Autopilot failure

[DonMuncy]

Returning home from GGG today, when I engaged the autopilot (KAP 150), the plane entered an abrupt, uncommanded (by me) descent. I don't remember looking, but I estimate it was about 10 degrees. The altitude hold was not engaged and the "up" rocker had no effect on it. I tried it several times and it consistently dived on its own. Any ideas that I can share with my avionics guy.

[jclemens]

Call the folks at http://autopilotcentral.com , they are the best when it comes to these issues.

[flyboy0681]

This had happened to me two times and each one was related to the AI sending faulty information to the head unit. It was abrupt each time.

[BobAustin]

It was my attitude indicator also...but only discovered after 10k autopilot overhaul at autopilots central This was with my Cessna 340.    Check Ai first. 

 

Bob

Edited October 29, 2015 by BobAustin

[jetdriven]

I agree, send the AI off to a shop than can test the pickoffs and verify they work properly. Also, the KAP150 has been known for pitch boards going out and its a used Mazda Miata priced replacement, around ten grand.

[Danb]

Don, in my 1988 J , I had numerous occasions one similar to yours. And another on a roller coaster, and lastly runaway trim twice in IMC. I believe the first was related to the attitude indicator, the second was the servos needed to be replaced and lastly it took numerous visits to avionics shop and the computer board needed replacing. Since in can be many different things JC makes sense to go to the specialists and get it done right although mine wasn't correct until sent back to King. You may need patience in this one good luck, and be cautious in IMC until your sure it's right. I was lucky in that my plane was under warranty by Mooney the first two items occurred in its first year after birth. I think Mooney just took old but new servos off the shelf when the plane was built. My first two years of ownership had many different items faulty.

[PTK]

Don, have you gone through ground tests with engine running to see how it behaves?

[flyboy0681]

You have to admit, when the KAP 150 works, it works really well. Hard to believe that it's early 80's (late 70's?) technology contained in a very compact unit.

[Piloto]

Before spending any money clean the tray contacts with contact cleaner.

José

[PTK]

Before spending any money clean the tray contacts with contact cleaner.

José

Isopropyl alcohol with a soft toothbrush works well also.

Edited October 29, 2015 by PTK

[DonMuncy]

Thanks for all the input. Still working on it. I will try to remember to post the outcome.