Ron,

 

Yes, now that I think about it, either the AOPA  or EAA got the FAA to accept the fact that a simple enroute/terminal/approach GPS installation was no different than any other simple avionic system.

 

To Wit:

 

AC-20-138A (canceling AC-20-138), 12/03, Airworthiness Approval of ...GNSS Equipment.

..........

.....8- Approval Process

.....c. Installation of GNSS Equipment

.....1. Evaluation of Installation

.....iii. Minor Alteration

.....(B) ........GNSS equipment that only interfaces with an antenna, power, ground, an external HSI/CDI with a single source selector switch, and a left/right (deviation-based) autopilot would typically be considered a minor alteration.

........

 

"Minor Alteration" is a powerful term in FAA land where all IFR GPS installs used to be considered a Major Alteration.

 

<<<Obtained by Google search "AC-20-138A">>>

 

Note.

1. No STCs for Experimental Aircraft.

2. TSO'd stuff loses its TSOedness after installation in an experimental aircraft.  Theoretically, stuff taken out of an experimental aircraft for installation on a commercially built STC'd aircraft must be re-TSO'd.

3. Even though S-TEC GPSS provides ARINC ground track guidance via replacing Turn Coordinator "deviation" data, it is still a minor alteration thus escaping FSDO scrutiny.

 

This AC and Transport Canada Policy Letter 553-003 does a good job justifying the simple approach to the simplification of a simple installation.  See:

 

 

It still would be interesting to hear from an avionics shop that builds Lancair panels..........