Yaw issues during takeoff

Hi everyone,

I started analysing my RCOU outputs after noticing my quad’s yaw spinning during takeoff.
I then decided to isolate the problem by removing my props and just arming it set throttle to 100%.
This is when I noticed that my RCOU.C2 values plunging over a period of 10 seconds despite my throttle being set to 100%
C3 and C4 has similar behaviour but always rebounds but never recovers as much as C1.
This behaviour/pattern is consistent even after I disconnect the power module from the power harness to my ESCs and motors.
Is this a software/firmware flaw? I am running the Navio2/Pi3 with Arducoptor 4.0.3 (latest stable version)

log_3_UnknownDate.bin (316.1 KB) log_4_UnknownDate.bin (362.0 KB) log_5_UnknownDate.bin (308.1 KB) log_6_UnknownDate.bin (326.6 KB)

Thanks everyone!

Behavior on the ground with no props is in no way representative of what will happen in the air.

Uncontrollable yaw is due to incorrect motor rotations or ordering. Double check the diagrams and do a motor test.



Hi Peter,
I have just double checked all wiring and completed the motor test. I confirmed that everything is wired correctly and motors are spinning in the right direction using QGC motor test.

I will attach props and give it another go before attaching my logs to this thread.


A vid or some pics would be usefull too

Hi Peter,
Just read this message. I will take a video of it during my next test as it is getting pretty late here.
I ran a tether from the drone to a weight on the ground as it was unsafe to fly it with it not properly tuned.
While flying, the yaw was rotating while moving in a clockwise direction around the weight in the middle.

I did retrieve some logs though:

I shall attach some photos or a video next time.


I found some useful information about the quad yawing to the right or left during take off here:

I will need to follow those steps first which may help me identify the source of the issue.

I should add that the ESCs and motors that I have are at least 7 years old which used to be part of an older Aeroquad build:
Turnigy 25A plush ESC
BP A2217-9 Brushless Outrunner Motor
10x4.7 APC props

I had to replace one of the motors so far due to the old one clacking after a crash.
I may need to purchase new ESCs and motors as the parts above (except prop) are obsolete and I would like to eliminate parts as a fault factor.

Any two cents are welcomed.


My $.02 is remove the access requirement for the log link and someone may take a look at it.

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Thanks for the prompt. I should have checked the permissions on the link.


As suggested by the documentation, I am going to do a couple of things to troubleshoot this:

  1. Re-calibrate all ESCs and their respective motors.
  2. Measure performance of each motor. I may get a tachometer for this and also measure the amount of thrust each motor produces at full throttle.
  3. Ensure that each motor shaft is not bent/wobbling from a previous crash.
  4. Test the whole setup with brand new motors.


I re-calibrated all ESCs and used a try square/steel ruler to inspect each motor.

Rotating the motor, I found that the shaft on 2 of my 4 motors were slightly out by 1-2mm.
The affected motors were 1 and 2. Top right and bottom left on my X frame configuration.

Are there any possible fixes I could do before changing all the motors?


Hi Peter,

As requested, I have uploaded my latest log with a video of the flight.

Link to quicktime mov video -

Link to smaller mp4 version:


Looks to be flying about as well as can be expect considering the tether, I would take it somewhere with more room and try it without.

Thanks for the suggestion Peter. I will give it a shot outdoors. My only concern as seen from the video is that the quad seems to be doing circles on its own while I am not touching the controls. Another issue that I have is the oscillation with the altitude. Tuning could perhaps fix it?


Its just the tether pulling on it, stabilize is just a angle control mode, it will try and stay level. This enviable means it will drift, the tether makes it drift in a circle rather than a constant direction.

Right, I guess the modes I am interested in are alt-hold and loiter.

Hi Peter,

I took the quad to the field for a proper test flight yesterday and I seem to be having pitch issues. I have not auto tuned the quad yet, just the basic one. When moving my pitch up and down, the quad did not seem to respond. This was confirmed when I checked the logs. My radio is properly calibrated and responds well when tested on QGC. Altitude hold mode also seems to be working well.

I have attached some log files and screenshots of the plot showing where the issue is.



Cant see anything causing it in the log. Could be mechanical. You can tune it out.

You battery is going dangerously low and is probably getting damaged - unless the voltage monitoring is slightly wrong. I would check that very carefully.
The current monitoring is definitely wrong.

Set these:

Your Roll vs Desire Roll is good

You Pitch vs Desired Pitch is very strange

Yaw is doing what it thinks your asking of it…

Maybe I would do careful calibration of accelerators again, and pay special attention to level horizon -> level the craft as whole, not just the flight controller.

Any chance you can change RC map back to standard and redo the radio calibration? It seems your radio is giving inputs and the flight controller is ignoring some. I’d definitely try this in case there’s a bug.
Normal is Roll ch1, Pitch ch2, Throttle ch3, Yaw ch4.

Also probably update firmware to 4.0.3 (or at least 3.6.12)

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Thanks for those wonderful insights, especially the battery one. Yes I am facing a lot of issues with my pitch as it does not seem to respond at all. My yaw inputs seem not to respond too. I have done levelling (accelerometer and compass) of my craft together with the flight controller several times. I will redo them again after upgrading to the latest firmware. (I have done the firmware upgrade before it’s just that it seems to cause issues with the Navio2’s LED, hence I rolled back)

Thanks for the suggestion on the RC map, will give it a go. I am using a temporary DIY PPM encoder (Arduino Nano) loaded with this firmware (while waiting for my ppm encoder to arrive):


I remember now why I was not using ch1 and 2. I was having issues with the Nano’s rx/tx inputs and could not get ch 1 or 2 work. hmmmm everything is starting to make sense now :slight_smile: