Hexa yaws CCW when raising throttle (update V/solved)

Dear all,

thanks to this forum I was able to build my first copter. It is a Hexa +, with 360kv motors, 15*5.5 props, an AUW of about 3.1 kg, and about 30 min loiter time. You can find some more details on the Ecosynth webpage

Basically, it now flies and loiters rock solid.

However, the copter yaws CCW when I raise throttle - at take off and in flight. There is no problem in loiter mode. As soon as there is some wind there is some CCW yaw in loiter too. Initially, I thought it were the ESCs, but after replacing all of them (different brand and firmware) as well as further PID tuning the problem stays the same. Magnetic declination is set fixed to the correct value.

Compassmot is at 2% and vibration seems to be ok:


The corresponding motor log however looks rather strange with all CCW props generally requiring more power after take off:


From a longer flight (mostly in loiter):


One idea is that the CW props are more efficient, causing a CCW momentum that cannot be compensated by the less efficient CCW props!?

It seems that the motors caused the problem, or more precisely the direction of rotation. Somehow, they prefer to run CCW as suggested here. So I mounted the CCW motors and props on top of the arm. Looks strange but works. This is a log analysis from a short "flight" on my "test stand":


If it ever stops raining I'll make some more test outside. 

Test done: same as before! Back to the props?

New test: I did some quick and dirty correction of the tilt of the motors/props like this using some tape and shrinking tube:


This is the result:


Not perfect but much much better! There was not that much wind so I have to test it again. However, this seems to be part of the problem.

I made another test under similar conditions as in the third figure of this post:


There are still differences between the motors/props but much smaller. Apart from the differences in thrust between the props my main problem seems to be solved - no more yaw. The hexa is also more responsive now.

Any kind of help, idea, or suggestion on this problem is greatly appreciated!

Thanks in advance,


You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


  • Thorsten, excellent improvements. I just came back and did some preliminary measurements, but I need a better level surface to make sure. Another thing I measured is the distance of the prop from the arm. With a couple of arms, there's some difference there too of about 2mm, so there's also some inward thrust.

    Motor 3 and 4 are opposites, suggesting a slight CG offset to the back and left. Should be easy to check by lifting the hexa on each opposite arm pair and see if it turns over, rather than finding the actual CG to support the whole frame on.

    I'm also seeing more dip in the arms where the landing gear is not mounted. Likely those arms are more flexible, which under load probably go up a bit more.

    Good to see such progress. Tomorrow I'll measure my hexa and probably will find similar issues.

    Did you find offsets on all motors and in the same direction?

  • T3

    It looks as if it is the motors: http://ecosynth.org/profiles/blogs/maiden-flight-of-stephen-s-long-...

  • T3

    As discussed here I moved all three feet of the landing gear which I had mounted under the CCW props under the CW props to test the effect of interference with prop wash. No influence.

  • T3

    It seems I am not the only one

  • T3

    Update 1: I added another screenshot of a longer flight and added some additional information.

This reply was deleted.


Neville Rodrigues liked Neville Rodrigues's profile
Jun 30
Santiago Perez liked Santiago Perez's profile
Jun 21