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I've been following this thread and find it quite interesting, but we seem to be going in circles. A fellow builder and I were discussing this a while back and his solution sounded ultra simple and foolproof (if that is truly possible). He suggests adding an ON-OFF-(ON) switch between the relay and the trim servo. Normal operation would be in the ON position. If the relay sticks, or the coolie switch sticks closed, you would momentarily move the switch to the (ON) position, thereby reversing the polarity to the servo and reversing its direction. Once yo get the trim back to a controllable trim setting, you would release the ON-OFF-(ON) switch and it would automatically spring back to the OFF position, interrupting power to the servo. Has anyone used this approach, and if so, how does it work?
Mark Steitle
Lancair ES
On Sat, Jun 28, 2008 at 11:06 PM, Steve Colwell < mcmess1919@yahoo.com> wrote:
My Legacy experienced Runaway Pitch Trim on the first flight.
Fortunately Test Pilot Josh Brungardt was at the controls, had previously
located the trim circuit breaker, pulled it, cycled the coolie hat, then was
ok. I called RAC about the problem and learned they have a new larger relay to
replace the older smaller one. I ran the pitch servo, wiggled the wires and
connectors many times with no faulting. RAC doubted the relay was the problem
but I replaced the pitch and roll relays anyway. I also installed the Adjustable
Trim Speed Control that allowed pitch trim to operate at ˝ the normal speed…….much
better.
Steve Colwell Legacy 15SC
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