I am using AC 3.2.` on pixhawk and it works good.

When I uploaded AC 3.3 I got compass issues, I was getting errors compass variance

Also when I tried to fly , I almost crashed it, my tarot got very unstable and banked to left and right

any thoughts about it?



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I did have some issues w/ it on the bench, not mounted in a copter.  At the time, I was anxious to get it built, and didn't look in to it much.

I just ordered some non ferrous screws, and will certainly try that! 

Regarding your bad ARHS readings with the Pixhawk, I just want to remind you about the barometer sunlight problem as you said you are using your own 3D printed case.

(with the APM2 I could get baro drift by shining a maglite torch onto the controller)

I think the best solution is to just recalibrate the compass in an open field. avoid doing it inside the building since there are hidden wires. keep compass away from high current wire. the problem should get resolved. also check orientation of compass.

I got rid of the 3D printed case and am using no case now, as it is too high to fit between the 2 center plates without producing vibrations.

I am aware of the sunlight problem, thanks for reminding.

Just did the still standing baro test and it climbed to 6,6m in around 1 hour...

The BAD AHRS error however didn't come back yet.

I disabled the internal compass now until my nylon screws arrive.


Don't know where to post my issue, but I think it's related to compass issue. Or IMU1 or IMU2 issue.

I'm not really familiar how things are going inside the Pixhawk, with IMU sensors and EKF. It's a bit complex, but maybe developers can help.

Very powerful, just the core things on board:

Y6B carbon frame
5010-360KV motors
17x5.5 CF props (balanced)
30A BLheli ESC
5.2 Ah LIPO
X8R and Taranis radio
NEO-M8N GPS with compass
v3.3.2 ArduCopter Y6B

The whole system is calibrated and pre tested, and necessary parameters set via Mission Planner.

The flight:
Calm weather, 1-2 m/s wind max. Takeoff was normal in stabilized mode. Copter was almost climbed in a steady position. Climbed to 3-4meter height. I've set back the throttle and climbing stopped at around 4 meters. And there the copter started drifting away from me to the left side.
I wanted to direct it back to me, but was still drifting away and ahead.
Turned the copter's nose towards me with yaw, and pushed the right stick to change flight direction but no respons. Still drifted away.
Copter was about 100meters away from me, descended a little, and hit ground around with speed of 10-15 km/h. Lawnmover mode 
Just minor crack in plastic part of landing skid.

2nd attempt:
Takeoff normal in stabilized mode again, climbed vertically to 3-4 meters again to headwind, and there a weird thing happened.
Copter made a swinging to forward and back, like if it would hanged in the CG and pushed from the back, and then immediately turned to its left side and crash landed.

I have log file attached. I'd more than happy if someone could help to analyze the log file that what could cause this faulty operation.
I suspect some kind of disorientation of Pixhawks inertial system. But there was no bad AHRS alam pre flight.
Bad quality GPS maybe? SAT coverage was 8 or more at the time of the flight, and HDOP close to 1.0.

For compass slow drift is not problem, it is caused by the heating, most of the barometers doing so.

Bad if oscillatiing in height more than 20-30 cm with period several seconds.

you will be right!, yesterday I had an another issue, hexa, custom build just just like DJI 550,  on APM2.6 with extrnal compass,   it was flying in stabilize mode, but position hold was bad, the quad was jumping up and down up and down,  for the second attempt, it was holding the position and went down, I was able to recover it, so I didn't crash, anyway I looked at the log, and there was some GPS issues, so  I need to try again, maybe the GPS didnt lock when I was taking off, or whatever hmm

I will try it all again today

I installed the screws, and the internal compass dropped from about 220 -50 -150 to about 150 -50 -150.  So, it did help. 

Doing further investigation, I discovered it's not my internal compass that puts my heading about 45 degrees off.. It's my external csgshop GPS/Compass...  When I use it, everything calibrates fine, but it is pointing off 45 degrees clockwise.  (when copter is facing north, the mission planner display shows it pointing north east)

I found this post about the same GPS, and the compass being connected incorrectly on this GPS, but I'm not sure I believe him... Else, I'd expect more complaints..

Did you set up the right rotation for your external GPS/Compass in Mission Planner?

I also installed nylon screws now and the offsets are still quite high..

369 -154 238

but a lot better than before

No rotation seems to be correct.  All the others give me big problems. 
But, that is a confusing topic.  The magnetometer is upside down, on the bottom of the GPS PCB, but apparently "no rotation" is correct because the code expects the compass to be upside down.   It's definitely not rotated by 45 degrees.

I've got another flight controller and compass on the way for a different project.. I'll try to do some testing with this questionable compass while I've got it on the bench and everything is easy to access..

Worst part about this hobby is trying to figure out which components actually work properly, from the factory.

I agree on that, you should keep the compass away from high current wire. I remember when the AC of my grandmother's room was getting damaged and pouring water on the walls, one of the neighbour suggested to call the professionals who will look after the issue and will give some helpful hints that will cover the future problems if they face any.

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