STEC Heading Hold Problems

[Marauder]

As most of you know, I have a dual Aspen 2000 linked to a Garmin 650 and a STEC 60-2. A couple of weeks ago, I was flying back from the shore and had the AP engaged in GPSS mode. I noticed the plane was drifting very slowly left of course. I disengaged the AP and reconnected using just the heading mode. Again the plane was AP not holding the heading. Resetting everything and reconnecting did not make a difference.

Over the next couple of weeks, all of the flights that I used the AP, I was able to do so without any problems. I was out shooting some LPV approaches over the weekend with and without the AP engaged. Again, no issues. As I returning home, I engaged the AP and noticed the same problem. I had a camera with me and I made a video of what I saw.

I think it is related to the single cue flight director. The bars were missing, except for a brief appearance at 27 seconds into the video.

Has anyone know seen this issue with their STEC flight director/AP? I think the Aspen has nothing to do with the problem. But I could be wrong.

Take a look at the video and let me know what you think. I have an email out to the avionics shop. Hopefully they can shed some light on this.

[John Pleisse]

Hey Chris, I have a similar set up (2000, 2x430w-55x). Why are you getting HDG on your AP when you double press NAV for GPSS? Is HDG your primary selection on the Aspen?

[Bob_Belville]

Chris, I have a 750, Aspen and a STEC 50. Should be very similar. The only idea I might have would be to be sure the Aspen has the right info from the GPS. Have you tried changing the WP on the 650 to see if the aircraft turns to the new course? If you choose to go DIR to the next WP what happens to the heading?  

 

Edit... I reread your note and see you have tried to simply fly a HDG, non-GPSS, and the AP does not fly the HDG you've selected on the Aspen. If that is so my comment about the GPS is off base. But in that mode the course line is not relevant to what the AP is being asked to do.

[Marauder]

Hey Chris, I have a similar set up (2000, 2x430w-55x). Why are you getting HDG on your AP when you double press NAV for GPSS? Is HDG your primary selection on the Aspen?

 

Hmmm... I'm not sure I am following what you are saying John. When I have the flight plan loaded in the Garmin, in order to get GPSS to work with the AP, I just make sure the GPSS button is green on the Aspen and I hit the HDG button on the AP controller (and ALT if I want altitude hold). If the GPSS button is deselected on the Aspen and I hit HDG on the AP controller, the AP follows the heading bug on the Aspen.

 

 The only time I use the NAV button is when I couple for an approach. The sequence to couple is to load and activate the approach, select GPSS on the Aspen, hit HDG & ALT or HDG/NAV together & ALT (if I want to manually use the heading bug to do my own intercept). If I do the latter, I am required to hit the NAV button a second time to get it to take over the approach. You do something different?

[Marauder]

Chris, I have a 750, Aspen and a STEC 50. Should be very similar. The only idea I might have would be to be sure the Aspen has the right info from the GPS. Have you tried changing the WP on the 650 to see if the aircraft turns to the new course? If you choose to go DIR to the next WP what happens to the heading?  

 

Edit... I reread your note and see you have tried to simply fly a HDG, non-GPSS, and the AP does not fly the HDG you've selected on the Aspen. If that is so my comment about the GPS is off base. But in that mode the course line is not relevant to what the AP is being asked to do.

 

Thanks Bob. Do you have the flight director (STEC ST-670) option? I have tried all sorts of things including canceling and reloading the flight plan, using the direct to function, using the heading bug only. When I load a new flight plan or waypoint, the correct heading shows up on the Aspen, the flight director bars are missing and the AP will not command a turn.

 

It really looks like it has something to do with the flight director. When the bars are there, it works like it supposed to. When they do not, it doesn't. I just don't the relationship of how the flight director works within the STEC environment.

[Cruiser]

There are two GPSS sources in your system. One from the Aspen and one from the A/P.

You could try flying with the GPSS selected from the autopilot and not from the Aspen or visa versa.

Does the autopilot follow the HDG without GPSS selected?

[Marauder]

There are two GPSS sources in your system. One from the Aspen and one from the A/P.

You could try flying with the GPSS selected from the autopilot and not from the Aspen or visa versa.

Does the autopilot follow the HDG without GPSS selected?

 

Hi Tom. Are you talking about the ST-901 GPSS converter in addition to the Aspen GPSS converter? If this is what you are referring to, I don't believe I have the ST-901 installed (at least it doesn't show up on my paperwork as being installed and I don't have the GPSS switch that you commonly see with it). I think the Aspen is the only source of GPSS conversion I have.

 

If the heading bug is selected and the GPSS is not selected, it does not follow it -- unless the flight director bars are present.

[Cruiser]

Ok, my mistake. I thought the 60-2 had GPSS.

 

Can you turn off the FD? If you still have a problem it is in the A/P

[Bob_Belville]

Thanks Bob. Do you have the flight director (STEC ST-670) option? I have tried all sorts of things including canceling and reloading the flight plan, using the direct to function, using the heading bug only. When I load a new flight plan or waypoint, the correct heading shows up on the Aspen, the flight director bars are missing and the AP will not command a turn.

 

It really looks like it has something to do with the flight director. When the bars are there, it works like it supposed to. When they do not, it doesn't. I just don't the relationship of how the flight director works within the STEC environment.

Chris, Either I don't have the FD feature or it is turned off if that is an option, I did not add anything to the basic STEC50 that was installed prior to the Aspen.  If there a menu on/off for the FD? 

 

Did you see the note in the Aspen manual (p. 4-58 in my edition) - "With the autopilot in HDG mode, if GPSS is automatically disabled, the autopilot will roll wings level, it will not follow the heading bug." That is reasonable but not necessarily intuitive. Is it possible something is occurring that automatically disables GPSS? Or maybe there's a similar feature when the FD is disabled for some reason.

[Marauder]

Ok, my mistake. I thought the 60-2 had GPSS.

 

Can you turn off the FD? If you still have a problem it is in the A/P

 

Interesting question. I have two switches. They work like in this video: http://www.youtube.com/watch?v=G9vlU9RBTG4

 

If the AP switch is switched "off" and I move the FD switch to "on" then the flight director bars come up (assuming a valid nav flight plan/waypoint is programmed) and provide guidance -- without the AP servos engaged.

 

If the AP switch is "on", then the FD switch is overridden and the servos are engaged with a valid nav source. The FD bars show up.

[Marauder]

Thanks Bob. Do you have the flight director (STEC ST-670) option? I have tried all sorts of things including canceling and reloading the flight plan, using the direct to function, using the heading bug only. When I load a new flight plan or waypoint, the correct heading shows up on the Aspen, the flight director bars are missing and the AP will not command a turn. It really looks like it has something to do with the flight director. When the bars are there, it works like it supposed to. When they do not, it doesn't. I just don't the relationship of how the flight director works within the STEC environment. Chris, Either I don't have the FD feature or it is turned off if that is an option, I did not add anything to the basic STEC50 that was installed prior to the Aspen. If there a menu on/off for the FD? Did you see the note in the Aspen manual (p. 4-58 in my edition) - "With the autopilot in HDG mode, if GPSS is automatically disabled, the autopilot will roll wings level, it will not follow the heading bug." That is reasonable but not necessarily intuitive. Is it possible something is occurring that automatically disables GPSS? Or maybe there's a similar feature when the FD is disabled for some reason.

Bob -- you would know if you had a flight director because the bars show up: There is no menu option in the Aspen to control it. It is a separate box in the STEC environment and is controlled by mechanical switches. This picture is the mock up my mechanic made when he moved all the switches together:

[John Pleisse]

Hmmm... I'm not sure I am following what you are saying John.

 

 

With the 55X, you depress NAV twice for GPSS. When I watched the video, I saw you hit a button twice. As mentioned above, I purchased my Aspen prior to software upgrades for the flight director. I had to buy the STEC FD announciator. Lastly, I saw no purpose in making AP inputs switchable to both sides of the Aspen. I tried a different logic. GPS #1 (also crossfillable from GPS2) and GPS 2 were hardwired to Aspen #1. For safety and redundancy, we made a discrete 232 switchable output from GPS#2, directly to the AP. That way, if ANYTHING went bad or if battery power was low, you could turn everything off except GPS #2 and the AP. It works great.

 

You have no other nav-heads in the panel, right Chris? Just the 2000? How do you know the 60-2 is in GPSS mode? Separate announciator?

[Marauder]

Did you see the note in the Aspen manual (p. 4-58 in my edition) - "With the autopilot in HDG mode, if GPSS is automatically disabled, the autopilot will roll wings level, it will not follow the heading bug." That is reasonable but not necessarily intuitive. Is it possible something is occurring that automatically disables GPSS? Or maybe there's a similar feature when the FD is disabled for some reason.

 

Hi Bob -- to answer the rest of your question. Yes, I saw this but I think it pertains to a situation when you have GPSS engaged and if you deselect GPSS, the AP will roll wings level. To get it to follow the heading bug at this point, you would need to cancel the AP and then re-engage it.

 

On page 4-59, a pretty good summary of how mine works is shown.

[Marauder]

With the 55X, you depress NAV twice for GPSS. When I watched the video, I saw you hit a button twice. As mentioned above, I purchased my Aspen prior to software upgrades for the flight director. I had to buy the STEC FD announciator. Lastly, I saw no purpose in making AP inputs switchable to both sides of the Aspen. I tried a different logic. GPS #1 (also crossfillable from GPS2) and GPS 2 were hardwired to Aspen #1. For safety and redundancy, we made a discrete 232 switchable output from GPS#2, directly to the AP. That way, if ANYTHING went bad or if battery power was low, you could turn everything off except GPS #2 and the AP. It works great.

 

You have no other nav-heads in the panel, right Chris? Just the 2000? How do you know the 60-2 is in GPSS mode? Separate announciator?

What you saw was me doing was a "let me press HDG and then realizing I had not turned on GPSS mode on the Aspen yet". I never really hit the HDG button, instead I moved over to the Aspen, pressed GPSS and then hit the HDG button.

 

I think I understand what you are doing with the direct connection to the AP. Mine is wired differently. The switch in the mockup labeled "Autopilot Input" allows me to switch between the PFD and MFD during reversion. If the PFD fails when the AP is connected, I hit the MFD reversion button and throw the switch over to MFD. Everything then runs off of the MFD as it did on the PFD.

 

I do not have any other CDIs in the panel. I can use the MFD to show any of the Nav signals (RMI mode). The way I know that GPSS is engaged is the green GPSS button on the PFD. Don't you have a GPSS button?

[John Pleisse]

Yes, but GPSS is also visible on the Stec LED, too. 60-2, not so much?

[Cruiser]

Do the FD command bars come up and work properly when the A/P is off?

[Marauder]

Yes, but GPSS is also visible on the Stec LED, too. 60-2, not so much?

 

Correct, there is nothing on the STEC 60-2 that would display GPSS mode.

[Marauder]

Do the FD command bars come up and work properly when the A/P is off?

 

No. When I first noticed the problem, it was under AP control. When I turned off the AP switch and left the FD switch on, the command bars were missing. Hence, why I think it is a FD problem. That said, the Aspen is responsible for displaying the bars, so it could still be an Aspen issue.

[Marauder]

Quick update and a long video...

Spoke with the avionics shop. He says the flight director displays what the autopilot is doing. So, if the flight director is not coming up, it is most likely an issue with the autopilot itself, not the flight director. The fact that it is intermittent, he believes it could be a connector issue. He told me that STEC made the harnesses for their installations and he has seen a number of connection issues with these harnesses. He is recommending that I bring the plane in to have him look the harnesses over and re-wire them if necessary.

On a related topic, here is a video link to a YouTube video showing me flying an approach using the coupled autopilot, GTN and Aspen. I apologize for the bumpy video. It was one of those bumpy flights below 3k. Also, I'm correcting my own English in the video. What pops up on the Aspen AI is the lateral deviation indicators, not command bars. Anyone who has rendered a video will know why I didn't go back in and fixed it...

And for Brett... I wished I had your traffic system. When I was on the approach you will hear me talk about a guy flying underneath me. That was fine until he turned in my direction! I continued on when I realized he was a small high wing and it was doubtful he would have caught me at 100 knots.

[Marauder]

Yes, but GPSS is also visible on the Stec LED, too. 60-2, not so much?

 

I finally pieced together what you and Tom were referring to. On the STEC 55 series, GPSS is integral to the autopilot, on the 60-2 it was not. Hence the reason you see it on the STEC LED display and I have nothing. To get GPSS I could have purchased the ST-901 GPSS upgrade for the STEC or in my case, use the GPSS functionality of the Aspen.

[AaronDC8402]

On 10/25/2013 at 3:53 AM, Marauder said:

The fact that it is intermittent, he believes it could be a connector issue. He told me that STEC made the harnesses for their installations and he has seen a number of connection issues with these harnesses. He is recommending that I bring the plane in to have him look the harnesses over and re-wire them if necessary.

 

 

Sorry to resurrect such an old thread. Did you ever confirm that you had a connector issue? Or was it something else?

 

[Marauder]

On 10/25/2013 at 3:53 AM, Marauder said: The fact that it is intermittent, he believes it could be a connector issue. He told me that STEC made the harnesses for their installations and he has seen a number of connection issues with these harnesses. He is recommending that I bring the plane in to have him look the harnesses over and re-wire them if necessary.

 

 

Sorry to resurrect such an old thread. Did you ever confirm that you had a connector issue? Or was it something else?

 

It was something else. My autopilot can be controlled by either the Aspen PFD or the MFD operating in the PFD reversion mode. In the picture above, I show a plate being made to hold a throw-over switch. It was this switch which was failing. When I was operating in the PFD mode, the switch would pop over to the MFD and shut off the GPSS.

Sent from my iPad using Tapatalk

[AaronDC8402]

Thanks for the reply! We're having the same problem with our S-TEC 60-2, but we don't have an Aspen or 2nd Aspen. The autopilot controller was recently removed and re-installed. We're hoping for just a poor electrical connection during installation.