ISSUE DESCRIPTION
Description of the issue:
I was doing a flight in the G1000 C172 and it felt like the autopilot was acting erratically. It would make hard turns, overshoot make another hard turn back, etc.
Another time I was trying to make a 180 turn with the heading indicator. I know you can’t turn the knob past 180 degrees or it should change direction. I was making a few small adjustments, about 20-40 degrees at a time. After getting though about a 90 degree turn the airplane suddenly made a dangerously steep bank in the opposite direction.
Do you have the same issue if you follow the OP’s steps to reproduce it?
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Provide extra information to complete the original description of the issue:
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If relevant, provide additional screenshots/video:
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Hi @Michail71
Concerning this issue, were you just following a flight plan while cruising and it was overshooting when going to the next waypoint, or were you in either an arrival or approach course? I’ve not been able to replicate the issue in cruise, but haven’t tried the other things I mentioned, since if you were in one of those, I’d like to try the same arrival/approach and see if I can duplicate it in the same manner you were flying (e.g. when you activated the approach in the MFD, and when you hit the APR button, etc).
Similar questions for your second issue. (by the way, thanks for eliminating a common issue by noting you were making small turns in heading) Were you using the heading mode while you still had either approach or NAV modes armed?
I’m trying to get the same conditions because I’m currently unable to replicate the issue, and haven’t seen this particular issue being pushed in the forum.
I’ll keep trying different things to see if I can force the problem to show up.
Regards
Thanks for the reply, I’ll try to re-fly that again and see if I can duplicate. I’m a bit rusty!
When I was in heading mode I had just taken off and activated the AP on heading mode once I had leveled off at 1000 feet. I set the ALT to 2,500 with FLC. I then started the tun on heading and it seemed to be banking a little harder than I remember. When I was heading NE I dialed in the final adjustment to intercept the NAV leg. It’s at that point I rolled hard in the other direction.
I disconnected the AP, got into stable flight and manually activated the AP on NAV. On that intercept It oscillated a bit to capture the magenta line. I think after that it was a bit more stable.
Here is the Fight plan. Flight Planner. The Flight Planners seems to be down for me at the moment.
I took off on 27R, leveled off and activated the AP on heading mode (set to runway direction). I was trying to turn back around to the right on the heading mode to intercept the magenta line just past the shoreline.
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Thanks for the detailed info!!
I’ll give it a try with your flight plan and see if I can duplicate it. If I can’t get that plan to duplicate, I’ll try some other/similar departures and see if I can get the responses you got! I love a good bug hunt!
Regards
P.S. question just came to mind… When you were banking around (HDG) to get back to the flight path, was the original waypoint after takeoff still the active waypoint? If so, the Garmin may have gotten close enough to being within guidance tolerance to activate the AP to turn back to the original waypoint, not onward toward the flight path. Sorry, I probably didn’t explain that well…but hopefully you can see what I’m trying to get at.
That’s a good theory! I don’t think I had hit the NAV button but yet, but it is a possibility.
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Well I’ve been known to swing at one “just a bit outside”…hopefully a reference you recognize. If not, just ignore.
LOL, I can sometimes be the same.
I gave your flight plan a try but didn’t have any issues on my first try. Unfortunately there are quite a few variables that could come into play to say my flight was exactly the same as yours. I intercepted the path quite a ways from the first waypoint without issue. Then I intercepted it very near the first waypoint and didn’t have a problem.
I could only get a “similar” issue if I used heading mode until I was past the first waypoint and then engaged the nav mode. At that point the plane turned back to the first waypoint. If I wasn’t too far past waypoint 1, the plane made a fairly tight turn (more than standard rate turn) but then accepted that it was at WP1 and moved on to WP2. That could have been the course reversal you mentioned, but not definitive at this point.
I’ll play around with a few more variations and see what happens.
Regards
I appreciate the testing! I’m curious what may have happened in my case.
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Yea, the biggest issue when tracking down a potential bug is getting the same conditions again to make it show up. At least we know there’s a potential one there that we need to keep an eye on and see if it shows up again.
One of my old crew chiefs told me, “sir, please don’t ever write up something as intermittent if it’s not mission critical. Just let it fail and then we’ll fix it.”. Hard to track some things down.
Thanks for ID’ing this issue.
Regards
Do you have the same issue if you follow the OP’s steps to reproduce it?
Yes.
Provide extra information to complete the original description of the issue:
I find it only significant while climbing. In that case it happens for both HDG changes and NAV intercepts
If relevant, provide additional screenshots/video:
See following video. Note that the video contains 4 clickable sections/chapters in Youtube:
0:00 Climbing HDG change
1:18 Climbing NAV intercept
2:20 Level HDG change
3:18 Level NAV intercept
