Copter 3.5.7 quad backward tip on takeoff


Having a frustrating time getting this quad not to flip over backwards on T/O. The thing is, it was flying fine until I partially disassembled it for transport, removing the props, folding in the arms and lowering the VTX and GPS masts – no wiring disconnects. The only thing between then and now is I added some trainer mix lines, which I have removed.

The quad is running V3.5.7.

Things I’ve checked:

-Correct props on motors

-Motors turning in correct direction and appear to have the same RPM at idle ( motor test correct )

-calibrated accelerometers, gyros and compass for the new location

-no messages indicating any failure

-ESC (Lumenier 4 in 1) wiring secure – ran the Mission Planner ESC calibration

-Cube is facing it the correct direction and the AHRS orientation parameter is 0.

-Good C.G. within 2mm of center.

-No odd Taranis mixes throwing in back ELE

This frame normally lifts straight up once the RPM comes up. Any tips are appreciated.