Appendix A A-71 Table A-11. Examples of Significant Changes for Engines (Part 33) (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 Piston Engines
11. Convert from spark-ignition to compression-ignition.
Yes No Yes Change in general configuration: installation interface of engine changed (no mixture lever).
Certification assumptions invalidated: change in operating envelope and performance.
Appendix A A-72 A.4.3 Table A-12 contains examples of changes that are “not significant” for engines (part 33).
Table A-12. Examples of Not Significant Changes for Engines (Part 33) 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 Turbine Engines
1. Change in the material from one type of metal to another type of metal of a compressor drum.
No No No No change in performance.
Assumptions are still valid.
2. Increase/decrease in the number of compressor/turbine stages without resultant change in operational performance envelope.
No No No No change in performance.
Assumptions are still valid.
Appendix A A-73 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Turbine Engines
3. Hardware design changes to the FADEC/EEC, the introduction of which do not change the function of the system.
No No No No change in configuration.
Retrofitable.
Assumptions used for certification are still valid.
Possible changes in principles of construction are insignificant.
4. Software changes. No No No
5. Rub-strip design changes. No No No Component level change.
6. A new combustor that does not change the approved limitations or dynamic behavior.* (*Exclude life limits.)
No No No Component level change.
7. Bearing changes. No No No Component level change.
Appendix A A-74 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Turbine Engines
8. New blade designs with similar material that can be retrofitted.
No No No Component level change.
9. Fan blade redesign that can be retrofitted.
No No No Component level change.
10. Oil tank redesign. No No No Component level change.
11. Change from one hydromechanical control to another hydro-mechanical control.
No No No Component level change.
12. Change to limits on life limited components supported by data that became available after certification.
No No No Extending or reducing the life limits. For example, extending life limits based on credits from service experience or new fatigue data.
13. Changes to limits on exhaust gas temperature.
No No No
Appendix A A-75 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Turbine Engines
14. Changes to Airworthiness Limitations section with no configuration changes.
No No No
15. Bump ratings within the product’s physical capabilities that may be enhanced with gas path changes such as blade restaggering, cooling hole patterns, blade coating changes, etc.
No No No
Appendix A A-76 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Piston Engines
16. New or redesigned cylinder head, valves, or pistons.
No No No
17. Changes in crankshaft. No No No Component level change.
18. Changes in crankcase. No No No Component level change.
19. Changes in carburetor. No No No Component level change.
20. Changes in mechanical fuel injection system.
No No No
21. Changes in mechanical fuel injection pump.
No No No Component level change.
Appendix A A-77 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Piston Engines
22. Engine model change to accommodate new airplane installation. No change in principles of operation of major subsystems; no significant expansion in power or operating envelopes or in limitations.
No No No
23. A simple mechanical change, or a change that does not affect the basic principles of operation.
For example, change from dual magneto to two single magnetos on a model.
No No No
Appendix A A-78 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Piston Engines
24. Subsystem change produces no changes in base engine input parameters, and previous analysis can be reliably extended. For example, a change in turbocharger where induction system inlet conditions remain unchanged, or if changed, the effects can be reliably extrapolated.
No No No
25. Change in material of secondary structure or not highly loaded component.
For example, a change from metal to composite material in a non-highly loaded component, such as an oil pan that is not used as a mount pad.
No No No Component level change.
Appendix A A-79 Table A-12. Examples of Not Significant Changes for Engines (Part 33) (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 Piston Engines
26. Change in material that retains the physical properties and mechanics of load transfer. For example, a change in trace elements in a metal casting for ease of pouring or to update to a newer or more readily available alloy with similar mechanical properties.
No No No Component level change.
Appendix A A-80 A.5 Examples of Substantial, Significant, and Not Significant Changes for Propellers (Parts 35).
A.5.1 Table A-13 contains an example of a change that is “substantial” for propellers (part 35).
Table A-13. Example of a Substantial Change for Propellers (Part 35) Example Description of change Notes
1. Change in the number of blades. Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.
A.5.2 Table A-14 contains examples of changes that are “significant” for propellers (part 35).
Table A-14. Examples of Significant Changes for Propellers (Part 35) 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. Principle of pitch change such as a change from single acting to dual acting.
Yes Yes Yes Requires extensive modification of the pitch change system with the introduction of back-up systems.
The inherent control system requires re-evaluation.
Appendix A A-81 Table A-14. Examples of Significant Changes for Propellers (Part 35) (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. Introduction of a different principle of blade retention such as a single row to a dual row bearing.
Yes Yes No Requires extensive modification of the propeller hub and blade structure.
The inherent strength requires re-evaluation.
3. A hub configuration change such as a split hub to a one-piece hub.
Yes Yes No Requires extensive modification of the propeller hub structure.
The inherent strength requires re-evaluation.
4. Changing the method of mounting the propeller to the engine such as a spline to a flange mount.
Yes Yes No Requires extensive modification of the propeller hub structure.
The inherent strength requires re-evaluation.
Appendix A A-82 Table A-14. Examples of Significant Changes for Propellers (Part 35) (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. Change in hub material from steel to aluminum.
Yes Yes No Requires extensive modification of the propeller hub structure and change to method of blade retention.
The inherent strength requires re-evaluation.
6. Change in blade material from metal to composite.
Yes Yes Yes Requires extensive modification of the propeller blade structure and change to method of blade retention.
Composite construction methods required.
The inherent strength requires re-evaluation.