United States (U.S.) National Aviation Standard for the Very High Frequency Omnidirectional Radio Range (VOR)/Distance Measuring Equipment (DME)/Tactical Air Navigation (TACAN) Systems

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AC N« 00-llA o.c 9/20/82 Avi&t1on Standard for the Ve...wy IU«;~h laltlatM ltJS MO-l i.O Frequency OMnldlreetlonal Radio knqe (\'t)Jtl/Diatanect Meaauring Equt.piM!\t (ONE) 1 Tactical Air Naviqation (TAC1N) Syat ...

1. PUlPOS!. Thi• Adviaory Circular i• iaa~ed to inform the aviation coaaun1ty of the eatabliah~Mnt and cont•nt of the United Statel (U. S.)

Kational Aviation Standard for the Very High Frequency C.nidirectional l.&dio kana• (\~1)/ Dietance M~aeurin& l~uipa•nt (OM!)/ Tactical Air Kaviaation (TAC".AN) Sye teal.

2. CAMC!LLATIOM. ~C OQ-31 entitled MU. s. National Aviation Standard tor the YOIUC Syatea dated 6/10/70 ia cancelled.

l. I!T!k!NC!. U. S. National Aviation Standard• are defined in Advi•ory Circvlar ~. 00-26.

4~ !A~CROUND. A Pu~lic Notice of Propoaed Standard for the aubject etandard vaa publlshed al Notice rR nac. 81-9128 in the ~al Reai•ter Volume 46, Nuab~r 58, dated M£rch 26, 1981. !hat notic~ stated that the federal Aviation Adainiatration (FAA) vaa conMiderina to update/aodify the exiatina Adviaory Circular oo-ll dated 6/10/70. Tbia propoted atandard wa• deecribed aa containinc change• in three aajor catecoriea: a) to form&t the docu-.nt to ... t current Department of !ran,portation (DOT)/ FAA 1tandarda: b) to reflect the preaeat operational characteriatica of the VOR/DH!/TACAM 1y1teaa and tu• expect•d perforaance of the Second Generation VORTAC and aolid atate equi~nt pro~ur-..ota; and c) to clarify area5 which were confusing in the previoua publi~•tioa by the addition of ••vera! appendices. The notice further atated that the FAA propoaed to adopt thiJ revi•ed 1tandard ~nd invited intere1ted peraoaa to auh.it written caameata aa they daaired.

All coaMnta received were evalu.ted in light of current •~1~ future need• of the ayatea and vith due to~i4eratioa conaiatent to the ~blic iatereet.

Thoae cumaenta con1ldered coaaistent vith the acop• and purpoae or th« atanGard vere accommodated to ths extent practic•ble. The 1tandard vaa approveJ by the Director. Syate .. ~ae4rch and Development Service. on September 2. 1~82. Tbie Adwi1ory Circular ia ieaued in accordance vith aa•ncy proce4ure for informing the public of the action by the Director, Syetema keae&rcb and Development Service.

At 00-31A

• 9/20/82 • 5. OESCRtPTION. Very Hfgh frequency Omnfdirectfonal Radfo Range (VOR)/ Distance ~asurfn9 EQuipment (DH£)/ Tactical Air Navfgatfon (TACAN) ts the pr1mlry short distance navigatt~n~l aid used in the National Airspace Syst~ (NAS) for atr navigation and trafffc control. Achte~ement of navtg&tton syste. perfonaance requtres the deftnttton of system functional and perfonaance rharactertsttcs. The purpose of publishing a National Avtatton St.~ndard ts to describe how t.he system ts operated and how the different elements ftt together. It should be noted that although the ten.s of aeasurement reference have b~n changed from Advisory Circular 00-31, dated 6/10/70, to allow sta~dardizatton, the effect on comp~nent and system perfo~ance ts •tnt~al.

It should be r~ogntzed that the frequency bands used by the systeas dtscr1bed in this standard have been exclusively alloc~ted for aviation navigation. Due to the lta1ted availability of frequencies, these bands will be 1ncre&s1ngly ut1l1z~d by common ~Quipment and other svst~s. For thi~ reason, designers, • anufacturers. and operators of VOR/OME/tACAN equipment should be especially conscious of those paragraphs in the standard which impact on spectrum uttlization. This is ~cessary to avoid present and future electromagnetic 1nterfer~r.ce not only between common tQuipments but also between other systems as well.

Attention 1s dr~wn to the fact t~at U. S. Nationa~ Aviation StandArds are not eQuipment specif;cations. nor are they standards pertaining to hardware, plannin9, prograrrning, ;nstallation, siting. avail4b1lity, reliabntty, or maintainability.

6. HOW TO OBTAIN THIS PUBLICATION. Additional copies of th1s circular may be obtained fr~ R-4~3.1 /J t/{1/ldtU ...

RWrfrt. II( !JAN

Director, Systems Research anrl Development Service, AR0-1 Enclosure Page I!

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9/20/82·.'

AC 00-31A CONTENTS CHAPTER 1 GENERAL SECTION 1. INTRODUCTION Paragraph Page 1. Purpose • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1 2. Distribution •••••••••••••.••••.•••••••••••••••.••••.•••• ..

3. Cancellation •••••••••••••.•••••••••••••••••.•••••••••••••• 1 4. Implementation Criteria .••••.••••.••••.••••• ..•••.•••••••• l 5. Directed Action .••••••••••••••••••••••.••••••.•••• ..•••••• * * * SECTION 2. OVERVIEW 7. The VOR/DNE/TACAN System Characteristics •• ..•.••••.••••••• 1 9. Reliability Required of the VOR/DME/TACAN System ••• ....••• 2

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CHAPTER 2. VOR/DME/TACAN SYSTEM 20. VOR/DME/TACAN System Description .• ..••••......•...••••..• 3 21. Ground Components •• ..•••..•••••••••••••••••.••••••••••••• 3 22. Station Type Designations ·············~·················· 3 23. Service Volumes •••.•••.••.••••••••••••.•••••••••••••••••• 3

24. Associated Components ····•c······························ 5

25. Collocation Limits for Associated Components •••••••.••••. 5 26. Radio Frequency Allocations •••••••••.••.••••••••••••••••• 8 27. Radio Frequency Assignments •••••••••••••••••••••••••••••• 8 28. Radio Frequency Channel Pairing ..•.•.••••..••••.••••.•.•• 8 29. Frequency Interference Protection .•• ..•••••••••.•••.••••• 8 30. Component Identification Signals ..•....••.••..•••.•..•.•. 10 31. Independent Components ••.......•..•....••.••....•..•..•.• 10 32. Identification of Associated Components ..•...•••.•..••.•• 11 33. Precedence of VOR Voice Communications •••.••••••••••••••• 11 34. VOR Voice Communications Signals •.••••••••••••••••••••••• 11 35. Airborne Components ..••••••..•••.•...••••.•.•.•••••••.••• 11 36. System Traffic Handling Capacity ••••.••••••••••••.•.••••• 12 37. VOR/DME/TACAN System Azimuth Accuracy •••••••••••.•.•••••• 12 38. System Distance Accuracy························~········ 12 39. High Accuracy Certification ••••••• ..•••...••.•.••.•..•.•• 12

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Page III 'AC 00-:-31A ~ · ··· .

9/20/82 '\ CHAPTER 3. VOR SYSTEM SECTION 1. OPERATIONAL CHARACTERISTICS FOR VOR GROUND COMPONENTS Paragraph •••••••••••• 50. Introduction •••••••••••••••••••••••••••••••• o 13 51. Polarization ••••••••••••••••••••••••••••••••••••••••••••• 13 52. Radio Frequency Accuracy ••••••••••••••••••••••••••••••••• 13 53. Signal Strength In Space ••••••••••••••••••••••••••••••••• 13 54. Azimuth Signal Characteristics •••.••••••••••••••••••••••• 13 56. Amplitude Modulation Frequency and Accuracy ••••••.••••••• 14 57. Depth of Reference and Variable Phase Modulations •••••••• 15 58. Phas~ Relationship of Reference and Variable Phase 59. Code Identification Signal Characteristics •••••••••.••••• 15 60. Voice Identification and Communications Signal Characteristics •.••••••••••••••••.•••••••••••••••.•.••••• 15 6 1 • Mo n i t or i n g • • • • • • .. • • • • • • • • • • ~ • • • • • • • • • • • • • 0 • • • • • • 15 • • • 0 • • • 62.-79. [Reserved] •••....••••••.••. 0 15 •••••• 0 ••••••••• o 0 •••••••

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SECTION 2. OPERATIONAL CHARACTERISTICS FOR VOR AIRBORNE COMPONENTS 80. Introduction .••.•.••.••••.•.••• ...••••.••••....••..••.••• 16

81. Receiver Stability ·····••o······························· l6

82. Receiver Sensitivity .••••.••••••.•••.••••.••••••••••.• ..• 16 83. Rejection of Undesired Signals .•••••••••••••.••••••••• H. 16

84. Mistuning Protection ··············•••<••················· 16

85. Facility Identification and Voice Signals ••••• ..•••••.•.• 16 86. Bearing and Course Deviation Information ••.•••••••••••••• 16 88. Course Deviation Display .••.•••.•.•••• ..•••••••••.•••••.• 16 88. Warning Function •••••••••••.• ..•••••••••••••.••••...••••• 16 89. Accuracy of Bearing and Course Deviation Information ••••• 17 90. Radiation .••.•.•••••••••• ...•.••••••••.••••••.••••••••••• 17 91.-109. [Re$erved] ••••.••.•••••••••.••••••.•••••••••••••• ..• 17

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CHAPTER 4. DME AND TACAN SYSTEMS SECTION 1. OPERATIONAL CHARACTERISTICS FOR DME AND TACAN GROUND COMPONENT 110. Introduction ••••••• ....•..••••••.•••••.•••••..••••.••••. 19 111. Polarization ••••••••.••.••.•.•••• ..••••.••..••.•...•••.. 19 112. Transponder Response to Interrogation Signals • ......•••• 19 113. Interrogation Radio Frequency ••• ..••..•••.•..••....•.•.. 19 115. On-channel Sensitivity ..••••••••.••••.•••••..•..•.••••.. 19 116. Sensitivity at other Pulse Spacings ••.•.•.•••••••.••.••• 20 117. Variation of Sensitivity with Interrogation Loading ••••• 20 118. Sensitivity to Adjacent Channel Interrogations •••••••.•• 20 119. Transponder Dead Time •.••.•.• ...•••••••..••••.•••.•..••. 20 Page IV 9/20/82 AC 00-31A Paragraph 120.' Echo Suppression Dead Time ............................. . 20 •• 121. Transponder Output Signal Characteristics •••••••••••• 4 20 122. 20 Frequency Stability··················~·················· 123. Signal Strength in Space •••••••••••••••••••••••••••••••• 124.· Radio Spectrum •••••••••••••••••••••••••••••••••••••••••• 21 Spurious Radiation •••••••••••••••••••••••••••••••••••••• 21 125.

126. Pulse Shape ••••••.••••••••••.•••••••••.••••••••••.•••••• 127. . Pu 1se Coding ~ ••••••••••.•••••••••••••••••••••••••••••••• 128. Pulse Power Variation ••••••••••••••••.••••••••••••.••••• 22 129.· Distance Reply Signals ••••••••••••••••••••••••••••.••••• 22 130. Reply Efficiency •••••••••••••••••••••••••••••••••••••••• 22 Reply Delay Time •••••••••••••••••••••••••••••••••••••••• 22 131.

132. Random Pulse Pair Signals ••••••••••••••••••••••••••••••• 22 133. DME Components •••••••••••••••••.•••••••••••••••••••••••• 22 134. TACAN Components •••••••••••••••••••••••••••••••••••••••• 23 135. Pulse Pair Rate •••••••••••••••••.••••••••••••••.•••••••. 23 Ground Component Range Accuracy •••••••••••••.••••••••••• 23 136.

137. Code Identification Signal Characteristics •••••••••••••• 23 138. TACAN Azimuth Signal Characteristics •.••.••••••••••.•••• 139. Bearing Reference Signals ...•.•.•.••.••.•••••..•.•..•.•• 25 140.

Variable Beariny Signals ······~························· 141. Relationships of Reference and Variable Bearing Signals ................................................ . 26 Precedence of Pulse Transmissions .•••.•••.••.•••.••••••• 26 142.

143.

Rejection of Undesired Signals ························~· 144. Receiver Decoder •••••••..•••••..•••••••••••••••••••••••• ?..7 145. Echo Suppression ••••.••••••••••.••.••••••••••.•••••••••• 27 146. Decoder Discrimination •••••••••••••••••••••••••••••••••• 28 147. Receiver Recovery Time •••••••••••••••••••••••••...•••••• 28 Desensitization By CW ••••.••••••••••••••••••.••••••••••• 28 148.

149 • Mo n i t o r i ng • • • • • • • • • , • • • • • • • • . • • . • • • . • • • • • . • • • • • • • • • • • • ~ .

150.-169. [Reserved]

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SECTION 2. OPERATIONAL CHARACTERISTICS FOR OME AND TACAN AIRBORNE COMPONENTS.

170. Introduction ····~········································ 29 171. Interrogator Signal Characteristics ···············~····· 29 172. Interrogation Radio Frequencies and Accuracy •••••••.•••• 29 173. Pulse Chardctaristics ••••••.••.••••••.••.••••.•.••...••• 29 174. Pul$e.Power Variation ••••••••.•••••••.••••••• , •.••.••••• 30 175. Pulse Coding •••••••••••••.••.•••••.••.••.•.••.•..•.••.•. 30 176. Interrogation Signal Repetition Rate ••...•.•••......•••• 30 177. Variation of Repetition R~te ••••••••••.••.•••••••.•••••• 38 178. Signal Strength in Space ·········~······················ 30 179. Radio Spectrum .••.•••••.•••••.•••.••••••••.••.•.••..•••• 31 180. Radiation .••••.••..••.•••••••••••••.••••..•.•••.•••••.•• 31 181. Component Functional Capabilities and Performance •...••• 31 182. Receiver Radio Frequencies •.•••••••••••••.••.•..••..•••• ~1 183. Receiver Sensitivity····························~······· 31 Page V AC OQ't31A 9/20/82 Paragraph Page 184. Rejection of Undesired Signals •••••••••••••••••••••••••• 31

1as. Distance Information ···························•w••••••• 31

187. Accuracy of Distance Information •••••••••••••••••••••••• 32 188. Memory Functions ••••••••••••••••••• , •••••••••••••••••••• 32 189. TACAN Bearing and Course Deviation Information •••••••••• 32 190. Course Deviation Displays .......... 32 H ...................

191~ Warning Function, Bearing ••••••••••••••••••••••••••••••• 32 192. Accuracy of Bearing and Course Deviation Information •••• 32 193.-209. [Reserved] ••••••••••••••••••••••••••••••••••••••••• 32

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APPENDICES APPENDIX 1. COVERAGE (16 pages) ••.••••.••••.•.••..•••••••..•••.• 1 1. Radio Prc._":~agation .•••.••••....•...•..•.••.•.•••. 1 2. Ground Stc.t ion . . . . . . . . . • . . . . . . . . • . • . • • . . . . • . • • . . 1 4. DME/TACAN (UPLINK) Coverage ••..•....•...••....•. 2 5. DME/TACAN (DOWNLINK) Coverage •...•....•.•. , ..••. 2 Figure l Signal Time Availability (1 Page) ....••.•.•..•.•.••• 4 Figure 2 VOR Sign&1 Strength in Space-Long Range (1 Page) .••• 5 Figure 3 TACAN (RTB-2) Signal Strength In Space-Long Range (l Page) .....•....•.•...••••.••• 6 Figure 4 Cardion DME Signal Strength In Space-Long Range (l Page) .•...••.•••.••..•••••••• 7 Figure 5 Cardion DME Sign~l Strength In Space-Len~ Range (l Page) ..••••...•••••..••.••••• 8 Figure 6 Montek DME S1gnal Strength In Space-Long Range (l Page) ••...••..•.••••.•••••••• 9 Figure 7 Montek DME Signal Strength In Space··Long Range ( 1 Page) .•.••••••••.•..••... -... 10 Figure 8 VOR Signal Strength In Space-Short Range (1 Page) .•• 11 Figure 9 TACAN (RTB-2) Signal Strength In Space-Short Range (1 Page) ...•.•...•••.•••.•••.•• 12 Figure 10 Cardion DME Signal Strength· In Space-Short Range ( 1 Page)... • •...•••••.••.•••.. 13 Figure 11 Cardion DME Signal Strength In Space-Short Range (1 Page) •.•.••...•.•••...•••••. 14 Figure 12 Nontek DME Signal Strength In Space-Short Range (1 Page) ...•......... ~········· 15 Figure 13 Montek DME Signal Strength Page VI AC 00~31A . ' t.

Page AP~ENDIX 2. SYSTEM ACCURACY (3 pages) ····~······················ 1 1. Sys tern Accuracy • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • l 2. Bearing Error Component Definitions ••••••••••••• l 3. Error Combination ••••••••••••••••••••••••••••••• 2 4. Distance Error •••••••••••••••••••••••••••••••••• 3 APPENDIX 3. VOR/DM~/TACAN CHANNEL FREQUENCIES AND PAIRING (7 pages) ••••••••••••••••••••••••••••••• APPENDIX 4. DEFINITIONS (2 pages) ••••••••••••••••••••••••••••••••

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Figure ~~ 2-1 Standard H (High) Altitude Service Volume •••••••••••••••• 6 2-2 Standard L (Low) Altitude Service Volume ••••••••••••••••• 6 ·2-3 Standard T (Terminal) Service Volume ••••••••••••••••••••• 6 2-4 Definition of the Lower Edge of the Standard T (Terminal) Service Volume .•••••••• ..•••.••.•••••••••• 7 2-5 Definition of the Lower Edge of the Standard H (High) and L (Low) Service Volume •.•• ..••.•••••.••••• 7

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Page VII ' 9/20/82 .' .

AC 00-31A CHAPTER 1. GENERAL SECTION 1. INTRODUCTION 1. PURPOSE. This order establishes the Very High Frequency Omnidirectional Radio Range {VOR)/Distance Measuring Equipment (DME)/Tactical Air Navigation {TACAN) standard defining the performance required of the system and its cbmponents.

2. DISTKIBUTION. This order is distributed to: a) br~nch level in the organizations of Flight Operations, Airway Facilities, Air Traffic, and Systems Research and Development in Washington headquarters; b) branch ievel in Airway Facilities Service in regions; and c) Level A in General Aviation District Offices.

3. CANCELLATION. Order 1010.55, "Selection Order: U. S. National Aviation Standard for the VORTAC System, dated 6/l/70 is cancelled.

4. IMPLEMENTATION CRITERIA. The National Aviation Standard applies to all

VOR, DM~, and TACAN ground and airborne equipments l~Sed in the National

Airspace System (NAS).

5. DIRECTED ACTION. Subject to applicable rulemaking, programming and budgetary procedures, actions shall be taken by the FAA elements concerned to implement this Standard.

SECTION 2. OVERVIEW 6. GENERAL. Under Public Law 85-726, the Federal Aviation Administration (FAAr-T$i5narged with providing for the regulation and promotion of civil aviation in order to best foster its development and safety, and to provide for the safe and efficient use of the airspace by both civil and military aircraft. Explicitly, the Administrator shall develop, modify, test, and evaluate systems, procedures, facilities, and devices, defining their performance characteristics as needed. This effort is directed toward meeting the need for safe and efficient navigation and traffic control of all civil and military aviation operating in a common Civil/Military System.

7. THE VOR/DME/TACAN SYSTEM CHARACTERISTICS.

a. This Standard defines the application and performance characteristics of VOR, DME, and TACAN systems in the United States (U. S.).

For ground and airborne components, the material identifies signal, functional, and performance characteristics required to meet operational requirements and to provide compatibility between components of the system.

b. The respective airborne component characteristics for VOR, DME, and TACAN apply in entirety to those components used in aircraft operations · performed under In.strument Flight. Rules ( IFR). However, for other aircraft operations the applicability is limited to requirements identified in chapter 3, section 2 and chapter 4, section 2 as essential to prevent impairment of services to other NAS users.

Chap 1 Par 1 Page 1 I 9/20/82'

c.· In a·n cases, where a parameter and associated tolerance is

identified herein, ground stations shall be maintained within these limits of quality assurance methods including either monitoring, periodic ground or flight inspections. or a combination of these methods.

d. Operators of airborne systems designed, installed, and operated in accordance with the Standard can expect to achieve the system performance which the standard is intended to provide.

e. It is recognized that certain existing components do not comply with all requirements of this Standard. Specific characteristics that are known to deviate from the require~ents of this Stand~rd will be corrected or replaced as practical.

8. RE1ISIONS. This Standard will be revised as the needs of the National Airspace System warrant.

9. RELIABILITY REQUIRED OF THE VOR/DME/TACAN SYSTE~. Due to the critical nature of the radionavigation service, it is essential that the VOR/DME/TACAN system provide high reliability. Both signal strength and frequency protection are provided on a basis of 95 percent time availability at the worst tase points of the service volume. At othe~ than worst case points, time dvailability substantially exceeds 95 percent. (See Appendix 1, paragraph 6.)

10.-19. RESERVED.

Chap 1 Par 7 Page 2

·• .... '

AC 00-31A C~TER 2. VOR/DME/TACAN SYSTEM 20. VOR/DME/TACAN SYSTEM DESCRIPTION. The VOR/OME/TACAN system is a short distance air navigation system •. the-ground components provide properly equipped aircraft with bearing, identification, and distance information . referenced to the selected ground component. When the aircorne equipment · includes a suitable area navigation (RNAV) device operating from data derived from··the system, both radial and non-radi~l routes are afforded. The system provides navigation signals to all civil and military aviation for the safe and efficient conduct of aircraft operations, exercise of air traffic control, and use of airspace.

21. GROUND COMPONENTS. The principal ground components are VOR, DME, and TACAN. VOR and DME are the International Civil Aviation Organization (ICAO) standard navigational aids. VOR provides azimuth information and ground-to-air communications for the common NAS. DME provides distance information to all users of the NAS. TACAN provides azimuth information primarily to military users and distance information to all users of the NAS.

22. STATION TYPE DESIGNATIONS. Ground components are identified by type designations which indicate the service provided. VOR type designations are prefixed by the letter "Bu when the component provides scheduled voice broadcasts. The letter "W" is used when the component does not provide voice transmissions.

Designation Type of Facilitx VHF navigation facility, VCR omni-directional azimuth only UHF navigation facility, DME distance only TACAN UHF navigational facility, omni-directional, azimuth and distance VOR/DME Associated VOR and DME navigational facilities Associated VOR and TACAN VORTAC navigational facilities 23. SERVICE VOLUMES. Maximum usable range is influenced by a large number of variables. These include factors such as antenna patterns, propagation variation, ground terrain, ground and avionics equipment performance~ ground and avionics equipment installation and maintenance, traffic loading and traffic distribution. It should be noted that the aviation community has many years of operational experience with the VOR/DME/TACAN system. Service volumes are predicated on both experience and empirical measurements.

Chap 2 Page 3 Par 20 9/20/82 :

~ .. •·

,:.*r~ Ac-· ... 00-31A~~:r: .. :';J''' ·

, ... -~~;y;•l~_ !.'_. • ·, •• •• . . .

· S~ffici~nt.s~fetymarg1n has been incorporatedlto assure highly reliable ··system operation. Under worst c~se conditions, it is recognized that some · '· combinations of avionics· and older. ground ·equipments may not provide service , · with.~ time availability of 95 percent. Based on operational experience and ::, ·.··:· user feedback, no substantial evidence :indicating an adverse operational ·-~.···:·impact has been shown.· In addition, all service volumes are flight inspected .: . prior to commissioning for operational use. Nonetheless, ground and airborne · equipment should be brought into full compliance with this Nat·'onal Aviation Standard as soon as it is practical • . ' ·- a. Standard Service Volumes ( SSV). _ (1) ·Ground stations are c~assifi~d according to their intended use. These stations are available for use within their ser~ice volume.

Outside the service volume, reliable service may not be available • For standard use, the airspace boundaries are called standard service volumes.

They are defined, in th2 table below, for the three station classes.

SSV CLASS DES I G~.~ TOR ALTITUDE AND RANGE BOUNDARIES T (Terminal) From 1000 feet (305 m) AGL up to and including 12,000 feet (3,658 m) AGL at radial distances out to 25 nmi (46 km). See Figures 2-3 and 2-4.

L (Low Altitude) From 1000 feet (305 m) AGL up to and including 18,000 feet (5,486 m) AGL at radial distances out to 40 nmi (74 km). See Figures 2-2 a~d 2-5.

From 1000 feet (305 m) AGL up to and H (High Altitude) including 14,500 feet (4,420 m) AGL at radial distances out to 40 nmi (74 km). See Figures 2-1 and 2-S. From 14,500 feet (4,420 m) AGL up to and including 60,000 feet (18,288 m) at radial distances out to 100 nmi (185 km). See Figures 2-1 and 2-5. From 18,000 feet (5,486 m) AGL up to and· including 45,000 feet (13,716 m) at radial distances out to 130 nmi (241 km). See Figures 2-1 and 2-5.

(2) These SSV'~, are graphically shown in Figure:; 2-1 through 2-5.

The SSV of a station is indicated by using the class designator as a prefix to the station type designation. (Examples: TVOR, LOME, and HVORTAC.)

Chap 2 Par 23 Page 4 9/20/82 AC 00-31A (3) Within 25 nmi (46 km), the bottom of the T Service is defined by the curve in Figure 2-4. Within 40 nmi (74 km), the bottoms of the L and H service volumes ~re defined by the curve in Figure 2-5. In some cases, local conditions (terrain, buildings, trees, etc.) may require that the stdndard service volume be restricted. The public shall be informed of iiny such restriction by a Notice to Airman (NOTAM).

NOTE: Metric measurements are given for convenienc~ and are approximations.

b. Expanded Service Volumes. When operational needs require facilities to be used beyond their standard service volumes, the same signal standards/tolerances and ground/flight check certification procedures will be met. Expanded service volumes (ESVs) will only be authorized when conditions permit (reference Figures 2 through 13 of Appendix 1.).

c. Operational Service Volume. The airspace available for operational use includes: (1) T~e SSV excluding any portion of the SSV which has been restricted, and (2) expanded service volumes (ESVs}.

d. Vertical Angle Covera~e Limitations. Within the operational service volume of each station, azimut signal information permitting sa~isfactory performance of airborne components is normally provided from the radio horizon up to an elevation angle of approximately 60 degrees for VOR components and approximately 40 degrees for TACAN components. At higher elevation angles, the azimuth signal information may not be usable. Distance information provided by DME and TACAN will permit satisfactory performance of airborne components from the radio horizon to an elevation angle of not less than 60 degrees. · 24. ASSOCIATED COMPONENTS. A VOR and either a DME or TACAN 3hall be considered as assoc1ated components only when: a. operated on a standard frequency pairing as associated with paragraph 28; b. collocated as defined in paragraph 25; and c. complying with the identification provisions of paragraph 32.

25. COLLOCATION LIMITS FOR ASSOCIATED COMPONENTS. DME or TACAN components are frequency-paired with VOR. For the common system, these components shall be collocated in accordance with one of the following.

a. Coaxial collocation. The VOR and OME or TACAN antenna are located on the same vertical axis. This is the usual collocation configuration.

Chap 2 Par 23 Page 5 9/2U/82 AC 00-31A FIGURE 2·1. STANDARD HIGH ALTITUDE SERVICE VOLUME (refer to FIGURE 6 for altitudes below 1000 feet (306m) 130 nmi (241 km) .. ~.000 ft.

(13,716 m) 18,000 ft.

:5.486 rr.)

FIGURE 2-2. STANDARD LOW AL TITUDF SERVICE VOLUME (refer to FIGURE 5 for altitudet oolow 1000 feet (305m) ~nmi(74km) 1.-- 18,000 ft.

-- ·-:_:..: (5,.,86 m)

-·------

___ ,_ I

FIGURE 2-3. STANDARD TERMINAL , ._. 1 ._ ....

, ' .....

SERVICE VOLUME 1,000 ft.

I , (305m) (refer to FIGURE 4 for altitudes below 1000 feet (305m) NOTE: All elevations shown are with respect 12.000 ft.

(3,658 ml to the station's site elentlon (AGL).

Metric Measurements art given for convenienc. and are approximations.

TheN figures do not rderenoe the an a defined as the Vertical Angle Cover;y;t Llmiutions f oaragraph 23..d.)

-----~ ... -- .....

, , ' ,,000 ft.

' (305m)

~

Page 6 9/20/82 AC 00-31A FIGURE 2-4. DEFINITION OF Tl-fE LOWER EDGE OF THE STANUARD T (TERMINAL) SERVICE VOLUME 100?

f-1/lt' LJ [7 250 ~ ~--- ~~-- ....

.........

w w ;.... t- w - u..

~to- 200 ~ z 1- z

""

!-"" w 150 w ~ c 1..!' ::l :::::> I' ....

.....

100 !:::: ~ t !.of' I""" ""' ...I ~--~ _J - L,.ol""" d; 50~ lo-"' _1 1·-""-- ~.--~ ·- ~~ ....

I ,0 15 20 0 25 DISTANCE TO THE STATION IN nmi I I I 5 10 40 45 50 15 20 25 30 35 ':'l DISTANCE TO THE STATION IN km FIGURE 2-6. DEFINITION OF THE LOWER EDGE OF THE: STANDARD H (HIGH) AND L (LOW) SERVICE VOLUMES

,,f-

I I .J 1- T ~ -I- - ··-- 1-- 25!) ~ ~r- 1-1- t- w w ....

w 1-f--1- 200 UJ LL IL ~ ,_ v z z ?

~ 1-- ioo"" w 150 ~ c J ::l !""' ::l t f- 100 1 io""' ~ ...I r-' ...I c( 50 ~ ""'~ 1--- ~ ~ .....

~ 5 0 10 15 ~0 25 30 35 40 DI4)TANCE TO THE STATION IN nrnl I I I I I I t I 1 10 0 20 30 4(1 50 60 70 80 DISTANCE TO THE STATION IN km Page 7 9/20/82 AC 00-31A b. Offset collocation.

(1) For those facilities used in terminal areas for approach purposes or other procedures where the highest po~ition fixing accuracy of system c~pability is required, the separation of the VOR and DME or TACAN antennas will not exceed 100 feet (30 ~). However, at Doppler VOR sit~s the antennas may be separated by not more than 260 feet (80 m).

(2) For purposes other than those indicated in (1), the separation of the VOR 3nd either the DME or TACAN antennas will not exceed 2000 feet (610 m).

26. RADIO FREQUENCY ALLOCATIONS. Radio frequencies allocated ferVOR, OME, and TACAN are those listed in Aprendix 3.

27. RADIO FREQUENCY ASSIGNMENTS. Radio frequency assignments for the pair·ed system components shall be selected from the frequency pairings 1 is ted in Appendix 3. Channels l through 16 and 60 through 69 for both X and Y modes of operation shall not be assigned to components of the comnon system.

28. RADIO FREQUENCY CHANNEL PAIRING. Appendix 3 shows the pairing of the VHF and UHF components of the VOR/DME/TACAN System. Components associated according to paragraph 24 sha11 be assigned on paired frequencies in accordance with this taole. Non-associated VOR, DME. and TACAN components shall not be assigned on paired frequencies unless the separation between the respective components is sufficient to satisfy paragraph 29. This latter separation ~hall be determined as if each station was in effect an associated frequency pair~ 29. FREQUENCY INTERFERENCE PROTECTION. Frequency assignments must not result in interference between stations. W1thin a station's operational service volume, the ratio of the desired signal to any undesired signal must not fa11 below t. e selection/rejection capability of the airborne equipment.

Paragraphs 29.a through 29.c discuss interference p:·otection needed. The usable distance and altitude of aeronautical navigation aids are often limited by the frequency protection provided from other ground stations. The operational service volume shall not extend beyond the fr2quency pr·otected service volume.

a. Interference Protection of VHF NAVAIDS ILS and VOR). The following interference s1gna pro ec 1on ra 1os s a e prov1 e w1t 1n the operational service volume of all Instrument Landing Syatem (ILS) and VOR stations with a 95 percent time availability. This is done by controlling the station separation in certain situations.

(1) The desired to undesired (DIU) signal ratio b~tween co-channel stations shall not be less than +20 dB.

Chap 2 Page 8 Par 25 1\.C 00-31A {2) The 0/U ratio between VHf NAVAJOS with a nomint11 50 kllz frequency separation shall be -34 dB or greater. (-34 dB or -JOdB are permissible; -40 dB is not.) Frequency assignments made under this criter·ia (called the "Final" criteria) insure protection to narrow bandwidth (i.e., 50 kHz) receivers considering both ground and airborne frequency tolerances. A minimum 0/U ratio of -7 dB is required to insure protection to wideband (i.e., 100kHz) receivers using 100kHz {i.e., even multiples of 50 kHz) ground 11 11 s t at i on s • Th i s v a 1u e i s c a 11 e d the I nt e r i m c r i t e r i a • I n h i g h 1 y conge s ted parts of the country, the "Interim" criteria may not allow frequency ass i gnrr1ents to any new systems. New assignments in these areas wou 1 d have to be made under the final criteria (-34 dB). As a safeguard when this is done, flight publications will indicate any nearby 100kHz ground stations which cannot be used without the narrow bandpass characteristics associated with a 50 kHz receiver. This is required due to the insufficient rejection, in the 100 kHz receivers, to signals 50 kHz removed.

(3} The DIU ratio between VHF NAVAIDS with 100 kHz frequency separation shall not be less than -46 dB. In those parts of the country where 50 kHz assignments are made, the D/U ratio between stations with 100 kHz frequency separation shall not be less than -50 dB.

(4) The D/U ratio between VHF NAVAJOS with more than 100 kHz frequency separatio~ shall not be less than -50 dB.

(5) Some peak power deterioration is allowed before the system is shut down. In order to account for this decrease in power, the actual 0/U values used for station separation calculations are 3 dB more protective, e.g +23 dB vice +20 dB, -31 vice -34 dB, etc.

b. Interference Protection of DME/TACAN. The following interference signal protection ratios shall be provided within the operational service volume of all DME/TACAN stations with a 9S percent time avail~bility. This is done by controlling the station separation in certain cases.

(1) The 0/U signal ratio between co-channel DME/TACAN stations shall not be less than +8 dB.

(2) The D/U signal ratio between adjacent ch~~nel OME/TACAN stations shall be as follows. The various 0/U ratios have been established recognizing the spectrum control chardcteristics reflected in paragrarh ·124 and the spectrum differences between DME and TACAN.

(a) When the undesired station is a TACAN, the DIU ratio shall not be less th~n -42 dB.

(b) When the undesired station is an LOME (1000 W transmitter), the 0/U ratio shall not be less than -39 dB.

(c) When the undesired station is a TOME (100 W transmitter), the 0/U ratio shall not be less than -29 dB.

Chap 2 Par 29 9/20/82 AC 00-31A (3) The DIU ratio between OME/TACAN stations with more than 1 Mliz frequency separation shall not be less than -50 dB.

(4) Some peak power deterioration is allowed before the system is shut down. In order to account for this decrease in power, the actual 0/U values used for station separation calculations are 3 dB more protective, e.g., +11 dB v~ce +8 dB, -39 dB vice -42 dB, etc.

c. Protection of Service Volum~s Which Extend Beyond National Borders.

Stations near the border are normally not frequency-protected for that airspace which lies beyond the national border. Standard service volume and expanded service volume protection may be provided upon proper coordination with Canada or Mexico. This must be done whenever specific airways, routes, or procedures beyond the border are based on ground stations in the U.S.A.

30. COMPONENT IDENTIFICATION SIGNALS. Each ground component shall transmit an ident1f1cat1on s1gnai cons1st1ng of three letters in International Morse Code. It shall be transmitted at a rate of approximately 7 words per minute.

In addition, voice identification in accordance with paragraphs 31 through 33 may be provided by a VOR.

a. Identification Code Characteristics. The identification code characteristics sha11 conform to the following.

(l) The dots shall be a time duration of 0.1 second to 0.125 second and the dashes three times thr. dot duration; (2) The duration between dots and dashes of a code letter shall be equal to that of one dot plus or minus 10 percent; (3) The time duration between consecutive letters of the identification code group shall 10t be less than three dots; and (4) The total period of transmission of an identification code group shall not exceed 5 seconds.

b. Identification Cycle and Synchronization. The repetition and synchronizat~on of component ~dentification signals shall conform to paragraphs 31 through 33.

31. INDEPENDENT COMPONENTS. Whenever a facility is operated as a ~OR, a OME, or a TACAN only, 1ts 1dent1fication signal shall be transmitted as follows.

a. For VOR providing only code identification signals, each 30 second interval is divided into either four or five equal periods. The code identification shall be transmitted during each periorl.

b. For VOR providing code and voice id~ntification signals, each 30 second interval is divided into four equal periods. The code identification signal shall be transmitted during alternate periods or during three of four periods. Subject to paragraph 33, voice identification signals will occur during the remaining period(s).

Chan 2 Page 10 rar 29 9/20/82 AC 00-31A c. When voice corTrnunication signals are being transmitted .by a VOR, the VOR code identification signals shall not be suppressed.

d. For DME and TACAN, the International Morse Code identification signal shall be repeated at intervals of 30 seconds.

32. IDENTIFICATION OF ASSOCIATED COMPONENTS. When a VOR and either a DME or TACAN are operated as collocated components(see paragraphs 24 and 25), the identification signals shall conform to the respective requirements of paragraph 31 except that: a. The identification code shall be the same for each component; b. For VOR of paragraphs 3l.a and 3l.b~ the DME or TACAN identification signal shall be transmitted during one of the periods allocated for VOR code identification. The VOR code shall not be transmitted during that period; c. The International Morse Code identification signals of VOR, DME, and TACAN sh~ll be synchronized and interlocked such that simultaneous identification transmissions of VOR/OME or VOR/TACAN or ILS/DME do not occur; d. When voice corrrnunications are being transmitted on the VOR, the Code identification signals of DME and TACAN shall not be suppressed; and e. Whenever one component is temporarily out of service, the component still operating shall transmit facility identification signals in accordance with paragraph 32 without regard to the facility type designation.

33. PRECEDENCE OF VOR VOICE COMMUNICATIONS. VOR voice identification signals shall not be suppressed for the durat1on cf voice communications or broadcasts.

34 • V 0 R V 0 I C E C0 MM UN I CAT I 0 N S S I G N A L S . I f r e q u i red , a V0H rna y pro v i de ground-to-a1r vo1ce corrrnun1cat1ons.

35. AIRBORNE COMPONENTS. Airborne components of the system consist of VOR components conforming to chapter 3, section 2 and DME and TACAN components conforming to the applicable requirements of chapter 4, section 2 of this Standard.

Chap 2 Par 31 Page 11 9/20/B2 AC 00-31A 36. SYSTEM TRAFFIC HANDLING CAPACITY. Each VOR and TACAN ground component of the system provides azimuth and tac11ity identification information to an unlin4ited number of ~irborne components. DME and TACAN ground components can provide slant range adequate for a peak traffic lo~d of 3375 interrogations per second.

NOTE: As the traffic density increases beyond full load, the system replies at a rate reduced proportionately to Ule number of additional interrogators. The ground component could be capable of servicing higher density traffic only if the airborr.e component could maintain satisfactory operations with reduced reply efficiency (see paragraph 130). The apparent change in numbers from Order 1010.55 dated 6/l/70 does not represent a change in beacon radiated power (for example, see Appendix 1). Therefore, increases in receiver sensitivities of existing airborne equipments are not required to achieve the same ranges that users have experienced in the past. Future des~gns should not be restricted by this fact.

37. VOR/TACAN/VORTAC SYSTEM AZIMUTH ACCURACY. System azimuth accuracy, expressed in tenms of error, is a function of the error factors associated with the ground and airborne components. The total system azi~uth accuracy is _: 4.5 degrees. (See Appendix 2) 38. SYSTEM DISTANCE ACCURACY. System distance accuracy is a function of the grouna-and airborne component accuracies. The component values in this standard provide a system distance accuracy of! 0.5 nmi (926 m) or 3 percent of the slant range distance, whichever is greater (95 percent probability), when the error values are combined by the root-sum-square method.

39. HIGH ACCURACY CERTIFICATION. Some system accuracy requirements exceed those specif1ed in paragraphs 37 and 38. Some area navigation routes are an example. In order to support prescribed operations, flight inspections will validate the signal and certify its adequacy.

40.-49. RESERVED.

C ha f:J 2 Page 12 Par 36 9/20/82 AC 00-31A CHAPTER 3. VOR SYSTEMS SECTION 1. OPERATIONAL CHARACTERISTICS FOR VOR GROUND COMP1NENTS 50. INTRODUCTION. This section identifies standard signal characteristics and tolerances for the VOR portion of the system. These characteristics represent perfonnance which shall be provided throughout the operational service volume as defined in paragraph 23.c.

51. POLARIZATION. The ground component antenna shall radiate horizontally polar1zed s1gnals. Any vertically polarized signal components shall be at least 26 dB weaker than the horizontally polarized component.

5?.. RADIO FREQUENCY ACCURACY. The radio frequency carrier shall be within ~ 0.002 percent of the ass1gned frequency.

53. SIGNAL STRENGTH IN SPA~E. The ground station shall provide a minimum signal power dens1ty of -120 dgw;mZ (95 percent time availability) throughout the operational service volume as r'lfined in paragraph 23.c. At the nearest aircraft position expected durin9 Jperations, the maxirnu111 signa1 power density expected at an aircr·aft will be on the order of -34 d!H.J;rn2.

NOTE: At 118 MHz, the value -120 dBW/m2 corresponds to -123 dBW at the output of a lossless isotropic receiving antenna. The apparent change in numbers from Order 1010.55, dated 6/l/70, does not represent a change in radiated power (for example, see Appendix 1). Therefore, increases in receiver sensitivities of existing airborne eq:.Jipments are not required to achieve the sarne service ranges that users have experienced in the past. Future designs should not be restricted by this fact.

54. AZIMUTH SIGNAL CHARACTERISTICS. The VOR shall radiate J radic frequency carrier' with two assoc1ated 30 Hz modulations. The phase of one of these modulations shall be independent of the azimuth of the point of observation (reference phase)e The other modulation (variable phase) shall differ from that of the reference phase by an angle equal to the magnetic bearing of the point of observation with respect to the VOR.

a. The radio frequency carrier shall be amplitude modulated by two signals in accordance with the following.

(1) Subcarrier Frequency Modulation. One signal component shall be a subcarrier of 9,960 Hz of constant amplitude. It shall be frequency modulated at 30Hz having a deviation ratio of 16 ~ 1 (i.e., 15 to 17) as follows.

NOTE: The deviation ratio of the signal from a Doppler VOR decreases from the value at the facility by the cosine of the vertical angle (i.e., will be as low as 8 at a point 60 degrees above the horizon).

Chap 3 Par 50 9/20/82 AC 00-31A (a) For the conventional VOR, the phase of the 30 Hz component of the FM subcarrier is fi)(ed without rfspect to aztmuth. It is termed the .. reference phase ...

(b) For the Doppler VOR, the phase of the 30 Hz component of the FM subcarrier varies with azimuth. It is termed the variable phase.

(2} Subcarrier Frequer:ct and Accuracy. The subcarrier modulation mid-frequency shall be 9,960 Hz wi hin + 1.0 percent, and shall carry the 30 Hz frequency modulation.

(3) Subcarrier Modulation Frequency and Accuracy. The modulJtion frequency shall be 30Hz within~ 1.0 percent.

(4) Subcarrier Amplitude Modulation. Amplitude m0dulation of the subcarrier shall conform to the following.

(a) For the conventional VOR, the percentage of amplitude modulation of the 9,960 Hz subcarrier shall not exceed 5 percent.

(b) i-or the Single Sideband Doppler VOR, the percentage of amplitude modulation of the 9,960 Hz subcarrier shall not exceed 40 percent when measured at a point at least 1000 feet from the VOR. When Double Sideband Doppler VOR is installed, this modulation, for each sideband, shall not exceed 50 percent.

(5) Sideband Level Subcarrier Harmonics. When 50 kHz channel assignments are made, the sideband level of the harmonics of the 9,960 Hz component in the radiated signal shall not exceed the following levels referenced to the level of the 9,960 Hz sideband.

Subcarrier Level 0 dB reference 9,960 Hz 2nd harmonic - 30 dB 3rd harmonic - 50 dB 4th harmonic and subsequent - 60 dB harmonics 55. 30Hz M~PLITUDE MODULATION. The other signal component shall be 30Hz amplitude modulation as fa~.

a. For the conventional VOR, this component results from a rotating field pattern, the phase of which varies with azimuth. It is termed the "variable phase" and is of constant amplitude.

b. For the Doppler VOR, this component of constant phase with relation to azimuth, is radiated omnidirectionally. It is termed the "reference phase" and is of constant amplitude.

56. AMPLITUDE MODULATION FREQUENCY AND ACCURACY. The modulation frequency shall be 30Hz within+ 1.0 percent.

Chap 3 Page 14 Par 54 9/20/82 AC 00-31A 57. DEPTH OF REFERENCE AND VARIABLE PHASE MODULATIONS. The depth of modulation of the radio frequency carrier due to the 30 Hz or 9,960 Hz signals shall be within the following limits for each signal.

a. 28 to 32 percent at all elevation angles from 0 to 5 degrees above the horizon; and b. 25 to 35 percent at all elevation angles between 5 and 60 degrees above the horizon.

58. PHASE RELATIONSHIPS OF REFERENCE AND VARIABLE PHASE SIGNALS. The fundamental of the reference and variable phase modulations shall be in phase along the radial corresponding to magnetic north.

NOTE: The reference and variable phase modulations are in phase when the maximum value of the sum of the radio frequency carrier and the sideband energy due to the amplitude modulation signal occurs at the same time as the highest frequency of the frequency modulation signal.

59. CODE IDENTIFICATION SIGNAL CHARACTERISTICS. The characteristics of the code identification signal shall conform to the following.

a. Tone Modulation Frequency and Accuracy. The modulation frequency shall be 1,020 ~50 Hz.

b. Depth of Modulation. The depth to which the radio frequency carrier is modulated by the code identification signal shall be: (1) 5.0! l percent where voice services are provided.

(2) 4 to 10 percent at components where voice services are not provided.

60. VOICE IDENTIFICATION AND COMMUNICATIONS SIGNAL CHARACTERISTICS. The characteristics of voice ident)fication and voice communications signals, when provided, shall conform to the following.

a. Voice Channel Frequency Respons~. Throughout the frequency range from 300 to 2,200 Hz, the frequency response characteristics for the voice channel shall be within 3 dB of the response at 1,000 Hz.

b. Depth of Modulation. The depth to which the radio frequency carrier is modulated by voice signals shall not be greater than 30 ~ 2 percent.

61. MONITORING. The radiated signal shall be monitored and removed from service upon recognition of unsafe operation.

62.-79. RESERVED.

Chap 3 Par 57 Page 15 9/20/82 AC 00-31A SECTION 2. OPERATIONAL CHARACTERISTICS FOR VOR AIRBORNE COMPONENTS 80. INTRODUCT!ON. This section specifies functional capability and performJnce characteristics required of VOR airborne components. The term "component .. describes the complete aircraft installation. This includes the antenna and its transmission line, the re~.-~iver, electricol power sourc1ds), identification and voice comnunications signal reproduction devices, and selector and display in~trumentation devices for bearing bnd course indication. Airborne components used in the performance of aircraft operations under IFR must meet all requirements. For other aircraft operations the requirements are limited to those of paragraphs 80 and 90.

Components should be capable of performing as ~pecified throughout the operational service volume of ground stations. The applicable performance requirements should be met when the ground stations are operating in accordance with this standard.

81. RECEIVER STABILITY. For each channel in use, the receiver's center frequency shall be 1n accordance with Appendix 3. The receiver stability shall be: 0.005 percent or better.

82. RECEIVER SENSITIVITY. Based on the signal power density of paragraph 53, the airborr.e component shall provide the sensitivity necessary to display navigation information to the accuracy specified. Clear and distinct reproduction of communications and identification signals shall be provided.

(See also Appendix 1.)

83. REJECTION OF UNDESIRED SIGNALS. The airborne component shall provide undesired signal rejection characteristics adequate to assure the specified performance. For co-channel and adjacent-channel ILS and VOR signals, the 0/U rctios of paragraph 29.a shall apply.

84. MISTUNING PROTECTION. Mistuning by 50 kHz may result in erroneous informat1on not read1ly apparent to the user if no VOR carrier is present on the tuned channel. Provision shall be made to protect against mistuning an airborne receiver by operational, mechanical, or electronic means.

85. FACILITY IDENTIFICATION AND VOICE SIGNALS. The airborne component shall provide the pilot with positive 1dentification of the ground component.

86. BEARING AND COURSE DEVIATION INFORMATION. The airborne component shall provide devices for unambiguous determinat1on of the aircraft magnetic bearing with respect to the selected ground component. This display shall show the aircraft deviation from the selected course.

87. COURSE DEVIATION DISPLAYS. The response, readability, and resolution of course deviation displays shall enable the pilot to determine the direction and extent of the aircraft deviation from the selected course.

88. WARNING FUNCTION. The airborne component shall provide a warning indicatTOn whenever the azimuth signals necessary for the prescribed performance are not present. This warning shall be clearly evident to the pilot.

Chap 3 Par 80 Page 16 9/20/82

AC 00-31A

89. ACCURACY OF BEARING AND COURSE DEVIATION INFORMATION. The ~otal airborne component error, in bearing and course deviation information ~s d!sp1ayed to the pilot, shall not exceed! 3.0 degrees (95 percent probability) at any bearing.

90. RADIATION. Radiation from airborne components shall not result in derogation of operational use to other system users or 1n the derogation of other aeronautical services.

91.-109. RESERVED.

Chap 3 Par 89 Page 17 9/20/82 AC 00-31A CHAPTER 4. DME AND TACAN SYSTEMS SECTION 1. OPERATIONAL CHARACTERISTICS FOR OME AND TACAN

GROUND COMPONENTS

110. INl~ODUCTION. This section identifies standard signal and performance characteristics for DME and TACAN ground components. These characteristics represent the performance which shall be provided throughout the operational service volumes defined in paragraph 23.c. Requirements apply to both DME and TACAN components, unless noted otherwise.

111. POLARIZATION. The ground component antenna shall radiate and receive a vertically polarized signal. Any horizontally polarized signal components shall be at least 26 dB weaker than the vertically polar~zed component.

112. TRANSPONDER RESPONSE TO INTERROGATION SIGNALS. The response of the ' transponder to interrogation signals shall conform to paragraphs 113 througn 120. .

NOTE: At the ground component antenna, the presence of Cl~ signals within~ 3.0 MHz of the nominal value of the interrogation frequency at a signal power density of -llJ dBW/m2 or more, will normally derogate the performance of the system. Steps should be taken to avoid this situation.

113. INTERROGATION RADIO FREQUENCY. For each channel in use, the center frequency of the· transponder's interrogation and reply frequencies shall be in accordance with Appendix 3.

114. SENSITIVITY TO INTERROGATION SIGNALS. Transponder sensitivity is specified as that minimum value of peak pulse power density (prior to intercept by the ground component antenna) which wi11 result in a transponder reply efficiency of 70 percent. (See Appendix 1) NOTE: Ground components may not respond to interrogations as specified if the difference in level of the constituent pulses of interrogation pulse pairs is greater than 1 dB.

115. ON-CHANNEL SENSITIVITY. For interrogation signals within~ 100 kHz of the assigned frequency, having a .repetition rate no greater than 200 pulse pairs per second and pulse pair spacing of exactly 12.0 microseconds (36.0 micro~econds for Y channel), OME sensitivity shall be not less than -101.5 dBW/m • Under th2 same conditions, the TACAN sensitivity shall be not less . than -104.5 dBW/m. · NOTE: At 1150 MHz, the value -101.5 dBW/m2 corresponds to -124.0 dBW at the output of a lossless isotropic receiving antenna. Similarly, the value -104.5 dBW/m2 corresponds to -127.0 dBW. (See Appendix 1) Chap , Par 110 Page 19 AC 00-31A 9/20/82 116. SENSITIVITY AT OTHER PULSE SPACINGS. When the spacing of the constituent pulses of interrogation pulse pairs differs from the design center value (12.0 microseconds for X channel; 36.0 microseconds for Y channel) by ~ 0.5 microseconds or less, the sensitivity of paragraph 115 shall not be reduced by more than 1 dB. When the spacing differs by ! 3 microsecond~ and more from nominal, the reduction in sensitivity shall be at least 70 dB with respect to the level of paragraph 115.

117. VARIATION OF SENSITIVITY WITH INTERROGATION LOADING. When the beacon is

loaded with 3175 additional pulse pairs per second at a level of -65 dBm

(referenced at the input to the transponder receiver with the transponder's echo suppression circuits disabled), the sensitivity of the receiver shall not be reduced by more than l dB from the value measured in paragraph 115.

118. SENSITIVITY TO ADJACENT CHANNEL INTERROGATIONS. Interrogation signals remove~OkHz or more from the assigned channel interrogation frequency and having an amplitude up to 80 dB above the on-channel sensitivity of the component shail not elicit a reply from that component.

119. TRANSPONDER DEAD TIME. Dead time is the time immediately following an accepted 1nterrogation decode for reply processing, during which succeeding interrogations receive no reply. The transponder dead time shall normally be 60 microseconds for X channels (72 microseconds for Y channels).

120. ECHO SUPPRESSION DEAD TIME. The retriggerable blanking gate (RTBG) (see paragraph 145.6) is typically set such that the effective dead time is a nominal 150 microseconds. When required for a particular site, the effective dead time may be increased up to d nominal 250 microseconds.

121. TRANSPONDER OUTPUT SIGNAL CHARACTERISTICS. The transponder shall conform to paragraphs 122 through 150.

122. FREQUENCY STABILITY. For each channel in use, the center frequencies of the ground station's transmitter and receiver shall be in accordance with Appendix 3. Frequency stability shall be! 0.001 percent or better for equipments purchased after July 1980. The stability of older ground stations shall be! 0.002 percent or better.

NOTE: Stabilities of older equipment need not be increased to ! 0.001 percent.

123. SIGNAL STRENGTH IN SPACE. Within that part of the operational service volume that is above 18,000 feet (5,486 m) AGL, a minimum signal power density of -91.5 dBW/m2 {95 percent time availability) shall be provided. Within that part of the operational service volume that is below 18,000 feet (5,486 m) AGL, a minimum signal power density of -86.0 dBW/m2 shall be provided.

Signal power shall be determined by the average over one second uf the equivalent peak pulse voltage waveform. At the nearest aircraft position expected during operations, the maximum si~nal power density expected during flight will be on the order of -17.0 dBW/m • Chap 4 Page 20 Par 116 9/20/82 AC 00-31A NOTE: At 1213 MHz, the value -91.5 dBW/m2 corresponds to -114.5 dBW at the output of a lo~sless isotropic receiving antenna. Similarly, -86.0 dBW/m corresponds to -109.0 dBW. The apparent change in numbers from the old stJndard does not represent a chanqe in beacon radiated power (for example, see Appendix 1). Therefore, increases in receiver sensitivities of existing airborne equipments are not required to achieve the same service ranges that users have experienced in the past. Future designs should not be restricted by this fact.

124. RADIO SPECTRUM. The spectrum of the pulse modulated signal shall be as follows.

a. The equivalent isotropic radiated power (EIRP) contained in a 0.5 MHz band centered on a frP1uency either 0.8 MHz above or 0.8 MHz below the nominal channel frequen~y shall (in both instances) not exceed 200 milliwatts (except that the power relati~e to center frequency shall not exceed -50 dB).

b. The EIRP conta~ned in a 0.5 MHz band centered on a frequency either 2.0 MHz above or 2.0 MHz below the nominal channel frequency shall (in both instances) not exceed 2 milliwatts (except that the power relative to center frequency shall net exceed -70 dB).

c. Each lobe of the spectrum will be generally of lesser amplitude than the adjacent lobe nearer the nominal channel frequency.

125. ~PURIOUS RADIATION. The RF output 1evel, during the interval between occurrence of the desired pulse ~airs, shall not exceed a level which is 80 dB below the maximum power level during a pulse. In addition, between the pulses of each pair there shall be an interval for 1.0 microsecond or greater in length during which the Rr output l~vel does not exceed a level which is 50 dB below the maximum po~er level of the weaker pulse of the pair.

126. PULSE SHAPE. The following, as limited by the requirP.ments of paragraphs 124 and 125, shall apply to all radiated pulses.

a. Pulse Rise Time. The time required for the pulse to rise from 10 to 90 percent of 1ts max1mum voltage amplitude shall not be less than 0.1 microsecond nor more than 3.0 microseconds.

b. Pulse To£. Between the points on the leading and trailing edges which are 95 percent of the maximum voltage amplitude, the instantaneous amplitude of the pulse shall not fall below a value which is 95 percent of the maximum voltage amplitude of the pulse.

c. Pulse Duration. The pulse duration, as measured at the 50 percent maximum voltage amplltude points, shall be 3.5:0.5 microseconds.

d. Pulse Decay Time. The puls~ decay time, from the 90 percent point to the 10 percent po1nt of the maximum voltage amplitude, shall be such that the remaining requirements of this standard shall be satisfied.

Chap 4 Par 123 Page 21 9/20/82 AC 00-31A 127. PULSE CODING. Transponder output signals shall consist of paired pulses·. The spacing of the pulses is measured between the 50 percent maximum voltJge amplitude points on the leading edge of each RF pulse. The pulse spacing shall be: a. 12.0! 0.25 microseconds for X channels; or · b. 30.0! 0.25 microseconds for Y channels.

128. PULSE POWER VARIATION. The peak power of the constituent pulses of any pair shall not differ by more than 1 dB.

129. DISTANCE REPLY SIGNALS. Distance reply signals, consisting of pulse pairs, are transmiffea in response to interrogations.

130. REPLY EFFICIENCY. Reply efficiency is defined as the percentage of interrogations from a specific interrogator to which the transponder replies within a given time interval when the transponder is under specified load conditions. The reply efficiency for interrogation signals at and above the minimum sensitivity levels of paragraph 114 shall be at least 70 percent for all interrogation loadings up to the maximum for which the transponder is designed (3375 interrogations per second).

To provide service under adverse echo conditions or to ~OTE: _l,l handle increased traffic, it may be necessary to reduce the reply efficiency. To be able to receive the same service during traffic oYerload conditions, airborne receivers should be capable of operating pro~erly with :i reply efficiencies at least as low as 50 percent.

131. REPLY DELAY TIME. Reply delay time is defined as the time of all delay introduced by the ground component in replying to interrogations. When airborne components are to indicate distance with respect to the transponder site, the zero-distance reply delay time shall be 50.0 microseconds ~ 0.25 microseconds for X channels (56.0 microseconds ! 0.25 microseconds for Y channels). This represents the time between the 50 percent voltage point on the leading edge of the first pulse of the interrogation pulse pair and the corresponding point o~ the first pulse of the reply pulse pair.

NOTE: In older facilities, the reply delay time is referenced to the second pulse of interrogation and reply pulse pairs. The nominal value of reply delay time in these instances is 50 microseconds for both X and Y channels.

132. RANDOM PULSE PAIR SIGNALS. In addition to distance reply pairs, the ground component shall radiate random pulse pairs, defined as squitter, in order to maintain a total pulse pair rate in accordance with paragraphs 133 und 134.

133. DME COMPONENTS. For OME ground components, the total pulse rate, exclus1ve of 1dent1fication pulses, shall be within the range of 700 up to 2850 pulse pairs per second, in the absence of high traffic density.

Char 4 Par 127 Page 22 9/20/82 AC 00-31A 134. TACAN COMPONENTS. For TACAN ground components, the total pulse pair rate, exclus1ve of code identification signal and reference burst pulses, shall be 2700 ~ 90 pulse pairs per second, in the absence of high traffic density. For a transponder dead time of 60 microseconds (for X channels)~ the distribution of random pulse pairs shall conform to Figure 4-1.

135. PULSE PAIR RATE. To provide greater traffic handling capacity (than the total output pulse pair rates of paragraph 133 and 134), the equipment shall have the capability to increase to as high as 5000 ~ 150 pulse pairs per second as a function of actual traffic loading. Under this condition it will be impossible to maintain the output pulse pair spacing distribution of Figure 4-1. Accordingly, new TACAN airborne equipment design should avoid the use of circuits in which azimuth indic~tion is sensitive to transponder output pulse count and spacing distribution. (See paragraph 130.)

136. GROUND COMPONENT RANGE ACCURACY. The ground component shall not contribute more than 0.1 nmi {185m) to overall system error.

137. CODE IDENTIFICATION SIGNAL CHARACTERISTICS. Subject to the provisions of paragraph 137.a, code 1dent1f1cation s1gnals shall consist of groups of two pulse pairs transmitted for the duration of dots and dashes in accordance with paragraph 30.a. The spacing between the first and second pulse pairs constituting each pulse group, as measured between the 50 pecent voltage amplitude points on the leading edge of the first pulse of each pair, shall be 100 ~ 10 microseconds. The repetition rate shall conform to the.following.

a. DME Components. For ground components providing DME service only, the identification signal may consist of either one or two pulse pairs in a group. The group repetition rate shall be 1350! 10 groups per second.

b. TACAN Components. For TACAN ground components, the repetition rate shall be 1350 groups per second (! 0.23 percent) which is phase-locked within ~0.0 microseconds of the tenth harmonic of the 135 Hz bearing reference signal. The first pulse of each identification signal pulse group shall occur 740 ~50 microseccnds after the first pulse of any 40 degree sector reference signals.

138. TACAN AZIMUTH S1GNAL CHARACTERISTICS. TACAN azimuth signals consist of North Tm!a1n or coarse) and 40 degree sector (auxiliary or fine) bearing reference signals and 15 Hz (coarse) and 135 Hz {fine) am~litude modulation variable bearing signals. The azimuth si9niils radiated by the antenna shall conform to the following.

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N 300 . .00 500 100 700 100 100 100 200 1000 1100 PULSE SPACING IN MICROSECONDS {TO NEAREST 25 MICROSECOND INTERVAL) AC 00-31A 9/20/82 139. BEARING REFERENCE SIGNALS. Transmission of the North and 40 degree sector bearing reference signals shall occur synchronously with antenna pattern rotation. For each rotation of the antenna pattern, one North reference signal shall be transmitted. Following the North reference signal at eac~ of eight consecutive angular increments of 40 degrees, the 40 degree sector reference signal shall be transmitted. A ninth 40 degree sector reference signal, which otherwise would coincide in time with the North reference signal, shall not be transmitted. The characteristics of reference signals shall be as follows.

a. North Reference Signal.

(1) For X channels, the North reference signal shall r.onsist of a group of 12 pulse pairs. Spacing between the two pulses of a pair shall be 12 + 0.25 microseconds. Spacing between the first pulse of each pulse pair shall be 30.0 ~ 0.3 microseconds. Spacings are measured at the 50 percent voltage amplitude points on the leading edges of the pulses.

(2) For Y channels, the North reference signal shall consist of a group of 13 single pulses. Spacing between the pulses shall be 30.0 ~ 0.3 microseconds. Spacings are measured at the 50 percent voltage amp1itude points on the leading edges of the pulses.

b. 40 Degree Sector Reference Signals.

(1) For X channels, the 40 degree sector reference signal shall consi~t of a group of 6 pulse pairs. Spacing between the two pulses of a pair shall be 12 ~ 0.25 microseconds. Spacing between the first pulse of each pulse pair shall be 24.0 ~ 0.25 microseconds. Spacings are measured at the 50 percent voltage amplitude points on the leading edges of the pulses.

(2) For Y channels, the 40 degree sector reference signal shall consist of a group of 13 single pulses having a spacing of 15.0 ~ 0.25 microseconds. Spacings are measured at the 50 percent voltage amplitude points on the leading edges of the pulses.

140. VARIABLE BEARING SIGNALS. The variable bearing signals shall be produced by a rotating directional antenna pattern which results in a composite amplitude modulation of the transponder radio frequency pulse signals at 15 and 135 Hz. The characteristics of the variable bearing signals shal 1 be as follows.

a. Amplitude Modulation Frequencies and Accuracy. The amplitude modulation frequencies shall nominally be 15.0 and 135.0 Hz. Each frequency shall vary from the nominal values in exact synchronism with an antenna pattern rotation rate of 900 (! 0.23 percent) rotations per minute.

Chap 4 Par 139 Page 25 9/20/82 AC 00-31A b. Depth of Modulation. At all elevation angles from -2 to +40 degrees relative to the horizon, the individual modulation c~nponents shall be 21 ~ 9 percent. At all elevation angles from -2 to 50 degrees, the sum of the 15 arid 135 Hz modulation components including the ha~onics shall not exceed 55 percent. Further, within the angles from -2 to +2 degrees relative to the horizon, the maximum variation in depth of modulation for the 15 and 135 Hz components shall not, for each frequency, vary more than~ 4 percent from the respective median values within the angles specified.

141. RELATIONSHIPS OF REFERENCE AND VARIABLE BEARING SIGNALS. On the .magnetic North radial from the antenna, the relationships of the reference and variable signals shall conform to the following.

a. Coarse Bearin~ Sitnal. The inflection point on the ne~ative slope of the 15 Hz amplitude mo ula 1on component shall coincide within_ 2.0 azimuth degrees of the 50 percent amplitude points on the leading edge of: (l) the tenth pulse of the North reference signals for X channels; or (2} the sixth pulse of the North reference signal for Y channe1s.

b. Fine Bearing Signals. The inflection point on the negative slope of the 135 Hz amplitude modulation component shall coincide within+ 0.33 degrees azimuth of the average position of the 50 percent amplitude point on the leading edge of: (l) the tweifth pulse of the 40 degree sector reference signal for X channels; or (2) the eleventh pulse of the 40 degree sector reference signal for Y channels.

142. PRECEDENCE OF PULSE TRANSMISSIONS. The order of precedence for transmTSSTon of transponder pulse signals shall be in accordance with the following.

a. DME Components. For ground components providing DME service only, the precedence shall be: (1) International Morse Code Identification Signals (2) Distance Reply Signals (3) Random Pulse Pair Signals Neither distance reply nor random pulse pair signals shall be transmitted during the "key-down., interval of International Morse Code identification signal transmission.

Chap 4 Page 26 Par 140 9/20/82 AC 00-31A b. TACAN Components. For TACAN components, the precedence shall be: (1) Bearing Reference Signals (2) International Morse Code Identification Signals (3) Distance Reply Signals (4) Random Pulse Signals Neither code identification, distance reply, nor random pulse pair signals shall be transmitted during the interval required for transmission of all pulses in each bearing reference signal. Distance reply and random pulse pair signals shall not be transmitted during the "key-down" interval of code identification signal transmissions.

143. REJECTION OF UNDESIRED SIGNALS. The ground component shall provide undes1red s1gnal reJeCtlon characteristics adequate to assure the specified performance. This includes co-channel and adjacent-channel DME/TACAN signals.

144. RECEIVER DECODER. The decoder shall decode and produce an output pulse from interrogation signal pulse pairs occurring at spacings within the range of: a. 12 ! 0.5 microseconds for X channels, or b. 36 ~ 0.5 microseconds for Y channels.

145. ECHO SUPPRESSION. Echo suppressions shall be provided in accordance with the following subparagraphs.

a. Short Distance Echoes. Synchronous pulse signals occurring between the constituent pulses of a direct path interrogation pulse pair and which are also superimposed on the leading or trailing edge of the second pulse of the direct path pulse pair, shall not affect the time of decoding of the direct pulse pair by an amount in excess of 0.15 microseconds. Neither shall the reply efficiency be reduced by more than 10 percentage points from that measured in the absence of the echo pulse. These requirements shall be met when the RF input signal level of the direct path pulse pair has any level from 10 dB above threshold triggering level to an absolute level of -10 dBm and the echo pulse has any level up to the level of the direct pulse pair and for all direct pulse pair spacings of paragraph 175.

Chap 4 page 27 Par 142 9/20/82 AC 00-31A b. Long Distance Echoes. A separate echo suppression (Retriggerable Blanking Gat~ (RfBG)) circuit shall be provided in order to prevent the generation of multiple replies to aircraft interrogations having echoes which ar~ delayed with respect to the direct path signal in excess of receiver dead time setting~ The echo suppression circuit shall be triggered by the decoding of the direct signal pulse pair only when the level of the pulses exceeds a pre-established level. Such triggering shall result in the generation of a receiver desensitizing pulse starting at the time of pulse decoding nominally adjusted to )50! 10.0 microseconds with an upper limit of 300 microseconds.

The degree of receiver desensitization shall be to a level 3.0 dB above the level of the direct path signal and shall hold over the entire duration of the echo suppression pulse, unless retriggered by a signal stronger by 0 to 6 dB than the direct path signal, and over a range of input signals from 10 dB above threshold triggering level to -15 dBm. The echo suppression circuit pre-established level will nominally.be -70 dBm.

146. DECODER DISCRIMINATION. The decoder shall provide a minimum of 70 dB rejection to: a. paired pulses whose spacing differs by 3.0 microseconds or more from the nominal· value given in paragraph 144, b. paired pulses with spacings within the range of paragraph 144 where either p_ulse has a width of 0.8 microsecond or less, and c. single pulses of any width including widths within the range· of pulse spacings of paragraph 144.

147. RECEIVER RECOVERY TIME. The recovery time of the receiver and its associated video circuitry shall be such that the sensitivity to desired interrogations is not reduced by more than l dB when desired interrogations occur 8.0 microseconds and more after the reception of undesired pulses of any width having levels up to 60 dB above the sensitivity of the receiver in the absence of such undesired pulses. The desired interrogations shall be RF pulse pairs conforming to the characteristics specified in paragraphs 173 through 179. Undesired pulses shall conform to the same requirements except that the pulse spacing shall be outside the limits of paragraph 175.

_148. DESENSITIZATION BY CW. The presence of CW interference signals on the assigned channel frequency or elsewhere within the receiver pass-band shall not reduce the on-channel sensitivity by more than 2 dB from the value measured in the absence of CW interference provided that the level of the interference is no higher than 10 dB below the level of the desired on-channel signal. Additionally, the reply efficiency to a single aircraft interrogation shall not be reduced by more than 10 percent when the level of the interrogation signal is 6 dB and more above the level of the interfering CW signal. The CW sensing circuit shall not reduce the receiver gain by more than 1 dB when pulses 8.0 microseconds wide or wider are received at a rate of 37,000 per second at a level 10 dB below receiver sensitivity. (This is to preclude premature receiver desensitization, if the receiver is exposed to a high Pulse Repetition Frequency (PRF) pulse multiplexed signal.)

Chap 4 Par 145 Page 28 9/20/82 AC 00-31A 149. MONITORING. The radiated signals shall be monitored and removed from service upon recognition of unsafe operations.

150.-169. RESERVED.

SECTION 2. OPERATIONAL CHARACTERISTICS FOR DME AND TACAN

AIRBORNE COMPONENTS

170. INTRODUCTION. This section specifies functional capability and performance characteristics required of DME and TACAN airborne components.

The term Component" as used in this order, includes the complete aircraft installation. This includes such items as the antenna and its transmission line, the interrogator, the electrical power source(s), identification signal reproduction or display devices, and the distance indicator; when applicable, it also includes select and display instrumentation devices for bearing and course indication. Airborne components used in the performance of aircraft operations under IFR must meet all requirements. For other aircraft operations the requirements are limited to paragraphs 170, 175, 176, 179 and 180. Requirements apply to both DME and TACAN components unless otherwise noted. Components should be capable of performing as specified throughout the operational service volume of ground stations. The applicable performance requirements should be met when the ground stations are operating in accordance with this standard.

171. INTERROGATOR SIGNAL CHARACTERISTICS. Paragraphs 172 through 180 identify interrogation signal characteristics and tolerances applicable to the radiated signal.

172. INTERROGATION RADIO FREQUENCIES AND ACCURACY. The interrogatori shall transmit on the appropriate frequency 1n accordance with Appendix 3. ·rhe center frequency of the interrogation shall be within~ 100 kHz of the channel frequency.

173. PULSE CHARACTERISTICS. The radio frequency pulse envelope shall have characteristics JS follows.

a. Pulse Rise Time. The time required for the pulse to rise from 10 to 90 percent ~f 1ts max1mum voltage amplitude ~hall nominally be 2.5 microseconds. It shall not exceed 3.0 microseconds. The minimum rise time is governed by the spectrum requirements of paragraph 179.

b. Pulse Top. Between the points on the leading and trailing edges which are 95 percent of the maximum voltage amplitude, the instantaneous amplitude of the pulse shall not fall below a value which is 95 percent of the maximum voltage amplitude of the pulse.

c. Pulse Duration. The pulse duration, as measured at the 50 percent max i m urn v O'Tta""g e amp 11 tude p o i nt s , s ha 11 be 3 • 5 _: 0 • 5 m i c r u second s • Chap 4 Par 149 Page 29 9/20/82 AC 00-31A 149. MONITORING. The radiated signals shall be monitored and removed from service upon recognition of unsafe operations.

150.-169. RESERVED.

SECTION 2. OPERATIONAL CHARACTERISTICS FOR DME AND TACAN

AIRBORNE COMPONENTS

170. INTRODUCTION. This section specifies functional capability and performance characteristics required of DME and TACAN airborne components.

11 11 The term component as used in this order, includes the complete aircraft installation. This includes such items as the antenna and its transmission line, the interrogator, the electrical power source(s), identification signal reproduction or display devices, and the distance indicator; when applicable, it also includes select and display instrumentation devices for bearing and course indication. Airborne components used in the performance of aircraft operations under IFR must meet all requirements. For other aircraft operations the requirements are limited to paragraphs 170, 175, 176, 179 and 180. Requirements apply to both DME and TACAN components unless otherwise noted. Components should be capable of performing as specified throughout the operational service volume of ground stations. The applicable performance requirements should be met when the ground stations are operating in accordance with this standard.

171. INTERROGATOR SIGNAL CHARACTERISTICS. Paragraphs 172 through 180 identify interrogation signal characteristics and tolerances applicable to the radiated signal.

172. INTERROGATION RADIO FREQUENCIES AND ACCURACY. The interrogatori shall transmit on the appropriate frequency in accordance with Appendix 3. The center frequency of the interrogation shall be within~ 100 kHz of the channel frequency.

173. PULSE CHARACTERISTICS. The radio frequency pulse envelope shall have characteristics JS follows.

a. Pulse Rise Time. The time required for the pulse to rise from 10 to 90 percent ~f 1ts max1mum voltage amplitude ~hall nominally be 2.5 microseconds. It shall not exceed 3.0 microseconds. The minimum rise time is governed by the spectrum requirements of paragraph 179.

b. Pulse Top. Between the points on the leading and trailing edges which are 95 percent of the maximum voltage amplitude, the instantaneous amplitude of the pulse shall not fall below a value which is 95 percent of the maximum voltage amplitude of the pulse.

c. Pulse Duration. The pulse duration, as measured at the 50 percent maximum v~ge ampl1tude points, shall be 3.5 ~ 0.5 micru~econds.

Chap 4 Par 149 Page 29 9/20/82 AC 00-31A d. Pulse Decay Time. The time required for the pulse to fall from 90 to 10 percent of the maximum voltage amplitude shall nominally be 2.5 microseconds. It shall not exceed 3.5 microseconds. The minimum decay time is governed by the spectrum requirements of paragraph 179.

174. PULSE POWER VARIATION. The peak power of the constituent pulses of any pair shall not differ by more than 1 dB.

Note: If the difference in level of the constituent pulses of interrogation pulse pairs is greater than 1.0 dB, ground components may not respond to interrogations.

175. PULSE CODING. Interrogation signals shall consist of paired pulses.

Spacin~s are measured ~t the 50 percent voltage amplitude points on the pulse rise t1me of each pulse. The pulse spacing shall be: a. 12.0 ~ 0.5 microseconds for X channels; or b. 36.0 ~ 0.5 microseconds for Y channels.

176. INTERROGATION SIGNAL REPETITION RATE. The average interrogator pulse pair repetit1on rate shall not exceed 30 pairs of pulses per second. This assumes that interrogators are tracking at least 95 percent of the time. The repetition rate may be increased during search, but it shall not exceed 150 pulse pairs per second.

177. VARIATION OF REPETITION RATE. The variation in time between successive interrogations shall be sufficient to preclude mistaking distance reply pulses intended for another airborne component tuned to the same ground facility. It shall also preclude capture of the interrogations of one interrogator within the ground component dead time caused by the interrogations of other avionics.

178. SIGNAL STRENGTH IN SPACE.

a. When referenced to a point in space prior to the ground station anter.na intercept, the airborne component of aircraft operatir1g above 18,000 feet ~5,486 m) AGL shall provide a minimum signal power density of -102.5 dBW/m (95 percent time availability). For aircraft operating below 1B,OOO (5,486 m) AGL, the minimum signal power density shall be -99.0 dBW/m .

b. These specified power densities will assure a minimum reply efficiency of 70 percent when: (1) the pulse frequency is within! 100kHz of the assigned center frequency; (2) the pulse spacing is within ! 0.5 microseconds of nominal design center; and (3) the beacon loading is 3375 pulse pairs per second with the echo suppression circuits disabled.

Chap 4 Page 30 Par 173 9/20/82 AC 00--31A c. For the various operational service volumes currently employed in the ATC envirorwent, the interrogator's EIRP shall be a minimum of +29.0 dBW for those aircraft operating above 18,000 feet (5,486 m) AGL and +19.0 dBW for those operating below 18,000 feet (5,486 m) AGL. These EIRP's will provide to the ground beacon the power densities necessary for satisfactory performance.

Since EIRP levels greater than +33.0 dBW may impair system performance, the interrogator's EIRP shall not exceed this value. (See Appendix 1) 179. RADIO SPECTRUM. The spectrum of the RF interrogation signal shall be such that at least 90 percent of the enetgy, including FM components, in each pulse shall be within a 0.5 MHz band centered on the nominal channel frequency.

180. RADIATION. Radiation from airborne components shall not result in derogation of the operational use of this system by other users or in the derogation of other aeronautical services. Neither shall other users der·ogate the operational use of tnis system by valid DME or TACAN users. At all frequencies between 960 and 1215 MHz, the level of radiated CW signals, as referenced to an isotropic radiator, shall not exceed -60 dBW.

181. COMPONENT FUNCTIONAL CAPABILITIES AND PERFORMANCE. These subpcragraphs identify functional and operational performance requirements applicable to the airborne component.

182. RECEIVER RADIO FREQUENCIES. For each cham;el in use, the receiver's ce~ter frequency shall be in accordance with Appendix 3 ..

183. RECEIVER SENSITIVITY. Based on the signal power density of pa~agraph 123, the airborne components shall provide the sensitivity necessary to acquire and display navigation information to the accuracy specified. Clear and distinct reproduction of identification signals sha11 be provided. (See Appendix 1) 184. REJECTION OF UNDESIRED SIGNALS. The airborne co1nponent shall provide undesired signal rejection characteristics adequate to assure the specified performance. For co-channel and adjacent channel DME and TACAN signals~ this requirement shall be met when the respective signals prov.ide desired to undesired (DIU) signal ratios up to the maximum values stated in paragraph 29.b. At these D/U ratios, a positive identification signal shall be provided to identify the ground component.

185. DISTANCE INFORMATION. The airborne component shall measure and display the slant range d1stance (in nautical miles) between the aircraft and the selected ground component.

Note: The airborne component should not be capable of displaying excessive distances. Distances should be considered excessive for a given receiver if that receiver cannot reasonably be expected to operate at that distance.

Chap 4 Par 178 9/20/82 AC 00-31A 186. WARNING FUNCTION, DISTANCE. The airborne component shall provide a warning indication wnenaver the airborne component is neither tracking a distance reply signal nor operating from memory (see paragraph 188). This warning shall be clearly evident to the pilot.

187. ACCURACY OF DISTANCE INFORMATION. When the airborne component error is combined by root-sum-square w1th a ground component error of 0.1 nmi (185m), the total error in slant ran~e distance inforn1atior., as displayed to the pilot, shall not (except dur1ng memory per paragraph 188) exceed 0.5 nmi (926 m) or 3 percent of the actual distance, whichever is greater (95 percent probability).

188. MEMORY FUNCTIONS. The airborne component shall provide a memory function which! upon loss of a suitable reply signal while tracking, will cause the display of distance information to cont~nue for a period not to exce~d 15 seconds. The minimum distance memory shall be sufficient to cover the loss of distance reply signals during tran5mission of the ground component identification signal. The distance displayed during memory shall be within 1.0 nmi (1852 m) of the inqication upon resumption of the tracking function.

189. TACAN BEARING AND COURSE DEVIATION INFORMATION. The airborne component shall provide devices for unambiguous determination of the aircraft magnetic bearing with respect to each selected ground component and for display of the aircraft deviation from the selected course.

190. COURSE DEVIATION DISPLAYS. The response, readability, and resolution of course deviation displays shall permit the pilot to determine the direction and extent of the aircraft deviation from the selected course.

191. WARNING FUNCTION, BEARING. The airoorne component shall provide a warning ind1cat1on whenever the azimuth signals are not present and when the component is not operating in memory. This warning shall be clearly evident to the pilot.

192. ACCURACY OF BEARING AND COURSE DEVIATION INFORMATION. At any bearing, the total airborne component error in bearing and course deviation information shall not exceed~ 3.0 degrees {95 percent probability) as displayed to the pilot.

193.-209. RESERVED.

Chap 4 Page 32 Par 186 9/20/82 AC 00-31A Appendix 1 APPENDIX 1. COVERAGE.

1. RADIO PROPAGATION. Propagation losses vary as a function of time. For a given ffiP, tli"ePower density at a point in space will fluctuate. In addition) propagation loss will vary from site to site. This variation is a function of several factors including atmospheric refractivity, surface reflectivity, wave polarization, etc. Since the VOR/DME/TACAN system is a safety service, signals must be highly reliable. With this in mind, conservative assumptions have been made for the inputs to the propagation model. Figures 2 through 13 show standard VOR, OME, and TACAN signal strengths (95 percent time availability) at varirus points in space. A time availability of 95 percent means that, at a given point in space, the instantaneous signal strength will be greater than or equal to the value shown 95 percent of the time. Although propagation losses will differ from site to site, the signal strength curves of this app2ndix are recommended for purposes of standardization. It is important to remember that for the distance function of OME and TACAN both the ground-to-air and air-to-ground transmissions must be consideted.

2. GROUND STATION. The EIRP's and resultant signal strength in space curves given in Figures 2 through 13 are nominal. Allowances should be r~ade for different EIRP's and for other vari3tions in sta'.ion characteristics.

Some ground stations may have higher cable losses (e.g., mountain top insta.llations sometimes require longer cable rl!ns). In addition, intervening terrain may increase the transmission ~ath loss. Should this occur, it may be necessary to reduce the ~ervic~ volume accordingly.

3. VOR ~OVERAGE.

a. The power density specified in paragraph 53 (-120 dBW/m2) is equivalent to -123 dBW power available at the output of a lossless isotropic antenna (at 118 MHz}. Allowance must be made for the airborne antenna and for cable and insertion losses. Us£rs will balance their airborne power budgets in different ways. Two examples are shown below.

Ex1rnple Example 2 Power Available -123 dBW -123 dBW Airborne Antenna G~in* -+2.2 dBi -1 dB i Airborne Los~es -2.2 dB -4 dB Receiver Sensitivity -123 dB':.' -128 dBW b. Many other examples could be given. It is the user's responsibility to insure that the airborne installation will allow proper o~eration at the mi~imum signal strength of p~ragraph 53. (In considerin~ a1rborne antenna ga1n, antenna pattern var1at1on should not be neglected.

Does not consider variations due to antenna locations or *NOTE: other factors which influence antenna gain due to shielding.

Page Par 1 AC 00-31A 9/20/82 Appendix 1 4. DME/TACAN (UPLINK) COVERAGE a. The power densities specified in p~ragraph 123 are referenced to the powers available at a point in space. Allowance must be made for the airborne antenna and for cable and insertion losses. Users will balance their airborne power budgets in d~fferent ways. Two examples of how users might balance their airborne power budgets for the DME and TACAN are shown as follows: Example Example DME DME { 1 oow) TACAN ( 1 oow) TACAN Power Available dBW -109.0 -114.5 -109.0 -114.5 dBW Airborne Antenna Gain* +2.0 · +2.0 dBi +0.5 +0.5 dBi Airborne Losses -3.0 -3.0 dB -1.5 - l. 5 dR Rx Sensitivity -110.0 -115.5 dBW -110.0 -115.5 dBW b. Many other examples could be given. It is the user's responsibility to insure that the airborne installation will allow proper operation at the minimum signal strengths of paragraph 123. An airborne OME installation with 1 dB of loss (antenna pattern, cable and insertion losses, signal splicters, etc.) would require a sensitivity of -110.0 dBW. An airborne TACAN installation with 1 dB of loss would require a sensitivity cf -115.5 dBW. When the total loss is different than 1 dB, a corresponding adjustment must be made to determine the required sensitivity. In considering airborne antenna gain, antenna pattern variation should not be neglected.

5. DME/TACAN (DOWNLINK) COVERAGE.

a. The minimum power density specified in paragraph 178 for the input to the ground station antenna is -99.0 dBW/m2 for DME and -102.5 dBW/m2 for TACAN. These power density values are necessary to generate a reply efficiency of 70 percent from the transponder during periods when the tr3nspor.der is under heavy load and when the interrogation signal is within + 100 kHz of the nominal channel frequency and its pulse pair spacing is within +0.5 microseconds of the nominal system value. The association of ~tterrogator signal strength and transponder sensitivity is as follows.

*Note: Does not consider variations due to antenna locations or other factors which influence antenna gain due to shielding.

Page 2 Par 4 9/20/82 AC 00-31A Appendix 1 DME TACAN Transponder Sensitivity per paragraph 115 -94.0 -97.0 dBm + 6.7 + 3.0 dB Net coupling to r·eceiver per (l) +8.2 dBi DME Ante~na Gain on horizon -1.5 dB Net Losses (cable and insertion) (2) +4.5 dBi TACAN Antenna Gain on horizon -1.5 dB Net Losses (cable and insertion) -87.3 -94.0 dBm Receiver input for 70 percent Efficiency per paragraph 115 + 2.0 + 2.0 dB Sensitivity Reduction per paragraphs 116 and 117 -85.3 -92.0 dBm Receiver Input for 70 percent efficiency b. It is the user's responsibility to provide that signal strength to insure proper operation for those conditions stated in paragraph 178. For the requirement of 70 percent reply efficiency: OME TACAN -85.0 -92.0 dBm Receiver Input per conditions of paragraph 178 - G.7 - 3.0 dB Net coupling per Antenna -91 . 7 Signal Strength at the antenna input -95.0 dBm -99.2 -102.5 dBW/m2 Power Density ~t the antenna input -102.5 dBW/m2 Value used in paragraph 178 -99.0 6. TIME AVAILABILITY. At a point in space, signal strength will vary with time even when the ground transmitter's EIRP remains constant. ~similar statement could be made for D/U signal ratios. This variation is largely d~e to propagation effects under different environmental conditions. Examples include atmospheric refractivity, seasonal changes in ground cover, and surface reflectivity. Numerous other factors are also involved. Although it is difficult to describe accurately all the variables 1nvolved, the situation can be adequately-covered by statistical treatment. A helpful concept, in a statistical discussion of reliability, is time availability. It is that percentage of time that a given signal strength or D/U ratio is met or exceeded. Figure 1 shows an example of signal strength as a function of time av3ilability. For a time availability of 95 percent, the signal strength is -120 dBW/m2. This means that a signal strength of -120 dBW/m2 or greater is present 95 percent of the ~ime. For a time availability of 50 percent, the signal strength is -117 dBW/m at the same point in space assuming the sarne constant ground station characteristics. In a similar manner, the signal strength present for any given percentage of the time can be read fr·orn the .graph. This graph does not, however, take transmitter downtime into account.

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N 9/20/82 AC 00-31A Appendix 2 APPENDIX 2. SYSTEM ACCURACY.

1. SYSTEM ACCURACY. The accuracies described and quantified below represent the normal error budget for a VOR/DME/TACAN system that includes basic avionics with analog indicators~ a typical ground station, and an environment that does not include errors caused by excessive multipath.

Margin.for pilot induced flight technical error is also included. The error terms* are defined as follows.

2. BEARING ERROR COMPONENT DEFINITION.

a~ Radial Signal Error (Eg). Radial signal error is the difference between the nominal magnetic bearing to a point of measurement from the ground component and the bearing indicated by the ground component signal at the same point. The radial signal error is associated with the ground component and nominal signal path errors but excludes other error factors. It is made up of the follo~ir.g.

(1) certain constant elements such as course displacement errors and most site and terrain effect errors which may be considered as fixed for long periods of time.

(2) certain random variable errors which can be expected to vary about the essentially ~onstant value.

b. Airborne Component Error (Ea). Airborne component error is that error attributable to the 1nab1l~ty or-the airborne equipment to translate correctly the bearing information contained in the rddial signal. This element embraces all factors in the airborne component whi~h intl'Oduce errors in the information presented to the pilot. (Errors resulting from the use of compass information in some VOR and TACAN displays are not included.)

c. Instrumentation Error (~. This component consists of the 1imitation of the omni-bearing selector (OBS) units due to the resolution of the device and the inherent error of translating the pilot input to the avionic comparator. This r.omparator derives the difference between the actual radial computed and the selected radial which the pilot requires. This difference is normally displayed on a co~rse deviation indicator (CDI) whose errors are con~idered a part of (Ea).

d. Ff~gh~ Technical Error (Ef). fl)ght technical error refers to the accuracy wi w ich the p1lot controls the aircraft as measured by his success in causing the indicated aircraft position to match the indicated command for desired position. It does not include procedural blunders.

*Note: Quantitative values assume 95 percentile distribution.

Page 1 Par 1 AC 00-31A.

9/20/82 Appendix ,2 e. ~gr~9ate Error (Es). Aggregate error is the differer.ce between the magnetic bearing to a point of measurement from the ground component and the bearing indicated by·airborne components. This 1s the error in the information presented to the pilot (exclusive of any errors resulting fr~n use of compass inf~rmation). It takes into account not only the ground component and propagation path errors but also the error contributed by the airborne component and its instrumentation. The entire radial signal error, both fixed and variable, fs used.

3. ERROR COMBI~ATION. Since the errors above, when considered on a total system basis (not any individual radials or compon~nts) are independent · Jritbles, they may be combined by t~e root-sum-square (RSS) method to calculate aggregate system error (Es) when the same probability is given to each elpment. For purposes of this standard, each element is considered to have 95 percent probability.

a. Radial Signal Error (Eg). In practice, based on a significant number of accumulated data points, the radial si9nal error value (Eg) has been found to be ~1.4 degrees (95 percent probability).

b. Airborne Component Error (Ea~. This component is strictly limited to those errors attr1butable to the av1onics. In other words, this value excludes that which is due to the auto-couple C'f navigation deviation signals to aircraft controls and other output devices such as the omni-bearing s~lector (OBS), either 1n the manual or auto-couple mode. This value (Ea) has been estimated to be approximately +3.0 degrees and may vary as to the quality of the avionics. This distribution-is considered normal both from a capability standpoint between manufacturers and a quality standpoint by any one manufacturer. Recent avionics have shown the capability to reduce this error.

c. Instrumentation Error (Ei. This represents the remainder of the avionics error t at 1s exc u e rom paragraph 3.b of this Appendix. This error is approximately +2.0 degrees when a manual analog OBS is utilized.

Digital OBS devices and-auto-couple would decrease this error significantly.

This latter configuration is not addressed in this analysis, but could represent a considerable improvement to the total error budget, if implemented.

d. Flight Technical Error (Ef). As defined in paragraph 2.d of this Appendix, £he value wh1ch 1s attr1butable to this error con1ponent is +2.3 degrees. Although this error may not be completely independent of other errors, independence is assumed in this analysis. Empirical data indicates that this value may be pessimistic.

Page 2 Par 2 AC 00-31A 9/20/82 Appendix 2 e. S stem Use Error (Es • Airways, routes, and terminal area procedures 1n e n1 e a es are designed on the basis of a system use accuracy of +4.5 degress (95 percent probability). The system u5e error value is derived as follows: Radial Signal Error (Eg): probability) +1.4 degrees (95% Airborne Component Error (Ea): +3.0 degrees probability) (95% Instrumentation Setting Error ( E i): +2.0 degrees (95% probability) -2.3 Flight Technical Error ( F.f) : degrees (95% probability) Ei2 + Ef2)l/2 (Eg2 + Ea2 + System Use Error = (1.42 +3.o2 +2.o2 +2.32)112 = (1.96 + 9.00 + 4.00 + 5.29)112 ·- (20.25) 12 = (95% probability) = ~ 4.5 degree Refer to paragraph 187 of this standard.

4. DISTANCE ERROR .

Page 3 Par 3 9/20/82 AC 00-31A Appendix 3 APPENDIX 3 VOR-DME-TACAN CHANNEL FREQUENCIES AND PAIRING VHF DME-TACAN Chan. Freq.

lnterr. Freq. Reply Freq.

Chan. No. MHZ MHZ MHZ lX 1025 962 lY 1025 1088 2X 10~G 963 2Y 1026 1089 3Y 1027 964 3Y 1090 4X 1028 965 4Y 1 f'91 sx 1029 966 SY 1029 1092 6X 1030 967 6Y 1030 1093 7X 1031 968 7Y 1031 1094 8X 1032 969 8Y 1032 1095 9X 970 9Y 1033 1096 lOX 971 lOY 1034 1097 1lX 1035 972 llY 1035 1098 12X 1036 973 12Y 1036 1099 13X 1037 974 13Y 1037 1100 14X 1038 975 14Y 1038 1101 lSX 1039 976 lSY 10J9 1102 16X 1040 977 16Y 1040 Page 1 9/20/82 AC 00-31A Appendix 3 VOR-DME-TACAN CHANNEL FREQUENCIES AND PAIRING-Continued VHF DME-TACAN Chan. Freq. Interr. Freq. R~)ly Freq.

Chan. No. MHZ MHz MHz 17X* 108.00 VOR 1041 17Y* 108.05 VOR 1041 1104 1042 979 18X* 108.10 ILS 18Y 108.15 ILS 1042 1105 19X 108.20 VOR 1043 980 1043 1106 19Y 108.25 VOR 20X 108.30 ILS 1044 981 20Y 108.35 ILS 1044 1045 982 21X 108.40 VOR 21Y 108.45 VOR 1045 22X 108.50 ILS 1046 933 22Y 108.55 ILS 1046 1109 1047 984 23X 108.60 VOR 108.65 VOR 1047 1110 23Y 24X 108.70 ILS 1048 24Y 108.75 ILS 1048 1111 1049 986 25X 108.80 VOR 25Y 103.85 VOR 1049 1112 26X 108.90 ILS 1050 987 26Y 108.95 ILS 1050 1113 1051 988 27X 109.00 VOR 1051 1114 27Y 109.05 VOR 28X 109. 10 I LS 1052 989 28Y 109.15 ILS 1052 29X 109.20 VOR 1053 990 29Y 109.25 VOR 1053 1116 1054 991 30X 109.30 ILS 30Y 109.35 ILS 1054 1117 31X 109.40 VOR 1055 992 31Y 109.45 VOR 1055 1118 1056 993 32X 109.50 ILS 32Y 109.55 ILS 1056 111~ 109.60 VOR 1057 994 33X , 120 33Y 109.65 VOR 1057 * The frequencies associated with Channels 17X, 17Y and 18X are test frequencies. Assignments may be made to VOR test signals (VOTs), ramp testers, radiating test generators, and other t~st facilities. ILS, VOR, and DME-TACAN assignments should not be made on these channels. This has been coordinated with the FCC. See 47 CFR Section 87.52l(d); FCC Rules and Regulations, Part 87, paragraph 87.52l(d).

Page 2 9/20/82 AC 00-31A Appendix 3 VOR-OME-TACAN CHANNEL FREQUENCIES AND PAIRING-Continued VHF DM£-TACAN Chan. Freq. Interr. Freq. Rep1y Freq.

Chan. No. MHZ MHZ MHZ 34X 109.70 1LS 1058 995 3/lY 109.75 ILS 1058 1121 1059 996 35X 109 .. 80 VOR 25Y 109.85 VOR 1059 1122 36).

109.90 ILS 1060 997 36Y 10~.95 !LS lCSO 1123 37X :10.00 VOR 1061 998 1061 1124 37Y 110.05 VOR 38X 110.10 ILS 1062 999 38Y 110.15 ILS 1062 39X 110.20 VOR 1063 1000 39Y 110.25 VOR 106~ 1126 40X 110.30 I LS 1064 1001 40Y 110.35 ILS 1064 1127 41X 110.40 VOR 1065 1002 1065 1128 41Y 110.45 VOR 42X 110.50 ILS l06o 1003 42Y 110.55 ILS 1066 1129 43X 106/ 1004 110.60 VOR 43Y 110.65 VOR 1067 1130 ~4X 110.70 ILS 1068 1005 44Y 110.75 ILS 1068 1131 45X 110.80 VOR 1069 1006 45Y 110.85 VOR 1069 1132 46X 110.90 ILS 1070 1007 46Y 110.95 ILS 1070 1133 111.00 VOR l 071 1008 47X 1071 1134 47Y 111.05 VOR 48X 111.10 ILS 1072 1009 48Y 111.15 ILS 1072 1135 1C73 1010 49X 111.20 VOR 1073 1136 49Y 111.25 VOR 1074 1011 50 X 111.30 ILS '1074 111.35 ILS 1137 5CY 51 X 111.40 VOR 1075 1012 SlY 111.45 VOR 1075 1138 111.50 ILS 1076 1013 52 X 111.55 ILS 1076 1139 52Y AC 00-31A 9/20/82 Appendix 3 VOR-DME-TACAN CHANNEL FREQUENCIES AND PAIRING-Continued VHF DME-TACAN Chan. Freq. Interr. Freq. Reply Freq.

Chan. No. MHZ MHZ MHZ 53 X 111.60 VOR 1077 1014 53Y 111.65 VOR 1077 1140 54 X 1078 1015 111.70 ILS 54Y 111.75 ILS 1078 1141 55 X 111.80 VOR 1079 1016 55Y 111 • 85 VOR 1079 1142 56 X 111.90 ILS 1080 1017 56Y 111.95 ILS 1080 1143 57X 112.00 VOR 1081 1018 57Y 112.05 VOR 1081 1144 sax 112.10 VOR 1082 1019 58Y 112. 15 VOR 1082 1145 59X 112.20 VOR 1083 1020 59Y 112.25 VOR 1083 60X 1084 1021 60Y 114 7 61X 1085 1022 61Y 1085 1148 62X 1086 1023 62Y 1086 1149 63X 1087 1024 63Y 1087 1150 64X 1088 1151 64Y 1088 1025 65X 1089 115 2 65Y 1089 1026 66X 1090 1153 66H 1090 1027 67X 1091 1154 67Y 1091 68X 1092 1155 68Y 1092 1029 69X 1093 1156 69Y 1093 1030 lOX 112.30 VOR 1094 1157 70Y 112.35 VOR 1094 71X 112.40 VOR l09S 71Y 112.45 VOR 1CJ5 1032 112.50 VOR 1096 1159 7.ZX 72Y 112.55 VGR 1096 10!3 Page 4 9/20/82 AC 00-31A A~pendix 3 VOR-OME-TACAN CHANNEL FREQUENCIES AND PAIRING-Continued VHF DME-TACAN Reply Freq.

Chan. Freq. ~nterr. Freq.

Chan. No. MHz MHZ MHZ 73X 112.60 VOR 1097 1160 73Y 112.65 VOR 1097 1034 74X 112.70 VOR 109B 74Y 112.75 VOR 109B 1035 75X 112.BO VOR 1099 1162 1099 1036 75Y 112.B5 VOR 76X 112.90 VOR 1100 1163 76Y 112.95 VOR 1100 1037 77X 113.00 VOR 1101 1101 103B 77Y 113.05 VOR 7BX 113.10 VOR 1102 1165 113.15 VOR 1102 1039 7BY 79X 113.20 VOR 1103 1166 79Y 113.25 VOR 1103 116 7 BOX 113.30 VOR 1104 BOY 113.35 VOR 1104 1041 116B BlX 113.40 VOR 1105 1105 1042 B1Y 113.45 VOR B2X 113.50 VOR 1106 1169 113.55 VOR 1106 82Y 1107 1170 B3X 113.60 VOR 83Y 113.65 VOR 1107 1108 1171 B4X 113.70 VOR 84Y 113.75 VOR 110B 1045 85X 113.80 VOR 1109 1172 1109 1046 85Y 113.85 VOR 1110 1173 86X 113.90 VOR 111 0 1047 B6Y 113.95 VOR 1111 117 4 B7X 114.00 VOR 87Y 114.05 VOR 1111 1048 117 5 88X 114.10 VOR 1112 114. 15 VOR 1112 1049 BBY 1113 1176 B9X 114.20 VOR 1113 1050 89Y 114.25 VOR 114.30 VOR 1114 1177 90X 1114 1051 114.35 VOR 90Y 1115 1178 91X 114.40 VOR 114.45 VOR 1115 91Y 1116 1179 92X 114.50 VOR 1116 1053 92Y 114.55 VOR 93X 114.60 VOR 1117 1117 1054 114.65 VOR 93Y Page 5 9/20/82 AC 00-31A Appendix 3 VOR-DME-TACAN CHANNEL FREQUENCIES AND PAIRING-Continued VHF DME-TACAN Chan. Freq. lnterr. Freq. Reply Freq.

Chan. No. MHZ MHZ MHZ 94X 114.70 VOR 1118 1181 94Y 114.7 5 'lOR 1118 1055 95X 114.80 VOR 1119 1182 95Y 114.85 VOR 1119 1056 96X 114.90 VOR 1120 1183 96Y 114.95 VOR 1120 1057 97X 115.00 VOR 1121 1184 97Y 115.05 VOR 1121 1058 98X 1122 1185 115. 10 VOR 98Y 115.15 VOR 1122 1059 99X 115.20 VOR 1123 1186 ggy 115.25 VOR 1123 1060 lOOX 115.30 VOR 1124 1187 100Y 115.35 VOR 1124 1061 101X 1188 115.40 VOR 1125 101Y 115.45 VOR 1125 1062 l02X 115.50 VOR 1126 1189 102Y 115.55 VOR 1126 1063 103X 115.60 VOR 1127 1190 .1127 103Y 115.65 VOR 1064 104X 115.70 VOR 1128 1191 104Y 115.75 VOR 1128 1065 l05X 115.80 VOR 1129 1192 105Y 115.85 VOR 1129 1066 106X 115.90 VOR 1130 1 06Y 115.95 VOR 1130 1067 107X 116.00 VOR 1131 1194 107Y 116.05 VOR 1131 1068 108X 116. 10 VOR 1132 1195 108Y 116. 15 VOR 1132 1069 109X 116.20 VOR 1133 1196 109Y 1133 116.25 VOR 1070 110X 116.30 VOR 1134 1197 llOY 116.35 VOR 1134 1071 111X 116.40 VOR 1135 1198 lllY 116.45 VOR 1135 1072 112 X 116.50 VOR 1136 1199 112Y 116.55 VOR 1136 l13X 116.60 VOR 1137 1200 113Y 116.65 VOR 1137 1074 114X 116.70 VOR 1138 1201 114Y 116.75 VOR 1138 1075 Page 6 AC 00-31A 9/20/82 Aroendix 3 VOR-DME-TACAN CHANNEL FREQUENCIES AND PAIRING-Continued DME-TACAN VHF Chan. Freq.

Interr. Freq. Reply Freq.

Chan. No. MHz MHz MHz 115X 116.80 VOR 1139 1202 115Y 116.85 VOR 1139 1076 116X 116.90 VOR 1140 1203 116Y 116.95 VOR 1140 1077 117X 117.00 VOR 1141 1204 117Y 117.05 VOR 1141 1078 118X 117.10 VOR 1142 1205 118Y 117.15 VOR 1142 1079 119X 117.20 VOR 1206 119Y 117.25 VOR 1143 1080 120X 117.30 VOR 1144 120 7 120Y 117.35 VOR 1144 1081 121X 117.40 VOR 1] 45 1208 121Y 117.45 VOR 1145 1082 122X 117.50 VOR 1146 122Y 117.55 VOR 1146 1083 123X 117.60 VOR 1147 1210 123Y 117.65 VOR 1147 1084 124X 117.70 VOR 1148 1211 124Y 117.75 VOR 1148 1085 125X 117.80 VOR 1149 1212 125Y 117.85 VOR 1149 1086 126X 117.90 VOR 1150 1213 126Y 117.95 VOR 1150 1087 Page 7 9/20/82 AC 00-31A Appendix 4 APPENDIX 4. DEFINITIONS.

AGL Above Ground Level AIM Airman's Information Manual ATC Air Traffic Control COl Course Deviation Indicator

cw

Continuous Wave dB Decibels.

dBi Gain in decibels relative to an isotropic antenna dBm Decibels of power with respect to a milliwatt dBW Decibels of power with respect to a watt dBW/m2 Power density per square weter DME Distance Measuring Equipment OSBOVOR Double Sideband Doppler Very High Frequency Omnidirectional Radio Range D/U Ratio Desired to Undesired Ratio E IRP Equivalent Isotropic Radiated Power ESV Expanded Service Volume FAA Federal Aviation Administration FTE Flight Technical Error H High Altitude Service Volume HVORTAC High Altitude Very High Frequency Omnidirectional Radio Range and Tactical Air Navigation Hertz Hz ICAO International Civil Aviat'on Organization IFR Instrument Flight Rules ILS Instrument Landing System kHz Kilohertz L Low Altitude Service Volume LOME Low Altitude Distance Measuring Equipment m meter MHz Megahertz NAS National Airspace System NAVAJOS Navigational Aids nmi Nautical Mile NOT AM Notice to Airman OBS Omni Bearing Selector RF Radio Frequency RNAV Area Navigation RSS Root-Sum-Square ssv Standard Service Volume Page 1 AC 00-31A 9/20/82 Appendix 4 DEFINITIONS (continued) APPENDIX 4.

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T Terminal Service Volume TACAN Tactical Air Navigation TVOR Terminal Very High Frequency Omnidirectional Radio Range UHF Ultra High Frequency VHF Very High Frequency VOR Very High Frequency Omnidirectional Radio Range VOR/DME Very High Frequency Omnidirectional Radio Range/ Distance Measuring Equipment VORTAC Very High Frequency Omnidirectional Radio Range and Tactical Air Navigation X Channel and Frequency pairing for Distance Measuring Y Channel Equipment and Tactical Air Navigation • u.s. GOYEMWNENT PRlWTl»G OFFICE& Page 2