Flight Test Guide for Certification of Transport Category Airplanes

6.2 [Reserved.] ................................................................................................................. 6-1 Chapter 7. Flight: Stability ........................................................................................................... 7-1 7.1 General—§ 25.171. [Reserved] ................................................................................. 7-1 7.2 Static Longitudinal Stability and Demonstration of Static Longitudinal Stability— §§ 25.173 and 25.175. ................................................................................................ 7-1 7.3 Static Directional and Lateral Stability—§ 25.177. ................................................... 7-5 7.4 Dynamic Stability—§ 25.181. ................................................................................. 7-10 Chapter 8. Flight: Stalls ............................................................................................................... 8-1 8.1 Stall Testing. .............................................................................................................. 8-1 Chapter 9. Flight: Ground and Water Handling Characteristics .................................................. 9-1 9.1 Part 25 Regulations. ................................................................................................... 9-1 9.2 Longitudinal Stability and Control—§ 25.231. ......................................................... 9-1 9.3 Directional Stability and Control—§ 25.233. ............................................................ 9-1 9.4 Taxiing Condition—§ 25.235. [Reserved]................................................................. 9-2 9.5 Wind Velocities—§ 25.237. ...................................................................................... 9-2 9.6 Spray Characteristics, Control, and Stability on Water—§ 25.239. .......................... 9-5 Chapter 10. Flight: Miscellaneous Requirements ...................................................................... 10-1 10.1 Vibration and Buffeting—§ 25.251. ........................................................................ 10-1 10.2 High Speed Characteristics—§ 25.253. ................................................................... 10-5 10.3 Out-of-Trim Characteristics—§ 25.255. ................................................................ 10-11 05/04/18 AC 25-7D CONTENTS (CONTINUED) Paragraph Page iv Chapter 11. Structure [Reserved] ............................................................................................... 11-1 Chapter 12. Design and Construction: General [Reserved] ....................................................... 12-1 Chapter 13. Design and Construction: Control Surfaces [Reserved] ........................................ 13-1 Chapter 14. Design and Construction: Control Systems ........................................................... 14-1 14.1 General—§ 25.671. .................................................................................................. 14-1 14.2 Flap and Slat Interconnections—§ 25.701. .............................................................. 14-1 14.3 Takeoff Warning System—§ 25.703. [Reserved].................................................... 14-2 Chapter 15. Design and Construction: Landing Gear ................................................................ 15-1 15.1 Retracting Mechanism—§ 25.729. .......................................................................... 15-1 15.2 Wheels—§ 25.731.................................................................................................... 15-2 15.3 Tires—§ 25.733. ...................................................................................................... 15-4 15.4 Brakes—§ 25.735. ................................................................................................... 15-4 15.5 Skis—§ 25.737. [Reserved] ................................................................................... 15-18 Chapter 16. Design and Construction: Floats and Hulls [Reserved] ......................................... 16-1 Chapter 17. Design and Construction: Personnel and Cargo Accommodations ....................... 17-1 17.1 Pilot Compartment View—§ 25.773. ...................................................................... 17-1 17.2 [Reserved.] ............................................................................................................... 17-1 Chapter 18. Design and Construction: Emergency Provisions .................................................. 18-1 18.1 Ditching—§ 25.801.................................................................................................. 18-1 18.2 Emergency Egress Assist Means and Escape Routes—§ 25.810. ........................... 18-1 Chapter 19. Design and Construction: Ventilation and Heating. ............................................... 19-1 19.1 Ventilation—§ 25.831.............................................................................................. 19-1 19.2 Cabin Ozone Concentration—§ 25.832. [Reserved] ............................................... 19-1 19.3 Combustion Heating Systems—§ 25.833. [Reserved] ............................................ 19-1 Chapter 20. Design and Construction: Pressurization ............................................................... 20-1 20.1 Pressurized Cabins—§ 25.841. ................................................................................ 20-1 20.2 Tests for Pressurized Cabins—§ 25.843. ................................................................. 20-3 05/04/18 AC 25-7D CONTENTS (CONTINUED) Paragraph Page v Chapter 21. Design and Construction: Fire Protection [Reserved]............................................ 21-1 Chapter 22. Design and Construction: Miscellaneous [Reserved] ............................................ 22-1 Chapter 23. Powerplant: General ............................................................................................... 23-1 23.1 Installation—§ 25.901. [Reserved] .......................................................................... 23-1 23.2 Engines—§ 25.903. .................................................................................................. 23-1 23.3 Automatic Takeoff Thrust Control System—§ 25.904............................................ 23-7 23.4 Propellers—§ 25.905. [Reserved] ............................................................................ 23-9 23.5 Propeller Vibration and Fatigue—§ 25.907. [Reserved] ......................................... 23-9 23.6 Propeller Clearance—§ 25.925. [Reserved] ............................................................ 23-9 23.7 Propeller Deicing—§ 25.929. .................................................................................. 23-9 23.8 Reversing Systems—§ 25.933. ................................................................................ 23-9 23.9 Turbojet Engine Thrust Reverser System Tests—§ 25.934. [Reserved] ............... 23-12 23.10 Turbopropeller-Drag Limiting Systems—§ 25.937. .............................................. 23-12 23.11 Turbine Engine Operating Characteristics—§ 25.939. .......................................... 23-14 23.12 Inlet, Engine, and Exhaust Compatibility—§ 25.941. [Reserved] ........................ 23-15 23.13 Negative Acceleration—§ 25.943. ......................................................................... 23-15 23.14 Thrust or Power Augmentation System—§ 25.945. [Reserved] ........................... 23-16 Chapter 24. Powerplant: Fuel System ........................................................................................ 24-1 24.1 Unusable Fuel Supply—§ 25.959. ........................................................................... 24-1 24.2 Fuel System Hot Weather Operation—§ 25.961. .................................................... 24-3 24.3 Fuel Tank Vents and Carburetor Vapor Vents—§ 25.975. ..................................... 24-5 Chapter 25. Powerplant: Fuel System Components .................................................................. 25-1 25.1 Fuel Jettisoning System—§ 25.1001. ...................................................................... 25-1 25.2 [Reserved.] ............................................................................................................... 25-3 Chapter 26. Powerplant: Oil System [Reserved] ....................................................................... 26-1 Chapter 27. Powerplant: Cooling............................................................................................... 27-1 27.1 Cooling Test Procedures—§ 25.1045. ..................................................................... 27-1 27.2 [Reserved.] ............................................................................................................... 27-8 05/04/18 AC 25-7D CONTENTS (CONTINUED) Paragraph Page vi Chapter 28. Powerplant: Induction System ............................................................................... 28-1 28.1 Air Induction—§ 25.1091. ....................................................................................... 28-1 28.2 Induction System Icing Protection—§ 25.1093. ...................................................... 28-3 Chapter 29. Powerplant: Exhaust System .................................................................................. 29-1 29.1 General—§ 25.1121. ................................................................................................ 29-1 29.2 [Reserved.] ............................................................................................................... 29-1 Chapter 30. Powerplant: Controls and Accessories [Reserved] ................................................ 30-1 Chapter 31. Powerplant: Fire Protection .................................................................................... 31-1 31.1 Drainage and Ventilation of Fire Zones—§ 25.1187............................................... 31-1 31.2 Fire Extinguishing Systems—§ 25.1197. ................................................................ 31-1 Chapter 32. Equipment: General................................................................................................ 32-1 32.1 Equipment: Function and Installation—§ 25.1301. ................................................. 32-1 32.2 Flight and Navigation Instruments—§ 25.1303..................................................... 32-39 32.3 Powerplant Instruments—§ 25.1305. [Reserved] .................................................. 32-40 32.4 Miscellaneous Equipment—§ 25.1307. [Reserved] .............................................. 32-40 32.5 Equipment, Systems, and Installations—§ 25.1309. ............................................. 32-40 Chapter 33. Equipment: Instruments Installation ...................................................................... 33-1 33.1 Arrangement and Visibility—§ 25.1321. [Reserved] .............................................. 33-1 33.2 Warning, Caution, and Advisory Lights—§ 25.1322. [Reserved] .......................... 33-1 33.3 Airspeed Indicating System—§ 25.1323. ................................................................ 33-1 33.4 Static Pressure Systems—§ 25.1325(d) and (e). ...................................................... 33-4 33.5 Pitot Heat Indication Systems—§ 25.1326. [Reserved] .......................................... 33-5 33.6 Magnetic Direction Indicator—§ 25.1327. [Reserved] ........................................... 33-5 33.7 Flight Guidance System—§ 25.1329. ...................................................................... 33-5 Chapter 34. Equipment: Electrical Systems and Equipment ..................................................... 34-1 34.1 General—§ 25.1351. ................................................................................................ 34-1 34.2 Electrical Equipment and Installations—§ 25.1353. [Reserved] ............................. 34-4 34.3 Distribution System—§ 25.1355. ............................................................................ 34-4 05/04/18 AC 25-7D CONTENTS (CONTINUED) Paragraph Page vii 34.4 Circuit Protective Devices—§ 25.1357. .................................................................. 34-4 34.5 Electrical System Tests—§ 25.1363. ....................................................................... 34-5 Chapter 35. Equipment: Lights .................................................................................................. 35-1 35.1 Instrument Lights—§ 25.1381. ................................................................................ 35-1 35.2 Landing Lights—§ 25.1383. .................................................................................... 35-1 35.3 Position Light System Installation—§ 25.1385. ...................................................... 35-1 35.4 Anti-Collision Light System—§ 25.1401. ............................................................... 35-2 35.5 Wing Icing Detection Lights—§ 25.1403. ............................................................... 35-3 Chapter 36. Safety Equipment [Reserved]................................................................................. 36-1 Chapter 37. Miscellaneous Equipment ...................................................................................... 37-1 37.1 Electronic Equipment—§ 25.1431........................................................................... 37-1 37.2 Equipment Standards for Oxygen Dispensing Units—§ 25.1447. .......................... 37-2 Chapter 38. Operating Limitations and Information: General [Reserved] ................................ 38-1 Chapter 39. Operating Limitations and Information: Operating Limitations [Reserved] ......... 39-1 Chapter 40. Operating Limitations and Information: Markings and Placards [Reserved] ........ 40-1 Chapter 41. Operating Limitations and Information: Airplane Flight Manual .......................... 41-1 41.1 General—§ 25.1581. ................................................................................................ 41-1 41.2 [Reserved.] ............................................................................................................... 41-1 Chapter 42. Airworthiness: Miscellaneous Items ...................................................................... 42-1 42.1 Design and Function of Artificial Stall Warning and Identification Systems. ........ 42-1 42.2 Reduced and Derated Power or Thrust Takeoff Operations. ................................... 42-5 42.3 Runway Gradients Greater than ±2 Percent. ............................................................ 42-6 42.4 Criteria for Approval of Steep Approach to Landing. ............................................. 42-8 42.5 Takeoff and Landing on Unpaved Runways. ........................................................ 42-12 42.6 Accounting for Performance Effects of Minor Design Changes and Configuration Deviation List Items. .............................................................................................. 42-15 42.7 Configuration Deviation List. ................................................................................ 42-16 42.8 Spare Engine Pod. .................................................................................................. 42-19 05/04/18 AC 25-7D CONTENTS (CONTINUED) Paragraph Page viii 42.9 Authorization for Ferry Flight with One Engine Inoperative—§ 91.611. ............. 42-19 42.10 Instrument Landing System Weather Minima. ...................................................... 42-20 42.11 Takeoff Performance Credit for Alternate Forward Center of Gravity Limits. ..... 42-21 42.12 Airplane Backing Using Reverse Thrust. .............................................................. 42-23 Appendix A. Acronyms, Abbreviations, Symbols, and Definitions ........................................... A-1 Appendix B. Function and Reliability (F&R) Tests ....................................................................B-1 Appendix C. Historical Development of Accelerate-Stop Time Delays .....................................C-1 Appendix D. History of Jet Transport Performance Standards .................................................. D-1 Appendix E. FAA Handling Qualities Rating Method ................................................................ E-1 Appendix F. Correction of Air Minimum Control Speed to Standard Conditions ...................... F-1 Appendix G. Rudder Pedal Force-Limited Air Minimum Control Speed .................................. G-1 05/04/18 AC 25-7D CONTENTS (CONTINUED) FIGURES Number Page ix Figure 3-1. Equivalent Weight Extrapolation .............................................................................. 3-6 Figure 3-2. Wind Profile Variation .............................................................................................. 3-9 Figure 4-1. Accelerate-Stop Time Delays ................................................................................. 4-23 Figure 4-2. Accelerate-Stop Speed versus Distance .................................................................. 4-25 Figure 4-3. Anti-Skid System Response Characteristics: On-Off System on Dry Runway ...... 4-30 Figure 4-4. Anti-Skid System Response Characteristics: On-Off System on Wet Runway ..... 4-30 Figure 4-5. Anti-Skid System Response Characteristics: Quasi-Modulating System on Dry Runway ............................................................................................................................... 4-31 Figure 4-6 Anti-Skid System Response Characteristics: Quasi-Modulating System on Wet Runway............................................................................................................................... 4-32 Figure 4-7. Anti-Skid System Response Characteristics: Fully Modulating System ................ 4-33 Figure 4-8. Instantaneous Brake Force and Peak Brake Force .................................................. 4-37 Figure 4-9. Anti-Skid Efficiency–Wheel Slip Relationship ...................................................... 4-39 Figure 4-10. Substantiation of the Optimal Slip Value ............................................................. 4-40 Figure 4-11. Takeoff Distance on a Dry Runway: Critical Engine Fails at VEF ........................ 4-53 Figure 4-12. Takeoff Distance: All-Engines-Operating ............................................................ 4-54 Figure 4-13. Takeoff Distance on a Wet Runway: Critical Engine Fails at VEF ....................... 4-54 Figure 4-14. Takeoff Run: Critical Engine Fails at VEF ............................................................ 4-55 Figure 4-15. Takeoff Run: All-Engines-Operating .................................................................... 4-56 Figure 4-16. Clearway Profiles .................................................................................................. 4-57 Figure 4-17. Takeoff Segments and Nomenclature ................................................................... 4-58 Figure 4-18. Net Takeoff Flight Path ......................................................................................... 4-59 Figure 4-19. Landing Time Delays ............................................................................................ 4-72 Figure 5-1. Sample Pitch Tracking Task ................................................................................... 5-10 Figure 7-1. Longitudinal Static Stability ..................................................................................... 7-4 Figure 7-2. Local Reversal ........................................................................................................... 7-5 Figure 8-1. Thrust Effect on Stall Speed ..................................................................................... 8-5 Figure 8-2. CLMAX and Load Factor ............................................................................................. 8-7 Figure 8-3. CLMAX versus Weight and Flap Setting ..................................................................... 8-8 05/04/18 AC 25-7D CONTENTS (CONTINUED) FIGURES Number Page x Figure 8-4. Stall Speed versus Weight and Flap Setting ........................................................... 8-10 Figure 10-1. Maneuvering Characteristics at Speeds up to VMO/MMO ...................................... 10-4 Figure 10-2. Mistrimmed Maneuvering Characteristics: Speeds Between VFC/MFC and VDF/MDF ............................................................................................................................ 10-13 Figure 33-1. Altitude Loss versus Altitude at Go-Around Mode Initiation ............................ 33-16 Figure 33-2. Deviation Profile Method .................................................................................... 33-26 Figure 33-3. Height Loss Method ............................................................................................ 33-27 Figure C-1. Accelerate-Stop Time Delays (Pre-Amendment 25-42) ..........................................C-2 Figure C-2. Accelerate-Stop Time Delays (Amendment 25-42 through Amendment 25-91) ... C-3 Figure E-1. Overall HQRM Process ............................................................................................E-2 Figure E-2. Sample Tasks for Evaluating Airplane Handling Qualities ......................................E-4 Figure E-3. Probability of Occurrence Guidelines ......................................................................E-5 Figure E-4. Flaps UP Flight Envelopes .......................................................................................E-7 Figure E-5. Flaps DOWN Flight Envelopes ................................................................................E-8 Figure E-6. Combining Values ....................................................................................................E-9 Figure E-7. Probability Guidelines to Determine HQ Requirements ........................................E-10 Figure F-1. Two-Engine Business Jet .......................................................................................... F-4 Figure F-2. Four-Engine Transport .............................................................................................. F-4 Figure F-3. Yawing Moment—Engine and Airframe.................................................................. F-5 Figure F-4. Yawing Moment—Engine and Airframe at Altitude of 3,000 Feet (Test Day) ....... F-7 Figure G-1. Rudder Force Versus WsinΦ................................................................................... G-2 Figure G-2. Plot to Determine VMCA .......................................................................................... G-3 Figure G-3. Plot to Determine VMCA for an Amendment 25-42 Airplane .................................. G-4 Figure G-4. Plot to Determine VMCA for Derate Thrust .............................................................. G-5 05/04/18 AC 25-7D CONTENTS (CONTINUED) TABLES Number Page xi Table 3-1. Weight Tolerance Limits ............................................................................................ 3-4 Table 3-2. Test Parameters that Normally can be Corrected ....................................................... 3-8 Table 5-1. PIO Rating Criteria and Comparison to MIL Standard ............................................ 5-11 Table 5-2. Example of Acceptable HQ Rating for PIO Tendencies .......................................... 5-12 Table 32-1. Radio Line-of-Sight Distance versus Flight Level or Altitude .............................. 32-5 Table 32-2. Marker Beacon System......................................................................................... 32-12 Table 32-3. Classification of LF/MF Radio Beacons in U.S. National Service ...................... 32-14 Table 32-4. Types of Aural Warnings ..................................................................................... 32-33 Table A-1. Terms and Definitions .............................................................................................. A-1 Table A-2. Symbols .................................................................................................................. A-10 Table E-1. Comparison of Handling Qualities Ratings ...............................................................E-2 Table E-2. Minimum HQ Requirements ....................................................................................E-11 Table F-1. Example Data for Typical Business Jet Engine ......................................................... F-5 Table F-2. Example Data for Typical Business Jet Engine at Altitude of 3,000 Feet ................. F-7 05/04/18 AC 25-7D 1-1 CHAPTER 1. INTRODUCTION 1.1 Purpose. 1.1.1 This AC provides updated guidance for the flight test evaluation of transport category airplanes. These guidelines provide an acceptable means of demonstrating compliance with the pertinent regulations of Title 14, Code of Federal Regulations (14 CFR) part 25. The methods and procedures described herein have evolved through many years of flight testing of transport category airplanes and, as such, represent current certification practice. 1.1.2 See appendix A for a list of acronyms and abbreviations used in this AC. 1.2 Applicability. 1.2.1 The guidance provided in this document is directed to airplane manufacturers, modifiers, foreign regulatory authorities, and Federal Aviation Administration (FAA) certification engineers, flight test pilots, and FAA designees. 1.2.2 This material is neither mandatory nor regulatory in nature and does not constitute a regulation. It describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. The Federal Aviation Administration will consider other methods of demonstrating compliance that an applicant may elect to present. 1.2.3 While these guidelines are not mandatory, they are derived from extensive FAA and industry experience in determining compliance with the relevant regulations. On the other hand, if we become aware of circumstances that convince us that following this AC would not result in compliance with the applicable regulations, we will not be bound by the terms of this AC, and we may require additional substantiation or design changes as a basis for finding compliance. 1.2.4 This material does not change, create any additional, authorize changes in, or permit deviations from, regulatory requirements. 1.3 Cancellation. This AC cancels AC 25-7C, Flight Test Guide for Certification of Transport Category Airplanes, dated October 16, 2012. 1.4 Background. 1.4.1 Since AC 25-7 was released on April 9, 1986, it has been the primary source of guidance for flight test methods and procedures to show compliance with the regulations contained in subpart B of part 25, which address airplane performance and 05/04/18 AC 25-7D 1-2 handling characteristics. AC 25-7 has been revised several times to reflect changes in the part 25 regulatory requirements, changes in guidance and policy, and advances in technology. 1.4.2 The first revision, AC 25-7A, updated the original AC to incorporate the policy and guidance material applicable to all sections of part 25, not just subpart B. The material related to regulations outside of subpart B superseded that contained in Order 8110.8, Engineering Flight Test Guide for Transport Category Airplanes, which was cancelled when AC 25-7A was issued. 1.4.3 Change 1 to AC 25-7A added acceptable means of compliance for the regulatory changes associated with amendments 25-92 and 25-98 to part 25. 1.4.4 AC 25-7B added acceptable means of compliance for the regulatory changes associated with amendments 25-108, 25-109, and 25-115 to part 25, and revised guidance for expanding takeoff and landing data for airport elevations higher than those at which flight testing was conducted. Means of compliance associated with flight in icing conditions were removed as this material is now contained in AC 25-25A, Performance and Handling Characteristics in Icing Conditions, dated October 27, 2014. 1.4.5 Change 1 to AC 25-7B added acceptable means of compliance for the regulatory changes associated with amendment 25-135. 1.4.6 AC 25-7C reduced the number of differences between the FAA and European Aviation Safety Agency flight test guides, provided acceptable means of compliance for the regulatory changes associated with amendments 25-107, 25-109, 25-113, 25-115, 25-119 and 25-123 to part 25, and included changes responding to safety recommendations from the FAA and National Transportation Safety Board. 1.5 Related Documents. 1.5.1 Orders. The following FAA orders are related to the guidance in this AC. The latest version of each order at the time of publication of this AC is identified below. If any order is revised after publication of this AC, you should refer to the latest version for guidance, which can be downloaded from the Internet at https://www.faa.gov/regulations_policies/orders_notices/.  Order 8100.5C, Aircraft Certification – Organizational Structure and Functions, dated July 14, 2017.  Order 8110.4C, with Change 6, Type Certification, dated March 3, 2017. 1.5.2 Advisory Circulars. The following FAA ACs are related to the guidance in this AC. The latest version of each AC at the time of publication of this AC is identified below. If any AC is revised after publication of this AC, you should refer to the latest version for guidance, which 05/04/18 AC 25-7D 1-3 can be downloaded from the Internet at www.faa.gov/regulations_policies/advisory_circulars.  AC 20-73A, Aircraft Ice Protection, dated August 16, 2006.  AC 20-124, Water Ingestion Testing for Turbine Powered Airplanes, dated September 30, 1985.  AC 20-131A, Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) and Mode S Transponders, dated March 29, 1993.  AC 20-138D, with Change 2, Airworthiness Approval of Positioning and Navigation Systems, dated April 7, 2016.  AC 20-147A, Turbojet, Turboprop, Turboshaft, and Turbofan Engine Induction System Icing and Ice Ingestion, dated October 22, 2014.  AC 20-161, Aircraft Onboard Weight and Balance Systems, dated April 11, 2008.  AC 20-168, Certification Guidance for Installation of Non-Essential, Non-Required Aircraft Cabin Systems & Equipment (CS&E), dated July 22, 2010,  AC 21-29D, Detecting and Reporting Suspected Unapproved Parts, dated July 12, 2016.  AC 21.101-1B, Establishing the Certification Basis of Changed Aeronautical Products, March 11, 2016.  AC 25-9A, Smoke Detection, Penetration, and Evacuation Tests and Related Flight Manual Emergency Procedures, dated January 6, 1994.  AC 25-11B, Electronic Flight Displays, dated October 7, 2014.  AC 25-12, Airworthiness Criteria for the Approval of Airborne Windshear Warning Systems in Transport Category Airplanes, dated November 2, 1987.  AC 25-13, Reduced and Derated Takeoff Thrust (Power) Procedures, dated May 4, 1988.  AC 25-15 Approval of Flight Management Systems in Transport Category Airplanes, dated November 20, 1989.  AC 25-17A, with Change 1, Transport Airplane Cabin Interiors Crashworthiness Handbook, dated May 24, 2016.  AC 25-20, Pressurization, Ventilation, and Oxygen Systems Assessment for Subsonic Flight Including High Altitude Operations, dated September 10, 1996.  AC 25-22, Certification of Transport Airplane Mechanical Systems, dated March 14, 2000.  AC 25-23, Airworthiness Criteria for Installation Approval of a Terrain Awareness and Warning System (TAWS) for Part 25 Airplanes, dated May 22, 2000.  AC 25-25A, Performance and Handling Characteristics in Icing Conditions, dated October 27, 2014. 05/04/18 AC 25-7D 1-4  AC 25.735-1, Brakes and Braking Systems Certification Tests and Analysis, dated April 10, 2002.  AC 25.773-1, Pilot Compartment View Design Considerations, dated January 8, 1993.  AC 25.939-1, Evaluating Turbine Engine Operating Characteristics, dated March 19, 1986.  AC 25.1309-1A, System Design and Analysis, dated June 21, 1988.  AC 25.1329-1C, with Change 1, Approval of Flight Guidance Systems, dated May 24, 2016.  AC 25.1357-1A, Circuit Protective Devices, dated October 22, 2007.  AC 25.1581-1, with Change 1, Airplane Flight Manual, dated October 16, 2012.  AC 43.13-1B, with Change 1, Acceptable Methods, Techniques, and Practices— Aircraft Inspection and Repair, dated September 27, 2001.  AC 90-100A, with Change 2, U.S. Terminal and En Route Area Navigation (RNAV) Operations, dated April 14, 2015.  AC 90-101A, with Change 1, Approval Guidance for RNP Procedures with AR, dated February 9, 2016.  AC 90-105A, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace, dated March 7, 2016.  AC 91-79A, with Change 1, Mitigating the Risks of a Runway Overrun Upon Landing, dated April 28, 2016.  AC 120-28D, Criteria for Approval of Category III Weather Minima for Takeoff, Landing, and Rollout, dated July 13, 1999.  AC 120-29A, Criteria for Approval of Category I and Category II Weather Minima for Approach, dated August 12, 2002.  AC 150/5320-12C, with Change 8, Measurement, Construction, and Maintenance of Skid-Resistant Airport Pavement Surfaces, dated February 7, 2007. 05/04/18 AC 25-7D 2-1 CHAPTER 2. GENERAL 2.1 Applicability—§ 25.1. [Reserved] 2.2 Special Retroactive Requirements—§ 25.2. [Reserved] 05/04/18 AC 25-7D 3-1 CHAPTER 3. FLIGHT: GENERAL 3.1 Proof of Compliance—§ 25.21. 3.1.1 Explanation. In an effort to provide the necessary guidelines for the flight test evaluation of transport category airplanes, without producing a cumbersome document, this AC assumes a conventional transport airplane configuration. In general, a conventional airplane configuration is one with distinct wing and fuselage elements that are joined together, aft-mounted horizontal and vertical stabilizers that are attached to the fuselage, and propulsion provided either by turbojet/turbofan engines that do not provide any significant increase in lift due to their operation or engine-driven propellers. The effects of non-conventional airplane configurations (e.g., blown flaps) on the compliance methods should be evaluated and determined based on the intent of the guidelines presented for conventional airplane configurations. 3.1.2 Section 25.21(a)—Proof of Compliance. 3.1.2.1 The burden of showing compliance with the flight requirements for an airworthiness certificate or a type certificate rests with the applicant. The applicant should, at his own expense and risk, conduct such official flight tests as required by the FAA to demonstrate compliance with the applicable requirements. During the certification process, the applicant should make available the airplane, as well as all of the personnel and equipment necessary to obtain and process the required data. 3.1.2.2 If the airplane flight characteristics or the required flight data are affected by weight and/or center of gravity (CG), the compliance data must be presented for the most critical weight and CG position per § 25.21(a). Unless the applicant shows that the allowable CG travel in one or more axes (e.g., lateral fuel imbalance) has a negligible effect on compliance with the airworthiness requirements, the applicant must substantiate compliance at the critical CG. 3.1.2.3 The gross weight and CG tolerances specified in paragraphs 3.1.4.3 and 3.1.4.5 are test tolerances and are not intended to allow compliance to be shown at less than critical conditions. 3.1.2.4 Section 21.35(a)(3) requires that the test airplane be in conformity with its type design specifications. This means that the test airplane must be in conformity with its type design specification as it relates to the particular test being conducted. Any deviation from conformity must be clearly shown to be of no consequence to the particular test being conducted. For example, if the slip resistant escape surface required by § 25.810(c) is not installed when conducting airplane performance and flight characteristics 05/04/18 AC 25-7D 3-2 tests, the applicant must show that its presence would have no effect on measured airplane performance and flight characteristics. 3.1.2.5 Section 21.35(b)(2) requires the applicant to conduct sufficient flight testing the FAA finds necessary to determine whether there is reasonable assurance that the airplane, its components, and its equipment are reliable and function properly. Appendix B to this AC provides guidance for showing compliance with this requirement. 3.1.2.6 Acceptable Use of Simulation in Lieu of Flight Testing. It is difficult to establish guidance for using simulation in lieu of flight testing that applies in all situations. However, the following general principles can be used as guidance for determining the acceptability for using simulation in lieu of flight testing: 3.1.2.6.1 In general, flight test demonstrations are the preferred method to show compliance. 3.1.2.6.2 Simulation may be an acceptable alternative to flight demonstrations in certain situations, such as the following: 1. A flight demonstration would be too risky even after attempts are taken to mitigate these risks (e.g., by mock takeoffs/landings in the air at a safe altitude); 2. The required environmental or airplane conditions are too difficult to attain, such as (1) validation of system safety analyses failure cases involving high crosswinds; (2) development of crosswind guidance for slippery runway operations; and (3) conditions involving minimum allowable weight where the minimum allowable weight cannot be achieved because of the weight of required test equipment. In case (3), simulation data can be used to supplement flight test data obtained at the minimum practicable test weight. 3. The simulation is used to augment a reasonably broad flight test program; or 4. The simulation is used to demonstrate repeatability, or to demonstrate performance of a specific scenario for a range of pilots. 3.1.2.6.3 Simulation Criteria. If it is agreed that a simulation will be used to establish compliance, then the simulation should meet the following criteria in order to be acceptable for showing compliance with the performance and handling qualities requirements: 1. The simulation should be of a type and fidelity that is appropriate for the task. For example, is motion or an exterior view needed, or is the fidelity or customizability of an engineering simulator needed? 05/04/18 AC 25-7D 3-3 2. The simulation should be suitably validated by flight test data for the conditions of interest. This does not mean that there must be flight test data at the exact conditions of interest. The reason simulation is being used may be that it is too difficult or risky to obtain flight test data at the conditions of interest. The level of substantiation of the simulator to flight correlation should be commensurate with the level of compliance (i.e., the closer the case is to being non-compliant, the higher the required fidelity of the simulation). 3. The simulation should be conducted in a manner appropriate to the case and conditions of interest. If closed-loop responses are important, the simulation should be piloted by a human pilot. For piloted simulations, the controls/displays and cues should be substantially equivalent to what would be available in the real airplane (unless it is determined that not doing so would provide added conservatism). 3.1.3 Section 25.21(c)—Proof of Compliance (Altitude Effect on Flight Characteristics). 3.1.3.1 Any of the flying qualities affected by altitude, including controllability, stability, trim, and stall characteristics, must be investigated at the most adverse altitude conditions approved for operations. 3.1.3.2 Consideration should be given in the test program to any aerodynamic control system changes that occur with changes in altitude (e.g., maximum control surface displacement or auto slats that may be inhibited by Mach number above a specific altitude). 3.1.4 Section 25.21(d)—Proof of Compliance: Flight Test Tolerances. 3.1.4.1 To allow for variations from precise test values, acceptable tolerances during flight testing must be maintained. The purpose of these tolerances is to allow for small variations in flight test values of certain variables from the targeted value. They are not intended for compliance tests to be planned for other than the critical condition, nor are they to be considered as an allowable measurement error. 3.1.4.2 Where variation in the parameter for which a tolerance is allowed will have an effect on the results of the test, the results should be corrected to the most critical value of that parameter within the approved operating envelope. If such a correction is impossible or impractical, the average test conditions should assure that the measured characteristics represent the actual critical value. 3.1.4.3 Weight Limits. 3.1.4.3.1 Table 3-1 below presents weight tolerances that have been found acceptable for the specified flight tests. Many flight tests need to be conducted at or very near the maximum operating weight for the airplane 05/04/18 AC 25-7D 3-4 configuration, particularly those tests used to establish airplane flight manual (AFM) performance information. As noted in paragraph 3.1.4.1 above, the purpose of the test tolerances is to allow for variations in flight test values, not to routinely schedule tests at less than critical weight conditions or to allow compliance to be shown at less than the critical weight condition. In addition, the tolerances can be used to help determine when to interrupt a series of test conditions in order to refuel the airplane if necessary to remain within the acceptable weight tolerance. Table 3-1. Weight Tolerance Limits 3.1.4.3.2 It can be difficult or impossible to conduct testing at the airplane’s minimum allowable weight with an airplane configured for conducting a flight test program. If the minimum weight cannot be obtained (within the specified tolerance limit) and compliance at the minimum weight cannot be clearly deduced from the results at the tested weight, the testing should be conducted on a production airplane (or other airplane on which the minimum weight can be obtained). If the instrumentation or equipment Flight Test Condition Weight Tolerance Limit ±5% ±10% Stall Speeds X Stall Characteristics X All Other Flight Characteristics X Climb Performance X Takeoff Flight Paths X Landing Braking Distance X Landing Air Distance X Takeoff Distance and Speed X Accelerate-Stop Distance X Maximum Energy RTOs X Minimum Unstick Speed X Minimum Control Speed X Note: A -5 percent tolerance limit means that the weight for the particular test may be up to 5 percent less than the test target value. A +5 percent tolerance limit means that the weight for the particular test may be up to 5 percent higher than the test target value. 05/04/18 AC 25-7D 3-5 needed to conduct safe testing cannot be installed on the production airplane configuration, or the weight of such instrumentation still prevents the minimum weight from being obtained, consider the use of simulation to extend the results obtained at the minimum practical test weight. (See paragraph 3.1.2.6 of this AC.) 3.1.4.3.3 For follow-on airplane certification programs involving an increase in the maximum allowable gross weight, the test weight limits of table 3-1 have been applied as extrapolation limits on the original test data in order to minimize additional testing. For the test weight tolerance limits to be applied in this manner, the original test data must be from an existing certificated database for an aerodynamically similar model of the same airplane type. The tolerance limit should be applied to the maximum weight at which the original testing was conducted, not to the maximum certified weight. 3.1.4.3.4 Equivalent Weight Extrapolation Limits. For follow-on airplane certification programs where it is desired to increase a maximum operating weight based on existing certified performance parameters that have weight as one of their independent terms, those parameters should be examined for equivalent compliance with the weight tolerance limits of table 3-1. An example would be the reduction of an airplane’s landing flap position, to one approved on a similar model of the same airplane type, which would incur an increase in landing speeds and brake energy, relative to the original certificated landing flap, at any given weight. The brake energy, at the maximum certificated landing weight, should be calculated for the reduced landing flap. This brake energy should account for the increased landing speeds and reduced aerodynamic drag associated with the reduced flap setting. It should then be determined what equivalent gross weight would have rendered that brake energy with the original landing flap. (See figure 3-1 below for an example of how this can be done.) If the resulting equivalent gross weight does not exceed the certificated maximum landing weight by more than the five percent weight extrapolation limit specified in table 3-1, the reduced flap certification may be eligible for a reduced flight test program (e.g., limited to stall speed verification, handling characteristics, and a qualitative landing demonstration). Further limitations may be imposed by the criteria of technical standard order (TSO) C135a, Transport Airplane Wheels and Wheel and Brake Assemblies, dated July 1, 2009. 05/04/18 AC 25-7D 3-6 Figure 3-1. Equivalent Weight Extrapolation ∆ G.W. Not greater than 5% Gross Weight - Pounds ∆ KE Max. Landing Wt. “Equivalent” Gross Wt . Flap Brake Energy Ori g in a l Reduced Flap 3.1.4.4 Wind Limits. A wind velocity limit of 10 knots (from any direction) or 0.11 VSR1 (whichever is lower) is considered the maximum acceptable for obtaining valid takeoff and landing flight test data. Takeoff and landing performance data obtained under runway wind conditions greater than 5 knots may be inconsistent and unreliable because winds of that magnitude are likely to be unsteady. However, performance data obtained with winds between 5 and 10 knots should not necessarily be discarded. Their validity should be checked against data obtained in conditions with lesser winds. Wind velocity should be measured at the height of the wing mean aerodynamic chord (MAC), as determined with the airplane in a static ground attitude. When measuring test wind velocity at the wing MAC height, a height of six feet above the ground should be considered as a minimum measurement height to avoid possible measurement inaccuracies due to surface interference. 3.1.4.5 CG Limits. A test tolerance of ±7 percent of the total CG range is intended to allow for inflight CG movement. This tolerance is only acceptable when the test data scatter is on both sides of the limiting CG or when adjusting the data from the test CG to the limit CG is acceptable. If compliance with a requirement is marginal at a test condition that is inside of the CG limits, the test should be repeated at the CG limits. 3.1.4.6 Airspeed Limits. Normally, tests conducted within 3 percent or 3 knots (whichever is the higher) of the desired test speed are considered acceptable. 05/04/18 AC 25-7D 3-7 3.1.4.7 Thrust/Power Limits. Thrust critical tests, such as minimum control speeds, should be conducted at the highest thrust (or power) allowable on the engine given the constraints of temperature and altitude. It is then permitted to calculate further corrections to allow extrapolation of data to cover the entire operating envelope. These thrust (or power) corrections should be limited to 5 percent of test day thrust (or power), unless a detailed analysis is performed. 3.1.4.8 It is not the purpose of these tolerances to allow flights at values in excess of those authorized in the type design. If such flights are to be conducted, adequate structural substantiation for the flight conditions should be available. These flights should always be conducted under controlled conditions and with the flight test crew’s full knowledge of the situation. Examples of such flights are: 3.1.4.8.1 Takeoff at greater than maximum takeoff weight to reach a test area at the maximum takeoff weight. 3.1.4.8.2 Landing at greater than maximum landing weights during the course of conducting takeoff tests. 3.1.4.8.3 Flights to obtain data for future approvals beyond that substantiated for the initial type design. 3.1.4.8.4 Table 3-2 below indicates the cases for which corrections are normally allowed. Any corrections to flight test data should be made by methods that are agreed to by the FAA. 05/04/18 AC 25-7D 3-8 Table 3-2. Test Parameters that Normally can be Corrected 3.1.4.9 All instrumentation used in the flight test program should be appropriately calibrated and acceptable to the FAA test team. 3.1.5 Section 25.21(f)—Proof of Compliance: Wind Measurement and Corrections. 3.1.5.1 The relationship between the wind measured at one height and the corresponding wind at another height may be obtained by the following equation: 𝑉𝑊2 = 𝑉𝑊1(𝐻2 𝐻1 ⁄ )1/7 Where: 𝐻 = 𝐻𝑒𝑖𝑔ℎ𝑡 𝑎𝑏𝑜𝑣𝑒 𝑡ℎ𝑒 𝑟𝑢𝑛𝑤𝑎𝑦 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑉𝑊2 = 𝑊𝑖𝑛𝑑 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝐻2 𝑉𝑊1 = 𝑊𝑖𝑛𝑑 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝐻1 3.1.5.2 This equation is presented graphically below. Values of H less than 5 feet should not be used in this relationship. Flight Test Condition Correctable Parameters Weight CG Airspeed Altitude Power/ Thrust Wind Airspeed calibration X --- --- --- --- --- Stall speeds X X --- --- X --- Climb performance X X X X X --- Landing performance X --- X X --- X Takeoff performance X X --- X X X Accelerate-stop performance X X --- X X X Minimum control speed --- --- --- --- X --- Minimum unstick speed X X X --- X --- Buffet boundary X X --- X --- --- 05/04/18 AC 25-7D 3-9 Figure 3-2. Wind Profile Variation 3.1.6 Wind Profile Variation for Test Data. The performance data of airplanes should be obtained in such a manner that the effect of wind on the test data may be determined. The test wind velocity should be corrected from the recorded height above the test surface to the height of the airplane wing mean aerodynamic chord. If the wind profile variation is not measured, the variation may be calculated using the equation in paragraph 3.1.5 above. The following examples are methods of handling wind profile variation data. Other methods have also been found acceptable. Example: Test Data Given:  Height of mean aerodynamic chord with airplane on surface 8.0 feet  Height of wind measurement 6.0 feet  Measured wind velocity 4.8 knots Results:  Test wind velocity with airplane 50 feet above landing surface 4.8((50 + 8)/6)1/7 = 6.6 knots  Test wind velocity with airplane 35 feet above takeoff surface 4.8((35 + 8)/6)1/7 = 6.4 knots  Test wind velocity with airplane on surface 4.8(8/6)1/7 = 5.0 knots 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 HEIGHT ABOVE FIELD ELEVATION - FEET WIND VELOCITY - KNOTS 10 meters 05/04/18 AC 25-7D 3-10 3.1.7 Wind Profile Variation for AFM Data. When expanding the data to the AFM conditions, the result should include the effective velocity, at the airplane’s wing mean aerodynamic chord, which corresponds to the wind condition as measured at 10 meters (32.81 feet) above the takeoff surface, and corrected for the wind factors of § 25.105(d)(1). Example: AFM Data Given:  Height of mean aerodynamic chord with airplane on surface 8.0 feet  Reported headwind at 10 meters 40.0 knots  Section 25.105(d)(1) wind factor 0.5 Results:  Factored wind velocity with airplane 50 feet above landing surface (0.5)(40)((50 + 8)/32.81)1/7 = 21.7 knots  Factored wind velocity with airplane 35 feet above takeoff surface (0.5)(40)((35 + 8)/32.81)1/7 = 20.8 knots  Factored wind velocity with airplane on surface (0.5)(40)(8/32.81)1/7 = 16.3 knots 3.1.8 Airplane Airspeed Variation Due to Wind Profile Variation Combined with Speed Changes Due to Airplane Dynamic Performance. In the reduction of test data and in the expansion of such data to AFM conditions, the increase or decrease of speed due to the dynamic effect of the forces on the airplane are shown only by the change in ground speed. These changes in ground speed may be generalized either as speed increments or speed ratios. The changes in airspeed due to wind profile variation are superimposed on these speed changes. Example: Determination of True Airspeed from Ground Speed—Takeoff Test Data Given:  Ground speed at liftoff, VLOF 139.0 knots  Ground speed at 35 feet above takeoff surface 140.6 knots  Speed change due to airplane dynamic performance 1.6 knots  Test headwind at liftoff 5.0 knots  Test headwind with airplane 35 feet above takeoff surface 6.4 knots Results:  True airspeed at liftoff, VLOF 139.0 + 5.0 = 144.0 knots  True airspeed at 35 feet above takeoff surface 140.6 + 6.4 147.0 knots 05/04/18 AC 25-7D 3-11 Example: Determination of Rotation Speed from True Airspeed at 35-Foot Height—AFM Data Given:  Factored headwind at liftoff 16.3 knots  Factored headwind with airplane 35 feet above takeoff surface 20.8 knots  Ground speed change, (V35 – VLOF) 1.6 knots  Ground speed change, (VLOF – VR) 0.5 knots  True airspeed required at 35 feet 150.0 knots Results:  Ground speed required at 35 feet 150 - 20.8 = 129.2 knots  Ground speed at liftoff 129.2 - 1.6 = 127.6 knots  True airspeed at liftoff 127.6 + 16.3 = 143.9 knots  Ground speed at rotation 127.6 - 0.5 = 127.1 knots  True airspeed at rotation (for AFM speed and distances) 127.1+16.3 = 143.4 knots Example: Landing—AFM Data Given:  Factored headwind with airplane 50 feet above landing surface 21.7 knots  Factored headwind with airplane on landing surface 16.3 knots  Ground speed change for 50 feet to touchdown (V50 – VTD) 4.0 knots  True airspeed required at 50 feet 130 knots Results:  Ground speed at 50 feet 130 - 21.7 = 108.3 knots  Ground speed at touchdown 108.3 - 4.0 = 104.3 knots  True airspeed at touchdown 104.3 + 16.3 = 120.6 knots 3.1.9 Expansion of Takeoff and Landing Data for a Range of Airport Elevations. 3.1.9.1 These guidelines apply to expanding AFM takeoff and landing data above and below the altitude at which the airplane takeoff and landing performance tests are conducted. 3.1.9.2 Historically, limits were placed on the extrapolation of takeoff data. In the past, takeoff data could generally be extrapolated 6,000 feet above and 3,000 feet below the test field elevation when proven testing and data reduction methods were used. For extrapolations beyond these limits, a 2 percent takeoff distance penalty was to be applied for every additional 1,000 feet extrapolation. Such limitations were generally not applied to 05/04/18 AC 25-7D 3-12 extrapolation of landing data, provided the effect of the higher true airspeed on landing distance was taken into account. 3.1.9.3 Since then, considerably more experience has since been gained both in terms of modeling airplane and propulsion system (i.e., turbine engines and propellers, where appropriate) performance and in verifying the accuracy of these models for determining high (and low) altitude takeoff and landing performance. This experience has shown that the soundness of the extrapolation is primarily a function of the accuracy of the propulsion system performance model and its integration with the airplane drag model. The basic aerodynamic characteristics of the airplane do not change significantly with altitude or ambient temperature, and any such effects are readily taken into account by standard airplane performance modeling practices. 3.1.9.4 As a result, with installed propulsion system performance characteristics that have been adequately defined and verified, airplane takeoff and landing performance data obtained at one field elevation may be extrapolated to higher and lower altitudes within the limits of the operating envelope without applying additional performance conservatisms. It should be noted, however, that extrapolation of the propulsion system data used in the determination and validation of propulsion system performance characteristics is typically limited to 3,000 feet above the highest altitude at which propulsion system parameters were evaluated for the pertinent power/thrust setting. (See paragraph 4.1 of this AC for more information on an acceptable means of establishing and verifying installed propulsion system performance characteristics.) 3.1.9.5 Note that certification testing for operation at airports that are above 8,000 feet should also include functional tests of the cabin pressurization system in accordance with paragraph 20.1.2.3 of this AC. Consideration should be given to any sensitivity to, or dependency upon airport altitude, such as: engine and auxiliary power unit (APU) starting, passenger oxygen, autopilot, autoland, autothrottle system power/thrust set/operation. 3.1.10 Tailwind Takeoff and Landing. 3.1.10.1 Wind Velocities of 10 Knots or Less. Approval may be given for performance, controllability, and engine operating characteristics for operations in reported tailwind velocities up to 10 knots without conducting additional flight tests at specific wind speeds. 05/04/18 AC 25-7D 3-13 3.1.10.2 Wind Velocities Greater than 10 Knots. 3.1.10.2.1 Performance. It is considered that takeoff, rejected takeoff, and landing distances, measured in tailwind conditions greater than 10 knots, are unreliable for use in determining airplane performance. Wind conditions of such magnitude are generally not sufficiently consistent over the length of the runway or over the time period required to perform the test maneuver. The 150 percent operational tailwind factor, required by §§ 25.105(d)(1) and 25.125(f), provides a satisfactory level of safety for operation in tailwinds up to 15 knots when using AFM data based on flight tests in nominally calm wind conditions. Note: The design requirements of § 25.479, Level landing conditions, also require the effects of increased contact speeds to be investigated if approval for landings with tailwinds greater than 10 knots is desired. 3.1.10.2.2 Control Characteristics. The test tailwind velocity for demonstrating handling qualities should be equal to the proposed limit tailwind factored by 150 percent. The intent of the 150 percent factor is to provide adequate margin for wind variability in operations, including currency of the wind data, averaging of the data by the measuring and reporting method, and the highly variable nature of higher wind conditions. Therefore, the test wind condition of 150 percent of the proposed tailwind limit should be an averaged or smoothed wind speed, not a peak wind speed. Airplane control characteristics should be evaluated under the following conditions with the CG at the aft limit and the test mean tailwind velocity equal to the proposed limit tailwind factored by 150 percent: 1. Takeoff. Both all-engines-operating and one-engine-inoperative (i.e., with a simulated failure of the critical engine at the engine failure speed) takeoffs should be evaluated at a light weight with maximum approved takeoff flap deflection. 2. Landing. Approach and landing at light weight with maximum approved landing flap deflection. 3. Determination of the increased ground speed effect on gear vibration or shimmy, and flight director, or autopilot instrument landing system (ILS) approaches, terrain awareness warning system (TAWS) sink rate modes, etc. 4. If engine idle power or thrust is increased to account for the increased tailwind velocity, ensure that deviations above the glideslope are recoverable. 05/04/18 AC 25-7D 3-14 3.1.10.2.3 Weight Limits. Consistent with the requirements of §§ 25.105(d)(1) and 25.125(f), the maximum takeoff and maximum quick turnaround weights should be determined using brake energies and tire speeds, as appropriate, calculated with the limit tailwind velocity factored by 150 percent. 3.1.10.2.4 Engine Operating Characteristics. Satisfactory engine operation should be demonstrated at the limit tailwind velocity factored by 150 percent. The demonstrations should include: 1. Zero groundspeed operation. 2. Takeoff power or thrust setting procedure used for AFM performance (typically completed by approximately 80 knots), both manually and automatically (autothrottle). 3. Reverse thrust operations. 3.1.10.2.5 Airplane Flight Manual. The AFM should contain a statement that the limitation for tailwinds greater than 10 knots reflects the capability of the airplane as evaluated in terms of airworthiness but does not constitute approval for operation in tailwinds exceeding 10 knots. 3.1.11 Procedures. 3.1.11.1 The performance-related flight test procedures are discussed in the following paragraphs of this AC:  Paragraph 4.2, Takeoff and Takeoff Speeds—§§ 25.105 and 25.107.  Paragraph 4.3, Accelerate-Stop Distance—§ 25.109.  Paragraph 4.4, Takeoff Path—§ 25.111.  Paragraph 4.5, Takeoff Distance and Takeoff Run—§ 25.113.  Paragraph 4.6, Takeoff Flight Path—§ 25.115.  Paragraph 4.7, Climb: General—§ 25.117.  Paragraph 4.8, Landing Climb: All-Engines-Operating—§ 25.119.  Paragraph 4.9, Climb: One-Engine-Inoperative—§ 25.121.  Paragraph 4.10, En Route Flight Paths—§ 25.123.  Paragraph 4.11, Landing—§ 25.125. 3.1.11.2 Performance Data for Multiple Flap or Additional Flap Positions. If approval of performance data is requested for flap settings at which no test data are available, the data may be obtained from interpolation of flight data obtained at no less than four flap settings that are within a 05/04/18 AC 25-7D 3-15 constant configuration of other lift devices. If the span of flap settings is small and previously obtained data provide sufficient confidence (i.e., the shapes of the curves are known and lend themselves to accurate interpolation), data from three flap settings may be acceptable. 3.1.11.3 Flight Characteristics for Abnormal Configurations. See § 25.671(c). 3.1.11.3.1 For purposes of this AC, an abnormal configuration is an operational configuration that results from any single failure or any combination of failures not shown to be improbable. 3.1.11.3.2 Flight characteristics for abnormal configurations may be determined by test or analysis to assure that the airplane is capable of continued safe flight and landing. Flight tests, if required, should be conducted at the critical conditions of altitude, weight, CG, and engine power or thrust associated with the configuration, and at the most critical airspeed between the speed reached one second after stall warning occurs (see paragraph 8.1.5.2.8 of this AC) and the maximum operating airspeed for the configuration. 3.2 Load Distribution Limits—§ 25.23. [Reserved] 3.3 Weight Limits and Center of Gravity Limits—§§ 25.25 and 25.27. [Reserved] 3.4 Empty Weight and Corresponding Center of Gravity—§ 25.29. [Reserved] 3.5 Removable Ballast—§ 25.31. 3.5.1 Explanation. None. 3.5.2 Procedures. Ballast may be carried during the flight tests whenever it is necessary to achieve a specific weight and CG location. Consideration should be given to the vertical as well as horizontal location of the ballast in cases where it may have an appreciable effect on the flying qualities of the airplane. The strength of the supporting structures should be considered in order to make sure they do not fail as a result of the anticipated loads that may be imposed during the particular tests. As required by § 21.35(a), applicants must show that these structures comply with the applicable structural requirements of part 25 before conducting flight tests with these structures in place. 05/04/18 AC 25-7D 3-16 3.6 Propeller Speed and Pitch Limits—§ 25.33. 3.6.1 Explanation. None. 3.6.2 Procedures. The tachometers and the airspeed indicating system of the test airplane should have been calibrated within the last six months. With that prerequisite satisfied, the following should be accomplished: 3.6.2.1 Determine that the propeller speeds and pitch settings are safe and satisfactory during all tests that are conducted in the flight test program within the certification limits of the airplane, engine, and propeller. This includes establishing acceptable low pitch (flight idle) blade angles on turbopropeller airplanes and verifying that propeller configurations are satisfactory at VMO/MMO to prevent propeller overspeed. 3.6.2.2 Determine that the propeller speeds and pitch settings are safe and satisfactory during all tests that are conducted to satisfy the performance requirements. 3.6.2.3 With the propeller governors operative and the propeller controls in full high revolutions per minute (RPM) position, determine that the maximum takeoff power settings do not exceed the rated takeoff RPM of each engine during takeoff and climb at the best rate-of-climb speed. 3.6.2.4 With the propeller governors made inoperative by mechanical means, determine the maximum power, no-wind, static RPMs. With the propeller governors operating on the low pitch stop, the engine speeds must not exceed 103 percent of the maximum allowable takeoff RPM or 99 percent of an approved maximum overspeed, as required by § 25.33(c). On turbopropeller engines, the engine speeds should not exceed the maximum engine speeds allowed by engine and propeller type designs. Note which systems were disabled and how the disablement was done. If maximum takeoff power torque or sea level standard conditions cannot be obtained on the test day, correct the data to these conditions by an acceptable means. A no-wind condition is considered to be a wind of 5 knots or less. The static RPM should be the average obtained with a direct crosswind from the left and a direct crosswind from the right. 3.6.2.5 If the above determinations are satisfactory, then measure the low-pitch stop setting and the high-pitch stop setting. These data may have been obtained from the propeller manufacturer and may be used, provided the pitch stops have not been changed since the manufacturer delivered the propeller. If measured, the blade station should be recorded. Include these blade angles in the type certificate data sheet. 05/04/18 AC 25-7D 4-1 CHAPTER 4. FLIGHT: PERFORMANCE 4.1 General—§ 25.101. 4.1.1 Explanation of Propulsion System Behavior. Section 25.101(c) requires that airplane performance “correspond to the propulsive thrust available under the particular ambient atmospheric conditions, the particular flight conditions….” The propulsion system’s (i.e., turbine engines and propellers, where appropriate) installed performance characteristics are primarily a function of engine power or thrust setting, airspeed, propeller efficiency (where applicable), altitude, and ambient temperature. Determine the effects of each of these variables to establish the thrust available for airplane performance calculations. 4.1.2 Procedures. 4.1.2.1 The intent is to develop a model of propulsion system performance that covers the approved flight envelope. Further, it should be shown that the combination of the propulsion system performance model and the airplane performance model is validated by the takeoff performance test data, climb performance tests, and tests used to determine airplane drag. Installed propulsion system performance characteristics may be established via the following tests and analyses:  Steady-state engine power (or thrust) setting versus power (or thrust) testing. See paragraph 4.1.2.2.  Lapse rate takeoff testing to characterize the behavior of power or thrust setting, rotor speeds, propeller effects (i.e., torque, RPM, and blade angle), or gas temperature as a function of time, thermal state, or airspeed, as appropriate. See paragraph 4.1.2.3.  Power/thrust calculation substantiation. See paragraph 4.1.2.4.  Effects of ambient temperature. See paragraph 4.1.2.5. 4.1.2.2 Steady-State Engine Power (or Thrust) Setting versus Power (or Thrust) Testing. Engines should be equipped with adequate instrumentation to allow the determination of thrust (or power). Data should be acquired in order to validate the model, including propeller-installed thrust, if applicable, over the range of power or thrust settings, altitudes, temperatures, and airspeeds for which approval is sought. Although it is not possible to definitively list or foresee all of the types of instrumentation that might be considered adequate for determining thrust (or power) output, two examples used in past certification programs are (1) engine pressure rakes, with engines calibrated in a ground test cell, and (2) fan speed, with engines calibrated in a ground test cell and the calibration data validated by the use of a flying test bed. In any case, the applicant should substantiate the adequacy 05/04/18 AC 25-7D 4-2 of the instrumentation to be used for determining the thrust (or power) output. 4.1.2.3 Lapse Rate Takeoff Testing to Characterize the Behavior of Power or Thrust Setting, Rotor Speeds, Propeller Effects, or Gas Temperature as a Function of Time, Thermal State, or Airspeed. These tests should include the operation of an automatic takeoff thrust control system (ATTCS), if applicable, and should cover the range of power or thrust settings for which approval is sought. 4.1.2.3.1 Data for higher altitude power or thrust settings may be acquired via overboost (i.e., operating at a higher than normal power or thrust setting for the conditions) with the consent of the engine and propeller manufacturer(s), when applicable. When considering the use of overboost on turbopropeller propulsion system installations to stimulate higher altitude and ambient temperature range conditions, the capability to achieve an appropriate simulation should be evaluated based on the engine and propeller control system(s) and aircraft performance and structural considerations. Engine (gearbox) torque, rotor speed, or gas temperature limits, including protection devices to prohibit or limit exceedances, may prevent the required amount of overboost needed for performance at the maximum airport altitude sought for approval. Overboost may be considered as increased torque, reduced propeller speed, or a combination of both, in order to achieve the appropriate blade angle for the higher altitude and ambient temperature range simulation. Consideration for extrapolations will depend on the applicant’s substantiation of the proper turbopropeller propulsion system simulated test conditions. 4.1.2.3.2 Lapse rate characteristics should be validated by takeoff demonstrations at the maximum airport altitude for which takeoff approval is being sought. Alternatively, if overboost (see paragraph above) is used to simulate the power or thrust setting parameters of the maximum airport altitude for which takeoff approval is sought, the takeoff demonstrations of lapse rate characteristics can be performed at an airport altitude up to 3,000 feet lower than the maximum airport altitude. 4.1.2.4 Power/Thrust Calculation Substantiation. Installed power or thrust should be calculated via a mathematical model of the propulsion system, or other appropriate means, adjusted as necessary to match the measured inflight performance characteristics of the installed propulsion system. The propulsion system mathematical model should define the relationship of power or thrust to the power or thrust setting parameter over the range of power or thrust settings, airspeeds, altitudes, and temperatures for which approval is sought. For turbojet airplanes, the propulsion system mathematical model should be substantiated by ground tests in which thrust is directly measured via a calibrated load cell or equivalent means. For turbopropeller airplanes, the engine power 05/04/18 AC 25-7D 4-3 measurement should be substantiated by a calibrated dynamometer or equivalent means, the engine jet thrust should be established by an acceptable engine model, and the propeller thrust and power characteristics should be substantiated by wind tunnel testing or equivalent means. 4.1.2.5 Effects of Ambient Temperature. The flight tests of paragraph 4.1.2.2 of this AC will typically provide data over a broad range of ambient temperatures. Additional data may be obtained from other flight or ground tests of the same type or series of engine. The objective is to confirm that the propulsion system model accurately reflects the effect of temperature over the range of ambient temperatures for which approval is being sought (operating envelope). Because thrust (or power) data can usually be normalized versus temperature using either dimensionless variables (e.g., theta exponents or a thermodynamic cycle model), it is usually unnecessary to obtain data over the entire ambient temperature range. There is no needed to conduct additional testing if:  The data show that the behavior of power or thrust and limiting parameters versus ambient temperature can be predicted accurately, and  Analysis based upon the test data shows that the propulsion system will operate at rated power or thrust without exceeding propulsion system limits. 4.1.2.6 Extrapolation of propulsion system performance data to 3,000 feet above the highest airport altitude tested (but no higher than the maximum takeoff airport altitude to be approved) is acceptable, provided the supporting data, including flight test and propulsion system operations data (e.g., engine and propeller control, limits exceedance, and surge protection devices scheduling), substantiates the proposed extrapolation procedures. Considerations for extrapolation depend upon an applicant’s determination, understanding, and substantiation of the critical operating modes of the propulsion system. This understanding includes a determination and quantification of the effects that propulsion system installation and variations in ambient conditions have on these modes. 4.2 Takeoff and Takeoff Speeds—§§ 25.105 and 25.107. 4.2.1 Explanation. Section 25.105 specifies the conditions that must be considered in determining the takeoff speeds, accelerate-stop distances, takeoff path, takeoff distance, and takeoff run in accordance with part 25 requirements. The primary objective of the takeoff tests required by § 25.107 is to determine the takeoff speeds for all takeoff configurations at 05/04/18 AC 25-7D 4-4 all weight, altitude, and temperature conditions within the operational limits selected by the applicant. 4.2.2 Procedures: General. 4.2.2.1 Section 25.105(c)(1) requires the takeoff performance data to be determined for smooth, dry and wet, hard-surfaced runways. Paragraph 4.3 of this AC describes methods for determining the accelerate-stop distances required by § 25.109. Paragraph 4.5 describes methods for determining the takeoff distance and takeoff run required by § 25.113. 4.2.2.2 In accordance with § 25.101(f), testing for determining the accelerate-stop distances, takeoff flight paths, and takeoff distances should be accomplished using procedures established by the applicant for operation in service. In accordance with §25.101(h), these procedures must be able to be consistently executed in service by crews of average skill, use methods or devices that are safe and reliable, and include allowances for any time delays in the execution of the procedures that may reasonably be expected in service. These requirements prohibit the use of exceptional piloting techniques, such as higher control force inputs or higher pitch rates than would occur in operational service, from being used to generate unrealistic takeoff distances. The intent of these requirements is to establish takeoff performance representative of that which can reasonably be expected to be achieved in operational service. 4.2.2.3 Attention should be paid to all potential sources of airspeed error, but special consideration should be given to airplanes with electronic instruments in the cockpit that apply electronic filtering to the airspeed data. This filtering, which causes a time delay in the airspeed indication, can be a source of significant systematic error in the presentation of airspeed to the flightcrew. With normal takeoff acceleration, the airplane will be at a higher speed than is indicated by the cockpit instrument, which can result in longer distances than are presented in the AFM, particularly in the event of a rejected takeoff near the indicated V1 speed. The effects of any time delays caused by electronic filtering, pneumatic system lag, or other sources should be adequately addressed in the AFM speed and distance presentations. Further explanation of airspeed lag, particularly pertaining to airplanes with electronic instruments in the cockpit, and procedures for calibrating the airspeed indicating system (§ 25.1323(b)) are presented in paragraph 33.3 of this AC. 4.2.3 Procedures: Section 25.107(a)(1)—Engine Failure Speed (VEF). The engine failure speed (VEF) is defined as the calibrated airspeed at which the critical engine is assumed to fail and must be selected by the applicant. VEF cannot be less than the ground minimum control speed (VMCG). 05/04/18 AC 25-7D 4-5 4.2.4 Procedures: Section 25.107(a)(2)—V1. V1 may not be less than VEF plus the speed gained with the critical engine inoperative during the time interval between VEF and the instant at which the pilot takes action after recognizing the engine failure. This is indicated by pilot application of the first deceleration means such as brakes, throttles, spoilers, etc. during accelerate-stop tests. The applicant may choose the sequence of events. Refer to paragraph 4.3 of this AC, addressing § 25.109, for a more complete description of rejected takeoff (RTO) transition procedures and associated time delays. 4.2.5 Procedures: Section 25.107(b)—Minimum Takeoff Safety Speed (V2MIN). 4.2.5.1 V2MIN, in terms of calibrated airspeed, cannot be less than: 4.2.5.1.1 1.1 times the VMC defined in § 25.149. 4.2.5.1.2 1.13 times VSR for two-engine and three-engine turbopropeller and reciprocating engine-powered airplanes and for all turbojet airplanes that do not have provisions for obtaining a significant reduction in the one-engine-inoperative power-on stalling speed (i.e., boundary layer control, blown flaps, etc.). The value of VSR to be used in determining V2MIN is the stall speed in the applicable takeoff configuration, landing gear retracted, except for those airplanes with a fixed landing gear or for gear-down dispatch. 4.2.5.2 V2MIN may be reduced to 1.08 times VSR for turbopropeller and reciprocating engine-powered airplanes with more than three engines, and turbojet powered airplanes with adequate provisions for obtaining significant power-on stall speed reduction through the use of such things as boundary layer control, blown flaps, etc. 4.2.5.3 For propeller-driven airplanes, the difference between the two margins, based upon the number of engines installed on the airplane, is because the application of power ordinarily reduces the stalling speed appreciably. In the case of the two-engine propeller-driven airplane, at least half of this reduction is eliminated by the failure of an engine. The difference in the required factors therefore provides approximately the same margin over the actual stalling speed under the power-on conditions that are obtained after the loss of an engine, no matter what the number of engines (in excess of one) may be. Unlike the propeller-driven airplane, the turbojet/turbofan powered airplane does not show any appreciable difference between the power-on and power-off stalling speed. This is due to the absence of the propeller, which ordinarily induces a slipstream with the application of power causing the wing to retain its lift to a speed lower than the power-off stalling speed. The applicant’s selection of the two speeds specified will influence the nature of the testing required in establishing the takeoff flight path. 05/04/18 AC 25-7D 4-6 4.2.6 Procedures: Section 25.107(c)—Takeoff Safety Speed (V2). 4.2.6.1 V2 is the calibrated airspeed that is attained at or before the airplane reaches a height of 35 feet above the takeoff surface after an engine failure at VEF using an established rotation speed (VR). From the liftoff point, the takeoff surface extends to the end of the takeoff distance continuing at the same slope as the runway. During the takeoff speeds demonstration, V2 should be continued to an altitude sufficient to assure stable conditions beyond the 35-foot height. V2 cannot be less than V2MIN. In addition, V2 cannot be less than the liftoff speed, VLOF, which is defined in § 25.107(f). In accordance with § 25.107(c), V2 in terms of calibrated airspeed may not be less than VR plus the speed increment attained before reaching a height of 35 feet above the takeoff surface and a speed that provides the maneuvering capability specified in § 25.143(h). In addition, § 25.111(c)(2) stipulates that the airplane must reach V2 before it is 35 feet above the takeoff surface and continue at a speed not less than V2 until it is 400 feet above the takeoff surface. These requirements were first expressed in Special Civil Air Regulation No. SR-422, Turbine-Powered Transport Category Airplanes of Current Design (SR-422A), paragraphs 4T.114(b)(4) and (c)(3) and 4T.116(e). The concern that the regulation change was addressing was the overshoot of V2 after liftoff under the previous requirement that the airplane attain V2 on, or near, the ground. The intent of the current requirement is to allow an acceleration to V2 after liftoff but not to allow a decrease in the field length required to attain a height of 35 feet above the takeoff surface by attaining a speed greater than V2, under low drag ground conditions, and using the excess kinetic energy to attain the 35-foot height. 4.2.6.2 In the case of turbojet powered airplanes, when most of the one-engine-inoperative data have been collected using throttle chops, V2, and its relationship to VR, should be substantiated by at least a limited number of fuel cuts at VEF. For derivative programs not involving a modification that would affect thrust decay characteristics, demonstrations of fuel cuts may be unnecessary. 4.2.6.3 For propeller-driven airplanes, the use of fuel cuts can be more important in order to ensure that the takeoff speeds and distances are obtained with the critical engine’s propeller attaining the position it would during a sudden engine failure. The number of tests that should be conducted using fuel cuts depends on the correlation obtained with the throttle chop data and substantiation that the data analysis methodology adequately models the effects of a sudden engine failure. 4.2.7 Procedures: Section 25.107(d)—Minimum Unstick Speed (VMU). 4.2.7.1 Section 25.107(d) states, “VMU speeds must be selected by the applicant.” An applicant can either determine the lowest possible VMU speeds or select 05/04/18 AC 25-7D 4-7 a higher speed that supports the takeoff performance targets of the airplane. Regardless of how the applicant selects the VMU speeds, compliance must be shown with § 25.107(d), (e)(1)(iv), (e)(3), and (e)(4) to show that the selected VMU speeds allow the airplane to safely lift off the ground and continue the takeoff. 4.2.7.2 An applicant should comply with § 25.107(d) by conducting VMU tests with all engines operating and also with one engine inoperative. During these tests, the takeoff should be continued until the airplane is out of ground effect. The airplane pitch attitude should not be decreased after liftoff. 4.2.7.3 VMU testing to demonstrate the lowest VMU speed is a maximum performance flight test maneuver, and liftoff may occur very near the angle-of-attack for maximum lift coefficient. Also, even though pitch attitude may be held fairly constant during the maneuver, environmental conditions and transiting through ground effect may result in changes in angle-of-attack. It is permissible to lift off at a speed that is below the normal stall warning speed, provided no more than light buffet is encountered. 4.2.7.3.1 It is important for the flight test team to understand the control laws and any transitions between control laws during takeoff (e.g., based on weight on wheels) for an electronic flight control system that may present unique hazards that should be taken into account. 4.2.7.3.2 An artificial stall warning system (e.g., a stick shaker) may be disabled during VMU testing, although doing so will require extreme caution and depend upon a thorough knowledge of the airplane’s stall characteristics, both in and out of ground effect. 4.2.7.3.3 If the airplane is equipped with a stick pusher, angle-of-attack limiter, or other system that may affect the conduct of the test, the angle of attack setting for activation of the system may be selected by the applicant and differ from the nominal setting. The system may alternatively be disabled or its activation delayed for test purposes until a safe altitude is reached. However, for airplanes equipped with a stick pusher that is not designed to be inhibited during takeoff, the VMU test demonstrations will need to be assessed and will only remain valid if the stick pusher would not have activated with the angle-of-attack indication means set at the lowest angle within production tolerances. 4.2.7.4 In lieu of conducting one-engine-inoperative VMU tests, the applicant may conduct all-engines-operating VMU tests if all pertinent factors that would be associated with an actual one-engine-inoperative VMU test are simulated or otherwise taken into account. To take into account all pertinent factors, 05/04/18 AC 25-7D 4-8 it may be necessary to adjust the resulting VMU test values analytically. The factors to be accounted for should include at least the following:  Thrust/weight ratio for the one-engine-inoperative range.  Controllability (may be related to one-engine-inoperative free air tests, such as minimum control speed in the air (VMCA)).  Increased drag due to use of lateral/directional control systems.  Reduced lift due to use of devices such as wing spoilers for lateral control.  Adverse effects of use of any other systems or devices on control, drag, or lift. 4.2.7.5 The number of VMU tests needed may be minimized by testing only the critical all-engines-operating and one-engine-inoperative thrust/weight ratios, provided the VMU speeds determined at these critical conditions are used for the range of thrust/weights appropriate to the all-engines-operating and one-engine-inoperative configurations. The critical thrust/weight is established by correcting, to the VMU speed, the thrust that results in the airplane achieving its limiting one-engine-inoperative climb gradient at the normally scheduled speed and in the appropriate configuration. 4.2.7.6 Amendment 25-42, effective March 1, 1978, revised §§ 25.107(d) and 25.107(e)(1)(iv) in order to permit the one-engine-inoperative VMU to be determined by all-engines-operating tests at the thrust/weight ratio corresponding to the one-engine-inoperative condition. As revised, § 25.107(d) specifies that VMU must be selected for the range of thrust/weight ratios to be certificated, rather than for the all-engines- operating and one-engine-inoperative conditions as was previously required. In determining the all-engines-operating thrust/weight ratio that corresponds to the one-engine-inoperative condition, consider trim and control drag differences between the two configurations in addition to the effect of the number of engines operating. The minimum thrust/weight ratio to be certificated is established by correcting, to the VMU speed, the thrust that results in the airplane achieving its limiting engine-out climb gradient in the appropriate configuration and at the normally scheduled speed. 4.2.7.7 To conduct the VMU tests, rotate the airplane as necessary to achieve the VMU attitude. It is acceptable to use some additional nose-up trim over the normal trim setting during VMU demonstrations. If additional nose-up trim is required, the additional considerations of paragraph 4.2.7.8 below apply. VMU is the speed at which the weight of the airplane is completely supported by aerodynamic lift and thrust forces. Some judgment may be necessary on airplanes that have tilting main landing gear bogies. 05/04/18 AC 25-7D 4-9 Determining the liftoff point from gear loads and wheel speeds has been found acceptable in past programs. After liftoff, the airplane should be flown out of ground effect. During liftoff and the subsequent climbout, the airplane should be fully controllable. 4.2.7.8 VMU Testing for Airplanes having Limited Pitch Control Authority. 4.2.7.8.1 For some airplanes with limited pitch control authority, it may not be possible, at forward CG and normal trim, to rotate the airplane to a liftoff attitude where the airplane could otherwise perform a clean flyaway at a minimum speed had the required attitude been achieved. This may occur only over a portion of the takeoff weight range in some configurations. Though generally associated with the inability of the pitch control surfaces to provide adequate pitching moment to rotate the airplane to the desired pitch attitude at low thrust/weight ratio conditions, the same phenomenon may occur at high thrust/weight ratio conditions for airplanes with high thrust lines (e.g., aft engines mounted high on the fuselage). When limited pitch control authority is clearly shown to be the case, VMU test conditions may be modified to allow testing aft of the forward CG limit and/or with use of more airplane nose-up trim than normal. The VMU data determined with this procedure should be corrected to those values representative of the appropriate forward limit; the variation of VMU with CG may be assumed to be like the variation of free air stalling speed with CG. Although the development of scheduled takeoff speeds may proceed from these corrected VMU data, additional tests are required (see paragraph 4.2.7.8.2 below) to check that the relaxed VMU criteria have not neglected problems that might arise from operational variations in rotating airplanes with limited pitch control authority. 4.2.7.8.2 In the following assurance test, the airplane should demonstrate safe flyaway characteristics: Minimum speed liftoff should be demonstrated at the critical forward CG limit with normal trim. For airplanes with a cutback forward CG at heavy weight, two weight/CG conditions should be considered. The heavy weight tests should be conducted at maximum structural or maximum sea level climb-limited weight with the associated forward CG. The full forward CG tests should be conducted at the highest associated weight. Alternatively, testing may be conducted at a single weight if an analysis is provided that identifies the critical weight/CG combination with regard to limited pitch attitude capability for liftoff. These assurance tests should be conducted at the thrust/weight ratio that is most critical for attaining a pitch attitude that will provide a minimum liftoff speed. 4.2.7.8.3 For airplanes that are limited by low thrust/weight conditions, tests should be conducted at the minimum thrust/weight ratio for both the simulated one-engine-inoperative test (i.e., symmetrical reduced thrust) case and the all-engines-operating case. 05/04/18 AC 25-7D 4-10 4.2.7.8.4 For airplanes that are limited by high thrust/weight conditions, tests should be conducted at the highest thrust/weight ratio within the airplane’s operating envelope for both the simulated one-engine-inoperative case (i.e., symmetrical reduced thrust) and the all-engines-operating case. 4.2.7.8.5 One acceptable test technique is to hold full nose-up control column as the airplane accelerates. As pitch attitude is achieved to establish the minimum liftoff speed, pitch control may be adjusted to prevent over-rotation, but the liftoff attitude should be maintained as the airplane flies off the ground and out of ground effect. 4.2.7.8.6 The resulting liftoff speeds are acceptable if the test proves successful and the liftoff speed is at least 5 knots below the normally scheduled liftoff speed. 4.2.7.8.7 This minimum 5 knot margin from the scheduled liftoff speed provides some leeway for operational variations such as mistrim, CG errors, etc., that could further limit the elevator authority. The reduced VMU margins arising from this test, relative to those specified in § 25.107(e)(1)(iv), are considered acceptable because of the reduced probability of a pitch control authority-limited airplane getting into a high drag condition due to over-rotation. 4.2.7.9 VMU Testing for Geometry Limited Airplanes. 4.2.7.9.1 For airplanes that are geometry limited (i.e., the minimum possible VMU speeds are limited by tail contact with the runway), § 25.107(e)(1)(iv)(B) allows the VMU to VLOF speed margins to be reduced to 108 percent and 104 percent for the all-engines-operating and one-engine-inoperative conditions, respectively. The VMU demonstrated should be sound and repeatable. 4.2.7.9.2 An airplane that is de