As others have said, there are details about how we maintain our old airplanes that reasonable people can disagree about.? What I think is noteworthy in our recent search for truth, is the contrast in quality among responses that were received from the FAA, AOPA and EAA.? Right or wrong, I really appreciate Joe Norris having a clear opinion, and not being afraid to speak to us so candidly about it.? Thank you Harry and Dan for digging into this.
Cheers, Bill Joe Norris said: You will find no requirement in any regulation that requires any piece of equipment to be built under a TSO authorization (commonly referred to as "TSOed"). However, some regulations require that a piece of equipment "meet the requirements" of a TSO. Examples would be transponders and IFR GPS units. But for the most part there is no requirement that any particular piece of equipment be "TSOed". Of course the installation of the equipment might need to be approved, such as modifying an instrument panel when the panel is a structural member of the fuselage, or when changes to the primary structure must be made to accommodate a particular piece of avionics. But the unit being installed does not necessarily have to be "TSOed". (This has nothing to do with whether the aircraft manufacturer is still in business or not.) You do have to make sure that the certification of the aircraft doesn't specifically prohibit or require certain equipment to be installed, but in the case of an Ercoupe that wouldn't be an issue (but can be an issue with later FAR Part 23 certificated aircraft).
