Autopilot Porpoises when Mike Keyed

rpellicciotti wrote:
jls wrote:
Also instrument needles go crazy.

Aircraft is a Lancair with antenna hidden in the horizontal stab. How
'bout directing us to some reading material about how to stop it.

Our local avionics guy says we may have to live with it, or install
external antennas, which will dirty up a Lancair in a hurry.

Jim Weir?

Thanks and happy holidays.

I'll take a completely different tack. Since your instrument needles
move when you key the mike, I suspect a ground loop. I would be
interested in knowing if you engine needles move when you turn on and
off other consumers like the strobes or nav lights.

I just finished working on a Lancair that had a similar problem. You
could turn the nav lights on and off and the CHT's would go up and
down. Keying the mic caused the trim indicators to change. We ended
up pulling out most of the wiring and redoing it for the plane's new
owner. Not cheap, but everything works now.

Rick Pellicciotti
Belle Aire Aviation

Thanks so much and thanks to all the others who responded with help.
I'm going to advise hangarmate to rewire his airplane.*

The com antenna is in the vertical stab, at least one of them. The
airplane was built by one of those shops that the owner sends the kit
to. We're trying to get in touch with the builder to find out where
the other com antenna, if any, is.



*Just kidding. We'll try all the other avenues first, but fact is the
more troublesome of the two radios does do a number on the egt and cht
readouts, as well as the autopilot and some of the other instruments.

Top o' the season to you. It's summer here in WNC at 70 deg. F. and
warm sunshine.