M100: consistent uncommanded spiral in P-mode, no problems in A-mode

[Peter G]

Hello,

(see attached file for details)

A local company donated an M100 to the school where I teach. I've been practicing flying it and experience a consistent problem: in P-mode, with good GPS, it quickly goes into an uncommanded spiral to the left (CCW from bird's-eye-view) with increasing roll and throttle. I can prevent it manually, but it's not something I want my students to have to deal with.

In Atti-mode, it autonomously maintains altitude and attitude very well, and just drifts gently with the wind.

The attached *.dat is a short flight that displays this:
-in Atti-mode
-auto takeoff
-drifts north with wind (no control inputs)
-control input to bring it back manually to home point approximately and land
-switch to P-mode
-auto take-off
-goes into spiral (no control inputs)
-control input to bring it back manually to home point approximately and land

I've calibrated the compass, IMU, and controller multiple times. AirData is happy with GPS signal strength (green), # of satellites (orange), and compass (green).

Has anyone experienced something like this and have a solution?

Thanks for any help,
-Peter

 

[Peter G]

We got the M100 sorted. Shame on me, we changed three variables at once:
-removed all custom electronics (possible source of RF interference?)
-corrected GPS puck position rel. to CG using DJI assistant (had reverted to factory coordinates)
-and...pointed the puck forward (yeah, shoulda known to check this first)

It now hovers in P-mode pretty perfectly. I pointed the puck about 30 deg west (rel to a/c), and it still hovered well. I then pointed the puck due SW, and it started doing the death spiral just like before.

Hope this helps others.