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.

 

[flyboy 1956]

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.

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.

Thanks Chip,

not sure what you're referring to as a converter? When I preformed the test in my hanger, the yoke turns left on the nav setting.

 

[Cricket1]

Did you have the STEC in Heading mode? Our Stec 50 with G5 HSI and GTN 650 will do exactly as you describe, IF you put the STEC in NAV mode. In heading mode, it will follow the GPSS.

When I'm getting vectors, etc I just turn off GPS steering in the G5 and use the heading bug. Works like a charm. But in NAV mode, the STEC just turns left.

 

[455 Bravo Uniform]

I still think it’s a dirty or broken HSI issue. The guy that fixed mine I think is the same guy Chip recommended, but let me check my logs/files (later today). I explained over the phone and he suggested what the issue might be.

 

[flyboy 1956]

I still think it’s a dirty or broken HSI issue. The guy that fixed mine I think is the same guy Chip recommended, but let me check my logs/files (later today). I explained over the phone and he suggested what the issue might be.

I would appreciate the number. Do you recall where he is located?

Thanks

 

[Chip Sylverne]

Thanks Chip,

not sure what you're referring to as a converter? When I preformed the test in my hanger, the yoke turns left on the nav setting.

Then try the roll adjustment. You'll need a long, very small screwdriver. I made a tool by taking a heavy paper clip, partially straightening it and filing z bevel at the tip. Turn the adjusting screw in very against the direction of the yoke until its steady. Small increments, don't get crazy.
If it has no effect, then it could be wiring or a dirty connector at the hsi.

A gpss converter takes the flightplan information from your GPS and converts them to signals your a/p can use to conduct the flight. Without it, the 430 cannot "talk" directly to your STEC, essentially by driving the needles on your HSI.

 

[Checkout_my_Six]

Guys.....Nav mode will not work properly with GPSS. It needs to be in HDG mode to track heading or the 430 GPS.

 

[Chip Sylverne]

This is a gpss converter. If you have a switch that looks like this, it must be in the gpss position and the a/p in hdg for gpss to work.

ST-901 GPSS

Roll Steering Converter

sarasotaavionics.com

 

[Chip Sylverne]

Guys.....Nav mode will not work properly with GPSS. It needs to be in HDG mode to track heading or the 430 GPS.

NAV mode works fine with the a/p in nav mode. It takes the converter out of play. GPSS only works with the A/P in heading, and gpss selected on the converter switch.

 

[Checkout_my_Six]

NAV mode works fine with the a/p in nav mode. It takes the converter out of play. GPSS only works with the A/P in heading.

Not with the CDI needed off more than a few degrees....it won't intercept the course.

 

[Chip Sylverne]

Not with the CDI needed off more than a few degrees....it won't intercept the course.

Mine does just fine, up to 45 degrees it'll turn toward the needle.

 

[Checkout_my_Six]

Mine does just fine, up to 45 degrees it'll turn toward the needle.

Merry Christmas Chip.....Blessing to you and your family.

 

[flyboy 1956]

I am more confused than when I started...the a/p works fine in heading mode and the alt hold and it tracks the hsi heading bug and follows the heading with each input. However, if you go from heading to nav (430w in my plane) the plane begins a gradual turn to the left and never recovers.

I am thankful for all the input and wish I had the understanding of this as you all do.

 

[455 Bravo Uniform]

My assumption was that it worked fine in NAV for you up until now. Or is this a new plane/config for you?

 

[flyboy 1956]

My assumption was that it worked fine in NAV for you up until now. Or is this a new plane/config

My assumption was that it worked fine in NAV for you up until now. Or is this a new plane/config for you?

Correct. I have owned this plane for 20 years and this is the 1st issue with the a/p I have had, and it began Friday. Nothing has changed with any avionics or maintenance.

 

[455 Bravo Uniform]

I would appreciate the number. Do you recall where he is located?

Thanks

616-822-1999
Muskegon, MI

Give him a call, it’s free to talk.

 

[455 Bravo Uniform]

Sorry, it was Robert Bramble, not Bob Weber. Weber wanted a consulting fee. Bramble diagnosed it over the phone.

Robert Bramble
Aerolab Aviation Services
www.aerolabaviation.com
FAA CRS#V0RR239Y
535 Airport Lane
Suite 1
McKenzie, TN 38201
Ph: (913) 680-4169

 

[455 Bravo Uniform]

PIREP: If you have a broken King KCS-55 / KI-525 / KG-102, Robert Bramble is the man!

The compass card on my King HSI had started to fail over the last year. I would have to toggle it from “slave” to “free” to “slave” multiple times after startup to get it to point to the correct magnetic heading. As I taxied, it would get stuck, requiring me to repeat the sequence. In the...

pilotsofamerica.com

 

[Chip Sylverne]

I am more confused than when I started...the a/p works fine in heading mode and the alt hold and it tracks the hsi heading bug and follows the heading with each input. However, if you go from heading to nav (430w in my plane) the plane begins a gradual turn to the left and never recovers.

I am thankful for all the input and wish I had the understanding of this as you all do.

See this is where you lose me. Going back to basics, the 430 is just a navigator. It uses either VLOC (ground based radio) or GPS signals to drive the hsi course needle. The a/p in NAV turns toward and follows whatever drives the course needle, either gps or vloc. In HDG mode the a/p ignores the course needle and follows the heading bug.

In the case of a gpss install, the a/p follows the signals generated by the gpss converter while in heading mode as though the gpss converter is electronically turning the hdg bug.

In your case if I understand you correctly, your a/p works fine in hdg, but turns when in NAV. I'm unclear what your 430 is doing . Are you in VLOC or GPS when this happens? Or does it happen in both? In your testing, the a/p turned when level with the needle centered VLOC, so that indicates a roll centering problem of some kind. Does it also turn with the 430 in gps course line centered when in flight?

I'm also unsure we have a clear understanding of GPSS. Have you ever flown a multiple waypoint flight plan and approach without any further inputs to the hsi in this airplane? That's gpss, and with a 430 and KCS 55, it requires an intermediate box and switch separate from the 430 and a/p, and will only operate with the a/p in hdg mode. If you have it I'm certain you would be familiar with that switch.

 

[Chip Sylverne]

Merry Christmas Chip.....Blessing to you and your family.

Back atcha Rick. Hope all is well with you and yours.

 

[Checkout_my_Six]

I am more confused than when I started...the a/p works fine in heading mode and the alt hold and it tracks the hsi heading bug and follows the heading with each input. However, if you go from heading to nav (430w in my plane) the plane begins a gradual turn to the left and never recovers.

I am thankful for all the input and wish I had the understanding of this as you all do.

So...here's my take....and how my 60-2 works. In heading mode "HDG"...the AP will track the heading bug on the DG or if the GPSS selects GPS will track what ever the 530/430 is calling on the pink line (GPS tracking).

If I press the "NAV" button it will do whatever the CDI tells it from the 530/430 (output to the CDI). If the needle is pegged, or more than a few degrees off, it will turn in circles and not intercept. This is normal for this setup. The only way for this to work is to use GPSS with GPS selected (or the HDG bug)....then when on or near course to select NAV. Only then will it follow the NAV signal from the CDI head. This is the process for tracking an approach and capturing the glide slope....cept ALT hold is also selected.

 

[Chip Sylverne]

So...here's my take....and how my 60-2 works. In heading mode "HDG"...the AP will track the heading bug on the DG or if the GPSS selects GPS will track what ever the 530/430 is calling on the pink line (GPS tracking).

If I press the "NAV" button it will do whatever the CDI tells it from the 530/430 (output to the CDI). If the needle is pegged, or more than a few degrees off, it will turn in circles and not intercept. This is normal for this setup. The only way for this to work is to use GPSS with GPS selected (or the HDG bug)....then when on or near course to select NAV. Only then will it follow the NAV signal from the CDI head. This is the process for tracking an approach and capturing the glide slope....cept ALT hold is also selected.

Try this. Put your gpss switch on hdg. Press the 60-2 hdg and nav at the same time. Set the hdg bug for a 45 deg or less intercept for the lpv, ils or loc course inbound. Once you get within a couple of dots of the intercept, the a/p will intercept the nav course an track inbound like on rails. If the alt is pressed too, it will start you down the glideslope at the intercept.

 

[flyboy 1956]

Try this. Put your gpss switch on hdg. Press the 60-2 hdg and nav at the same time. Set the hdg bug for a 45 deg or less intercept for the lpv, ils or loc course inbound. Once you get within a couple of dots of the intercept, the a/p will intercept the nav course an track inbound like on rails. If the alt is pressed too, it will start you down the glideslope at the intercept.

Next outing I will give it a shot.

Thanks all and merry Christmas1

 

[Chip Sylverne]

Next outing I will give it a shot.

Thanks all and merry Christmas1

Oops, posted that for Rick. That works for a 60-2, no idea if it will for a 50.

Merry Christmas!