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When replacing factory installed optional equipment with an aftermarket upgrade, is an STC always required?
For instance, today I found out that a plane I fly has an STC because the stock sun visors were replaced with aftermarket rosen sun visors. This resulted in no weight change, but the STC was still needed (some poor guy found this out the hard way after taking the plane to the FSDO for his CFI ride, had to get a special flight permit to ferry it back home for maintenance).
Does simply removing factory optional equipment require an STC, or is one only needed if new equipment is installed in it's place.
Also, when replacing a radio or other piece of avionics with the exact same make and model radio, what type of paperwork must be filed? Do you just need to get approval for the field alteration?
Thanks....
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Just to make it crystal clear what we're up against in this whole topic: The FAA is not consistent in its application of the FARs. Having said that, prepare to be confused.
Form 337 is used for Major Alterations and Major Repairs. Go ahead and read the list of things that Part 43 considers to be a Major Alteration, and then forget about that list. The FAA goes way beyond that list, in reality, in determining what is a Major Alteration. They claim that anything that is not original equipment in an aircraft (in other words, part of the Type Certificate Data Sheet) can only be installed if there is an STC or a Field Approval (one of the uses of Form 337). Which one you need depends on how Major your Major Alteration is.
For some things, the local FSDO can just do a Field Approval and you can be done with it (for example, GPS, Intercom and many other kinds of avionics installations).
For things which require more engineering (such as different engines, winglets, stuff like that) then an STC will be required.
Note that Form 337 will be used for all STC installations too, so pretty much anything that has changed on the aircraft is gonna have a 337 with it. Some will have STCs as well, some won't.
Anytime you permanently remove a piece of equipment from an aircraft, you need to fill out a Form 337. Any time you permanently add a piece of equipment to an aircraft, you need Form 337. I say "you", your shop will do this for you.
If you are replacing a part which is included on the Type Certificate, or on an STC which has been legally installed in the ircraft, then all you need is an entry in the maintenance records of the aircraft.
I'm not even gonna get into Parts Manufacturing Approval since the water gets consideralby muddier in this area.
I learned these lessons while we underwent 6 long months of trying to get our Kingair put on our 135 cert. Our Principal Maintenance Inspector considers himself to be THE authority on anything airworthiness related, regardless of what the regulations say, the aircraft manufacturer says, or even FAA engineers at the Acircraft Certification Office say. He knows best and made us jump through countless hoops to get the aircraft approved.
Hope this helps,
Ray
P.S. Form 337, when detailing a Major Alteration, becomes part of the permanent aircraft records and must be kept indefinitely. Form 337 when detailing Major Repairs, need only be kept for 1 year after the repair was made, and then is no longer required to be part of the aircraft maintenance records.