Right, but that's what Tom says a PMA is NOT.
If a PMA still requires a 337, then why have a PMA instead of an STC?
And a STC holder can sell the components without a PMA, so a PMA is not necessarily required to make and sell components.
Parts manufacturing authority will allow the manufacturer to prove the product they produce is the equivalent to the parts used in the Production certificate, The Type certificate or the production certificate in this case is not modified or altered.
Cessna for years built the 17- series aircraft with Bendix Brake systems, after a few years Cleveland came out with a brake system that was better and would replace the Bendix, so they proved to the FAA that their system would work on the 17-series, the FAA then gave Cleveland a STC to alter the 17- series to use the new brake system.
In the mean time Bendix went out of the brake business, and Cessna started using their own McCauley brakes, then Cleveland bought the McCauley line of products, so now any Cessna brake is replaceable by a Cleveland part with out a STC or PMA.
It's a complicated paper trail but it must be in place to use certain parts.
The use of LED lights and Strobes have become such a standard usage that the FAA has basically said go head and use them as direct replacement parts as long as the are a major brand of light.
If I were going to change the type of light I was installing, I'd give my A&P-IA a call and have them get guidance from their PMI at FSDO.
Some of these inspectors are still pretty up tight over these mods.
If I were buying any aircraft with Strobes and or LED lighting, I'd ask my A&P-IA if they will pass the annual with no paper, on the instal.