KAP-140 Check-Pitch-Trim Warning
Of course two weeks before Oshkosh 2021, my KAP-140 started giving an audio alert of “Check Pitch Trim”. It started after I disconnected the A/P on approach to my destination airport. I pressed the A/P disconnect again, and the warning stopped for about 10 seconds before resuming. I pulled the A/P circuit breaker since I did not want to deal with the issue until after landing.
On the ground, I powered the A/P back up, and it went through the POST (Power On Self Test) without an issue and no warning lights. About 10 seconds after the POST was complete, the audio warning came back and continuously repeated. Even during this time I could run the manual electric trim to both extremes. As a further test, I tuned in a VOR and centered the course. I then engaged the autopilot (still on the ground) and the bank servo worked as it should as I set the heading left/right of direct course. Since I had 2000 ft in the Altitude window for altitude preselect, the auto trim did trim up for a climb.
I was able to get ahold of a KC-140 Flight Computer with the same part number, hardware revision, and software revision. I swapped the Flight Computers and ran the ground test above with the same results.
The only mention of this warning in all the manuals is in the Pilots Guide. The PG said to do what I did, disconnect the A/P, fly the airplane, and pull the breaker when able.
I have the KAP-140 Installation Manual, Maintenance Manual, and Flight Line Maintenance Manual, besides the Pilot’s Guide.
Since no shops want to deal with the KAP-140 since Bendix-King does not support it (or apparently any of their other products), I am looking for help to diagnose the problem.
I know I can download the error logs from the KC-140 flight computer, but I do not have the U-174 plug to wire up as a serial port. I do have a plug on order and will be picking it up at Oshkosh on Monday 7/26. Hopefully, the logs will show some light as to the problem.
Not exactly fun flying 11.4 hours in IMC by hand to Oshkosh.