"Michael" wrote in message
ups.com...
My S-Tec 50, a 2-axis, rate-based unit, has operated with only one
glitch-- a
bad switch--in 700+ hours since installation.

A friend of mine has a 50 in his Bo, and it hasn't fared as well as
yours. If went 'dead' - meaning no action on aileron control and no
annunciation - multiple times before the problem was resolved. Usually
by the time he got it to the A/P shop it was working again, and the
shop could not figure out what was wrong. Eventually it died for good.
It was a bad motor in the roll servo.

On the flip side, I once instructed a student in an Ovation who told me
his KFC-225 never hiccupped.

Michael

Some autopilot failures are very subtle. I was shooting a coupled ILS to
minimums with a King autopilot in a Mooney. After capturing the glideslope,
I noticed the rate was about 75'/min more than I was used to. As we got
closer to DH, the DME was still showing about 2 miles to the airport. I
leveled at DH, and while motoring along 200' above the houses, I tapped the
Vor/loc. The GS needle snapped to the top of the case. It was "stuck"
centered, and the autopilot
was literally flying the needle. Iron Mike, indeed.

Al