Trutrak AP ground test rolls full left & pitches full down

I've just finished the install of a used Trutrak AP (old DFC-250). I've completed the ground calibration steps.

When I run the first ground test - engage the autopilot for the first time - it runs the roll servo full left and the pitch servo full down. It takes 5-10 seconds before they hit the stops.

I've spoken to Trutrak and after walking thru the setup to insure everything was as they expected, they suggested an inflight test. If the issue is still occurring to send in the controller. The bad news is these units are long out of warranty and if it is not "something simple" I'm back to square one.

I'm posting on the off chance the symptoms sound familiar to someone.

Most AP's will slowly drive to full deflection when not in flight.

The reason for this is the algorithm inside is trying to get the plane to respond. It can't of course so it just keeps adding more and more control input.

Try it in the air if all the other checks are OK. Just be ready to disconnect it or override it. Have plenty of safe altitude....

Make sure no control links can go over center and bind up!!!!

Make sure you can override the torque of the servo!!!

With my Dynon AP, I can get the ground deflection to change directions by moving the altitude or heading bug.

I wouldn't be concerned at all... as Brian said this is normal for almost any autopilot sitting on the ground without anything feeding it (if your plane isn't perfectly level in both pitch/roll then it wants to get there). No need for the frowny face when you don't even know if it's good or bad yet.

.....I wouldn't call them symptoms until I knew if it is ill or not....

Cheers,
Stein

I'm just nervous. I'm an old school pilot and the whole idea of an autopilot is a bit scary. I'm really looking forward to having it in the plane, but just being a nervous-nelly until I know it's all good.

Thanks for the affirmation of what the staff at TruTrak suggested. I'll button up the plane and plan out my first test flight (at altitude and multiple contingencies)

BTW: I have been really happy with the support and assistance from TruTrak. They have been exceptionally helpful and patient !

SUCCESS !

It turned out the flight tests were confusing until I had time to digest what all the behaviors were trying to tell me. I eventually figured out that BOTH the roll and pitch servos were reversed. The pitch was not a huge surprise singe I wired for that possibility. However, I installed the roll server "just like everyone else". At least I thought I had

Anyway, the entire saga is on the blog. Thanks for everyone's encouragement and the usual great appreciation to the support team at TruTrak !

The GPS that I'm suing is a bit unusual but it's working well until I can upgrade that piece of tech

Glen, it seems we are traveling in a parallel universe with out newly purchased RV8's....well almost. I picked up a Trio autopilot head recently from a member on this site to replace the aging Navaid.

With some trepidation I engaged it at altitude and after some trimming it was good.

It was an interesting sensation to have the stick taken out of my hand for the first time. I have had plenty of aircraft with sticks and some with autopilots, but this is the first stick with autopilot aircraft.

I was trying to guess what GPS you might have driving your unit and I admit to grinning when I read what you were using.

I've never flown with an autopilot so the first time I set course and it politely "took the helm" I was really questioning if this was a good idea

The little Garmin is pretty funny but works great. Gradually it will collect my usual way pints for flights up/down the east coast. Then I can creat flight plans just by adding together the waypoints. It's got WAAS so it regularly reports 5ft accuracy.

On anecdote. While on the phone with TruTrak asking all my questions, I asked why my roll servo was so big and had a clutch but the pitch servo was smaller and no clutch. The first comment back was "did this unit come out of a Lanceair?". "Yes, yes it did." "you've got more servo han you'll ever need "