Erratic movement in Loiter & FS Land


I’ve had a problem that when I switch to loiter the copter basically takes off in a direction, even reversing the direction on the sticks basically only manages to keep it stationary.

I then had FS Land kick in for low battery and it started to land (which I can see in the log) and again moved off away from me, I tried to reverse the direction but it didn’t seem to help.

I don’t know how to diganose this, so any help would be appreciated.


You definitely have vibration issues, potentially problems with compass EMI (interference from battery wires) or offsets.

Yeah, I’ve redone my compass calibration a number of times and keep getting significantly different offsets. The most recent are attached - do they look correct for a pixhawk with an external 3dr compass attached? I was concerned that one set is positive and the other is negative, and the numbers aren’t that similar.

I was out flying again today and the magX and magY values for both sensors seem very similar but the magZ is way off… what could be causing that? offsets? orientation? I selected pixhawk in MP which seems to map to no_rotation, is that valid when I have an external compass/gps also? does it automatically know what orientation that sensor is in?

No rotation is normal if you have a 3dr ublox in the correct orientation (antenna up, arrow forwards).

Do you mean offsets or the logged measurements when you say Z is off? Z is the component of magnetic field in the down direction, which is generally going to be big when the copter is level because most people fly in places with steep magnetic inclination.

Anyway, again, you have vibration problems.

I guess both actually but I was referring to the logged measurements




magZ closeup:

The compass offsets from a live calibration are:
COMPASS_OFS_X -93.3105
COMPASS_OFS_Y -5.132282
COMPASS_OFS_Z -117.5667
COMPASS_OFS2_X 86.6073
COMPASS_OFS2_Y 60.91835
COMPASS_OFS2_Z 41.18768

Full log from flight yesterday attached.

I accept the point about vibration, I have my APM 2.6 mounted on one of these … -v1-5.html and printed one for the pixhawk but just didn’t have the space in the body of the discovery due to the gimbal etc. As a result I have it mounted on the foam pads it shipped with… I’ll see what else I could do to reduce vibration.

Compass looks great, still failing vibration tests.