Another AltHold problem thread


so I am new to the Arducopter software and I have a question regarding the AltHold mode.

The way I think the AltHold mode should work is: If I hold the throttle stick at neutral position, the copter should maintain its current altitude and not climb or descend. Right?

The way I am experiencing it is completely different (and I dislike it very much), as you can see in the log: When I switch to AltHold mode, the copter is maintaining its climb rate. So when I give a little throttle input, the copter starts climbing, and putting it back to neutral is making it keep climbing until I give a little negative throttle stick input. Is that intended? Can I change it somehow to behave like I want it to (described at the beginning)?

The log shows desired alt and throttle input scaled down. 15 is neutral throttle. And yes, I did the throttle hover calibration with the parameter.

Thanks for your input,

Very difficult to help with out a .log or .bin file to look at.

No, this is clearly not the expected behavior in AltHold mode. As MarkM said, the .bin would help a lot.

Hi, thanks for your answers. I thought this was a common problem and the pic would be enough for the diagnosis, but I can give you the complete log AS well ofc. I uploaded it to my dropbox as the uplad here somehow didnt work… Link:

Thanks! Malte

Your Z vibrations might be a little high, not 100% sure I’m reading it right for AC3.3
If they are it would explain your problem as everything else looks OK to me.

Indeed, your vibrations are a bit high at the end of the flight. See VIBE. But this is not your issue with AltHold.

It seems you have a sonar or at least the system seems to be configured for one and I guess this is your problem with AltHold. Check CTUN.SAlt and CTUN.DSAlt. If you don’t have a sonar, then these should be zero. At least, this is my experience. I don’t have further knowledge about sonar since I never used one. But since you did not mention it in your first post, you probably don’t have one and you should check your configuration.


Hi Cyril, hi Mark,

the SAlt indeed is not zero. But I have configured the sonar to be “None” in the mission planner configuration… anyone knows whats that all about or how to fix this?

Thanks! Malte

Switched to the px4 flight stack, all working perfectly out of the box. Thanks for your help anyway.