Backward Pitch when flying at AltHold

Hoang_Minh_Nguyen · January 8, 2026, 3:54pm

Continuing the discussion from Problem with altitude hold-tuning:

Hi guys. I have the same problem exactly like those topic. The Stabilize is good, but the AltHold always try to positive pitch (the quad lean to back direction) when I release stick after moving the quad to any direction.
How can I fix that, I can not found any solution.

mike_tk · January 8, 2026, 5:06pm

Don’t see anything like that in the log, maybe you can specify time when this problem occurs. See only some minor CoG issue and throttle controller not configured correctly, tune psc_accz_p / accordingly.

Allister · January 8, 2026, 5:30pm

Have a good look at motor 2. How are the props mounted? Any chance it came loose?

Hoang_Minh_Nguyen · January 8, 2026, 5:48pm

Hi, you right, the CoG is a little bit at the back of quad, so Motor 2 and 4 is higher PWM out. About the tunning, what should I do? Change P and I term of Atitude follow to Hover Thrust?

And should I set the ATC_THR_MIX_MAN to 0.5?

Hoang_Minh_Nguyen · January 8, 2026, 5:56pm

I have a good check about the prop before the flight, so I can make sure it is not the problem. It’s 24inch quad, 8.5kg with battery.

I have a good Stabilize flight, no pitch back.

When I change to AltHold with no wind, no stick input, I saw the drone seem good. But for a while, or with a large stick input, it start to pitch back. With any stick direction, drone still pitch back when I release stick. Anyway, I saw this problem is clearly when I use a big battery, which about 2.5kg.

Last week I use 1.6kg battery, and the pitch back not happen, or just a little bit so maybe Im not recognize this. When I change to Loiter, the drone still good hold position.

So I wonder should I change the ATC_THR_MIX_MAN from 0.1 to 0.5, like the ATC_THR_MIX_MAX,0.5?

Allister · January 8, 2026, 6:12pm

Motor 2 is sitting out of line with the other motors. That could be C of G, but when motor 1 starts increasing with it that’s no longer a weight and balance issue. It’s a mechanical or electrical one.

The MOT_THST_HOVER is about 0.2 so you should set:

PSC_ACCZ_P, 0.2
PSC_ACCZ_I, 0.4

What tuning guide are you using? If you are using AMC you would probably catch these. It will also tell you when to adjust ATC_THR_MIX

Hoang_Minh_Nguyen · January 8, 2026, 6:31pm

Thanks for your help. Anyway, I wonder that the ATC_THR_MIX_MAN is use for Acro and Stabilize, or it also AltHold?