Procedure turn avidyne /stec 55x

Salty

Salty

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Salty
Ok, I flew 3 approaches yesterday and they did everything exactly like I expected.

Tried again today and not once did it work right. I set up for an IAF with a procedure turn and it showed up in the fms right, the next leg was the hold, it annunciated parallel entry, then as soon as I hit the waypoint it turned the wrong way and started to turn to the next waypoint in the approach, skipping the hold. The “delete hold” button was still there until I crossed the waypoint and I never pushed it. In all three scenarios it took me outside the protected space and I couldn’t get it to do anything “safe” so had to cancel and hand fly it ignoring the gps track. In one case it actually was still showing the correct track but the stec was turning the other direction.

also, the stec wouldn’t capture the glide slope on any of these approaches either, and manually selecting approach mode did nothing.

the only difference between yesterday and today is that there were scattered clouds right at the altitude the approaches start, so twice I was above the clouds maybe 500 feet above the approach altitude, and once I was a few hundred feet below.

what the heck did I do wrong today?
 
alt yes, gs never happened
 
Hmmm. Really hard to tell without seeing it. I know the Precision Approach Procedures section of the manual gives a number of conditions for ALT GS to annunciate and GS to capture. Perhaps one of them wasn't met? Or the GPS hadn't sequenced properly. That happened to a friend of mine, The backward procedure turn makes it sound like a possibility. Hope you figure it out.
 
Never was in gpss either when it worked or didn’t.
 
Salty said:
Never was in gpss either when it worked or didn’t.
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If you're not in GPSS mode, it's not going to do the PT by itself. Again, I don't know for sure without seeing it in action, but during a PT, I expect to see the HSI course pointer on the inbound course. That is what pure analog NAV or APR mode follows. GPSS mode basically tells the AP to disregard the course pointer and take turn instructions directly from the GPS.

KISS:
NAV/APR = follow the HSI
GPSS = follow the GPS

(That doesn't necessarily apply to newer digital APs where GPSS is integrated into the NAV function.)

That could also account for the failure to capture the glidepath.
 
Well that would make sense if it hadn’t worked the day before without gpss.
 
Salty said:
Well that would make sense if it hadn’t worked the day before without gpss.
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What Mark describes is accurate. So we're left with one of two possibilities.

Either:
1) You did something different (intentionally or not) in either the button-pressing, autopilot mode selections, or procedure selection, or:
2) Your autopilot/GPS broke between the two flights.

Neither one can we answer without seeing it in action. Maybe take some short video next time you're flying?

It might help if you told us which approaches you flew each day (and which entry direction/fix).
 
I've been using the aspen for gpss so I don't even remember how to put the stec into gpss mode, I'll re-read the manual again. maybe it put itself in somehow, but I'm not seeing how.
 
Pressing the NAV button twice will put the 55X in GPSS mode, but I'm not sure if that setting is disabled or not when you have an external GPSS device (like the Aspen). May depend on how the shop configured it.
 
RussR said:
Pressing the NAV button twice will put the 55X in GPSS mode, but I'm not sure if that setting is disabled or not when you have an external GPSS device (like the Aspen). May depend on how the shop configured it.
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Ok, so that's another difference. I DID use GPSS on the aspen yesterday, but not the day before. I wonder if that put the stec in a different mode?
 
RussR said:
Pressing the NAV button twice will put the 55X in GPSS mode, but I'm not sure if that setting is disabled or not when you have an external GPSS device (like the Aspen). May depend on how the shop configured it.
Click to expand...
Yes. The configuration can vary when the PFD has its own GPSS capability. That's an installation preference. I know of installs where you can do it either way - and, for example, when you set it with PFD, it doesn't annunciate on the 55X. So some choose to have it set on only one. I have a client with a 55X coupled to a G5 (I'm teaching him how to use the new setup which makes this thread interesting). His installer made a point of telling me that he did not enable the G5's GPSS capability but left it to the 55X. I think that's a good idea – you only have one place to turn it on/off and only one place where it is annunciated.
 
midlifeflyer said:
Yes. The configuration can vary when the PFD has its own GPSS capability. That's an installation preference. I know of installs where you can do it either way - and, for example, when you set it with PFD, it doesn't annunciate on the 55X. So some choose to have it set on only one. I have a client with a 55X coupled to a G5 (I'm teaching him how to use the new setup which makes this thread interesting). His installer made a point of telling me that he did not enable the G5's GPSS capability but left it to the 55X. I think that's a good idea – you only have one place to turn it on/off and only one place where it is annunciated.
Click to expand...

That fits with what I thought - thanks.

And on the G5, isn't it a knob press, couple of turns, then a touch-scree button press to engage GPSS anyway? One button on the 55X seems easier and less distracting anyway.
 
I have a similar scenario with my older Aspen/55x install in my Bonanza. I have the Aspen/IFD/55X combo, but can NOT put the 55x into NAV mode until inbound after the PT. Must remain in HDR/GPSS until then. My install was circa 2006, so no altitude preselect, nor double-clicking NAV for GPSS. This setup was a definite surprise after coming from a 55x Cirrus that I thought I had figured out. Imagine the first few gentle holds I attempted to enter with some speed, thinking I could bled off in the hold, but instead the AP attempts to turn 160 degrees aggressively to intercept the inbound path. I'm carrying speed, thinking I'm only going to turn 15-20 degrees for the outbound heading, but get whipped around and blow through the course. This is when you're glad for good transition training and testing everything out with your instructor before true IMC. Evidently my install was an early one and not how most are setup now.
 
RussR said:
That fits with what I thought - thanks.

And on the G5, isn't it a knob press, couple of turns, then a touch-scree button press to engage GPSS anyway? One button on the 55X seems easier and less distracting anyway.
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It is. I'm not sure about being too distracting. It's right in front of you and you'd be using the menu for other things. Unless you also have the remote annunciator at eye level, it also takes a look downward where a lot of 55x are installed.
 
Ok, tried it again today and same problem RNAV 9 into KBKV direct ASKEH parallel entry, but as soon as it hits ASKEH it turns right instead of left. You can also see me double clicking NAV and it does not go into gpss mode.


And here's a simpler case. I put in direct to ASKEH and it painted a nice magenta turn to the right, but the STEC turned left and flew the long way round

 
Salty said:
Ok, tried it again today and same problem RNAV 9 into KBKV direct ASKEH parallel entry, but as soon as it hits ASKEH it turns right instead of left. You can also see me double clicking NAV and it does not go into gpss mode.


And here's a simpler case. I put in direct to ASKEH and it painted a nice magenta turn to the right, but the STEC turned left and flew the long way round

Click to expand...

Hey that looks exactly like my situation..... Both of your videos appear to be in NAV mode, but the second shows that your aspen also does not have GPSS enabled. To avoid what you're showing, I have to stay in HDY mode on 55x with the Aspen on GPSS until exiting the hold/PT and ready to execute the approach. Then I just hit NAV and it follows the proper course. I'm not sure if this is a particular generation of installs, installer preference, or what, but mine is very reliable if I remain in GPSS until exiting the hold/
PT.
 
With no GPSS mode, I'm seeing what I expect. Basically, in NAV mode, the AP has no idea what to do with a procedure turn or hold. If you don't have GPSS, use the heading bug.

Why you can't toggle into GPSS mode is a separate question. With the Aspen/55X combo, AFAIK, there were three GPSS installation options. GPSS controlled by the Aspen, in which case the 55X selection might be disabled (55X in HDG mode). GPSS controlled by the 55X, with the Aspen capability disabled. Or enabled on both, which is a recipe for confusion. Do you know what your installer did? Is GPSS working outside the approach environment? Basically, if you are using GPS to navigate, there's no reason not to be in GPSS mode from departure until tapping APR for the FAC.
 
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Salty said:
Ok, tried it again today and same problem RNAV 9 into KBKV direct ASKEH parallel entry, but as soon as it hits ASKEH it turns right instead of left. You can also see me double clicking NAV and it does not go into gpss mode.


And here's a simpler case. I put in direct to ASKEH and it painted a nice magenta turn to the right, but the STEC turned left and flew the long way round

Click to expand...

Well sure it doesn't work. You don't have GPSS enabled via any method. Since the "double press" apparently isn't enabled on your 55X, you need to be in HDG mode on the 55X and in GPSS mode on the Aspen.

The behavior you experienced is pretty much what I'd expect just being in NAV mode on any older autopilot. GPSS works through the HDG mode of such autopilots, it's like the GPS constantly changing the heading bug as necessary to drive the plane onto/along the magenta line. Understand, GPSS is ultimately a "hack" to get older autopilots to do the fancy GPS stuff.
 
If the second "NAV" push is successful, the 55X shows "GPSS" on the display. I did not see that in your video. No clue why not - but it answers why the autopilot did not follow the procedure in your flight plan.

See the picture (GPSS annunciation) and description from the STEC 55X manual:

upload_2022-5-5_9-33-14.png
 
A few more test approaches this weekend and I'm solid on how it works. Apparently the first day I was using gpss off the aspen and just forgot. Because that's the only way it will work (as some said above).

I also found this video on the subject, which didn't do me any good because I'd already figured it all out, but it did confirm my understanding that I got from reading this thread and my own experimentation.

https://www.absweb.org/27.html
 
Okay, I need some help from you guys that replied to this earlier.

I had the Aspen /Stec 55x integration upgrade installed. Doing some ground testing everything seems to be working, but one thing doesn’t seem right, but since everything is different now I’m not for sure if it’s normal or abnormal.

With the upgrade, you lose the gpss button on the Aspen and you have to wire 429 to the 55x, which I did not have previously. Now, you’re supposed to use the double nav click to engage gpss on the 55x instead of the Aspen. Single nav click works, but double nav click says nav / gpss / fail. Double click hdg nav puts it in hdg / nav / GPSs with no fail flag

 
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Salty said:
paging @midlifeflyer @RussR @Martin Pauly
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I'm kind of back to where I was earlier. Since there are potentially multiple ways for the Aspens, the GPS, and the STEC to interface for the purpose of enabling GPSS, it still sounds like something that was done in the installation.

NAV-NAV is the standard for enabling GPSS directly on the STEC. Why that's not working and HDG-HDG is is, is above my pay grade. The STEC remaining in HDG mode would be expected if the Aspen rathe than the STEC were controlling GPSS. What would happen if you ended up enabling both, other than pilot confusion, no clue. Best WAG is that there is a configuration mix that is confusing the system?
 
We've reviewed the configuration a zillion times. The thing is, I'm not sure it's really an error. For example, when selecting NAV on the ground from a VOR source that is flagged, it annunciates NAV / fail. That's normal, not a problem with the equipment, it's what is supposed to happen. It's also documented in the manual. There's nothing in the manual for Nav / GPSS / Fail. But it may be normal when trying to use GPSS from the ground. Perhaps not having a course, because you're on the ground not moving, for example confuses the 55x so it says fail. Or perhaps not. I'd kinda like to know. Avionics shop says test fly it and see.....
 
When I do my practice approaches I always do one by hand and one full on the autopilot (GNS480 -> 55X). This sounds more like a problem with your GPS than the autopilot. I can't vouch for the rest of main Garmin line but the 480 is pretty straight forward. I leave it in GPSS until I'm inbound on the final and then engage APR. With ALT on it should capture the glideslope needle. Never had any problems with either regular or hold-in-loo PTS.
 
maybe it was a mistake to use the same thread. New problem now.
 
Salty said:
We've reviewed the configuration a zillion times. The thing is, I'm not sure it's really an error. For example, when selecting NAV on the ground from a VOR source that is flagged, it annunciates NAV / fail. That's normal, not a problem with the equipment, it's what is supposed to happen. It's also documented in the manual. There's nothing in the manual for Nav / GPSS / Fail. But it may be normal when trying to use GPSS from the ground. Perhaps not having a course, because you're on the ground not moving, for example confuses the 55x so it says fail. Or perhaps not. I'd kinda like to know. Avionics shop says test fly it and see.....
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Certainly a possibility.
 
It seems to me that the HDG mode is allowing the ARINC 429 to issue forth from the Aspen. I am guessing the ARINC 429 should be wired directly to the GPS, then when the 55X is in Nav mode and you toggle Nav mode, you would get NAV GPSS.
 
John Collins said:
It seems to me that the HDG mode is allowing the ARINC 429 to issue forth from the Aspen. I am guessing the ARINC 429 should be wired directly to the GPS, then when the 55X is in Nav mode and you toggle Nav mode, you would get NAV GPSS.
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That’s correct. Arinc is now wired to the 55x
 
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