S-Tec 50 autopilot issues

[flyboy 1956]

Hello all,

New to the program and seeking assistance with a current issue with my S-Tec 50. Always worked well until yesterday, when the flying and selected the nav function on the unit.
Instead of capturing the route from the 430w, my plane began a left turn and would not intercept or capture the route?

Works fine with the heading bug and all ground functions seem fine during pre-flight. The altitude select also works well.

All help is appreciated.

 

[Chip Sylverne]

Sound like you do not have gpss. Therefore, the a/p will follow the course line on your HSI or OBS, not the magenta line. You need to turn the OBS so the course selected and GPS match when in NAV. Otherwise, the a/p will turn toward the line.

 

[flyboy 1956]

I do have gpss, and I have never ( I can't say this anymore) had any issues? The autopilot does seem to be turning to a specific destination just keep going left.

I appreciate your thoughts, keep thinking.

 

[flyboy 1956]

sorry, does NOT seem to have a destination

 

[455 Bravo Uniform]

What HSI do you have? Does it follow a VOR or ILS on your HSI's course setting?

 

[flyboy 1956]

KCS 55 A. Yes, HSI works as intended and the a/p follows the heading bug with no issues. As soon as the nav function is selected the plane goes left at a moderate rate.

 

[455 Bravo Uniform]

So the HSI works with your NAV radio (VORs, ILS, LOC), but not GPS - does the HSI throw its red NAV flag on GPS nav mode?

 

[flyboy 1956]

Yes. No flags. All seems to be working with the HSI. I have put the plane on a route manually, with the HSI and heading bug on the intended route prior to activating the nav selection on the ST50 and once selecting nav the plane goes left and will not intercept or even follow straightforward.

 

[Checkout_my_Six]

Leave the AP in heading mode… press the gpss button to go into gps tracking vs heading.

Once close in on the approach in term mode press the nav button.

 

[flyboy 1956]

The a/p will not even tack a straight line enroute on the nav function.

Ie: if you put in a flight direct to anywhere and select nav it starts to turns left immediately.

 

[flyboy 1956]

Has anyone had any good experiences with an avionics shop that specializes in S-Tec in Fl or south Ga?

I have read some very disturbing reviews however no acknowledgement to the names of them.

 

[455 Bravo Uniform]

I don’t know if this will help, but it’s worth a shot. I have a different HSI and had the opposite issue where HDG was like yours but NAV worked fine. Ended up being the HSI, something to do with an LED light, window, and receiver; sometimes the LED is bad, sometimes the receiver lens is dirty. Again, different HSI and was HDG. I sent it out and back and all was fixed.

HSI heading bug issue

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...

www.pilotsofamerica.com

 

[MooneyDriver78]

Bad computer or a bad connection.
Any work done behind the panel lately?
STec repaired my computer for a flat fee of around $600 (minor fix), a major repair would have been $1500. This was about 8 years ago

Now might be a good time for an avionics upgrade.

 

[FORANE]

TDS

 

[flyboy 1956]

I don’t know if this will help, but it’s worth a shot. I have a different HSI and had the opposite issue where HDG was like yours but NAV worked fine. Ended up being the HSI, something to do with an LED light, window, and receiver; sometimes the LED is bad, sometimes the receiver lens is dirty. Again, different HSI and was HDG. I sent it out and back and all was fixed.

HSI heading bug issue

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...

www.pilotsofamerica.com

455,

Thanks for the insight. I have decided to seek a reputable S-Tec shop.

 

[flyboy 1956]

Bad computer or a bad connection.
Any work done behind the panel lately?
STec repaired my computer for a flat fee of around $600 (minor fix), a major repair would have been $1500. This was about 8 years ago

Now might be a good time for an avionics upgrade.

I agree. Thanks for your thoughts. If anyone has an experience with avionics shop that has experience in a/p in Fl or South Ga I would appreciate the info.

 

[Chip Sylverne]

Have you done the roll centering ground check of the stec? On the ground, make sure wings are leveled. Tune the 430 nav to an unused VOR frequency. Center the CDI lubber line and engage the NAV on both STEC and converter. The yoke shouldn't turn. If if does, there is an adjustment behind one of the faceplate screws you can try. If there's no roll, you probably have a converter issue. If it rolls and won't adjust out, it's on the a/p side someplace.

What type of gpss converter do you have, STEC or DAC?

You might call Bob Weber, Webair Consulting. Knows these things inside out.