Autopilot Problem

SoCal 182 Driver

SoCal 182 Driver

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Sep 11, 2019
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SoCal 182 Driver
Avidyne IFD 540, dual G5s, and AeroCruze 100 (TruTrak) autopilot.

I had a problem with my autopilot today. No matter what I did, or how many times I baro-synced, it wanted to climb. This occurred both when working off the G5 for heading and altitude, and also in GPSS mode, with altitude set on the autopilot itself. Altitude was 10,500'.

I tried baro-syncing several times, but no joy. I tried trimming the plane manually, with the autopilot off, and then engaging the autopilot. No joy. I tried shutting down the autopilot and restarting. No luck. No matter what I did, the plane wanted to climb. And, while climbing, the autopilot would be asking for up trim.

Any thoughts on what might be causing this?

Advice and comments appreciated.
 
Static leak, both the autopilot and the G5 have a connection. When was the last IFR/Pitot check?
 
Florida Flyer said:
Static leak, both the autopilot and the G5 have a connection. When was the last IFR/Pitot check?
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This got me thinking. If I had accidentally activated the alternate static source switch, could that have caused the autopilot behavior I experienced?
 
Clip4 said:
No
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Admittedly, I am not an avionics expert, but if the pitot-static system was functioning properly, and I accidentally activated the alternate static source, wouldn't that essentially be opening a leak to the pitot-static system?
 
My older STEC 60-2 AP has dedicated static ports in the rear, so no connection to OEM ship’s pitot-static system. How is your AP connected?
 
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When you had it in GPS mode. What did the autopilot show for an altitude?
 
AlphaMike said:
When you had it in GPS mode. What did the autopilot show for an altitude?
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When in GPSS mode, I set the altitude for 10,500' on the autopilot control head. The plane would continuously want to climb above 10,500', and in the process the autopilot was asking for up trim.
 
SoCal 182 Driver said:
When in GPSS mode, I set the altitude for 10,500' on the autopilot control head. The plane would continuously want to climb above 10,500', and in the process the autopilot was asking for up trim.
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If you push the right-side button twice it will show you what altitude the autopilot thinks it’s at. Its where you set the altimeter if you are in GPS mode. Just curious if the altitude matched your pre-selected altitude? did the control unit say "alt hold" ?
 
By the way. My TruTrak had an issue holding altitude when it was first installed. It would overshoot and begin to porpoise. I worked with some other 182 guys that were experiencing the same issue. These are the numbers we are running now, and everything has been fine for the last 4 years running these numbers.
*** The chart shows 182RG but those numbers work perfectly in my fixed gear 182P
 

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AlphaMike said:
If you push the right-side button twice it will show you what altitude the autopilot thinks it’s at. Its where you set the altimeter if you are in GPS mode. Just curious if the altitude matched your pre-selected altitude? did the control unit say "alt hold" ?
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That's how I baro-sync the autopilot to the altitude shown on the G5. They were within 50' of each other, and when I would sync, they would be within 10' of each other.

Yes, the control head did say "alt HOLD," but it wanted to climb regardless.
 
AlphaMike said:
By the way. My TruTrak had an issue holding altitude when it was first installed. It would overshoot and begin to porpoise. I worked with some other 182 guys that were experiencing the same issue. These are the numbers we are running now, and everything has been fine for the last 4 years running these numbers.
*** The chart shows 182RG but those numbers work perfectly in my fixed gear 182P
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I've had the TruTrak for over a year, and it's been pretty solid. As recently as the day before the flight in question, I flew for two hours at various altitudes assigned by ATC, and did not have a problem with climbing. It held altitude. This is something new.
 
SoCal 182 Driver said:
I've had the TruTrak for over a year, and it's been pretty solid. As recently as the day before the flight in question, I flew for two hours at various altitudes assigned by ATC, and did not have a problem with climbing. It held altitude. This is something new.
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I know that I’m resurrecting an old thread here, but I am experiencing the same issue with my TruTrak and G5. Did you figure out the issue with yours?

If my source is connected to the G5, then swapped to GPS, sometimes it will immediately initiate a climb to 100’ higher. The altimeter sync page on the TruTrak will show 100’ lower than actual after this happens. It will level off at this new altitude, G5 altitude will show 100’ higher, TruTrak shows alt hold, and altimeter sync page shows original altitude. I have also tested going back to the G5 to try to resync the altimeter setting, then going back to GPS. I have gotten it to then command another 100’. This does not happen every time I use the unit, it seems intermittent so very difficult to figure out. It is something to do with the altimeter setting syncing.
 
DrGoodBurger said:
I know that I’m resurrecting an old thread here, but I am experiencing the same issue with my TruTrak and G5. Did you figure out the issue with yours?

If my source is connected to the G5, then swapped to GPS, sometimes it will immediately initiate a climb to 100’ higher. The altimeter sync page on the TruTrak will show 100’ lower than actual after this happens. It will level off at this new altitude, G5 altitude will show 100’ higher, TruTrak shows alt hold, and altimeter sync page shows original altitude. I have also tested going back to the G5 to try to resync the altimeter setting, then going back to GPS. I have gotten it to then command another 100’. This does not happen every time I use the unit, it seems intermittent so very difficult to figure out. It is something to do with the altimeter setting syncing.
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It turned out that I was not in trim. What I do now is get to altitude, turn off the autopilot, and trim the plane. Then I re-engage the autopilot, and do minor trim adjustments as necessary based on the autopilot prompts. Just did a couple of 2+ hour flights over the long weekend, and it was solid. I also baro-sync when ATC gives me new altimeter settings.
 
SoCal 182 Driver said:
It turned out that I was not in trim. What I do now is get to altitude, turn off the autopilot, and trim the plane. Then I re-engage the autopilot, and do minor trim adjustments as necessary based on the autopilot prompts. Just did a couple of 2+ hour flights over the long weekend, and it was solid. I also baro-sync when ATC gives me new altimeter settings.
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Interesting. Thanks for the update. My problem happens after I have been in cruise for a while on GPSS and trimmed.

Example- Altitude hold set at 5,500 and on GPSS. It is holding correct altitude. Get new altimeter setting from ATC and set it on the G5 (say 0.01 or 0.02 different). Switch to G5 source and wait a bit for it to connect/sync. Switch back to GPS source. It will then climb 100’ and level off. The alt sync screen will still show 5,500 when I look at it. Actual is 5,600 now. Trim annunciation may or may not be showing since it is so sensitive, but I am very close to the correct trim setting in any case. Have gotten it to do it again by repeating the process and it goes to 5,700 while alt sync still shows 5,500.

Just trying to figure out what the issue may be. Seems like a firmware bug or something.
 
DrGoodBurger said:
Interesting. Thanks for the update. My problem happens after I have been in cruise for a while on GPSS and trimmed.

Example- Altitude hold set at 5,500 and on GPSS. It is holding correct altitude. Get new altimeter setting from ATC and set it on the G5 (say 0.01 or 0.02 different). Switch to G5 source and wait a bit for it to connect/sync. Switch back to GPS source. It will then climb 100’ and level off. The alt sync screen will still show 5,500 when I look at it. Actual is 5,600 now. Trim annunciation may or may not be showing since it is so sensitive, but I am very close to the correct trim setting in any case. Have gotten it to do it again by repeating the process and it goes to 5,700 while alt sync still shows 5,500.

Just trying to figure out what the issue may be. Seems like a firmware bug or something.
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Why are you switching between GPSS and the G5 to sync? IMHO, the better course of action when getting a new altimeter setting is to change the altimeter setting on the G5, then double-push the altitude button on the autopilot and manually adjust to baro-sync the autopilot to match the altitude reading on the G5. Then press the enter button and watch as the plane climbs or descends, as necessary, to the altitude set on the autopilot.
 
SoCal 182 Driver said:
Why are you switching between GPSS and the G5 to sync? IMHO, the better course of action when getting a new altimeter setting is to change the altimeter setting on the G5, then double-push the altitude button on the autopilot and manually adjust to baro-sync the autopilot to match the altitude reading on the G5. Then press the enter button and watch as the plane climbs or descends, as necessary, to the altitude set on the autopilot.
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That's what I've been doing for the most part. But it is also supposed to sync it when switched. For instance cruising on GPSS, then being given VTF and switch to G5 for external heading/altitude mode, then switch back to GPSS when intercepting final to couple to the RNAV glidepath. I've had it then try to shoot up 100'. Not a very good time for that to happen. If I ever figure out what is going on, I'll be sure to update. Thanks for your help!
 
DrGoodBurger said:
That's what I've been doing for the most part. But it is also supposed to sync it when switched. For instance cruising on GPSS, then being given VTF and switch to G5 for external heading/altitude mode, then switch back to GPSS when intercepting final to couple to the RNAV glidepath. I've had it then try to shoot up 100'. Not a very good time for that to happen. If I ever figure out what is going on, I'll be sure to update. Thanks for your help!
Click to expand...
Have you tried doing a gyro reset on the autopilot?
 
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