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.
5 Thrust Limits. Thrust critical tests, such as minimum control speeds, should be conducted at the highest thrust (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 corrections should be limited to 5 percent of test day thrust, unless a detailed analysis is performed. (See Appendix 7 of this AC).
(c) Because the tolerance values normally are not considered in the airplane design substantiation, 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, however, are always conducted under controlled conditions and with the flight test crew’s full cognizance of the situation. Examples of such flights are:
1 Takeoff at greater than maximum takeoff weight for the purpose of reaching a test area at the maximum takeoff weight.
2 Landing at greater than maximum landing weights during the course of conducting takeoff tests.
3 Flights to obtain data for future approvals beyond that substantiated for the initial type design.
(d) The table in figure 3-3 indicates the cases in which corrections are normally allowed. Any corrections to flight test data should be made by methods that are agreed to by the FAA.
Figure 3-3. Test Parameters That Normally Can Be Corrected
Flight Test Condition Correctable Parameters Wt. C.G. 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 perf. X X --- X X X Minimum control speed --- --- --- --- X --- Minimum unstick speed X X X --- X --- Buffet boundary X X --- X --- ---
(e) All instrumentation used in the flight test program should be appropriately calibrated and acceptable to the FAA test team.
(4) Section 25.21(f) - Proof of Compliance (Wind Measurement and Corrections).
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 V W2 = Wind velocity at H2 V W1 = Wind velocity at H1
This equation is presented graphically below. Values of H less than 5 feet should not be used in this relationship.
Figure 3-4. Wind Profile Variation
(5) 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 (4) above. The following examples are methods of handling wind profile variation data. Other methods have also been found acceptable.
Example: Test Data
Given:
o Height of mean-aerodynamic-chord with airplane on surface 8.0 ft.
o Height of wind measurement 6.0 ft.
o Measured wind velocity 4.8 kts.
0 10 20 30 40 50 60 70 0 1 02 03 04 05 06 0
WIND VELOCITY - KNOTS
HEIGHT ABOVE FIELD ELEVATION - FEET 10 meters
Results:
o Test wind velocity with airplane 50 ft. above landing surface
4.8((50 + 8)/6) 1/7 = 6.6 kts.
o Test wind velocity with airplane 35 ft. above takeoff surface
4.8((35 + 8)/6) 1/7 = 6.4 kts.
o Test wind velocity with airplane on surface
4.8(8/6) 1/7 = 5.0 kts.
(6) 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 meanaerodynamic-chord, which corresponds to the wind condition as measured at 10 meters (32.81 ft.) above the takeoff surface, and corrected for wind factors of § 25.105(d)(1).
Example: Airplane Flight Manual Data
Given:
o Height of mean-aerodynamic-chord with airplane on surface 8.0 ft.
o Reported head wind at 10 meters 40.0 kts.
o Section 25.105(d)(1) wind factor 0.5
Results:
o Factored wind velocity with airplane 50 ft. above landing surface
(0.5)(40)((50 + 8)/32.81) 1/7 = 21.7 kts.
o Factored wind velocity with airplane 35 ft. above takeoff surface
(0.5)(40)((35 + 8)/32.81) 1/7 = 20.8 kts.
o Factored wind velocity with airplane on surface
(0.5)(40)(8/32.81) 1/7 = 16.3 kts.
(7) Airplane Airspeed Variation Due to Wind Profile Variation With Simultaneous 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 manifested by only the change in ground speed. These changes in speed (zero wind speed changes) may be generalized either as speed increments or