Skymaster Forum - Snag #2 - Autopilot Not Working

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Snag #2 - Autopilot Not Working

I have the 400A autopilot and it has been acting up on the last couple of flights. Often it will take 2-3 tries to get it to engage and sometimes when it does engage I will get an elevator trim runaway which sends me into a short lived dive before I hit yoke switch OFF.

Last week it stopped working all together in both HEADING and NAV modes. I tried changing all parameters but no luck. Today as well there was no response from the autopilot apart from a slight stiffening of the yoke control. Heading bug had no effect and there were none of those little robotic whining noises although the HDG button was light green on the FDI and the autopilot switch remained ON. After a minute or so the HDG went back to orange on its own. Bummer...

Any ideas..?

If you don't have the Autopilot maintenance manual, separate from the standard maintenance manual, it's really hard to trouble shoot. The next problem is most avionics shop will refuse to work on these units as they have been burned by working on them and finding more problems than they started with.

Some of the issues are connections being corroded from the computer and all the components in the computer are aging. There is one shop that I know will still work on them in Tulsa but most shops I have talked to are really hesitant to dig in. I'm not saying you can't find a shop to help you so do ask. But Tulsa might be worth a call to discuss.

Ultimately we will need to replace these antique boxes for the new low cost Garmin or Tru Trac units. I know a couple guys with 182's that are having the Garmin unit installed with two G5 for AI and HSI. $18 to $20k installed. Sounds like a lot of money but considering the price of an Stec it's a bargin.

http://www.autopilotcentral.com/

Quote:

Originally Posted by hharney (Post 22322)

Thanks for this Herb. Others have suggested this shop as well. My avionics will all be opened up in the next couple of weeks as I update to GEM G4, Avidyne IFD 440 and GPS roll Steer. I will get my shop to go over the unit as best they can then and see how that turns out first off.