DJI Wookong yawing right in Manual but not in GPS or ATTi

[hellafilming]

Hi Guys,
I have a X8 on a cinestar 8 frame with T-motor 4014- 400kv mayatech 65 amp SC, and some foxtexh 16x5.4 CF props

I have a few gain and "twitch" (may be prop related) problems but the one that need attention first is the difference in flight characteristics between modes. In GPS and ATT it will hover and fly good, no yawing or sideways flight. When I fly in manual mod it yaws to the right rather fast. I can trim out on my futaba14sg some where around 52 and it will fly correct. If I leave the TX trimmed and fly in GPS and ATT mode the copter yaws to the left like it would in manual. Normally I have the same flight characteristics in all modes. Anybody have any experience with this? Thank You

 

[Carapau]

Check your motor alignment and that all your motors are exactly vertical. If there is a bias to one side eg more motors than not are slightly off vertical to one side rather than the other you will have a yaw. The reason you wont see it in GPS or ATTI is that the WKM is automatically compensating for this.

 

[PeterLester]

I have see multiple postings on this issue most specifically to the coax designs both here and on Freefly forum.
This can occur even when all motor thrust lines are totally vertical.
But there is a fix for it..... just don't recall exactly where/how.

 

[hellafilming]

Yeah I used a bubble level to an leveled them all out. I've put the system on 2 different frames (but in X8) pattern but it is still there. could it be that my top and bottom prop are the same size?

 

[PeterLester]

No.... My understanding is that the yaw issue tends to become aggravated as MR arm length increases and/or the payload is positioned further from the center of the MR hub.

Apparently the cw motors need to be canted about 3 deg in the MR hub clockwise direction and the MR hub ccw motors canted about 3 degrees in the ccw direction. Can't remember if it is just the top or bottom motors that require this. What this does is give the FC yaw output more effective control of yaw in both directions including yaw rotation speed. I think "Ferdinand" here on MRF from Austria commented on this.... search his name and see what he says.

 

[deluge2]

This topic comers up periodically. FWIW, on DJI's s800, s800 EVO, and AFAIK s1000, DJI intentionally tilts the CW motors one way and the CCW motors the other way (using shims or dampers of different thicknesses). As Peter mentions this provides added control for the FC about the yaw axis. The tilt is small and of the same magnitude for all motors.

Do you have iOSD logs to look at motor RPM in manual vs attitude-stabilized modes? Since you've aligned the motors and have seen the same behavior on 2 different frames, maybe it's not motor tilt. Could there be an issue with ESC calibration such that on manual, some net imbalance in FC outputs vs. RPM across the motors is created? This would show up in Manual mode, but the FC attitude stability algorithms would compensate when you're in ATTI or GPS-ATTI modes.

I don't have any experience with co-ax setups so I don't know about prop size. However I've certainly seen descriptions of successful co-ax setups with same size and with different size top vs. bottom props so I don't think there's a definitive answer as to which works best in all situations. I would be surprised if prop size was the primary issue since everything is symmetrical and the differential effects should counterbalance...

Steve

Yeah I used a bubble level to an leveled them all out. I've put the system on 2 different frames (but in X8) pattern but it is still there. could it be that my top and bottom prop are the same size?