HSI heading bug issue

[455 Bravo Uniform]

KI-525
S-TEC 60-2

When A/P heading mode is engaged, I get a continuous uncommanded standard-rate turn to the left, regardless of heading bug position. Nav mode works great.

Am I more likely looking at an A/P issue or HSI issue? Any way to diagnose as a pilot? Something simple like contact cleaner?

Or should I start shopping used HSI or new G5s?? Not really ready, next upgrade was supposed to be EDM-830.

 

[Chip Sylverne]

Contact Bob Weber, Webair Aircraft Consulting. Pretty sure he has a website. Knows this stuff like the back of his hand.

https://webairconsulting.com/

 

[Josh Mac]

You might need to redo the roll centering? Had a similar issue where my NAV worked but I was always in a turn in heading mode. You can do this test on the ground and takes 10-15 mins. I can't post any links yet, but if you Google 'Aeroelectric STEC' you should see the service manual as the first link.

 

[Chip Sylverne]

You might need to redo the roll centering? Had a similar issue where my NAV worked but I was always in a turn in heading mode. You can do this test on the ground and takes 10-15 mins. I can't post any links yet, but if you Google 'Aeroelectric STEC' you should see the service manual as the first link.

Could be, but usually it's more of a drift than a standard rate turn if it's a roll centering problem. To set roll center, remove the top left screw on the face of the control head. There is an adjustment pot behind it.Take a heavy wire paper clip and unfold it so it has a couple inch shank, and bevel the tip so in essence you have a long thin shank screwdriver with a 90 deg handle. Level the airplane and engage heading mode. Turn the screw inside the adjusting pot A LITTLE BIT AT A TIME opposite the turning motion of the yoke. If you need to recenter the yoke, just turn it back against the clutch pressure. IT DOESN'T TAKE MUCH ADJUSTMENT to see if that's the problem. Monkey around too much and you open a whole can of worms.

But quite frankly, if this came on all at once, I doubt it's a roll centering issue.