Appendix A A-49 A.3 Examples of Substantial, Significant, and Not Significant Changes for Rotorcraft (Parts 27 and 29).
A.3.1 Table A-7 contains examples of changes that are “substantial” for rotorcraft (parts 27 and 29).
Table A-7. Examples of Substantial Changes for Rotorcraft (Parts 27 and 29) Example Description of change Notes
1. Change from the number and or configuration of rotors
(e.g., main & tail rotor system to two main rotors).
Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
2. Change from an all-metal rotorcraft to all-composite rotorcraft.
Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
Appendix A A-50 A.3.2 Table A-8 contains examples of changes that are “significant” for rotorcraft (parts 27 and 29).
Table A-8. Examples of Significant Changes for Rotorcraft (Parts 27 and 29) 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. Comprehensive flightdeck upgrade, such as conversion from entirely federated, independent electro-mechanical flight instruments to highly integrated and combined electronic display systems with extensive use of software and/or complex electronic hardware.
No No Yes Affects avionics and electrical systems integration and architecture concepts and philosophies.
This drives a reassessment of the human-machine interface, flightcrew workload, and re-evaluation of the original design flightdeck assumptions
2. Certification for flight into known icing conditions.
No No Yes
3. (Fixed) flying controls from mechanical to fly by wire.
No No Yes This drives a complete reassessment of the rotorcraft controllability and flight control failure.
Appendix A A-51 Table A-8. Examples of Significant Changes for Rotorcraft (Parts 27 and 29) (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. Addition of an engine;
e.g., from single to twin or reduction of the number of engines; e.g., from twin to single.
Yes Yes Yes
5. A change of the rotor drive primary gearbox from a splash type lubrication system to a pressure lubricated system due to an increase in horsepower of an engine or changing from a piston engine to turbine engine.
No Yes Yes
6. A fuselage or tail boom modification that changes the primary structure, aerodynamics, and operating envelope sufficiently to invalidate the certification assumptions.
Yes No Yes
Appendix A A-52 Table A-8. Examples of Significant Changes for Rotorcraft (Parts 27 and 29) (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. Application of an approved primary structure to a different approved model (e.g., installation on a former model of the main rotor approved on a new model that results in increase performance).
No Yes Yes
8. Emergency medical service (EMS) configuration with primary structural changes sufficient to invalidate the certification assumptions.
No No Yes Many EMS configurations will not be classified as significant. Modifications made for EMS are typically internal, and the general external configuration is normally not affected. These changes should not automatically be classified as significant.
Note: Door addition or enlargement involving structural change would be significant.
Appendix A A-53 Table A-8. Examples of Significant Changes for Rotorcraft (Parts 27 and 29) (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. Skid landing gear to wheel landing gear or wheel landing to skid.
Yes No Yes
10. Change of the number of rotor blades.
Yes No Yes
11. Change tail anti-torque device (e.g., tail rotor, ducted fan or other technology).
Yes Yes No
12. Passenger configured helicopter to a Firefighting equipment configured helicopter.
Yes No Yes Depends on the firefighting configuration.
13. Passenger configured helicopter to an agricultural configured helicopter.
Yes No Yes Depends on the agricultural configuration.
14. An initial Category A certification approval to an existing configuration.
No No Yes
Appendix A A-54 Table A-8. Examples of Significant Changes for Rotorcraft (Parts 27 and 29) (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. IFR upgrades involving installation of upgraded components for new IFR configuration.
No No Yes Changes in architecture concepts, design philosophies, human-machine interface, or flightcrew workload.
16. Human external cargo (HEC) certification approval.
No No Yes Must comply with the latest HEC certification requirements in order to obtain operational approval.
HEC include fatigue, quick release systems, HIRF, one engine inoperative (OEI) performance, and OEI procedures.
17. Reducing the number of pilots for IFR from two to one.
No No Yes
18. An avionics upgrade that changes a federated avionics system to a highly integrated avionics system.
No No Yes This change refers to the avionics system that feeds the output to displays and not the displays themselves.
Appendix A A-55 Table A-8. Examples of Significant Changes for Rotorcraft (Parts 27 and 29) (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
19. An avionics upgrade that changes the method of input from the flightcrew, which was not contemplated during the original certification.
No No Yes A change that includes touchscreen technology typically does not invalidate the assumptions used for certification.
A change that incorporates voice activated controls or other novel human-machine interface would likely invalidate the assumptions used for certification.
Appendix A A-56 A.3.3 Table A-9 contains examples of changes that are “not significant” changes for rotorcraft (parts 27 and 29).
Table A-9. Examples of Not Significant Changes for Rotorcraft (Parts 27 and 29) 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. Emergency floats. No No No Must comply with the specific applicable requirements for emergency floats. This installation, in itself, does not change the rotorcraft configuration, overall performance, or operational capability. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.
Appendix A
Table A-9. Examples of Not Significant Changes for Rotorcraft (Parts 27 and 29) (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
2. FLIR or surveillance camera installation.
No No No Additional flight or structural evaluation may be necessary but the change does not alter the basic rotorcraft certification.
3. Helicopter terrain awareness warning system (HTAWS) for operational credit.
No No No Certificated under rotorcraft HTAWS AC guidance material and FAA TSO-C194. Does not alter the basic rotorcraft configuration.
4. Health usage monitoring system (HUMS) for maintenance credit.
No No No Certificated under rotorcraft HUMS AC guidance material.
Does not alter the basic rotorcraft configuration.
A-57
Appendix A A-58 Table A-9. Examples of Not Significant Changes for Rotorcraft (Parts 27 and 29) (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. Expanded limitations with minimal or no design changes, following further tests/justifications or different mix of limitations (CG limits, oil temperatures, altitude, minimum/ maximum weight, minimum/ maximum external temperatures, speed, engine ratings).
No No No Changes to an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, flight over water, or operations in snow conditions) that are not so different that the original certification assumptions remain valid.
6. Change from a single channel FADEC to a dual channel FADEC.
Change does not change the overall product configuration or the original certification assumptions.
7. Installation of a new engine type, equivalent to the former one, leaving aircraft installation and limitations substantially unchanged.
No No No Refer to AC 27-1 or AC 29-2 for guidance. Does not alter the basic rotorcraft configuration, provided there is no additional capacity embedded in the new design.
Appendix A A-59 Table A-9. Examples of Not Significant Changes for Rotorcraft (Parts 27 and 29) (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
8. Windscreen installation. No No No Does not change the rotorcraft overall product configuration.
9. Snow skis, “Bear Paws.” No No No Must comply with specific requirements associated with the change. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.
Appendix A A-60 Table A-9. Examples of Not Significant Changes for Rotorcraft (Parts 27 and 29) (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. External cargo hoist. No No No Must comply with the specific applicable requirements for external loads. This installation, in itself, does not change the rotorcraft configuration, overall performance, or operational capability. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations excluding HEC, flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.