EKF3 imu1 in-flight yaw alignment

Hey guys,

Yesterday we had a strange behavior. We have upgraded one of our drone from 4.0.7 to 4.1.1 (as another is already flying this firmware without issue).
Then we made a test flight, and after EKF3 imu1 in-flight yaw alignment message the copter automatically yaw about 20°.
We did not make compass calibration, that’s the next step, but is that a must? the only difference is we use here3 on this drone…

Thank you for your help

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Please update to ArduCopter 4.1.5, there is no need to re-calibrate the compass, unless the original compass calibration was not correctly done.

My guess is that you did not do the initial configuration correctly.

thank you for your reply, I forgot to mention that this drone was flying without this strange behavior before.

Post a .bin log file from the flight you mentioned above using something like wetransfer.com


Please find the requested log.



Hi @amilcarlucas ,

Did you have time to look at the log? Did you notice anything obvious?

Best regards

Hello, I have the same problem, Does anyone have any idea to fix this issue?

When I take of about 2m after ground and I got the messenger" [EKF3 imu1 in-flight yaw alignment]"
and then the drone tends to destabilize and align the yaw axis.
Thank all!

in-flight yaw alignment is a common message and not necessarily a fault.
It means the GPS course and compass course may differ and have been compensated for.
You should probably do the compass calibration again, outside after you have a good GPS 3D fix.

If there’s instability when the yaw realigns, then it’s likely you have other tuning issues too.
Best to supply a .bin log file to check out what is really going on.

Hi Shawn, thank you for your suggestion, I have a log file, if you have time free help me analys to check out what is really going on.

Thank you so much!

As expected the compass heading versus IMU predicted heading (based on all sensors) is different.

Other points to note are:

  • Vibrations need to be improved or they will give you trouble.
  • The copter is severely underpowered and is lucky to fly at all - this will give you major trouble and you should rethink the motor and prop choice at least. If there is a payload remove it and tune without the payload. Even if you get this copter tuned you will never be able to add back on the same payload.

First sort out the compasses and order - there appears to have been 3 but one is missing, and of the two remaining the one selected for use doesnt look calibrated as well as the disused compass.
Use the Compass page in MissionPlanner, and do the calibration again while you have a good 3D Fix.

As for tuning - there is a lot to do.
Describe you copter please - motors props, ESCs, battery, take off weight…

Start by going back into the Initial Parameters screen, put in you prop size and battery cell count and select “Suggested” settings too - Now accept everything it offers and write, DO NOT skip any.

I know you already started doing some tuning but it’s not helping you at the moment.
After the Intiial Parameters set these:

If you can provide more info I can provide more settings to do before the next flight.

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Hi Shawn, thank you so much, I will try it step by step and will respond to you soon.

May i know what should be the value of following parameters.


There is no such parameter - find the exact name, but much better to describe what you are trying to fix rather than ask for a value of a parameter