I am developing a new PMA based on Test and Computation and I have a question about the OEM parts used for testing. FAA order 8110.42C, Chapter 2, 6 Special Requirements for Test and Computation Applications, b, (1) Comparative Test and Analysis states “Side-by-side testing of proposed and original parts with zero service time”. That is a fairly clear statement that would infer a new OEM part must be used fro comparison. Then the same order under Chapter 2, c (1) Sample Size states “Sampling used parts may provide some characteristics that do not deteriorate during use, such as material composition, grain size and grain flow”. My problem is some of these parts are extremely hard to come by, is there a precedent for the use of used parts for dimensional inspections for reverse engineering. If I have a used OEM part that is not altered by time installed would it be acceptable to use such a part for dimensional checks on any detail of the part that does not wear.

PMA = Parts Manufacturing Approval (FAA approved replacement parts).

Thanks you for any help,
James

I am developing a new PMA based on Test and Computation and I have a question about the OEM parts used for testing. FAA order 8110.42C, Chapter 2, 6 Special Requirements for Test and Computation Applications, b, (1) Comparative Test and Analysis states “Side-by-side testing of proposed and original parts with zero service time”. That is a fairly clear statement that would infer a new OEM part must be used fro comparison. Then the same order under Chapter 2, c (1) Sample Size states “Sampling used parts may provide some characteristics that do not deteriorate during use, such as material composition, grain size and grain flow”. My problem is some of these parts are extremely hard to come by, is there a president for the use of used parts for dimensional inspections for reverse engineering. If I have a used OEM part that is not altered by time installed would it be acceptable to use such a part for dimensional checks on any detail of the part that does not wear.

PMA = Parts Manufacturing Approval (FAA approved replacement parts).

Thanks you for any help,
James
Tests and Computations is a difficult route to PMA. I suggest you discuss your plan with the Aircraft Certification Office (ACO). You may want to engage the services of a Designated Engineering Representative (DER) as well.

Chapter 2, c (1) is covering part features that are constant over time with a design. Metal Alloy does not change, HT condition the same. They drive the zero time requirement to ensure that there is no posability of any degradation for any reason from what they classify as a New part. The same emphisis applies to the issuing of the 8130-3 for a new part.
You will have a hard time to objectivly show that you have validated to a approved type design if you can not show that you used a "new" part (and of course do not have access to the approved design data so can not validate to that).
Keep in mind that the current owner of the design is going to defend their market make sure that these types of concerns are put forth to the FAA.
A long shot but you can try a freedom of info request for the data from the FAA.
:2cents: