Michael R wrote:

Another possibility:


http://www.sportys.com/acb/showdetl....ID=7439&DID=19

I first read of this in a CPA email message. But they didn't provide a URL.

This instrument is interesting. It's apparently not solid state, but
instead uses the "old" approach of an electrically spun gyro (as most TCs
do). Therefore, I'd expect it to live less long than the Mid-continental
solid-state "equivalent".

But the Mid-continental has but a single year warranty. So...?

And this is cheaper by a factor of about four. However, it lacks an
electrical backup. So I'd not want to use it as a replacement for an AI in
my aircraft, where an electrical loss would mean losing both AI and TC.

Instead, this appears intended as a TC replacement. And that raises some
questions.

First, what about rate-based autopilots? How would they work where there
was no device reporting on the rate of a turn?

Second is the loss of the ability to do a timed turn. Perhaps this is no
big deal, as that's something we do only when the AI has failed.
Interesting.

Third, how would I go about determining if I could replace a TC with this in
one of my club aircraft (which all fly IFR)? I understand STCs, which are
model specific. Do I need to find an STC for a 172 or 182 for this?

Or does the fact that this is "TSOed" eliminate the need for an STC? Would
a field approval still be required, or not?

[And on the same theme: is there something I can read that discusses all
these concepts: PMA, STC, TSO, field approvals, etc.? I feel like I'm
groping my way in the dark on these. It sounds like the perfect topic for
a FAQ or tutorial for the O in AOPA.]

Thanks...

Andrew