PMA Test and Computation Question - FAA order 8110.42C Chapter 2 section 6 b

[jameslaz]

I am trying to find and answer to what I thought was a simple question, I am hopping someone can set me straight. My company is just starting up in the PMA world and I have questions about Test and Computation data. In FAA order 8110.42C Chapter 2 section 6 b. It states Comparative Test and Analysis, or General Test and Analysis. I am not really sure what is meant by General Test and Analysis. We have a new employee who is stating that you can get a PMA supplement approved by test and computation with out actually making the new PMA part and testing it. I do not see how this is possible but I may be wrong, I have gone under the assumption of Comparative Test and Analysis which clearly states “This method entails analysis and test of the original and proposed parts”. Me fellow employee is stating as long as it is not a critical part just reverse engineering and creating a print based on the reverse engineering data is enough for an approval. If anyone has any information to share on this subject this I would be grateful for any help.

Thank you,
James

[Marc]

Can anyone help with this one?

[BadgerMan]

It seems pretty straight forward to me but I would not proceed too far without discussing your plans with your DER and/or your ACO.

From 8110.42C, Chapter 2:

6. Special Requirements for Test and Computation Applications. Applications submitted on the basis of test and computation should specifically address:

a. Compliance with Airworthiness Standards. Applications based on test and computation, either comparative or general test and analysis, must demonstrate compliance with applicable airworthiness standards. These include special conditions that apply to the respective products. The certification basis for the PMA part is the same as the basis for products affected by part installation (see the TCDS). Find minimum performance standards in applicable TSOs and airworthiness requirements in the following 14 CFR parts:



b. Substantiation. The applicant can prove compliance with applicable airworthiness standards by comparative or general test and analysis. Comparative test and analysis substantiates that the PMA part is at least equal to the approved original part. Thus, the PMA part meets the same airworthiness standards as the original part. General test and analysis shows the part complies directly with all airworthiness regulations applicable to the product affected by part installation. Tests support each type of analysis and confirm significant assumptions, findings or conclusions.

[BadgerMan]

Reading on we find:

(1) Comparative Test and Analysis. Expect the applicant to demonstrate the functional design of the proposed part is at least equal that of the original TC, STC, or TSO part. This method entails analyses and tests of the original and proposed parts. The criticality of the part and the complexity of its design will dictate the rigor of the comparative analysis and the extent of testing. Side-by-side testing of proposed and original parts with zero service time under the same procedures and conditions provide the standard to evaluate the adequacy of the replacement part. The results of the analyses and tests will note any differences and provide sound technical justifications for these differences. Reverse engineering of the original part supports a comparative analysis. However, comparison of the respective PMA and product designs may suffice for simple, non-critical parts.

(2) General Test and Analysis. The applicant shows the part complies directly with the product’s airworthiness requirements and applicable TSO requirements. For example, certification of a proposed replacement part for an engine by this method would require compliance with all regulations of 14 CFR part 33 applicable to the affected product.

(3) Test Scope and Plan.

(a) Part criticality and complexity determines the need, type, and scope of testing to support either a comparative or general analysis. Testing ranges from functional to component to flight. This verifies the performance and durability of the part for compliance with applicable airworthiness standards. Simple, non-critical parts may need little or no testing.

As I said above, get some direction from your DER or the ACO.