Appendix A Table A-1. Terms and Definitions (continued)
Term Definition TIA Type inspection Authorization TIR Type Inspection Report TOW Takeoff Warning TSO Technical Standard Order T/W Thrust-to-Weight Ratio UNSAT 1. Unsatisfactory
2. Failed V1 Maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. It also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
V2 Takeoff safety speed V2MIN Minimum takeoff safety speed V35 Speed at a height of 35 feet above the takeoff surface VD Design diving speed VDF Demonstrated flight diving speed VEF Speed at which the critical engine is assumed to fail during takeoff VFC Maximum speed for stability characteristics VFE Maximum flap extended speed VFR Visual Flight Rules VG Vertical Gyros A-8
Appendix A Table A-1. Terms and Definitions (continued)
Term Definition VHF Very High Frequency VLE Maximum landing gear extended speed VLO Maximum landing gear operating speed VLOF Lift off speed VMC Visual Meteorological Conditions VMC Minimum control speed with the critical engine inoperative VMCA Minimum control speed in the air VMCG Minimum control speed on the ground VMCL Minimum control speed during approach and landing with all engines operating VMCL(1 out) Minimum control speed during approach and landing with one engine inoperative VMCL-2 Minimum control speed during approach and landing with one critical engine inoperative (for airplanes with three or more engines) VMCL-2(2 out) Minimum control speed during approach and landing with two engines inoperative (for airplanes with three or more engines) VMO Maximum operating limit speed VMU Minimum unstick speed VNAV Vertical Navigation VOR Very High Frequency Omnidirectional Range VORTAC Very High Frequency Omnidirectional Range Tactical Air Navigation VREF Reference landing speed VS Stalling speed or the minimum steady flight speed at which the airplane is controllable A-9
Appendix A Table A-1. Terms and Definitions (continued)
Term Definition VS0 Stalling speed or the minimum steady flight speed in the landing configuration VS1 Stalling speed or the minimum steady flight speed in a specific configuration VSR Reference stall speed VSR0 Reference stall speed in the landing configuration VSR1 Reference stall speed in a specific configuration VSW Speed at which the onset of natural or artificial stall warning occurs WAT Weight, Altitude, Temperature W/δ Weight/Delta Table A-2. Symbols and Definitions
Symbol Definition Δ Incremental change in value δ Ratio of atmospheric pressure at any altitude to the pressure at sea level max Maximum friction coefficient available between a tire and the runway surface A-10
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AC 25-7D Appendix B APPENDIX B. FUNCTION AND RELIABILITY (F&R) TESTS
B.1 Explanation.
B.1.1 Section 21.35(b)(2) requires applicants for a type certificate (including an amended type certificate, supplemental type certificate (STC), or amended STC) to conduct all flight tests that the FAA finds necessary to determine whether there is reasonable assurance that the airplane, its components, and its equipment function properly (i.e., perform their intended function without introducing safety hazards) and are reliable (i.e., will continue to function properly in service).
Note: To obtain wider experience, manufacturers are encouraged to cooperate with operators in operating airplanes with provisional type certificates under service conditions.
B.1.2 However, the applicant must discontinue flight testing until appropriate corrective action has been taken, in accordance with § 21.35(e)(2), when it finds items of non-compliance with requirements that may make additional test data meaningless or that would make further testing unduly hazardous. The applicant must address any non-compliance with the functionality or reliability standards in the applicable airworthiness standards and any unsafe feature or characteristic identified during the test program prior to approval of the design under § 21.21(b)(1) and (2). Additional compliance demonstration testing and/or F&R testing may be necessary if the applicant introduces a design change.
B.1.3 Section 21.35(b)(2) applies to all type certification programs (except those covered under §§ 21.24 through 21.29), including those involving new type certificates, amended type certificates (including type design changes), STCs, and amended STCs.
B.2 Procedures.
The principal FAA flight test pilot for the project will act as coordinator of all flight activities during the official program, and that pilot (or a designated alternate) will participate in all flights. Other FAA personnel will not board the F&R airplane(s) during these activities unless authorized by the flight test pilot. The manufacturer’s pilot should be in command of all flights, but FAA pilots will fly the airplane to determine compliance with § 21.35(b)(2). Other FAA personnel (e.g., representatives of other divisions and specialists) will participate in the flight tests, when deemed necessary, to accomplish the purpose of the tests.
B.2.1 Test Time.
It is highly desirable that the FAA administer F&R test programs uniformly so that the program and flight time for similar projects will be approximately the same, regardless of which ACO administers the project. This can be difficult to achieve without establishing fixed test times that would be contrary to the FAA’s intent that § 21.35 (b)(2) be a performance-based standard. The applicant should use the following procedure as a guide for developing F&R test programs:
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Appendix B B.2.1.1 For a new or changed turbine engine-powered airplane incorporating engines of a type not previously used on a type-certificated airplane, § 21.35(f)(1) requires an F&R test program of at least 300 hours.
(“Engines of a type not previously used on a type-certificated airplane” means engines of a new or changed type design that require a substantially complete investigation of compliance with the applicable regulations, regardless of whether a new engine type certificate was issued.) Though some F&R test requirements can be completed concurrently with certification testing (if relevant design conformity can be shown), experience has indicated the desirability of obtaining at least 150 hours of the minimum required 300 hours of F&R test time as dedicated F&R test time on a production configured airplane for these types of certification programs. However, § 21.35(f)(1) requires the applicant to perform a minimum of 300 hours of F&R time on a full complement of engines installed on the airplane that fully conform to the production configuration. To accomplish the intent of the reliability demonstration required by § 21.35(b)(2), the applicant must use the same full complement (single ship set) of engines for at least 300 airplane test hours.
B.2.1.2 For a new turbine engine-powered airplane (i.e., a new type certificate program) that is conventional with regard to complexity and design features, and does not incorporate “engines that have not been previously used on a type-certificated airplane” as defined above, the FAA has found that F&R can normally be proven by less than 300 hours of testing. The ACO can reduce the amount of required F&R test time below 300 hours by granting credit for certain types of component testing (see paragraph B.2.5.2 of this appendix) and for supplementary experience (see paragraph B.2.1.4.3 of this appendix). However, the test time may not be reduced below the minimum 150 hours required by § 21.35(f)(2). More than 150 hours of F&R testing may be necessary if difficulties are encountered or for unusual cases of complexity.
B.2.1.3 For airplanes incorporating design changes, the FAA can give full or partial credit for F&R testing performed previously on sufficiently similar configurations of that aircraft type. The FAA should require an amount of new dedicated F&R testing commensurate with the level of change made to the airplane design, the potential effect of the change on the F&R of the airplane, the amount of flight testing performed to show compliance with airworthiness requirements, and the configuration of the aircraft used in the flight testing performed to show compliance with airworthiness requirements. The FAA may choose to give the applicant credit, reducing the amount of dedicated F&R test time, for test time from the flight testing compliance demonstration for type certification, provided that:
The changed and potentially affected areas of the airplane conform to the production configuration, and B-2
Appendix B
The test activities are consistent with the intent of the F&R testing required for the design change.
B.2.1.4 When satisfactory supplementary experience gained from operators’ route proving tests; or from the applicant’s or operator’s ferry flights, customer demonstration flights, or training flights; is available and taken into account, the following allowances should be used as a guide and applied with judgment in reducing the official flight test time. However, in any case, the official F&R test program should provide sufficient time to accomplish the objective of paragraph B.1 in accordance with the procedures described in paragraphs B.2.5.3 and B.2.5.4.
1. Intensive Experience. When the allowance is based on the total time of any one airplane in airline crew training and similar intensive operations, two hours of such operation may be considered equivalent to one hour of official testing.
2. For Miscellaneous Experience. When the allowance is based on the total time of any one airplane, five hours of such experience may be considered equivalent to one hour of official testing.
3. Reduction for Supplementary Experience. Whenever a reduction of official test time is desired on the basis of supplementary experience, such experience should be adequately recorded and submitted to the responsible FAA aircraft certification office as described in paragraph B.2.6.2 of this appendix.
B.2.1.5 The FAA should only consider giving credit for F&R test activities or test time required under § 21.35(b)(2) for compliance demonstration testing performed under § 21.35(b)(1) when:
The changed and potentially affected areas of the airplane conform to the production configuration, and The test activities are consistent with the intent of the F&R testing determined to be required for the design change.
B.2.2 Test Airplane.
To facilitate completion of the type certification procedure, the applicant should use one airplane, in production configuration or equivalent, for the official F&R tests and use another airplane (or airplanes) for the compliance demonstration tests for type certification. In this case, the test time on at least one airplane would be sufficient to accomplish the reliability demonstration objective of § 21.35(b)(2). That is, the applicant should perform the reliability demonstration (normally either 150 or 300 hours, but potentially longer if problems are discovered) on a single airplane as implied by § 21.35(c). All engines of the F&R test airplane are required, in accordance with § 21.35(f)(1), to fully conform to the production configuration for all credited F&R test time. This engine conformity requirement was specifically discussed in the preamble to amendment 21-40.
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Appendix B
B.2.3 Modified Types.
The procedure outlined in paragraph B.2.4 below applies to new type designs. When a design employs components (parts) identical to those used in previous designs, the applicant may receive credit for the supplementary experience available for such components. When a design is modified (e.g., one certification program covers several versions of the same basic type with different engines, propellers, etc.), the modified features and components should be rechecked in accordance with paragraph B.2.5.6 below.
B.2.4 Test Program.
The project engineers of the responsible FAA ACO will propose guidelines for developing an F&R test program at the preflight type board meeting (prior to commencement of FAA certification flight tests) and coordinate this with the airplane manufacturer. Near the conclusion of the type certification tests, the FAA certification engineers will again meet with the manufacturer to review the experience gained in those tests, review changes made in the design, consider any additional supplementary experience, and revise the proposed F&R test program accordingly. In application, there is generally considerable overlap of the certification and F&R test programs, thus making a definite transition point indiscernible.
B.2.5 Planning and Execution of Test Program.
The following points should be considered:
B.2.5.1 The test program should be sufficiently well planned to enable its execution in an efficient manner without overlooking important items.
Documentation should focus on the test objective(s) but does not necessarily require the type of detail maintained for type certification testing. The FAA project engineers will review the design features and equipment (appliances) with respect to the general objective and prepare a list showing:
Components and systems to be checked in accordance with the procedures described in the paragraph B.2.5.4 below.
A brief description of the operations to be performed, where these are not obvious (referencing any necessary operating instructions).
Special checks or likely critical conditions.
Estimated flight time required.
B.2.5.2 Allowance may be made for those functional tests whose requirements are covered by part 25 type certification tests. Allowance may also be made for qualification-type testing of new features and equipment; however, the flight test program should be planned to determine the adequacy of these tests and the accuracy of the simulated operating environment (e.g., to determine whether the actual environmental conditions such as temperature variation, etc., are covered by the test simulations) when these B-4
Appendix B may be critical, and to determine whether the installation and connected systems are satisfactory. This does not imply that flight tests must be conducted under the most severe outside air temperatures likely to be encountered in service. It should normally be possible to determine the effects of extreme outside temperatures on local temperatures by extrapolation or by suitable correction factors. The FAA project engineers will then make a consolidated estimate of the total flight time required, allowing for overlapping, and adjust this in accordance with the Test Time outlined in the paragraph B.2.1 above.
B.2.5.3 This program will be arranged to permit the principal FAA flight test pilot to become thoroughly familiar with the operational aspects of the airplane in its anticipated service environment.
B.2.5.4 All components of the airplane should be intensively operated and studied under all operating conditions expected in service and obtainable within the time and geographical limitations of the tests. Intensive operation means repeated operation of components in various sequences and combinations likely to occur in service. Particular attention should be given to potential sources of crew error, excessive crew workload or coordination, and the procedures that would be required in the event of malfunction of any component. The testing should also include an evaluation of operations with various MEL items declared/simulated inoperative. This intensive type of testing should be conducted in all cases, but the length of time for which it is continued will depend upon the supplementary experience available for the particular type, as outlined in paragraph B.2.1 above.
B.2.5.5 Ground inspections should be made at appropriate intervals during the test program to determine whether there are any failures or incipient failures in any of the components that might be a hazard to safe flight. The normal maintenance procedures should be employed during the F&R program and carefully documented for review.
B.2.5.6 When design changes are made during the course of the test, or when the designated test airplane differs from those on which supplementary experience is obtained, the modified items will be rechecked on the designated F&R test airplane in accordance with the above procedures.
Every effort should be made to include such items in the program in such a way as to avoid unduly extending the overall test time. To this end, the Administrator may accept, in lieu of additional flight tests:
Special tests of the original and revised components in which the conditions causing failure are intensified.
Ground qualification tests of differing components when the test methods have been validated as being representative of actual flight conditions.
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AC 25-7D Appendix B
B.2.6 Reports and Records.
B.2.6.1 Either the FAA or the applicant should keep a log of all flights, according to agreements made prior to start of the F&R test program. The log should include accurate and complete records of all defects, difficulties, and unusual characteristics and sources of crew error discovered during the tests, and of the recommendations made and action(s) taken. If the applicant is responsible for keeping the flight logs, the applicant will report to the responsible ACO all items for which design changes may be required.
B.2.6.2 If supplementary experience is to be taken into account, the applicant should submit records of such experience to the responsible ACO, together with a list of the differences between the airplane on which the experience was obtained and the official test airplane. When supplementary experience is obtained on a large fleet of airplanes (for example, military operations) of the same or a comparable type (see paragraph B.2.5.6 above), these records may consist of statistical summaries in lieu of complete records for each individual airplane.
B.2.6.3 At the conclusion of the official tests, a summary report should be prepared and made a part of the type inspection report. Either the FAA or the applicant may prepare the report, according to agreements made prior to start of the F&R test program.
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AC 25-7D CHG 1 Appendix C APPENDIX C. HISTORICAL DEVELOPMENT OF ACCELERATE-STOP TIME DELAYS
C.1 Explanation.
C.1.1 As the rules pertaining to transport category airplane accelerate-stop distances have developed over the years, the interpretation of those rules, with regard to pilot actions, recognition times, and delay times, has also changed. The paragraphs below provide a historical perspective on the application of pilot recognition and delay times, with references to the applicable part 25 amendment number.
C.1.2 In accordance with § 21.101 (a) and (b) the certification basis for a derivative airplane type may be the regulations specified in the type certificate of the basic airplane, depending upon the extent and nature of the changes to the airplane. For those cases where the original certification basis can be retained, the guidance presented in paragraphs C.2.1 and C.2.2 below may be used to show compliance with the appropriate regulations. (For more information related to determining a derivative airplane’s certification basis, see AC 21.101-1B.)
C.1.3 Regardless of the certification basis, the effects of brake wear state on energy absorption capability and stopping performance must be addressed to comply with § 21.21(b)(2). The responsible FAA ACO should be contacted to establish the applicable brake wear criteria for a specific airplane type.
C.2 Procedures.
C.2.1 Pre-Amendment 25-42 Accelerate-Stop Time Delays.
Parts 1 and 25 of 14 CFR, prior to amendments 1-29 and 25-42, respectively, defined V1 as the critical engine failure speed. When this definition of V1 was applied to the accelerate-stop criteria of § 25.109 and the V1 criteria of § 25.107(a)(2), the implication was that engine failure and engine failure recognition could occur simultaneously. It was recognized that this simultaneous occurrence could not be achieved in actual operations, and that defining V1 as the engine failure speed resulted in a conflict with § 25.101(h), which requires allowance for time delays in execution of procedures. To resolve this conflict, V1 was applied as the engine failure recognition speed, and appropriate time delays were developed for showing compliance with § 25.101(h).
Figure C-1 shows a pictorial representation of the accelerate-stop time delays that were considered acceptable for compliance with § 25.101(h) before amendment 25-42 (effective March 1, 1978). Paragraph C.2.1.7 of this appendix provides guidance on reflecting these time delays in the AFM accelerate-stop distances.
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AC 25-7D Appendix C Figure C-1. Accelerate-Stop Time Delays (Pre-Amendment 25-42)
C.2.1.1 trec = engine failure recognition time. The demonstrated time from engine failure to pilot activation of the first deceleration device, this action indicating recognition of the engine failure. For AFM data expansion purposes, to provide a recognition time increment that can be executed consistently in service, it has been found practical to use the demonstrated time or 1 second, whichever is greater. If the airplane incorporates an engine failure warning light, the recognition time includes the time increment necessary for the engine to spool down to the point of warning light activation, plus the time increment from light “on” to pilot action indicating recognition of engine failure.
C.2.1.2 ta1 = the demonstrated time interval between activation of the first and second deceleration devices.
C.2.1.3 ta2 = the demonstrated time interval between activation of the second and third deceleration devices.
C.2.1.4 t = a 1-second reaction time delay to account for in-service variations. If a command is required for another crewmember to actuate a deceleration device, a 2-second delay, in lieu of the 1-second delay, should be applied for each action. For automatic deceleration devices that are approved for performance credit for AFM data expansion, established times determined during certification testing may be used without the application of the additional time delays required by this paragraph.
C.2.1.5 The sequence for activation of deceleration devices may be selected by the applicant in accordance with § 25.101(f). If, on occasion, the desired sequence is not achieved during testing, the test need not be repeated;
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Appendix C
however, sufficient tests should be conducted to establish acceptable values of ta.
C.2.1.6 If additional devices are used to decelerate the airplane, their respective demonstrated times, plus any additional required time delays, should be included until the airplane is in the full braking configuration.
C.2.1.7 For the purpose of flight manual calculations, the 1-second delay for each action may be added at the end of the total demonstrated time. Regardless of the manner in which the time delays are applied, the flight manual calculations should assume the airplane does not decelerate during the delay time increments.
C.2.2 Amendment 25-42 through Amendment 25-91, Accelerate-Stop Time Delays.
Amendment 25-42, effective March 1, 1978, introduced several new requirements affecting accelerate-stop distance determination. One of the most significant changes of amendment 25-42 was the requirement to determine an all-engines-operating accelerate-stop distance to account for the many rejected takeoffs that were not the result of an engine failure. Amendment 25-42 also introduced into the regulations an engine-failure speed, VEF; redefined the takeoff decision speed, V1; revised the accelerate-stop distance criteria to correspond to the VEF and V1 definitions; and added a 2-second time delay between V1 and the first action to decelerate the airplane during which the airplane continues accelerating with the operating engines at takeoff thrust.
Figure C-2 shows a pictorial representation of the accelerate-stop time delays in accordance with the provisions of part 25, including amendment 25-42:
Figure C-2. Accelerate-Stop Time Delays (Amendment 25-42 through Amendment 25-91)
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