Hard Yaw on take off

Hello all,

This is my first post to the forum, I have usually been able to troubleshoot things myself, but I am a total n00b to APM. I just built a quad set up with Pixhawk running 3.1.5 Arducopter with the Ubox GPS+Compass on a mast. I have gone through all the set ups and calibrations and everything seemed to be working fine.

The problem I am having is in “Stabilize Mode” when I go to lift off, the copter yaws hard to the right, and then hard to the left and oscillates back and forth. I picked it up and raised the throttle and it does the same thing. Hard yaw to the right, and then to the left and then repeats, changing direction about every second.

I was able to check out the logs and there are some pretty weird things going on with the compass. Not sure what it is, possibly interference?

The logs are here.

dropbox.com/sh/r1z2hj3lwtq2 … mqgga?dl=0

Any help would be appreciated!!

Thanks in advance,


I really need some HELP!! I am at my wit’s end with this problem.

I’ve taken a look at the logs and the Channel 4 output shows the beginning of the oscillation (yaw) that is causing the hard yaw problems (I think). These flights were with the quad in my hand and resisting to any movement. I just starts to yaw back and forth right after i raise the throttle. The more throttle I give it, the harder the yaw.

I’ve included two more graphs and logs showing the oscillation. The Yaw, desired yaw, Mag X, Mag Y and channel 4 output all show the same thing. This has to be a malfunctioning compass or some very high level of interference. I have done the compass vs motor calibration and it was only 16%. The GPS+Compass is mounted on a mast above the autopilot and power distribution board, see photo.

I am also using a remote satellite receiver from Spektrum to run the PPM signal to the Pixhawk. The receiver is the satellite of the AR6210. They were bound to the radio and then the satellite is plugged into the SPKT/DSM port on the Pixhawk.

I will offer a $50 visa gift card to anyone who can explain what is going on and help me end this problem.

Logs are here:

dropbox.com/sh/r1z2hj3lwtq2 … mqgga?dl=0


I think you may have the props on wrong.

See attached image.

  • Negative Z gyro means that the copter is rotating counter clockwise.
  • Motors 1 and 2 (red green) are the counter clockwise motors, which apply a clockwise torque to the copter.
  • The copter is correctly attempting to apply a clockwise torque to correct the counterclockwise rotation, but is not succeeding. This means that the torque is not being applied -> props are rotating the wrong direction (possibly applying an opposite torque)

fyi - please post logs to the log analysis forums.

wOw… :confused:

I feel like a total ass… I spent all my time looking at the complex stuff, when I should have returned to the basics first. I was so sure they were in the right spot, but after checking, you are correct.

I will fly tomorrow to confirm, but I’m pretty sure you nailed it.

Reply to my email with a way for me to get you the gift card I promised(hand deliver if you’re in San Diego, mail or paypal), and I will get it to you ASAP.

Thanks Jonathan.

Don’t worry, I find that is usually the case as well. Always look at the simple things first. :slight_smile: