Quadcopter starts yawing immediatelly after takeoff

I got problem with my quadcopter and writing here to 3.6 section but I guess it is not related only to this version. I flew with this configuration many times without problems but after some upgrades (guess the problems started with 3.6.7) the copter started yawing without rc-input or another symptom was it didn’t yaw at all even with full left/right rc-lever.
Arducopter with fresh loaded (all params reset to defaults) 3.6.10 running on RBPi 3 + PXFMini on it.
On the field I just did Compass callibration and motor/compass calibration.
Then I tookoff in stabilize mode, but right after copter elevated bit above ground it started yawing notable in CW direction. And because yaw couldn’t be corrected with my radio I only landed somehow with little damages on the frame.
So I downloaded the log but only thing I could read from it is the channel 4 out was not corresponding to my rc-input (RCIN-4). In fact it didn’t react to my rc-input 4 at all.
One can see it on the graph here:

Where the blue curve is my rc-4 input (at the begin very high - as I armed the copter with yaw lever) and then after approx. in the intersection of red and blue lines I started with correction - opposite to yawing, but the red line is still rising up and I really don’t understand what’s wrong with my setup.
Perhaps the driver for my compas changed default alignemt of the sensor so I checked also compass when yawing the frame in my hands - in the MP it seemed the rotation is correct. Please can somebody here check my log from this flight and point me what happened to my copter?
2019-08-07 11-02-34.zip (209.4 KB)

Have a look at your RCout.
Theres your problem.

Check your motor order, prop directions, ESC calibration, motor mounts, etc.

Just to be clear, RCOU.C4 records output of the 4th motor rather than rudder channel. A significant imbalance in motor outputs usually suggests problems Mike just mentioned.

I also encountered a similar situation with my hexa. After calib it many times, it will work correctly.

Thanks sq-meng, did’t realize it.

@ [Tan_Ph_m]: After repeating what?

sorry I fixed it! calib compass and sensor, gyro,… step by step…

1 Like