reported Autopilot oscillation

[Ironhand]

3 hours ago, Skuva said:

Yes, the aileron wiggle waggle. All it takes to reproduce it is spawn on the mig and press H. Not only it makes unbearable to use at speeds above 650kmh, it also mess up your trim, requiring you to always reset it and adjust againg after disengaging the AP.

 

For starters, I never use the “H” key if there’s an “Alt+” alternative. It’s been my impression that it never worked as well as the Alt+ function. And I also almost never use the AFCS on either the MiGs or Su-27/33 but that’s another matter. What does matter is that, after seeing your post, I did as you suggested and had no issues with either Attitude Stabilization Hold or Baro Altimeter Hold at speeds well in excess of 650 km/hr.

I did not, however use the “H” key which, if memory serves, is the equivalent of activating Attitude Hold and Baro Altimeter Hold together and that is not how the system works. You must first activate Attitude Hold when close to level flight, if you want to use Baro Altitude Hold. With Baro Hold now engaged, you can use the temporary override to either put yourself in straight level flight or a level turn, when the override is released. Using Attitude Hold alone, you can set yourself up for climbing or descending turns and or straight climbs or descents. But I’m guessing that you already know all of that.

As far as the trim being out of whack when you switch the AFCS off is concerned, that’s a trimmer issue not an AFCS issue. In FC 3 aircraft anyway, once you move the trim from its start position you can never manually set it back to its original position. That’s true of pitch, roll, and yaw. Even though you can get back to “neutral trim” (green light is lit), it’ll always be a little off. The only thing that the aileron flutter does is toss the trim off in either a right or left roll with no ability to know which it will be ahead of time.

I’ve included a track of my short air start flight. If you keep an eye on the AFCS lights, you’ll know what I’m doing when. On my end, everything went smoothly.

MiG-29 AFCS.trk

[Skuva]

17 hours ago, Ironhand said:

For starters, I never use the “H” key if there’s an “Alt+” alternative. It’s been my impression that it never worked as well as the Alt+ function. And I also almost never use the AFCS on either the MiGs or Su-27/33 but that’s another matter. What does matter is that, after seeing your post, I did as you suggested and had no issues with either Attitude Stabilization Hold or Baro Altimeter Hold at speeds well in excess of 650 km/hr.

I did not, however use the “H” key which, if memory serves, is the equivalent of activating Attitude Hold and Baro Altimeter Hold together and that is not how the system works. You must first activate Attitude Hold when close to level flight, if you want to use Baro Altitude Hold. With Baro Hold now engaged, you can use the temporary override to either put yourself in straight level flight or a level turn, when the override is released. Using Attitude Hold alone, you can set yourself up for climbing or descending turns and or straight climbs or descents. But I’m guessing that you already know all of that.

As far as the trim being out of whack when you switch the AFCS off is concerned, that’s a trimmer issue not an AFCS issue. In FC 3 aircraft anyway, once you move the trim from its start position you can never manually set it back to its original position. That’s true of pitch, roll, and yaw. Even though you can get back to “neutral trim” (green light is lit), it’ll always be a little off. The only thing that the aileron flutter does is toss the trim off in either a right or left roll with no ability to know which it will be ahead of time.

I’ve included a track of my short air start flight. If you keep an eye on the AFCS lights, you’ll know what I’m doing when. On my end, everything went smoothly.

MiG-29 AFCS.trk 82.69 kB · 0 downloads

What is this mental gymnastics of yours?

I said "H" just as an example, it happens with all modes/shortcuts.

Your trackfile clearly show the problem. Look at the stick shaking and the trim lights going crazy. Also of course it will look smooth flying high inside clouds, you cant see anything apart from your cockpit.

The scenario I was referencing was the same depicted by OP, flying low above 650kmh (not that the problem simply disappear below this, it just less noticeable).

Also you CAN reset the trim (LCtrl+T). And the autopilot is messing with the trim, because on most modes (if not all) when you disengage the autopilot, the sitck WILL get trimmed at whatever position the autopilot left it, which due to the shaking will always end up offcenter.

Here is a proper track showing it better:

MiG-29 AFCS.trk

[Ironhand]

I stand corrected then.

[Skuva]

How do you "stand corrected"??? I showed how every point you made is wrong.

Edited April 27, 2023 by Skuva

[Ironhand]

44 minutes ago, Skuva said:

How do you "stand corrected"??? I showed how every point you made is wrong.

 

https://dictionary.cambridge.org/us/dictionary/english/i-stand-corrected

I reflew at low altitude and can see how it would be annoying. Like I said previously, I seldom us the AP (and, if I do, it’s normally at high altitude). So I’ve never noticed the effect on the airframe.

However, it terms of recentering trim, I’m aware of LCtrl+T. I was referring to using the trim keys themselves to get back the neutral.

Edited April 27, 2023 by Ironhand

[Skuva]

1 minute ago, Ironhand said:

https://dictionary.cambridge.org/us/dictionary/english/i-stand-corrected
 

Sorry, I was not familiar with that term and thought you were being stuborn. In a literal translation in my language that reads very much like "I'm still correct/right"

[Ironhand]

2 minutes ago, Skuva said:

Sorry, I was not familiar with that term and thought you were being stuborn. In a literal translation in my language that reads very much like "I'm still correct/right"

Oh, I can be stubborn. Just ask my wife. But not on this occasion.

[Volator]

When using the MiG-29 AP in attitude or altitude hold, the aileron trim jitters. You can see it in the stick movements, the trim indicator lights and the flight path.

 

Test_MiG-29A_AP_trim.trk

[draconus]

[Flappie]

I was not aware of this issue. I'll ask for all three threads to be merged into one and I'll add this issue to my todo-list.

[BIGNEWY]

threads merged

[Flappie]

Issue reported.