Appendix A A-18 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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. Limited changes in a pressurization system,
e.g., number of outflow valves, type of controller, or size of pressurized compartment, but the system must be resubstantiated if the original test data are invalidated.
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
17. Install a different exhaust system.
No No No Not an airplane-level change.
18. Changes in engine cooling or cowling.
No No No Not an airplane-level change.
19. Changing fuels of substantially the same type, such as AvGas to AutoGas, AvGas (80/87) to AvGas (100LL), ethanol to isopropyl alcohol, Jet B to Jet A.
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
Appendix A A-19 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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
20. Fuels that specify different levels of “conventional” fuel additives that do not change the primary fuel type. Different additive levels (controlled) of MTBE, ETBE, ethanol, amines, etc., in AvGas would not be considered a significant change.
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
21. A change to the maximum takeoff weight of less than 5 percent, unless assumptions made in justification of the design are thereby invalidated.
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
22. An additional aileron tab
(e.g., on the other wing).
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
Appendix A A-20 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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. Larger diameter flight control cables with no change in routing, or other system design.
No No No Not an airplane-level change.
24. Autopilot installation (for IFR use, unless the original certification indicates that the airplane is not suitable as an IFR platform).
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
25. Increased battery capacity or relocate battery.
No No No Not an airplane-level change.
26. Replace generator with alternator.
No No No Not an airplane-level change.
27. Additional lighting (e.g., navigation lights, strobes).
No No No Not an airplane-level change.
28. Higher capacity brake assemblies.
No No No Not an airplane-level change.
Appendix A A-21 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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. Increase in fuel tank capacity.
No No No Not an airplane-level change.
30. Addition of an oxygen system.
No No No Not an airplane-level change.
31. Relocation of a galley. No No No Not an airplane-level change.
32. Passenger to freight (only) conversion with no change to basic fuselage structure.
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
Requires certification substantiation applicable to freighter requirements.
33. New cabin interior with no fuselage length change.
No No No
34. Installation of new seat belt or shoulder harness.
No No No Not an airplane-level change.
Appendix A A-22 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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
35. A small increase in center of gravity (CG) range.
No No No At airplane level, no change in general configuration, principles of construction, and certification assumptions.
36. Auxiliary power unit (APU) installation that is not flight essential.
No No No Although a major change to the airplane level, likely the original general configuration, principles of construction, and certification assumptions remain valid.
Requires certification substantiation applicable to APU installation requirements.
37. An alternative autopilot. No No No Not an airplane-level change.
38. Addition of Class B terrain awareness and warning systems (TAWS).
No No No Not an airplane-level change.
Appendix A A-23 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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
39. Extending an established life limit.
No No No This extension may be accomplished by various methods, such as ongoing fatigue testing, service life evaluation, component level replacement, and inspections based on damage tolerance principles.
40. Flightdeck replacement of highly integrated and combined electronic display systems with other highly integrated and combined electronic display systems.
No No No Not significant if the architecture concepts, design philosophies, human-machine interface, or flight crew workload assumptions are not impacted.
41. Interior cabin reconfigurations are generally considered not significant. This includes installation of in-flight entertainment (IFE), new seats, and rearrangement of furniture.
No No No
Appendix A A-24 Table A-3. Examples of Not Significant Changes for Small Airplanes (Part 23) (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
42. Modification to ice protection systems.
No No No Re-certification required, but certification basis should be evaluated for adequacy.
Appendix A A-25 A.2 Examples of Substantial, Significant, and Not Significant Changes for Transport Airplanes (Part 25).
A.2.1 Table A-4 contains examples of changes that are “substantial” for transport airplanes (part 25).
Table A-4. Examples of Substantial Changes for Transport Airplanes (Part 25) Example Description of change Notes
1. Change in the number or location of engines, e.g., four to two wing-mounted engines or two wing-mounted to two body-mounted engines.
Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
2. Change from a high-wing to low-wing configuration. Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
3. Change from an all-metal to all-composite airplane. Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
4. Change of empennage configuration for larger airplanes (cruciform vs. ‘T’ or ‘V’ tail).
Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
5. Increase from subsonic to supersonic flight regime. Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
Appendix A A-26 A.2.2 Table A-5 contains examples of changes that are “significant” for transport airplanes (part 25).
Table A-5. Examples of 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. Reduction in the number of flightcrew (in conjunction with flightdeck update).
No No Yes Extensive changes to avionics and aircraft systems. Impact to crew workload and human factors, pilot type rating.
2. Modify an airplane to add certification for flight in icing conditions by adding systems such as ice detection and ice protection.
Yes No Yes New aircraft operating envelope. Requires major new systems installation and aircraft evaluation. Operating envelope changed.
3. Conversion—passenger or combination freighter/passenger to all freighter, including cargo door, redesign floor structure and 9g net or rigid barrier.
Yes No Yes Extensive airframe changes affecting load paths, aeroelastic characteristics, aircraft related systems for fire protection, etc. Design assumptions changed from passenger to freighter.
Appendix A A-27 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
4. Conversion from a cargo to passenger configuration.
Yes No Yes Completely new floor loading and design. Redistribution of internal loads, change in cabin safety requirements, system changes.
5. Increase in cabin pressurization greater 10 percent.
than No No Yes A change greater than 10 percent in operational cabin pressure differential is a significant change since it requires extensive airframe changes affecting load paths, fatigue evaluation, or aeroelastic characteristics, invalidating the certification assumptions.
6. Addition of leading slats.
edge Yes No Yes The addition of leading edge slats is significant since it requires extensive changes to wing structure, adds aircraft systems, and requires a new AFM to address performance and flight characteristics.
Appendix A A-28 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
7. Fuselage stretch or shortening in the cabin or pressure vessel.
Yes No Yes Cabin interior changes are related changes since occupant safety considerations are impacted by a cabin length change.
Even if a new cabin interior is not included in the product level change, the functional effect of the fuselage plug has implications on occupant safety (e.g., the dynamic environment in an emergency landing, emergency evacuation, etc.), and thus the cabin interior becomes an affected area.
8. Extensive structural airframe modification, such as installation of a large telescope with large opening in the fuselage.
Yes No No These types of structural modifications are significant since they require extensive changes to fuselage structure, affect aircraft systems, and require a new AFM to address performance and flight characteristics.
Appendix A A-29 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
9. Changing the number of axles or number of landing gear done in context with a product change that involves changing the airplane gross weight.
Yes No No This type of landing gear change with an increase in gross weight is significant since it requires changes to aircraft structure, affects aircraft systems, and requires AFM changes, which invalidate the certification assumptions.
10. Primary structure changes from metallic material to composite material.
No Yes No Change in principles of construction and design from conventional practices.
11. An increase in design weight of more than 10 percent.
No No Yes Design weight increases of more than 10 percent result in significant design load increase that invalidates the assumptions used for certification, requiring re-substantiation of aircraft structure, aircraft performance, and flying qualities and associated systems.