Appendix A A-83 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
7. Change from hydro-mechanical to electronic control.
Yes Yes Yes Electronic manufacturing and design methods required.
Assumptions used for certification are no longer valid or not addressed in the original certification, i.e., HIRF and lightning protection, fault tolerance, software certification, and other aspects.
Appendix A A-84 A.5.3 Table A-15 contains examples of changes that are “not significant” for propellers (part 35).
Table A-15. Examples of Not 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. Change in the material of a blade bearing.
No No No Component level change.
2. Change to a component in the control system.
No No No Component level change.
3. Change to a propeller de-icer boot.
No No No Component level change.
4. Changes to the operational design envelope such as increase in power.
No No No Propeller’s operating characteristics and inherent strength require re-evaluation.
5. Change to the intended usage such as normal to acrobatic category.
No No No Propeller’s operating characteristics and inherent strength require re-evaluation.
Appendix B B-1 APPENDIX B. APPLICATION CHARTS FOR CHANGED PRODUCT RULE Table B-1. Application Chart for § 21.101(a) and (b) and § 21.19 Substantial (§ 21.19) (§ Significant
21.101(a) and (b)) Not Significant (§ 21.101)(b)(1)) Substantially changed product Compliance to all latest regulatory standards required for product certification.
Previously approved type design and compliance data may be allowed if valid for the changed product.
Affected area (Changed and/or affected areas) New showing of compliance is required Unaffected area No new showing of compliance is required.
Unaffected area continues to comply with the existing certification basis.
Affected area (Changed and/or affected areas) New showing of compliance is required.
The applicant may propose a certification basis using an earlier amendment but not earlier than in the existing TC basis.
Unaffected area No new showing of compliance is required.
Unaffected area continues to comply with the existing certification basis.
Compliance with the latest amendment materially contributes to safety No material contribution to safety Practical Impractical The applicant may propose a certification basis using earlier regulatory requirement(s), but not earlier than the existing TC basis.
The applicant may propose a certification basis using earlier regulatory requirement(s), but not earlier than the existing TC basis.
Certification Basis Proposed by Applicant New certification basis using standards.
latest regulatory Latest regulatory standards, with earlier amendments with supporting rationale.
Existing certification basis.
Existing certification basis including elect to comply.
Existing certification basis.
FAA Resultant Type Certification Basis New certification basis using the latest New certification basis using the latest Existing certification Existing certification Existing certification regulatory standards, and special conditions if regulatory standards with earlier approved basis. basis (if adequate); if basis.
required. amendments, and special conditions if required. not, first appropriate later amendment(s) and/or special condition including elect to comply.
Appendix B B-2 Table B-2. Application Chart for § 21.101(c) Excepted Products Affected Area (Changed areas and/or unchanged New showing of compliance is but affected) required.
Unaffected Area No new showing of compliance is required.
Unaffected area continues to be compliant with the existing TC basis.
Type Certification Basis Proposed by Applicant The existing TC basis, including “elects to comply.” The existing TC basis.
Found by the FAA to be “significant in an area.” Not significant in an area.
Compliance with a later amendment materially contributes to safety. No material contribution safety.
to Practical Impractical FAA Resultant Type Certification Basis The latest amendment designated by the FAA including special conditions and including elect to comply.
The existing TC basis. If inadequate, the first special conditions, appropriate later amendment.
including elect to comply.
If not appropriate, add The existing TC basis.
Appendix C C-1 APPENDIX C. A METHOD TO DETERMINE THE CHANGED AND AFFECTED AREAS C.1 Overview.
C.1.1 When you make a change to a product, some areas you change physically, while others you change functionally. The FAA refers to this combination as changed and affected areas. For example, if you extend the wing of a fixed wing aircraft, you would physically change the wing tip and likely other wing structure. Some areas of the airframe may have sufficient strength for the increase in load and would change functionally, i.e., carry greater load, but it would not change physically. These areas have associated airworthiness requirements, which become part of the certification basis for the change.
C.1.2 Figure C-1 below provides an overview of one method you can use to determine the changed and affected areas and the applicable airworthiness requirements.
Figure C-1. Method to Determine the Changed and Affected Areas
Appendix C C-2 C.2 Physical Changes.
C.2.1 Steps.
• Step 1. Make a list of the physical changes.
• Step 2. List the corresponding airworthiness requirements applicable to the physical changes.
• Step 3. List the amendment level recorded on the existing certification basis of the baseline product and the amendments on the date of application.
C.2.2 Example.
The change is adding a winglet to a fixed wing aircraft and a change to the leading edge slats for a performance increase. As part of the change, you modify an electrically driven slat actuator by changing the mounting structure of the actuator used to connect the actuator to the slat. The actuator structure is changed. The electrical system in the actuator is not affected. You would list airworthiness requirements applicable to the actuator. You would not list the airworthiness requirements applicable to the electrical system of the actuator. See table C-1 below for an example of how to chart a physical change and the associated airworthiness requirements.
Table C-1. Example of Associating a Physical Change with the Applicable Airworthiness Requirements Physical Change Applicable Regulations* Amendment of Existing Certification Basis Amendment on Application Date Structural change to slat actuator § 25.xxx 25-aaa 25-ddd § 25.yyy 25-bbb 25-eee § 25.zzz 25-ccc 25-fff * These would be airworthiness requirements related to structural aspects only.
C.3 Functional Changes.
C.3.1 Steps.
• Step 1. Describe each change.
• Step 2. Describe the effects of the change (e.g., structural, performance, electrical, etc.).
• Step 3. List the areas, system, component, and appliance that are affected by that effect.
Appendix C C-3
• Step 4. List the airworthiness requirements associated with the effect for each area, system, component, or appliance.
• Step 5. List the amendment level recorded on the existing certification basis of the baseline product and the amendments on the date of application.
C.3.2 Example.
The change is adding a winglet to a fixed wing aircraft and a change to the leading edge slats for a performance increase. The wing root bending moment has increased. The loads in the wing box are increased but the wing box has sufficient structural margins to carry the higher loads. Thus, the wing box is not physically changed but its function has changed because it carries greater loads. See table C-2 below for an example of how to chart a functional change, its effects, and the affected areas (steps 1 through 3 above).
See table C-3 below for an example of how to chart an area affected by a functional change and the associated airworthiness requirements (steps 4 and 5 above).
Table C-2. Example of a Functional Change, Affected Areas, and Associated Effects Description of Change Effects Affected Areas Installation of winglet Increased loads in wing structure Wing spars Wing skins Effect 2* Area 1 Area 2 Effect 3* Area 3 * There may be other effects as well.
Appendix C C-4 Table C-3. Example of Associating Affected Areas with the Applicable Airworthiness Requirements Impacted Area Applicable Regulations* Amendment of Existing Certification Basis Amendment on Application Date Wing spar § 25.xxx 25-aaa 25-ddd § 25.yyy 25-bbb 25-eee § 25.zzz 25-ccc 25-fff * These would be structural airworthiness requirements only. There could be other requirements applicable to the wing box. But since the effect is structural, then only the structural requirements are applicable.
C.4 Combine the Lists.
C.4.1 The FAA typically presents the certification basis for a product by regulation and not by area. The next step is to combine these two lists. However, since you are only changing a portion of the product, you will need to identify the changed and affected area of the new certification basis. The unchanged area is not required to comply with the airworthiness requirements in effect at the date of application. (See § 21.101(b)(2).)
C.4.2 When the change is quite extensive, you will save time by listing all the airworthiness requirements applicable to the category of product you are certifying. You can use table C-4 below in the next step where you will identify other exceptions you would like the FAA to consider.
C.4.3 Example.
If we use the examples above for the combined list for the actuator structural changes and the wing box functional change, then you would list the certification basis as shown in table C-4 below.
Appendix C C-5 Table C-4. Example of a Combined List of Physical and Functional Changes with Applicable Airworthiness Requirements Amendment Levels Amendment of Existing 14 CFR Certification Amendment on Section Basis Application Date Change and Affected Area § 25.xxx* 25-aaa 25-ddd • Wing spar § 25.yyy* 25-bbb 25-eee •
• Leading edge actuator Wing loads § 25.zzz* 25-ccc 25-fff * These represent structural requirements.
Appendix D D-1 APPENDIX D. OTHER GUIDANCE FOR AFFECTED AREAS D.1 Sample Questions in Determining Affected Areas.
Below are sample questions to assist in determining whether an area is affected by the change. If the answer to any of these questions is yes, then the area is considered affected.
1. Is the area changed from the identified baseline product?
2. Is the area impacted by a significant product level change?
3. Is there a functional effect on the unchanged area by a change to the system or system function that it is a part of?
4. Does the unchanged area need to comply with a system or product level requirement that is part of the change?
5. Are the product level characteristics affected by the change?
6. Is the existing compliance for the area invalidated?
D.2 Sub-Areas within an Affected Area.
Within areas affected by a change, there may be “sub-areas” of the area that are not affected. For those sub-areas, the amendment levels at the existing certification basis remain valid, along with the previous compliance findings. For example, if a passenger seat fitting is changed as part of a significant change, then the structure of the seat is affected. Thus, the amendment level for §§ 25.561 and 25.562, along with other applicable structural requirements, would be at the amendment level on the date of application (unless an exception is granted). However, the seat fabric is not affected, so the amendment level for § 25.853 (flammability) may remain at the existing certification basis, and a new compliance finding would not be required.
Appendix E E-1 APPENDIX E. PROCEDURE FOR EVALUATING MATERIAL CONTRIBUTION TO SAFETY
OR IMPRACTICALITY OF APPLYING LATEST REQUIREMENTS
TO A CHANGED PRODUCT E.1 Introduction.
E.1.1 The basic principle of enhancing the level of safety of changed aeronautical products is to apply the latest regulations for significant design changes to the greatest extent practical. In certain cases, the cost of complying fully with a later regulation may not be commensurate with the small safety benefit achieved. These factors form the basis where compliance with the latest standard may be considered impractical, thereby allowing compliance with an earlier regulation. This appendix gives one method of determining if compliance with a later regulation is impractical; however, it does not preclude the use of other methods for improving the safety of aeronautical products.
E.1.2 The FAA recognizes that other procedures can be used and have historically been accepted on a case-by-case basis. The acceptance of results through the use of these procedures may vary from State to State. Consequently, they may not be accepted through all bilateral certification processes. Regardless of which method is used, the process must show that a proposed certification basis is able to achieve a positive safety benefit for the overall product.
E.1.3 In regard to impractical, any method used must encourage incorporating safety enhancements that will have the most dramatic impact on the level of safety of the aircraft while considering effective use of resources. This important point is illustrated graphically in figure E-1 below. This figure notionally shows the interrelation between the total resources required for incorporating each potential safety enhancement with the corresponding net increase in safety benefit.
Appendix E E-2 Figure E-1. Safety Benefits versus Resources
E.1.4 Typically, you will find that, for impractical, there are proposals that can achieve a positive safety benefit that are resource effective. Conversely, there are proposals that may achieve a small safety benefit at the expense of a large amount of resources to implement. Clearly, there will be a point where a large percentage of the potential safety benefit can be achieved with a reasonable expenditure of resources. The focus of the methods used should be to determine the most appropriate regulatory standards relative to the respective incremental cost to reach this point.
E.1.5 This appendix provides procedural guidance for determining the material contribution to the level of safety, or the practicality of applying a requirement at a particular amendment level to a changed product. The procedure is generic in nature and describes the steps and necessary inputs that you can use on any project to develop a position.
E.1.6 The procedure is intended to be used, along with good engineering judgment, to evaluate the relative merits of a changed product complying with the latest regulations.
It provides a means, but not the only means, for you to present your position regarding an exception under § 21.101(b)(3).
E.1.7 The certification basis for a change to a product will not be at an amendment level earlier than the existing certification basis or any requirement found in §§ 23.2, 25.2,
27.2, and 29.2, or part 26, that is related to the change.