Gary

 

We just found out after about 160 Hrs on My Lancair IV that My Stec Autopilot 60-2 altitude hold takes off (climbs) when we transmit on Comm 2 which is a KX-155,  we have no problem with Com 1 ( Garmin AT GX-60) ( I have a plate with Bulkhead connectors mounted to the side of the radio stack and they are accessible)  To trouble shoot, we exchanged the cables that go from the radio stack to the antennas.  When we did that the problem changed to Com 1 and Com 2 was fine.  From that we deduced (I hope correctly) that the problem is either the original Com 2 antenna cable routing or the antenna itself which is mounted in the vertical fin.  Our plan is to try and reroute the cable when we are doing the annual and have the interior out.  If I remember right,  The cable is routed in the same bundle as the auto pilot wiring.  I will report after we make the change.  In the mean time it does not pose  a threat as we rarely use both com 1 and com 2 at the same time.  After all after 160 hours it was the first time that  we had actually used both radios at the same time and we now know about the problem and can avoid it.  We can also duplicate the problem in the hanger.  I will report the results after we make the change in October.

 

Tom Byrnes Lancair IV N54TB