I am sure that this topic is getting beat to death but i can't find a working solution.

my bird is a 76 cm Hexa with the APM 2.0. It has 1000 kv motors with 10.5" props. It flies great in stabilized mode but when I switch to altitude hold it slowly descends and then shoots up a what sounds like full throttle.

I am using sonar and I believe that I have my vibrations well within tollerance.

I have been trying to get it to work properly by changing the throttle accel settings but to no avail.

I have included a log file and a couple of pics of my bird. It's been a build going on for about a year but im still to nervous to put on my FPV gear.

It's outfitted for night flying too.

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Have you tried without sonar?

Super build. I'd also try without the sonar.


I had a look at your logs and at first sight it seems that your average throttle is about 361 which means that you are under the deadband limit (40% - 60%).
I saw that you already reduced the Thr_mid to 480 but I would suggest to lower it even more to match your hoover throttle (370).
It is no issue of vibrations as your AccZ seems fine except for 2 spikes but that must be due to landing I supose.

Thank you for the replies and suggestions. I've got rain for the next five days now but as soon as it stops I will disable the sonar and try again. If that works, where would I go from there?
Jan, I will lower my throttle mid more and yes the spikes are landing.
Thanks again.
I am open to other suggestions as well while I'm waiting for the rain to stop.

Do you have a current/voltage sensor? I believe there was a bug fixed in 3.0-rc1 that could affect sonar when they are in use...

Anyway, when troubleshooting - easier to work with fewer variables. See if you can get it working well without the sonar. If so, great - I'd suggest you wait until 3.0 is out and then try that. If still happy, then re-introduce sonar.

Yes - frustrating to move slowly, but its probably easier. Good luck :)

Thanks Rick, I will try that. I am running the version that you mentioned and will load the final version when it becomes available. I also did the sonar test and on the floor it reads 20cm and climbs in number the way you would think the farther up I lift it. You said there might be a voltage problem?
Damn rain.
Thanks a million.

Hey people.....


I just lowered my throttle mid to 380 and disabled my sonar. Same thing, it hovers for a second then slowly falls and then shoots up like a rocket about 10 feet. I turn it back to stabilize as soon as it happens to regain full control.

I will upload my latest log files in a minute.

here are two logs, the first one is adjusting throttle_mid to 380 and the second one is with throttle_mid at 380 and sonar disabled.

sorry, here they are


my bad, second log file i turned the compass off by mistake. Here is the log file with sonar disabled. It is the best that alt hold has been. Where do i go from here?


here is a log file of a long hover, I just have to work on the loiter or should i use position hold? For the most part we are on track. Yipeeeeeee, just about ready to put the headgear on.


I am having the same kind of problem. Very surprised.

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