On August 29, the FAA held their Engines Aftermarket Meeting in Burlington, MA. The meeting included too much information to recap it all in a short blog post, but I wanted to include a few highlights:
Additive Manufacturing
Michael Gorelich is the FAA’s Chief Scientist for Damage Tolerance, but he is also the FAA’s additive manufacturing guru. He explained that there are many different ways to accomplish additive manufacturing. A wide variety of processes , physical activities and media mean that it can be tough for the FAA to provide catch-all additive manufacturing guidance. Nonetheless, Gorelich provided a thought-provoking discussion of the factors that the FAA considers important in the development of a production system element that relies on additive manufacturing.
Tim Mouzakis of AIR-6A0 specializes in Life Limited Parts, and he has been working on developing draft guidance on one of the additive manufacturing processes – specifically, the use of Powder Bed Fusion Additive Manufacturing Processes for the production of turbine engine parts (including repair parts). Mouzakis told us that he would share a copy of this draft AC 33.15-4 (Turbine Engine Parts and Repairs Produced by Powder Bed Fusion Additive Manufacturing Process) with anyone that wanted to see it, and would be open to comments. It seems to be a complicated piece of guidance, and engineers in the room suggested that the draft guidance could create an unnecessary entry barrier if it seems to require common problems to be solved using unique solutions. MARPA is following up on this and has requested a review copy of the draft.
PMA Guidance
Ian Lucas discussed PMA guidance updates in the pipeline, including an amendment to FAA Order 8120.22, Chapter 4, section 12 that woudl provide new guidance on how to reissue or “transfer” PMAs when mergers and acquisitions affect the corporate structure. The FAA is also working on a significant update to the PMA Order (FAA Order 8110.42E). Expect the new Order 8110.42E to include:
- Adjust for AIR transformation reorganization
- Update out-of-date references
- Incorporate policy memos and policy statements
- Clarify gray areas in current policy
The policy updates could be very significant. Here are my notes on what is expected to be changed/added/amended:
- Previously approved data AIR100- policy memo will get incorporated into 8110.42E
- PMA of a top assembly does not mean that subcomponents are interchangeable with OEM subcomponents. You need the detail parts on the supplement to get them as interchangeable. You must prove each is equivalent to the OEM corollary. If the OEM data does not include the replacement of the subcomponent then you may need supplemental ICA.
- PMA of a PMA – typically not allowed but if the PMA was listed as part of the TC or was a PMA by a license agreement then you can reverse engineer the PMA for a new PMA because of the control over the design by the TC holder
- PMA of TSOA sub-articles; PMA is against the product, and cannot impact the TSOA minimum performance standards
- PMA of base material and sealant – this is permitted as long as there is no further manufacturing when the material is installed. – they will look into a bright line clarification
- Clarify the CAGE code is OK to identify a company under Part 45 marking requirements
- Improve guidance for eligibility expansion
- Clarify when AMOCs are needed
- Additional guidance for life-limited parts, and additional testing for lifing programs – in the engine world there is still an expectation for rotating life limited parts to get STC as the basis for approving the lifing program; but Part 25 and rotorcraft life limited parts may not need STC
- Using identicality data to support the T&C application
- Use of suffixes on PMA part numbers to identify minor variations (e.g. color) but the scope of the minor variations must be defined – usually on the drawing or as a drawing supplement – the table would get FAA approved, and additions to the table are minor changes
- Different definition of minor change to design for PMA – it is appreciable effect on approval basis (as opposed to appreciable effect on product)
- Increased guidance on safety assessment
- Encourage use of product safety assessment terminology in lieu of the term “critical” e.g. AC 33-8 categories 1, 2, 3, Parts 23, 25, 27, 29, terms like minor, hazard effect etc.
- PMA of subcomponent with no discernible artic number
- Special considerations for articles made from process intensive materials; like forgings, composites, AM materials
- Consideration of special operational requirements
- Additional information on possible acceptable means of showing eligibility
- Guidance on limiting eligibility to STCs or TC options
- How do we ship our parts overseas using the bilaterals?
- Where is the existence of Supplemental ICA annotated? New example in the order.
- Removing ACO Manager signature from T&C supplements – ACO issues a letter saying that the design is compliant and the letter goes to the MIDO, and then we let the MIDO issue the supplement themselves; MIDO will be permitted to correct small errors without going back to the ACO for subsequent approval of the small error fix
One of the issues we discussed at the meeting is the treatment of post-AD PMAs. After the AD is issued, affected PMAs would need to reflect the safety concern. Sometimes the new PMAs are obtained specifically to correct the safety issue from the AD. But if they are obtained after the AD is issued then it is too late to list them as terminating actions for the AD. This can mean that a known safe design is precluded by technical language in an AD. This is the sort of situation that Alternative Methods of Compliance (AMOCs) are supposed to correct. Where the PMA design adequately corrects an AD issue to the satisfaction of the FAA, then it seems logical that the FAA should issue an automatic AMOC for the PMA, to allow it to be installed (if FAA engineers weren’t satisfied then the lingering safety issue should preclude issue of the PMA).
Other FAA Guidance
Chris Richards provided an update on several pieces of FAA guidance that are making their way through the system.
Statistics AC
The focus of the statistics AC has been dramatically altered. It will be focused on identifying minimum acceptable parts sample size for identicality showings on Category 1 and 2 engine and APU parts. It should be clear that it is not appropriate for other analyses. This is welcome news, as the prior version of the AC seemed to impose requirements to use statistical analysis where it was not appropriate, and it also imposed significant burdens on the analysis that would make it practically unusable.
The FAA agreed that many parts don’t need this guidance – even many category 2 parts do not need statistical analysis – and the purpose will be to support those who want to use such analysis. The FAA hopes to have this out for comment in 2020, and we look forward to seeing a much-improved draft.
Geometry AC
The Geometry AC will apply to PMA by comparative test & analysis for turbine engine & APU parts. MARPA commented on a prior version of this guidance and found it to need minor revision but also foudn tahthe core focus was a useful one. FAA confirmed that there were few significant industry comments, and expects to issue this guidance, soon.
Materials AC
The Materials AC would apply to PMA by comparative test & analysis for metal turbine engine & APU parts. It would address proposals to change the materials (showing that the new material is equivalent to the material properties of the replace materials). The AC identifies five metallurgical properties that define a material: chemical composition, material form, microstructure, hardness, and surface coatings.
This draft AC generated significant industry concerns in the initial comments, so the FAA is reworking it to reflect the industry comments. FAA management explained that they are going “to infuse some sanity into this guidance.” The FAA believes that this one may go out for new comments but has not made a final decision on that point.
This was a great meeting – anyone involved in engine PMAs should definitely consider attending the 2020 edition of this meeting.