Pixhawk - Loiter not stable / Toiletbowl


My setup is:

  • Quad based on DJi F450
  • Extended Aluminum arms instead of original plastic arms
  • 4 x MT4006 T-Motors
  • 4 x T-Motor 40A Pro ESC
  • Futaba FASST receiver
  • 4S Gens Ace LiPo
  • Pixhawk with FW 3.15

Problem is: flying great in stabilize and Alt-Hold. When switch to Loiter it is stable. The problem starts once I maneuver…

  1. When flying fast forward it is ascending fast even though the Throtle remains in middle position
  2. Then when stopping the movement it starts moving around like it has life of it’s own and then gets into growing toilet bowl circles.

Here are the compass offsets that I get:
PARM, COMPASS_OFS_Z, -73.18955

PARM, COMPASS_OFS2_X, 0.000000
PARM, COMPASS_OFS2_Y, 0.000000
PARM, COMPASS_OFS2_Z, 0.000000

I attach the log file, help with diagnosis would be greatly appreciated.

When you are in Loiter and push the stick straight forward does the copter fly at an angle or does it fly dead straight?

Typically when you have a toilet bowl effect it’s caused from your Mag getting interference. I had this problem so I made a bracket that mounts the GPS/Mag about 4 inches off the top of the frame.

Another Param to look at is your PID settings for Rate Roll I and Rate Roll Pitch I. It will hold a lot better with higher values. I think it’s almost double than what Rate “P” is but don’t quote me.