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.


  • Scott ShererScott Sherer COO Forum Moderator
    edited July 27

    I'm sorry for your labors. The KAP140 has been a great autopilot but, unfortunately, Bendix-King has imploded leaving lots of good people like you AOG. Good luck with diagnosing the problem.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Thanks Scott. Yes, imploded is correct, as far as GA is concerned.

    At least at Oshkosh there is a lot of knowledge to tap into. I did get some great input from Mid-Continent and a couple of others.
    1) Check elevator cable tension and possible obstruction for full elevator travel.
    2) Check Auto Trim Servo is capable of full elevator travel.

    That is the easy stuff. The rest will be a little more work. If the servo needs refurbishing, Mid-Continent does have the parts.
  • Begs the question! Are pilots purchasing the AeroCruze 100 autopilot going in the right direction?
    Mid Continent handles most of the repairs for Bendix King. If you have technical or repair questions, I would start there!

  • Bob. Good point. I would sure not go the AeroCruze direction.

    I intend to get rid of the dual Garmin G5’s and put in the Aspen Pro first then add an Stec-3100. That setup, along with my Avidyne IFD550 and IFD540, make an almost perfect combination. At least Avidyne, Aspen, Genesis, and Dynon work together to provide a seamless integration of devices.

    As for the KAP-140, as noted, I already talked with Mid-Continent and have a plan for trouble shooting. If possible, I would like to keep the KAP-140 going until I set aside enough funds for the other upgrades. I have been kicking myself for going with the G5’s and not the Aspen ever since I had the major upgrades done.

  • Scott ShererScott Sherer COO Forum Moderator

    Well, I can attest to most of your plan. I have an Aspen ((being upgraded to a max in a month), an STEC 55x, and Avidyne 540. I'm using a garmin 345 transponder and an ipad mini with foreflight. All are seamless.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

Sign In or Register to comment.