A couple more things that I worked on when dealing the potential runaway elevator trim.  First, I tried to locate the double trim switch that I had on my Mooney yoke, no luck.  It appears to be part of the King autopilot installation, not a Mooney part.  So I still have my coolie hat.

 

I agree with Gary Casey that runaway down trim not detected in time, at least in an ES, would be uncontrollable.  In a typical flight, I use about .3" of trim travel (servo travel) from trim down for descent to full flap short final.  After allowing for the variables in weight and CG, I figured I could remove the standard 1.0" travel RAC servo and replace it with the .7" servo.  I would leave the up trim travel the same because I need it in forward CG situations, but remove useless down trim travel.  That may or may not be enough to make my ES controllable at full down trim, but it would definitely help.

 

Here's how I determined the servo travel.  The 1.0" servo takes ~16 seconds to travel stop-to-stop.  I counted approximately 3-4 seconds total that my thumb was on the coolie hat in the transition from high speed descent to short final.  The LED indicators aren't very accurate for estimating servo position, so I used time.

 

Ray Allen also makes an inexpensive adapter to reduce the .7" servo to .5" travel, something to consider for the rudder trim.

 

Maybe I'm off base here, but don't certified aircraft have to be controllable at the trim limits?

 

My ES is set up with the KISS trim system, nothing on the copilot side.  I'm considering adding at least elevator trim to the copilot side so Karen can take a pinch hitter course and be able to fly from the right seat.

 

Mike Easley

Colorado Springs