Change 1 viii Table of Contents (continued)
Paragraph Page No.
Section 4. Airplane Flight Manual __________________________________________ 271
224. General - § 25.1581 _______________________________________________ 271 [225. - 227.] [Reserved]_________________________________________________ 271 Chapter 8 - Airworthiness: Miscellaneous Items _________________________________ 272
228. Design and Function of Artificial Stall Warning and Identification Systems. __ 272
229. Reduced and Derated Thrust Takeoff Operations ________________________ 275
230. Runway Gradients Greater Than ± 2 Percent. ___________________________ 276
231. Criteria For Approval of Steep Approach To Landing.____________________ 277
232. Takeoff and Landing On Unpaved Runways. ___________________________ 281
233. Accountability of Performance Degradation Relative to Both Minor Design Changes (External Posture) and Configuration Deviation List (CDL) Items. _______ 284
234. Configuration Deviation List. _______________________________________ 285
235. Spare Engine Pod. ________________________________________________ 287
236. Authorization For Ferry Flight With One Engine Inoperative - § 91.611. _____ 287
237. Instrument Landing System Weather Minima. __________________________ 288
238. Takeoff Performance Credit For Alternate Forward Center of Gravity Limits. _ 289
239. Performance Credit For Automatic Propeller Drag Reduction Devices._______ 292
240. Airplane Backing Using Reverse Thrust. ______________________________ 293
Change 1 ix
Table of Contents (continued)
Figures
Figure Page No.
Figure 3-1. Weight Tolerance Limits_____________________________________________ 6 Figure 3-2. Equivalent Weight Extrapolation ______________________________________ 7 Figure 3-3. Test Parameters That Normally Can Be Corrected ________________________ 9 Figure 3-4. Wind Profile Variation _____________________________________________ 10 Figure 11-1. Accelerate-Stop Time Delays _______________________________________ 35 Figure 11-2. Accelerate-Stop Speed vs. Distance __________________________________ 37 Figure 11-3. Anti-Skid System Response Characteristics____________________________ 41 Figure 11-4. Anti-Skid System Response Characteristics____________________________ 42 Figure 11-5. Anti-Skid System Response Characteristics____________________________ 44 Figure 11-6. Instantaneous Brake Force and Peak Brake Force _____________________ 47 Figure 11-7. Anti-Skid Efficiency – Wheel Slip Relationship ________________________ 49 Figure 11-8. Substantiation of the Optimal Slip Value______________________________ 51 Figure 13-1. Takeoff Distance on a Dry Runway __________________________________ 63 Figure 13-2. Takeoff Distance _________________________________________________ 64 Figure 13-3. Takeoff Distance On a Wet Runway _________________________________ 65 Figure 13-4. Takeoff Run_____________________________________________________ 65 Figure 13-5. Takeoff Run_____________________________________________________ 66 Figure 13-6. Clearway Profiles ________________________________________________ 67 Figure 14-1. Takeoff Segments & Nomenclature __________________________________ 68
Change 1 x
Table of Contents (continued)
Figure Page No.
Figure 14-2. Net Takeoff Flight Path ___________________________________________ 69 Figure 19-1. Landing Time Delays _____________________________________________ 78 Figure 20-1. Sample Pitch Tracking Task________________________________________ 89 Figure 20-2. A-PC Rating Criteria and Comparison To Mil Standard _________________ 90 Figure 20-3 Example of Acceptable HQ Rating For A-PC Tendencies_________________ 91 Figure 26-1. Longitudinal Static Stability _______________________________________ 111 Figure 29-1. Thrust Effect On Stall Speed ______________________________________ 123 Figure 29-2. CLMAX and Load Factor___________________________________________ 124 Figure 29-3. CLMAX vs Entry Rate _____________________________________________ 126 Figure 29-4. CLMAX vs Weight and Flap Setting __________________________________ 126 Figure 29-5. Stall Speed vs Weight and Flap Setting ______________________________ 128 Figure 31-1. Maneuvering Characteristics ______________________________________ 142 Figure 31-2. Maneuvering Characteristics ______________________________________ 142 Figure 33-1. Mistrimmed Maneuvering Characteristics____________________________ 150 Figure 181-1 Altitude Loss versus Altitude Go-Around Mode _______________________ 255
Change 1 xi
Table of Contents (continued)
Appendices Appendix Page No.
Appendix 1 _______________________________________________________________ A1-1 Acronyms and Abbreviations _____________________________________________ A1-1 Appendix 2 _______________________________________________________________ A2-1 Function and Reliability Tests - § 21.35(b)(2) ________________________________ A2-1 Appendix 3 _______________________________________________________________ A3-1 Correction of Air Minimum Control Speed To Standard Conditions_____________ A3-1
1. Theoretical Basis___________________________________________________ A3-1
2. Constant C n Method ________________________________________________ A3-2
3. Graphical Method __________________________________________________ A3-3
4. Equation Method___________________________________________________ A3-7 Appendix 4 _______________________________________________________________ A4-1 History of Jet Transport Performance Standards_____________________________ A4-1 Special Civil Air Regulation No. SR-422 ____________________________________ A4-2 Performance __________________________________________________________ A4-5 Airplane Flight Manual_________________________________________________ A4-14 Operating Rules ______________________________________________________ A4-14 Special Civil Air Regulation No. SR-422A __________________________________ A4-17 Performance _________________________________________________________ A4-25 Airplane Flight Manual_________________________________________________ A4-35 Operating Rules ______________________________________________________ A4-36 Special Civil Air Regulation No. SR-422B __________________________________ A4-40 Performance _________________________________________________________ A4-43 Airplane Flight Manual_________________________________________________ A4-54
Change 1 xii
Table of Contents (continued)
Appendices
Appendix Page No.
Operating Rules ______________________________________________________ A4-55 Appendix 5 _______________________________________________________________ A5-1 Historical Development Of Accelerate-Stop Time Delays ______________________ A5-1 Figure 1. Accelerate-Stop Time Delays___________________________________ A5-2 Figure 2. Accelerate-Stop Time Delays___________________________________ A5-4 Appendix 6 _______________________________________________________________ A6-1 FAA Handling Qualities Rating Method ____________________________________ A6-1 Figure 1. Airworthiness HQ Regulations Impacted/Outpaced by Technology _____ A6-2 Figure 2. Probability vs. Consequence Graph ______________________________ A6-3 Figure 3. Development of FAA HQRM Criteria____________________________ A6-4 Figure 4. Major Elements of Task-Oriented Handling Qualities Rating Method ___ A6-4 Figure 5. Probability Guidelines for Combined Occurrence Flight Conditions ____ A6-5 Figure 6. Flaps UP Flight Envelopes _____________________________________ A6-7 Figure 7. Flaps DOWN Flight Envelopes _________________________________ A6-8 Figure 8. Pilot Ratings ________________________________________________ A6-9 Figure 9. Probability Combination Leading to HQ Rating ___________________ A6-10 Figure 10. Probability Guidelines to Determine HQ Requirements ____________ A6-11 Figure 11. General HQ Task Categories _________________________________ A6-12 Figure 12. Minimum HQ Requirements _________________________________ A6-13 Appendix 7 _______________________________________________________________ A7-1 Rudder Pedal Force-Limited Air Minimum Control Speed_____________________ A7-1
Change 1
1 Introduction
1. Purpose.
a. This Advisory Circular (AC ) provides upda ted 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 This AC is not mandatory and does not constitute a regulation. It describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulation(s). The FAA will consider other methods of demonstrating compliance that an applicant may elect to present. 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.
This material does not change, create any additional, authorize changes in, or permit deviations from existing regulatory requirements.
b. See Appendix 1 for a list of acronyms and abbreviations used in this AC.
2. Applicability. These methods and procedures are provided in the interest of certification approval for use during all transport category airplane flight test certification activities. This material is not to be construed as regulatory or having a mandatory effect. The procedures set forth herein are one acceptable means of compliance with applicable sections of part 25. Any alternative means proposed by the applicant should be given due consideration. Applicants are encouraged to use their technical ingenuity and resourcefulness in order to develop more efficient and less costly methods of complying with the requirements of part 25. Since these methods and procedures are only one acceptable means of compliance, individuals should be guided by the intent of the methods provided in this AC. As deviations from the methods and procedures described in this AC may occur, FAA certification personnel will coordinate what they consider to be major deviations with the Transport Standards Staff (ANM-110) of the Transport Airplane Directorate. If in their judgment, however, a deviation is considered to be minor, coordination with ANM-110 may not be necessary.
3. Cancellation. AC-25-7B, “Flight Test Guide for Certification of Transport Category Airplanes, “dated March 29, 2011, is cancelled.
4. Background. 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 handling characteristics. AC 25-7 has been revised three times to reflect changes in the part 25 regulatory requirements, changes in guidance and policy, and advances in technology. 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, which was cancelled when AC 25-7A was issued.
Change 1 to AC 25-7A added acceptable means of compliance for the regulatory changes
Change 1 2 associated with amendments 92 and 98 to part 25. AC 25-7B added acceptable means of compliance for the regulatory changes associated with amendments 108, 109, and 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 is removed as this material is now contained in AC 25-25. AC 25-7B Change 1 provides updated guidance material to ensure consistent application of airworthiness requirements adopted by Amendment 25-135 to 14 CFR part 25.
5. Related Publications. Certification personnel should be familiar with FAA Order 8110.4c, “Type Certification,” and FAA Order 8100.5A, “Aircraft Certification Service Mission, Responsibilities, Relationships, and Programs.” In this AC, reference is made to other FAA advisory circulars that provide guidance on various aspects of type certification and supplemental type certification.
3 Chapter 1 - General
1. Applicability - § 25.1 [Reserved]
2. Special Retroactive Requirements - § 25.2 [Reserved]
Chapter 2 - Flight
Section 1. General
3. Proof of Compliance - § 25.21.
a. 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, aftmounted 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.
(1) Section 25.21(a) - Proof of Compliance .
( a) 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.
( b) If the airplane flight characteristics or the required flight data are affected by weight and/or center of gravity (c.g.), the compliance data must be presented for the most critical weight and c.g. position per § 25.21(a). Unless the applicant shows that the allowable c.g. 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 c.g.
( c) The gross weight and c.g. tolerances specified in paragraphs 3a(3)(b)1 and 3 are test tolerances and are not intended to allow compliance to be shown at less than critical conditions.
(d) Section 21.35(a)(3) requires that the test airplane be in conformity with its type design specifications.
1 This means that the test airplane must be in conformity with its type design specification as relates to the particular test being conducted.
2 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, the applicant must show that its presence would have no effect on measured airplane performance and flight characteristics.
(e) 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 2 to this AC provides guidance for showing compliance with this requirement.
(2) Section 25.21(c) - Proof of Compliance (Altitude Effect on Flight Characteristics ).
(a) Any of the flying qualities, including controllability, stability, trim, and stall characteristics, affected by altitude must be investigated for the most adverse altitude conditions approved for operations.
(b) Consideration should be given in the test program to aerodynamic control system changes with altitude (e.g., control throws or auto slats which are sometimes inhibited by Mach number at altitude).
(3) Section 25.21(d) - Proof of Compliance (Flight Test Tolerances).
(a) 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 variations in flight test values from which data are acceptable for reduction to the value desired. They are not intended for tests to be routinely scheduled at the lower weights, or to allow for compliance to be shown at less than the critical condition; nor are they to be considered as allowable inaccuracy of measurement. As an example, when demonstrating stability with a specified trim speed of
1.3 VSR1, the trim speed may be 1.3 VSR1 +3 knots or 3 percent; however, no positive tolerance is permitted when demonstrating the minimum prescribed trim speed of 1.3 VSR1 (Ref. § 25.161).
(b) Where variation in the parameter on 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 operating envelope being approved. If such a correction is impossible or impractical (e.g., performance at forward c.g.), the average test conditions should assure that the measured characteristics represent the actual critical value.
1 Weight limits. Figure 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 configuration, particularly those tests used to establish airplane flight manual (AFM) performance information. As noted in paragraph
(a) 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 for compliance to be shown at less than the critical weight condition.
Figure 3-1. Weight Tolerance Limits
Flight Test Conditions Weight Tolerance Limit +5% +10% Stall Speeds X Stall Characteristics X Climb Performance X Takeoff Flight Paths X Landing Braking Distance X Landing Air Distance X Takeoff Distance & Speed X Accelerate-Stop Distance X Maximum Energy RTOs X Minimum Unstick Speed X
(aa) For follow-on airplane certification programs (e.g., minor gross weight increase), where it is desired to use an existing certificated data base from an aerodynamically similar model of the same airplane type, the test weight tolerance limits of figure 3-1 have also been applied as extrapolation limits to minimize additional test requirements.
(bb) For follow-on airplane certification programs, test data may be extrapolated to higher gross weights than specified in figure 3-1, if the available test data include an adequate range of weights and an appropriate number of points at the highest weight tested.
If the test data analysis verifies the predicted effect of weight, then other extrapolation limits may apply.
(cc) 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 figure 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 3-2). The resulting equivalent gross weight should not exceed the certificated
7 maximum landing weight by more than the five percent weight extrapolation limit specified in figure 3-1. If the equivalent gross weight (at the existing landing flap setting) is not more than five percent greater than the certificated maximum landing weight, the reduced flap certification may be eligible for a limited flight test program (e.g., stall speed verification, handling characteristics, and 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).
Figure 3-2. Equivalent Weight Extrapolation
2 Wind Limits. For takeoff and landing tests, a wind velocity limit of 10 knots (from any direction) or 0.11 VSR1 (whichever is lower) at the height of the mean aerodynamic chord (MAC), as determined with the airplane in a static ground attitude, has been considered the maximum acceptable. When test wind velocity is to be measured at the wing MAC height, a measurement height of six feet above the ground should be considered as a limit to avoid possible measurement inaccuracies due to surface interference. Because of likely unsteady wind conditions, it is generally considered that takeoff and landing performance data obtained under runway wind conditions greater than 5 knots are likely to be inconsistent and unreliable. If performance data are obtained with winds greater than 5 knots, these data should not necessarily be ignored.
3 C.G. Limits. A test tolerance of + 7 percent of the total c.g. range is intended to allow some practical relief for inflight c.g. movement. This relief is only acceptable when the test data general scatter is on both sides of the limiting c.g. or when c.g. correction from test c.g. to limit c.g. is acceptable.
4 Airspeed Limits. Normally, tests conducted within 3 percent or 3 knots (whichever is the higher) of the desired test speed are considered acceptable.