Appendix A A-35 Table A-5. Examples of Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
23. Expansion of an aircraft’s operating envelope.* No No Yes* *Some changes may be deemed “not significant” depending on the extent of the expansion.
An expansion of operating capability is a significant change (e.g., an increase in maximum altitude limitation, approval for flight in icing conditions, or an increase in airspeed limitations).
24. Changing the floor from passenger carrying to cargo carrying capability.
Yes No Yes Completely new floor loading and design. Redistribution of internal loads, change in cabin safety requirements, system changes. If a cargo handling system is installed, it would be a related change.
25. Initial installation of an APU essential for aircraft flight operation.
No No Yes Changes emergency electrical power requirements, change in flight manual and operating characteristics.
Appendix A A-36 Table A-5. Examples of Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
26. Conversion from hydraulically actuated brakes to electrically actuated brakes.
No No Yes Assumptions of certification for airplane performance are changed.
27. Installation of engine thrust reversers.
Yes No Yes
28. Request for extended operations (ETOPS) type design approval for:
(a) airplanes without an existing ETOPS type design approval, and
(b) extension of an airplane’s diversion time.
No No Yes An expansion of diversion capability for ETOPS would normally be a significant change. However, expanding the diversion capability for which it was originally designed is generally not a significant change. In this case, the assumptions used for certification of the basic product remain valid, and the results can be applied to cover the changed product with predictable effects or can be demonstrated without significant physical changes to the product.
Appendix A A-37 Table A-5. Examples of Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
29. Installation of an engine with a FADEC on an airplane that did not previously have a FADEC engine installed.
No No Yes A changed from a mechanical control engine to a FADEC engine may be so extensive that it affects basic aircraft systems integration and architecture concepts and philosophies. This drives a complete reassessment of flightcrew workload, handling qualities, and performance evaluation, which are different from the original design assumptions.
Appendix A A-38 A.2.3 Table A-6 contains examples of changes that are “not significant” for transport airplanes (part 25).
Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
1. Alternate engine installation or hush kit at same position.
No No No It is not significant so long as there is less than a 10 percent increase in thrust or there is not a change in the principles of propulsion. A change in position to accommodate a different size engine could influence airplane performance and handling qualities and result in a significant change.
2. A small change in fuselage length due to refairing the aft body or radome.
No No No For cruise performance reasons, where such changes do not require extensive structural, systems, aerodynamic, or AFM changes.
Appendix A A-39 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
3. Refairing of wing tip caps (for lights, fuel dump pipes) and addition of splitter plates to the trailing edge thickness of the cruise airfoil.
No No No Does not require extensive structural, AFM, or systems changes.
4. Additional power used to enhance high altitude or hot day performance.
No No No Usually no change in basic operating envelope. Existing certification data can be extrapolated. Could be significant product change if the additional power is provided by installation of a rocket motor or additional, on demand engine due to changes in certification assumptions.
Appendix A A-40 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
5. Installation of an autopilot system.
No N/A See notes It may be possible that the modification is adaptive in nature, with no change to original certification assumptions. However, in certain cases the installation of an autopilot may include extensive changes and design features that change both the general configuration and the assumptions for certification
(i.e., installation of the autopilot may introduce a number of additional mechanical and electronic failure modes and change the hazard classification of given aircraft-level failures).
6. Change from assembled primary structure to monolithic or integrally machined structure.
No No No Method of construction must be well understood.
Appendix A A-41 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
7. Modification to ice protection systems.
No No No Recertification required, but certification basis is adequate.
8. Brakes: design or material change, e.g., steel to carbon.
No No No Recertification required, but certification basis is adequate.
9. Redesign floor structure. No No No By itself, not a significant product change. It is significant if part of a cargo conversion of a passenger airplane.
Appendix A A-42 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
10. New cabin interior with no fuselage length change.
No No No A new cabin interior includes new ceiling and sidewall panels, stowage, galleys, lavatories, and seats.
Novel or unusual design features in the cabin interior may require special conditions.
Many interior related requirements are incorporated in operational rules. Even though the design approval holder may not be required to comply with these requirements, the operator may be required to comply.
11. A rearrangement of an interior (e.g., seats, galleys, lavatories, closets, etc.).
No No No
Appendix A A-43 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
12. Novel or unusual method of construction of a component.
No No No The component change does not rise to the product level.
Special conditions could be required if there are no existing regulations that adequately address these features.
13. Initial installation of a non-essential APU.
No No No A stand-alone initial APU installation on an airplane originally designed to use ground- or airport-supplied electricity and air conditioning. In this case, the APU would be an option to be independent of airport power.
Appendix A A-44 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
14. Increasing the life limit as § 25.571 fatigue testing progresses for a recently type certificated airplane.
No No No For example, a recently type certificated airplane may undergo fatigue testing as part of compliance with § 25.571.
In this case, the TC holder may specify an initial life limit in the airworthiness limitations section (ALS) and gradually increase that life limit as fatigue testing progresses. Such change to the ALS is considered not significant.
Appendix A A-45 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
15. Extending limit of validity (LOV) pursuant to § 26.23.
No No No Extending an LOV pursuant to § 26.23 without any other change to the airplane is not a significant change. However, if extending the LOV requires a physical design change to the airplane, the design change is evaluated to determine the level of significance of the design change. Note that if design approval holders are developing modifications to support an extended LOV, they must also comply with the requirements of subpart E of part 26.
Appendix A A-46 Table A-6. Examples of Not Significant Changes for Transport Airplanes (Part 25) (continued) Example Description of change Is there a change to the general configuration?
§ 21.101(b)(1)(i) Is there a change to the principles of construction?
§ 21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
§ 21.101(b)(1)(ii) Notes
16. Airframe life extension. No No No This does not include changes that involve changes to design loads, such as pressurization or weight increases. Also, this does not include changing from safe life to damage tolerance.
17. Changes in the type or number of emergency exits by de-rating doors or deactivating doors with corresponding reduction in passenger capacity.
No No No The new emergency egress does not exceed that previously substantiated because the certificated number of passengers is reduced.