AP doesn't hold altitude

[Corrado Marchetti]

Hi All,

as the title, it seems the AP can't hold the altitude.

As you can see in the following pic, i set the Altitude at 1500ft but after reaching 1500ft, a small drift continues to increase Altitude depending by speed.

If i decrease the speed the altitude decreases... so i need to keep a certain speed to avoid drifting in altitude in both sides.

Anybody can help?

TIA

Corrado

[jeff64]

I have had the same problem on ALL of my aircraft, intermittently.

 

I tried to troubleshoot this evening, and think this can be cause by activesky xp.

Do you have this problem on this addon only ?

[qazme]

Just a note I fly with activesky xp, don't have this issue at all. It can, depending on winds overshoot by 50-100 feet depending on when a gust hit etc. However it always settles back to where it should be.

[Corrado Marchetti]

Thank you for your replies but i don't have activesky for the moment.

I have also Pocket Rocket (nice aircraft) but i don't have the same issue, neither in all my planes.

I use XPforce and I want to investigate on it if i missed to set some parameters.

I'll let you know.

Corrado

[qazme]

It's possible since you're getting haptic feedback into your stick. Since it changes with speed it sounds like you it's possible it could be fighting with the APs trim setting?

[Aleksandar]

What are your autopilot modes set to? My altitude capture is perfect, even if the altimeter setting isn't

[stelaninja]

Anyone solved this? This problem makes the aircraft useless. 

[Coop]

Nobody on our development team can replicate this issue. It is most likely either due to hardware conflicting with X-Plane's autopilot logic (as our autopilot is using the base X-Plane adjustment system) or a plugin/script install that is interfering. 

If you can come up with the exact steps that you took to get it to this situation, that would be massively helpful in debugging. 

[Tiktok4321]

Some of this might seem like "is the refrigerator plugged in" type of troubleshooting but bear with me. I found this thread because I was having the same problem.

Turns out, in my case, I had a notch of flaps in that I didn't notice. Note that on autopilots that don't have auto throttle, the aircraft can only adjust its altitude using pitch trim. If your power setting is too high, you will drift up. If your power setting is too low, you will drift down. If you have a notch in like I did, or a speed break inadvertently deployed, your trim cannot be enough to compensate for the lift and/or drag generated by these conditions.

I noticed in your screenshot that you are considerably slower than your VMO, so I think my analysis bears some merit.

Also, don't forget, when you're cruising in a high-performance aircraft, you must set your manifold pressure and your throttle to an appropriate cruise range.

I hope this obvious answer can be found by others that share the same issue without going through copious amounts of manuals and YouTube tutorials that don't address these sort of common errors.

Good luck!

[dlrk]

I'm also having this issue (not as bad as in the OP though). When I disconnect the autopilot to correct, it winds up pitching up rapidly due to apparently being out of trim. With regard to the throttle setting, this does seem more likely to occur in the 2 minute phase of cruise where power is set at full

[dlrk]

Still having this. No hardware plugged in except Saitek rudder pedals and a thrustmaster t.16000m.

[rubber]

I had the same problem and today I found the answer below. I hope it solves your problem too.

Cheers. 

https://forums.x-plane.org/index.php?/forums/topic/242028-ap-altitude-hold-oscillates/&do=findComment&comment=2163604

 

"Ok I have done some further testing with the above method, it seems the issue comes from what exact disco servos button you have setup on your controller. I had "Disco servos, yaw damp and trim, any side" which seemed to make the trim not work at all whenever the autopilot was reapplied. I switched the disco servos command to "Disco servos and yaw damp, any side." and have not noticed any weirdness with the trim and autopiltot. Seems like disconnecting the trim is causing some sort of conflict with the plane's autopilot."