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PMA Primer

I was having a conversation with an airline friend once, and the subject of PMA’s somehow came up. He said “We’ll never install PMA parts on our airplanes!”, to which I responded, “Oh really? Lets walk over to one of your jets. Let me get in the avionics compartment, and in minutes I’ll show you all the PMA parts you already have.” A quizzical look was seen to alight upon his visage

Fewer topics arouse more passion and confusion than the subject of PMA parts. In this blog I hope to dispel the confusion, and to inject reality, while staying away from the all the references to the plethora of FAA Orders, FAR’s and Advisory Circulars that would detract from a proper primer. First we need to generally categorize the two types of PMA parts that exist:

• PMA gained through licensing agreements

• PMA “substitution” parts (yes, this is the hot button category)

Lets say for example, that you’re RestoJet, the fine manufacturer of Engines such as APU’s. As the Type Certificated Production Approval Holder, they hold all the design approvals and the data for the same, which of course is proprietary. One of their suppliers of engine controls is RoyboyControls. RestoJet can grant RoyboyControls their proprietary, approved design data for the controls, and RoyboyControls would then apply for PMA. With PMA, they (RoyboyControls) are now a Production Approval Holder (PAH), and you can purchase the RoyboyControls parts directly from them instead of having to go to RestoJet. Of course, RestoJet would not be in business if they were in the habit of giving away their proprietary data! Enter the licensing agreement, whereby RestoJet will expect a royalty for their “assistance” in RoyboyControls’ PMA application. Of course RestoJet could have chosen to sell outright all the data to RoyboyControls, but this would cost much more. Here is the common distinguishing characteristic of all such PMA’s in this category: the part number remains the same as the part number found in the Maintenance Manual’s IPC for the example APU. Not so with PMA substitution parts. Most people are not even aware they have these PMA licensed parts in their aircraft because the part number is the OEM’s. By the way, it’s these types of licensed PMA parts I would have no doubt discovered on my friend’s aircraft.

Let’s say there’s a part whom the OEM has exclusive rights to, and the lead time and price have escalated through the roof. This has been the classic formula for persons to consider using PMA substitution parts. Someone other than the OEM will have to engineer the part from scratch using methods variously termed, for example, “Reverse Engineering”. If the design, and means of production are approved by the FAA, the PMA will be granted, and you then have an alternate part to use. Here are some issues you will have to carefully consider:

• Since the substitution part is not the original OEM proprietary part, this part cannot have the same part number. This raises other issues to be considered as discussed below.

• This substitution part number will typically not appear in the OEM’s Next higher assembly Maintenance Manual, so...

• OPERATORS: Just because this type of part has an official PMA, does not mean you can automatically start using them. You must have a means in your written procedures (usually your GMM or GPM) to approve the use of these parts (because of the different P/N). Typically, your ultimate authority will be your engineering department. If you use these parts and they have not been approved by your system, you’ve busted the approved configuration of your aircraft and will be heavily fined by the FAA

• Does the new PMA part carry with it Maintenance Instructions peculiar to it? These maintenance procedures are called Instructions for Continued Airworthiness (ICA’s). Yes, you’d better have them.

• REPAIR STATIONS: You have the Maintenance Manuals for the parts on your capabilities list. Let’s say a customer sends you an assembly for overhaul, and one of it’s subassemblies is a PMA part. You perform the maintenance and are ready to return it to service. Can you cite the OEM’s Maintenance Manual as your basis for having processed the assembly if the PMA part is not contained in the Manual’s IPC? You’d better think hard about that one.

• What about warranties? If an OEM has extended a warranty to you for an assembly, and you use PMA parts in the subassemblies, is the OEM going to honor the warranty? After all, if you’ve altered an assembly by using a PMA part, can you even continue to use the Assembly Part Number? Hmm, another basis for profound thought! Conversely, does the PMA manufacturer extend any warranties for its product?

• PURCHASERS/SALESPERSONS: Remember that for these substitution parts, the OEM part number cannot be used. Some PMA manufacturers try to soften this distinction by slightly altering the OEM P/N. For example, the OEM P/N might be 12345-6. The PMA P/N might appear as 12345-6RR, the initials being those of the manufacturer. Regardless, if you’ve ever seen the FAA’s PMA paperwork, you’ll see that the FAA cites the PMA P/N as an approved substitution for the OEM P/N. Beware of those that would list the OEM P/N in ILS for example, but send you a PMA part. The same goes for searching on the web. You might enter an OEM part number and be directed to a PMA site. Just be careful.

• DISTRIBUTORS: If a customer sends you a PO for an OEM part number, and you locate a PMA substitution, and the customer approves of it, get it in writing, such as an amendment to the PO. Royboy cannot overstress this counsel

The industry has developed some best practices to successfully address all the issues and concerns I’ve just cited. The use of PMA parts is growing astonishingly because of pressure to contain costs.

REALITY CHECK PLEASE! Not surprisingly, some OEM’s have taken the position that PMA’s erode safety. I have yet to see conclusive evidence of that, save the occasional anecdotal story or two. Even if I had seen such proof, for every one occurrence, we could easily cite one hundred more of OEM parts failing. On the other hand there have been stories of some PMA’ers who took an OEM’s proprietary blueprints and copied them to some extent. In this case I fully support the OEM’s right to protect their intellectual property.

• The parts must be marked “FAA-PMA”

• The design must be approved by the FAA

• The means of production and inspection must be approved by the FAA

Besides the obvious rise in independent PMA houses manufacturing parts, a curious development is that some OEM’s are getting PMA’s for parts made by competing OEM’s. For example, two OEM’s make competing widgets. One OEM will get PMA for parts that go into their competitors widget. That’s chutzpah!

In parting, I just want to stress that this blog is a highly paraphrased, simplistic characterization of the PMA world

OK, OK, if you REALLY want the official guidance on PMA’s, the document to access is the FAA’s Order 8110.42 titled Parts Manufacturing Approval, all 93 pages.

tHIs STuFF cAn drIVE yOU CRaZy...

10/3/05

Roy Resto - VP Technical Operations, FAA-DAR
Phone: 414 875-2191   Fax: 414 875-0200
royboy@mbtrepair.com

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