyover noise tests conducted under this rate of atmospheric attenuation greater than appendix.

10 dB per 100 meters (30.5 dB per 1000 ft) in (b) A test series must consist of at least six the one-third octave band centered at 8 kilo- flights. The number of level flights made Hertz. with a headwind component must be equal to

Federal Aviation Administration, DOT Pt. 36, App. J

the number of level flights made with a tail- noise evaluation measurements required wind component over the noise measurement under this appendix. Paragraphs (c) and (d) station: of this section prescribe the required acous- (1) In level flight and in cruise configura- tical equipment specifications. Paragraphs tion; (e) and (f) of this section prescribe the cali- (2) At a height of 492 feet ± 50 feet (150 ± 15 bration and measurement procedures re- meters) above the ground level at the noise quired under this appendix.

measuring station; and (b) Noise unit definition. (1) The value of (3) Within ± 10 degrees from the zenith.

sound exposure level (SEL, or as denoted by (c) Each flyover noise test must be con- ), is defined as the level, in deci- symbol, L AE ducted: bels, of the time integral of squared ‘A’- (1) At the reference airspeed specified in ) over a given weighted sound pressure (P A section J36.3(c) of this appendix, with such time period or event, with reference to the airspeed adjusted as necessary to produce square of the standard reference sound pres- the same advancing blade tip Mach number ) of 20 micropascals and a reference sure (P O as associated with the reference conditions; duration of one second.

(i) Advancing blade tip Mach number (M ) AT (2) This unit is defined by the expression: is defined as the ratio of the arithmetic sum of blade tip rotational speed (V R ) and the ) over the speed

helicopter true air speed (V T P t t ⎛ ⎞ ( )

1 2

A

of sound (c) at 77 degrees Fahrenheit (1135.6 L Log dt dB = 10

AE 10

⎜ ⎟ ∫

t

ft/sec or 346.13 m/sec) such that M = (V + T P ⎝ ⎠ 1

AT R 0 0 V )/c; and T Where T is the reference integration time of O (ii) The airspeed shall not vary from the -t ) is the integration one second and (t 2 1 adjusted reference airspeed by more than ± 3 time interval.

knots ( ± 5 km/hr) or an equivalent FAA-ap- proved variation from the reference advanc- (3) The integral equation of paragraph ing blade tip Mach number. The adjusted ref- (b)(2) of this section can also be expressed as: erence airspeed shall be maintained through-

out the measured portion of the flyover. t 1

L t 0 1 . ( ) A

(2) At rotor speed stabilized at the power L Log dt dB = 10 10

AE ∫ 10

t on maximum normal operating rotor RPM 1

T

( ± 1 percent); and Where L (t) is the time varying A-weighted A (3) With the power stabilized during the pe- sound level.

riod when the measured helicopter noise level is within 10 dB of the maximum A- (4) The integration time (t -t ) in practice 2 1 weighted sound level (L ).

AMAX shall not be less than the time interval dur- (d) The helicopter test weight for each fly- ing which L (t) first rises to within 10 dB(A) A over test must be within plus 5 percent or of its maximum value (L ) and last falls AMAX minus 10 percent of the maximum takeoff below 10 dB(A) of its maximum value.

weight for which certification under this (5) The SEL may be approximated by the part is requested.

following expression: (e) The requirements of paragraph (b)(2) of L = L + <delta>A AE AMAX this section notwithstanding, flyovers at an where <delta>A is the duration allowance FAA-approved lower height may be used and given by: the results adjusted to the reference meas- urement point by an FAA-approved method <delta>A = 10 log (T) if the ambient noise in the test area, meas- where T = (t -t )/2 and L is defined as the 2 1 AMAX ured in accordance with the requirements maximum level, in decibels, of the A- prescribed in section J36.109 of this appendix, weighted sound pressure (slow response) is found to be within 15 dB(A) of the max- with reference to the square of the stand- imum A-weighted helicopter noise level ard reference sound pressure (P ).

(L ) measured at the noise measurement AMAX (c) Measurement system. The acoustical station in accordance with section J36.109 of measurement system must consist of FAA- this appendix.

approved equipment equivalent to the fol- Section J36.107 [Reserved] lowing: (1) A microphone system with frequency Section J36.109 Measurement of helicopter noise response that is compatible with the meas- received on the ground.

urement and analysis system accuracy pre- scribed in paragraph (d) of this section; (a) General. (1) The helicopter noise meas- ured under this appendix for noise certifi- (2) Tripods or similar microphone mount- cation purposes must be obtained with FAA- ings that minimize interference with the approved acoustical equipment and measure- sound energy being measured; ment practices. (3) Recording and reproducing equipment (2) Paragraph (b) of this section identifies with characteristics, frequency response, and and prescribes the specifications for the dynamic range that are compatible with the

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. J

response and accuracy requirements of para- (2) If the helicopter acoustic signal is di- graph (d) of this section; and rectly measured by an integrating sound (4) The calibration and checking of meas- level meter: urement systems must use the procedures (i) The overall sensitivity of the measuring described in Section A36.3.9. system shall be checked before and after the series of flyover tests and at intervals (not (d) Sensing, recording, and reproducing exceeding one-hour duration) during the fly- equipment. (1) The noise levels measured from over tests using an acoustic calibrator using helicopter flyovers under this appendix may sine wave noise generating a known sound be determined directly by an integrating pressure level at a known frequency.

sound level meter, or the A-weighted sound (ii) The performance of equipment in the level time history may be written onto a system will be considered satisfactory if, graphic level recorder set at ‘‘slow’’ response during each day’s testing, the variation in from which the SEL value may be deter- the calibration value does not exceed 0.5 dB.

mined. With the approval of the FAA, the The SEL data collected during the flyover noise signal may be tape recorded for subse- tests shall be adjusted to account for any quent analysis.

variation in the calibration value.

(i) The SEL values from each flyover test (iii) A performance calibration analysis of may be directly determined from an inte- each piece of calibration equipment, includ- grating sound level meter complying with ing acoustic calibrators, reference micro- the standards of IEC 804 (Incorporated by ref- phones, and voltage insertion devices, must erence, see § 36.6) for a Type 1 instrument set have been made during the six calendar at ‘‘slow’’ response.

months proceeding the beginning of the heli- (ii) The acoustic signal from the heli- copter flyover series. Each calibration shall copter, along with the calibration signals be traceable to the National Institute of specified under paragraph (e) of this section Standards and Technology.

and the background noise signal required (f) Noise measurement procedures. (1) The under paragraph (f) of this section, may be microphone shall be of the pressure-sensitive recorded on a magnetic tape recorder for capacitive type designed for nearly uniform subsequent analysis for an integrating sound grazing incidence response. The microphone level meter identified in paragraph (d)(1)(i) shall be mounted with the center of the sens- of this section. The record/playback system ing element 4 feet (1.2 meters) above the (including the audio tape) of the tape re- local ground surface and shall be oriented for corder must conform to the requirements grazing incidence such that the sensing ele- prescribed in section A36.3.6 of appendix A to ment, the diaphragm, is substantially in the this part. The tape recorder shall comply plane defined by the nominal flight path of with the specifications of IEC 561 (Incor- the helicopter and the noise measurement porated by reference, see § 36.6).

station.

(iii) The characteristics of the complete (2) If a tape recorder is used, the frequency system shall comply with the recommenda- response of the electrical system must be de- tions given in IEC 651 (Incorporated by ref- termined at a level within 10 dB of the full- erence, see § 36.6) with regard to the speci- scale reading used during the test, utilizing fications concerning microphone, amplifier, pink or pseudorandom noise.

and indicating instrument characteristics.

(3) The ambient noise, including both (iv) The response of the complete system acoustical background and electrical noise of to a sensibly plane progressive wave of con- the measurement systems shall be deter- stant amplitude shall lie within the toler- mined in the test area and the system gain ance limits specified in Table IV and Table V set at levels which will be used for helicopter for Type 1 instruments in IEC 651 for noise measurements. If helicopter sound lev- weighting curve ‘‘A’’ over the frequency els do not exceed the background sound lev- range of 45 Hz to 11500 Hz.

els by at least 15 dB(A), flyovers at an FAA- (2) [Reserved] approved lower height may be used and the (v) A windscreen must be used with the results adjusted to the reference measure- microphone during each measurement of the ment point by an FAA-approved method.

helicopter flyover noise. Correction for any (4) If an integrating sound level meter is insertion loss produced by the windscreen, as used to measure the helicopter noise, the in- a function of the frequency of the acoustic strument operator shall monitor the contin- calibration required under paragraph (e) of uous A-weighted (slow response) noise levels this section, must be applied to the meas- throughout each flyover to ensure that the ured data and any correction applied must be SEL integration process includes, at min- reported. imum, all of the noise signal between the (e) Calibrations. (1) If the helicopter acous- maximum A-weighted sound level (L ) AMAX tic signal is tape recorded for subsequent and the 10 dB down points in the flyover analysis, the measuring system and compo- time history. The instrument operator shall nents of the recording system must be cali- note the actual db(A) levels at the start and brated as prescribed under section A36.3.6 of stop of the SEL integration interval and doc- appendix A of this part. ument these levels along with the value of

Federal Aviation Administration, DOT Pt. 36, App. J

L and the integration interval (in sec- (6) Helicopter position and performance AMAX onds) for inclusion in the noise data sub- data required to make the adjustments pre- mitted as part of the reporting requirements scribed under section J36.205 of this appendix under section J36.111(b) of this appendix. and to demonstrate compliance with the per- formance and position restrictions pre- Section J36.111 Reporting Requirements.

scribed under section J36.105 of this appendix must be recorded at an FAA-approved sam- (a) General. Data representing physical pling rate.

measurements, and corrections to measured data, including corrections to measurements Section J36.113 [Reserved] for equipment response deviations, must be recorded in permanent form and appended to P ART C—N OISE E VALUATION AND the record. Each correction is subject to C ALCULATIONS U NDER § 36.803 FAA approval.

Section J36.201 Noise Evaluation in SEL.

(b) Data reporting. After the completion of the test the following data must be included The noise evaluation measure shall be the in the test report furnished to the FAA: sound exposure level (SEL) in units of dB(A) (1) Measured and corrected sound levels ob- as prescribed under section J36.109(b) of this tained with equipment conforming to the appendix. The SEL value for each flyover standards prescribed in section J36.109 of this may be directly determined by use of an in- appendix; tegrating sound level meter. Specifications (2) The type of equipment used for meas- for the integrating sound level meter and re- urement and analysis of all acoustic, aircraft quirements governing the use of such instru- performance and flight path, and meteoro- mentation are prescribed under section logical data; J36.109 of this appendix.

(3) The atmospheric environmental data Section J36.203 Calculation of Noise Levels.

required to demonstrate compliance with this appendix, measured throughout the test (a) To demonstrate compliance with the period; noise level limits specified under section (4) Conditions of local topography, ground J36.305 of this appendix, the SEL noise levels cover, or events which may interfere with from each valid flyover, corrected as nec- the sound recording; essary to reference conditions under section (5) The following helicopter information: J36.205 of this appendix, must be (i) Type, model, and serial numbers, if any, arithmetically averaged to obtain a single of helicopter, engine(s) and rotor(s); SEL dB(A) mean value for the flyover series.

(ii) Gross dimensions of helicopter, loca- No individual flyover run may be omitted tion of engines, rotors, type of antitorque from the averaging process, unless otherwise system, number of blades for each rotor, and specified or approved by the FAA.

reference operating conditions for each en- (b) The minimum sample size acceptable gine and rotor; for the helicopter flyover certification meas- (iii) Any modifications of non-standard urements is six. The number of samples must equipment likely to affect the noise charac- be large enough to establish statistically a 90 teristics of the helicopter; percent confidence limit that does not ex- (iv) Maximum takeoff weight for which ceed ± 1.5 dB(A).

certification under this appendix is re- (c) All data used and calculations per- quested; formed under this section, including the cal- (v) Aircraft configuration, including land- culated 90 percent confidence limits, must be ing gear positions; documented and provided under the report- (vi) V or V (whichever is less) and the ing requirements of section J36.111 of this H NE adjusted reference airspeed; appendix.

(vii) Aircraft gross weight for each test Section J36.205 Detailed Data Correction run; Procedures.

(viii) Indicated and true airspeed for each test run; (a) When certification test conditions (ix) Ground speed, if measured, for each measured under part B of this appendix differ run; from the reference test conditions prescribed (x) Helicopter engine performance as deter- under section J36.3 of this appendix, appro- mined from aircraft instruments and manu- priate adjustments shall be made to the facturer’s data; and measured noise data in accordance with the (xi) Aircraft flight path above ground methods set out in paragraphs (b) and (c) of level, referenced to the elevation of the noise this section. At minimum, appropriate ad- measurement station, in feet, determined by justments shall be made for off-reference al- an FAA-approved method which is inde- titude and for the difference between ref- pendent of normal flight instrumentation, erence airspeed and adjusted reference air- such as radar tracking, theodolite triangula- speed.

tion, laser trajectography, or photoscaling (b) The adjustment for off-reference alti- techniques; and tude may be approximated from:

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. K

<delta>J = 12.5 log (H /492) dB; not exceed the following (with appropriate 1 10 T interpolation between weights): where <delta>J is the quantity in decibels (a) For primary, normal, transport, and re- that must be algebraically added to the stricted category helicopters having a max- measured SEL noise level to correct for imum certificated takeoff weight of not is the an off-reference flight path, H T more than 7,000 pounds that are noise tested height, in feet, of the test helicopter under this appendix: when directly over the noise measure- (1) Stage 2 noise limit is constant at 82 ment point, and the constant (12.5) ac- decibels SEL for helicopters up to 1,737 counts for the effects on spherical pounds (787 kg) maximum certificated take- spreading and duration from the off-ref- off weight (mass) and increases linearly with erence altitude.

the logarithm of the helicopter weight at a (c) The adjustment for the difference be- rate of 3.0 decibels SEL per the doubling of tween reference airspeed and adjusted ref- weight thereafter. The limit may be cal- erence airspeed is calculated from: culated by the equation: <delta>J = 10 log (V /V ) dB; 3 10 RA R L (limit) = 82 + 3.0 [log (MTOW/1737)/ AE 10 Where <delta>J is the quantity in decibels log (2)] dB, that must be algebraically added to the where MTOW is the maximum takeoff measured SEL noise level to correct for weight, in pounds, for which certification the influence of the adjustment of the under this appendix is requested.

reference airspeed on the duration of the (2) Stage 3 noise limit is constant at 82 measured flyover event as perceived at decibels SEL for helicopters up to 3,125 is the the noise measurement station, V R pounds (1,417 kg) maximum certificated reference airspeed as prescribed under takeoff weight (mass) and increases linearly section J36.3.(c) of this appendix, and V RA with the logarithm of the helicopter weight is the adjusted reference airspeed as pre- at a rate of 3.0 decibels SEL per the doubling scribed under section J36.105(c) of this of weight thereafter. The limit may be cal- appendix.

culated using the equation: (d) No correction for source noise during L AE (limit) = 82 + 3.0 [log10(MTOW/3125)/ the flyover other than the variation of log10(2)] dB, source noise accounted for by the adjust- where MTOW is the maximum takeoff ment of the reference airspeed prescribed for under section J36.105(c) of this appendix need weight, in pounds.

be applied.

(b) The procedures required in this amend- (e) No correction for the difference be- ment shall be done in accordance with the tween the reference ground speed and the ac- International Electrotechnical Commission tual ground speed need be applied.

IEC Publication No. 804, entitled ‘‘Inte- (f) No correction for off-reference atmos- grating-averaging Sound Level Meters,’’ pheric attenuation need be applied.

First Edition, dated 1985. This incorporation (g) The SEL adjustments must be less than by reference was approved by the Director of 2.0 dB(A) for differences between test and ref- the Federal Register in accordance with 5 erence flight procedures prescribed under U.S.C. 552(a) and 1 CFR part 51. Copies may section J36.105 of this appendix unless a larg- be obtained from the Bureau Central de la er adjustment value is approved by the FAA.

Commission Electrotechnique Inter- (h) All data used and calculations per- nationale, 1, rue de Varembe, Geneva, Swit- formed under this section must be docu- zerland or the American National Standard mented and provided under the reporting re- Institute, 1430 Broadway, New York City, quirements specified under section J36.111 of New York 10018, or at the National Archives this appendix.

and Records Administration (NARA). For in- formation on the availability of this mate- P ART D—N OISE L IMITS P ROCEDURE U NDER rial at NARA, call 202–741–6030, or go to: § 36.805 http://www.archives.gov/federal _ register/ Section J36.301 Noise Measurement, Evaluation, code _ of _ federal _ regulations/ibr _ locations.html.

and Calculation.

[Doc. No. 26910, 57 FR 42855, Sept. 16, 1992, as amended by Amdt. 36–20, 57 FR 46243, Oct. 7, Compliance with this part of this appendix 1992; 69 FR 18803, Apr. 9, 2004; Amdt. 36–25, 69 must be shown with noise levels measured, FR 31234, June 2, 2004; Amdt. 36–30, 79 FR evaluated, and calculated as prescribed 12045, Mar. 4, 2014; FAA Doc. No. FAA–2015– under parts B and C of this appendix.

3782, Amdt. No. 36–31, 82 FR 46131, Oct. 4, Section J36.303 [Reserved] 2017] Section J36.305 Noise Limits.

A PPENDIX K TO P ART 36—N OISE R E- For compliance with this appendix, the QUIREMENTS FOR T ILTROTORS U NDER calculated noise levels of the helicopter, at S UBPART K the measuring point described in section J36.101 of this appendix, must be shown to K1 General

Federal Aviation Administration, DOT Pt. 36, App. K

K2 Noise Evaluation Measure Section K3 Noise Measurement Reference Points K3 Noise Measurement Reference Points The following noise reference points must K4 Noise Limits be used when demonstrating tiltrotor com- K5 Trade-offs pliance with section K6 (Noise Certification K6 Noise Certification Reference Procedures Reference Procedures) and section K7 (Test K7 Test Procedures Procedures) of this appendix: (a) Takeoff reference noise measurement Section K1 General points — As shown in Figure K1 below: This appendix prescribes noise limits and (1) The centerline noise measurement procedures for measuring noise and adjusting flight path reference point, designated A, is the data to standard conditions for tiltrotors located on the ground vertically below the as specified in § 36.1 of this part.

reference takeoff flight path. The measure- ment point is located 1,640 feet (500 m) in the Section K2 Noise Evaluation Measure horizontal direction of flight from the point The noise evaluation measure is the effec- Cr where transition to climbing flight is ini- tiated, as described in section K6.2 of this ap- tive perceived noise level in EPNdB, to be pendix; calculated in accordance with section A36.4 (2) Two sideline noise measurement points, of Appendix A to this part, except correc- designated as S(starboard) and S(port), are tions for spectral irregularities must be de- located on the ground perpendicular to and termined using the 50 Hz sound pressure symmetrically stationed at 492 feet (150 m) level found in section H36.201 of Appendix H on each side of the takeoff reference flight to this part.

path. The measurement points bisect the centerline flight path reference point A.

(b) Flyover reference noise measurement located on the ground 492 feet (150 m) points — vertically below the reference flyover flight As shown in Figure K2 below: path. The measurement point is defined by (1) The centerline noise measurement the flyover reference procedure in section flight path reference point, designated A, is K6.3 of this appendix;

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. K

(2) Two sideline noise measurement points, flight path. The measurement point is de- designated as S , are located on the fined by the approach reference procedure in ( sideline ) ground perpendicular to and symmetrically section K6.4 of this appendix. On level stationed at 492 feet (150 m) on each side of ground, the measurement point corresponds the flyover reference flight path. The meas- to a position 3,740 feet (1,140 m) from the urement points bisect the centerline flight intersection of the 6.0 degree approach path path reference point A. with the ground plane; (c) Approach reference noise measurement (2) Two sideline noise measurement points, points — designated as S(starboard) and S(port), are As shown in Figure K3 below: located on the ground perpendicular to and (1) The centerline noise measurement symmetrically stationed at 492 feet (150 m) flight path reference point, designated A, is on each side of the approach reference flight located on the ground 394 feet (120 m) path. The measurement points bisect the vertically below the reference approach centerline flight path reference point A.

Federal Aviation Administration, DOT Pt. 36, App. K

Section K4 Noise Limits takeoff weight (mass) of 176,370 pounds (80,000 kg) or more, in VTOL/Conversion For a tiltrotor, the maximum noise levels, mode, 108 EPNdB, decreasing linearly with as determined in accordance with the noise the logarithm of the tiltrotor weight (mass) evaluation in EPNdB and calculation method at a rate of 3.0 EPNdB per halving of weight described in section H36.201 of Appendix H of (mass) down to 88 EPNdB, after which the this part, must not exceed the noise limits as limit is constant. Figure K4 illustrates the follows: (a) At the takeoff flight path reference point: flyover noise limit as a dashed line.

For a tiltrotor having a maximum certifi- (c) At the approach flight path reference cated takeoff weight (mass) of 176,370 pounds point: For a tiltrotor having a maximum cer- (80,000 kg) or more, in VTOL/Conversion tificated takeoff weight (mass) of 176,370 mode, 109 EPNdB, decreasing linearly with pounds (80,000 kg) or more, in VTOL/Conver- the logarithm of the tiltrotor weight (mass) sion mode, 110 EPNdB, decreasing linearly at a rate of 3.0 EPNdB per halving of weight with the logarithm of the tiltrotors weight (mass) down to 89 EPNdB, after which the (mass) at a rate of 3.0 EPNdB per halving of limit is constant. Figure K4 illustrates the weight (mass) down to 90 EPNdB, after which takeoff noise limit as a solid line.

the limit is constant. Figure K4 illustrates (b) At the Flyover path reference point: For a the approach noise limit as a dash-dot line.

tiltrotor having a maximum certificated

14 CFR Ch. I (1–1–25 Edition) Pt. 36, App. K

Section K5 Trade-Offs this appendix, except as specified in section K6.1(d) of this appendix.

If the noise evaluation measurement ex- (d) If the design characteristics of the ceeds the noise limits described in K4 of this tiltrotor prevent test flights from being con- appendix at one or two measurement points: ducted in accordance with section K6.2, K6.3 (a) The sum of excesses must not be great- or K6.4 of this appendix, the applicant must er than 4 EPNdB; revise the test procedures and resubmit the (b) The excess at any single point must not procedures for approval.

be greater than 3 EPNdB; and (e) The following reference atmospheric (c) Any excess must be offset by the re- conditions must be used to establish the ref- maining noise margin at the other point or erence procedures: points.

(1) Sea level atmospheric pressure of 2,116 pounds per square foot (1,013.25 hPa); Section K6 Noise Certification Reference (2) Ambient air temperature of 77 Procedures ° Fahrenheit (25 ° Celsius, i.e. ISA + 10 ° C); K6.1 General Conditions (3) Relative humidity of 70 percent; and (a)–(b) [Reserved] (4) Zero wind.

(c) The takeoff, flyover and approach ref- (f) For tests conducted in accordance with erence procedures must be established in ac- sections K6.2, K6.3, and K6.4 of this appendix, cordance with sections K6.2, K6.3 and K6.4 of use the maximum normal operating RPM

Federal Aviation Administration, DOT Pt. 36, App. K

corresponding to the airworthiness limit im- (3) The rotor speed must be stabilized at posed by the manufacturer. For configura- the maximum normal operating RPM certifi- tions for which the rotor speed automati- cated for level flight.

cally links with the flight condition, use the K6.4 Approach Reference Procedure. The ap- maximum normal operating rotor speed cor- proach reference procedure is as follows: (a) The tiltrotor must be stabilized to fol- responding with the reference flight condi- low a 6.0 degree approach path; tion. For configurations for which the rotor (b) An approved airworthiness configura- speed can change by pilot action, use the tion in which maximum noise occurs must be highest normal rotor speed specified in the maintained; flight manual limitation section for the ref- (1) An airspeed equal to the best rate of erence conditions.

climb speed corresponding to the nacelle K6.2 Takeoff Reference Procedure. The take- angle, or the lowest approved airspeed for off reference flight procedure is as follows: the approach, whichever is greater, must be (a) A constant takeoff configuration must stabilized and maintained; and be maintained, including the nacelle angle (2) The tiltrotor power during the approach selected by the applicant; must be stabilized over the flight path ref- (b) The tiltrotor power must be stabilized erence point, and continue as if landing; at the maximum takeoff power cor- (c) The rotor speed must be stabilized at responding to the minimum installed en- the maximum normal operating RPM certifi- gine(s) specification power available for the cated for approach; reference ambient conditions or gearbox (d) The constant approach configuration torque limit, whichever is lower. The used in airworthiness certification tests, tiltrotor power must also be stabilized along with the landing gear extended, must be a path starting from a point located 1,640 maintained; and feet (500 m) before the flight path reference (e) The weight (mass) of the tiltrotor at point, at 65 ft (20 m) above ground level; landing must be the maximum landing (c) The nacelle angle and the cor- weight (mass) as requested for noise certifi- responding best rate of climb speed, or the cation.

lowest approved speed for the climb after Section K7 Test Procedures takeoff, whichever is the greater, must be maintained throughout the takeoff reference K7.1 [Reserved] procedure; K7.2 The test procedures and noise meas- (d) The rotor speed must be stabilized at urements must be conducted and processed the maximum normal operating RPM certifi- to yield the noise evaluation measure des- cated for takeoff; ignated in section K2 of this appendix.

(e) The weight (mass) of the tiltrotors K7.3 If either the test conditions or test must be the maximum takeoff weight (mass) procedures do not comply to the applicable as requested for noise certification; and noise certification reference conditions or procedures prescribed by this part, the appli- (f) The reference takeoff flight profile is a cant must apply the correction methods de- straight line segment inclined from the scribed in section H36.205 of Appendix H of starting point 1,640 feet (500 m) before to the this part to the acoustic test data measured.

center noise measurement point and 65 ft (20 K7.4 Adjustments for differences between m) above ground level at an angle defined by test and reference flight procedures must not best rate of climb and the speed cor- exceed: responding to the selected nacelle angle and (a) For takeoff: 4.0 EPNdB, of which the for minimum specification engine perform- arithmetic sum of delta 1 and the term ¥ 7.5 ance.

log (QK/QrKr) from delta 2 must not in total K6.3 Flyover Reference Procedure. The fly- exceed 2.0 EPNdB; over reference flight procedure is as follows: (b) For flyover or approach: 2.0 EPNdB.

(a) The tiltrotor must be stabilized for K7.5 The average rotor RPM must not vary level flight along the centerline flyover from the normal maximum operating RPM flight path and over the noise measurement by more than ± 1.0 percent throughout the 10 reference point at an altitude of 492 ft (150 m) dB-down time interval.

above ground level; K7.6 The tiltrotor airspeed must not vary (b) A constant flyover configuration se- from the reference airspeed appropriate to lected by the applicant must be maintained; the flight demonstration by more than ± 5 kts (c) The weight (mass) of the tiltrotor must ( ± 9 km/h) throughout the 10 dB-down time be the maximum takeoff weight (mass) as re- interval.

quested for noise certification; K7.7 The number of level flyovers made (d) In the VTOL/Conversion mode: with a head wind component must be equal (1) The nacelle angle must be at the au- to the number of level flyovers made with a thorized fixed operation point that is closest tail wind component.

to the shallow nacelle angle certificated for K7.8 The tiltrotor must operate between zero airspeed; ± 10 degrees from the vertical or between ± 65 (2) The airspeed must be 0.9V and feet ( ± 20 m) lateral deviation tolerance, CON

14 CFR Ch. I (1–1–25 Edition) Pt. 38 whichever is greater, above the reference Subpart A—General track and throughout the 10 dB-down time interval.

§ 38.1 Applicability.

K7.9 The tiltrotor altitude must not vary (a) Except as provided in paragraph during each flyover by more than ± 30 ft ( ± 9 (c) of this section, an airplane that is m) from the reference altitude throughout subject to the requirements of 40 CFR the 10 dB-down time interval.

K7.10 During the approach procedure, the part 1030 may not exceed the fuel effi- tiltrotor must establish a stabilized constant ciency limits of this part when original speed approach and fly between approach an- type certification under this title is gles of 5.5 degrees and 6.5 degrees throughout sought. This part applies to the fol- the 10 dB-down time interval.

lowing airplanes: K7.11 During all test procedures, the (1) A subsonic jet airplane that has— tiltrotor weight (mass) must not be less than (i) Either— 90 percent and not more than 105 percent of (A) A type-certificated maximum the maximum certificated weight (mass).

passenger seating capacity of 20 seats For each of the test procedures, complete at or more; least one test at or above this maximum cer- (B) A maximum takeoff mass tificated weight (mass).

(MTOM) greater than 5,700 kg; and K7.12 A tiltrotor capable of carrying exter- nal loads or external equipment must be (C) An application for original type noise certificated without such loads or certification that is submitted on or equipment fitted after January 11, 2021; K7.13 The value of V used for noise cer- CON (ii) Or— tification must be included in the approved (A) A type-certificated maximum Flight Manual.

passenger seating capacity of 19 seats or fewer; [78 FR 1139, Jan. 8, 2013] (B) A MTOM greater than 60,000 kg; and PART 38—AIRPLANE FUEL (C) An application for original type EFFICIENCY CERTIFICATION certification that is submitted on or after January 11, 2021.

Subpart A—General (2) A subsonic jet airplane that has— (i) A type-certificated maximum pas- Sec.

senger seating capacity of 19 seats or 38.1 Applicability.

fewer; 38.3 Definitions.

(ii) A MTOM greater than 5,700 kg, 38.4 Compatibility with airworthiness re- but not greater than 60,000 kg; and quirements.

(iii) An application for original type 38.5 Exemptions.

certification that is submitted on or 38.7 Incorporation by reference.

after January 1, 2023.

38.9 Relationship to other regulations.

(3) A propeller-driven airplane that Subpart B—Determining Fuel Efficiency for has— Subsonic Airplanes (i) A MTOM greater than 8,618 kg; and 38.11 Fuel efficiency metric.

(ii) An application for original type 38.13 Specific air range.

certification that is submitted on or 38.15 Reference geometric factor.

after January 11, 2021.

38.17 Fuel efficiency limits.

(4) A subsonic jet airplane— 38.19 Change criteria.

(i) That is a modified version of an 38.21 Approval before compliance testing.

airplane whose type design was not cer- 38.23 Manual information and limitations.

tificated under this part; A PPENDIX A TO P ART 38—D ETERMINATION OF (ii) That has a MTOM greater than A IRPLANE F UEL E FFICIENCY M ETRIC 5,700 kg; V ALUE (iii) For which an application by the A UTHORITY : 42 U.S.C. 4321 et seq., 7572; 49 type certificate holder for a type de- U.S.C. 106(g), 40113, 44701–44702, 44704; 49 CFR sign change is submitted on or after 1.83(c) January 1, 2023; and (iv) For which the first certificate of S OURCE : Docket No. FAA–2022–0241, Amdt.

airworthiness is issued with the modi- No. 21–107, 89 FR 12654, Feb. 16, 2024, unless otherwise noted. fied type design.