On Aug 3, 11:00 pm, One's Too Many wrote:

Thanks, I'll probably need it, but my IA did say that the 337 for the
PSE intercom should slide right thru the bureaucracy like greased
butter since a TSO'd part is already an approved part and its
installation manual also constitutes "approved data" for the 337

Just hope they don't go tell you the intercom must also be STC'ed for
your aircraft before they allow it or to go hire a DER to create
approved data or to take it to one of those big city multi-million
dollar avionics shops to get installed. Up here in northern Texas, an
intercom installation is also considered a major alteration. My AP
says they claim it modifies the basic design of the comm radio system.
Must be a Texas thing.

OTOH, the Air Gizmo dock for a Garmin x96 is deemed a minor alteration
in this region and the GPS and dock can be installed for VFR-only
under reference of AC-20-138a with only a logbook entry, even when
hooked up to the ship's power and an external antenna mounted. Go
figure.