Cessna 172 Autopilot Shaking

Is it normal for the plane to behave like this on autopilot?It was shaking alot worse, but I could only record this part.


It was even worse during the beta but the wobbling/rocking got reduced somewhat after we reported it.

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Interesting, I never noticed. Thanks

Yeah, it feels like winds had much stronger effects on the hull of the plane now, shakeing it a bit more. But i like it somehow, it´s not so much like “riding in a bus” anymore.

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I think a bit weird. Seems like the plane is “dancing”, lol

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So you may have gone through a similar situation as mine, in which it was really difficult to catch just because of how random it may be. So I filmed some entire flights I’ve done and got a similar issue. Yours seems to me as the autopilot rocking situation, but maybe triggered by something else, and the AP recovered after some time. I’ve done some very extensive screen recording to capture this issue, which surely isn’t related to some sort of turbulence.

It happens to me at every command change to AP, such as a mode change (eg. VS to ALT) or waypoint changes. Sometimes it is very minor and AP recovers itself very quickly. Sometimes it just doesn’t stop. See below the videos I recorder and my explanations to facilitate you guys looking into the lengthy videos.

The video is long. At 56:18 min, I tried to activate vnav for descent but it didn’t work (I forgot to reduce altitude on the PFD), then tried to switch ALT mode off, and then on again. Nothing else changed I guess, and I don’t think it should affect anything. At the exact moment it reached NANIT at 56:40 min, it stated to rock side to side.
In every transition there was some very small wobbling from which it recovered, but not on this last one.

I wish I caught all the process in one video, but consider that I was in a more than 1h long flight being absolutely stable over the sea. Then I increased the sim speed to 3x, and when I came back the plane was going side to side totally crazy (as I’ve seen with other planes in AP, both in normal and increased sim rate, many updates ago), but it also had the rocking movement mixed with it. Then I went back to regular sim speed, and the side to side movement stabilized, but the rocking was still there. I know it’s not my controller because it turned itself off a long time ago before anything happened. I turned AP off and rocking immediately stopped. Turned it back on and it started again. Same behavior with HDG mode.

That rocking effect looks more like a very poorly controlled PID loop, oscillating badly, would certainly be making the passengers chuck-up :frowning:

So I take it, then, that this is a “bug” and not some known aerodynamic phenomenon?

I suppose it’s a bug - I’m flying the C172 G1000 in the beta right now at 10’000 and the wobbling/shaking is terrible in NAV mode… I hope it will be fixed in the final release!

Personal Comments and Observations

I fly the 172 very often. Note that turbulence effects are modeled in the sim now, and that’s what I notice while under AP control. Otherwise, the AP is stable for my flights. Time compression will exaggerate certain effects - which is why I prefer Slew to TC. I wouldn’t use TC beyond 2x - this is not FSX where world effects and the infrastructure beyond player aircraft have limited effect.

I don’t know… this can’t be turbulence… it’s constant and regular, very rhythmic, not “turbulent” at all, at all altitudes, all speeds, all weather conditions. And if it were turbulence, the rocking wouldn’t immediately quit as soon as the AP is turned off, then start up again when the AP is re-enabled. I’m going with bug. I’m also glad to hear that this isn’t the final release, it’s a work in progress!

This was reported over 8 months ago, when this post started.
A lot has changed with both the C172, and the Sim weather modeling.

This was also reported when the weather / temperatures were probably a lot hotter than now ? That could also affect turbulence, which had several issue back 8 months ago, some of which have since been addressed

So – to the OP, is this still an issue for you ?

So in my opinion, the movement shown in the video that initiated this topic is turbulence. I believe that the one I posted, which happened to me is due to some issue with the AP itself (the PID, I guess). One of the evidences it the extremely constant and consistent movement. It also always start when the AP needs to command something different, example, when it is transitioning from one waypoint to the other, or when it finished a climb and start to move the trim to level the airplane.

This is happening on my sim as well. (Xbox X) For those saying that the cause of the issue is turbulence, why would the turbulence disappear after disengaging the AP? This appears to be a bug that needs fixing. Also, not only do the wings start to rock after engaging the AP but the C172 starts “porpoising” at lower altitudes in some flights as well. Not very realistic.


Exactly. I should have pointed it out as well. Definitevly not turbulence.


Excessive “Proportional Gain” in the AP Roll PID, causing Oscillation “excited” and made more apparent by the current level of turbulence :woozy_face:

Tuning of the AP Pids is a Compromise, between calm & turbulent weather conditions – unless it is an Advance AP system, with a control to help match the tuning to differing “Turbulence levels”

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To N6722C: OK… but are you saying that this is realistic? That if you have a 172 with an AP, this is what you will actually experience? Or is this a flaw in the way that FS displays the phenomenon?

To put it crudely, I am saying that AP’s “OVER TWITCHIENESS” (quote) , that is reasonably stable in calm air, is being shaken around by the turbulence so that its over twitchiness causes it to oscillate around in a very undesirable way.

(ie Incorrect AP Tuning, that may be marginally acceptable in calm weather, is not grossly inappropriate in any sort of turbulence)

N6722C: With all due respect, I would ask that you provide further clarification. Are you referring to actual, real world, in-flight behavior, or to what we are experiencing in the simulator?

In MSFS – the oscillation YOU are experiencing in the sim … :woozy_face: