Twin Vectored Belly Sitter : Terribly Unstable on takeoff

Hi, the above video shows my first TVBS was flying very well about 4 months ago

But…she changed terribly ( She has been stored for 4 months just after flying )

Please watch below video . . .

The tilt servos seem like jittering but in fixed wing mode, no problem.

what I did In order to fix this problem

  1. Conduct all calibration
  2. Change FC ( of course all calibration done again )
  3. FW downgrade ( 3.8.5 to 3.8.4 becuase it was 3.8.4 when she flied well )
  4. Change EKF3 to EKF2
  5. Change power to servo rail

Even after No4 she was skyrocketing when I did throttle up with QHover mode
( The attached log file has it. )

looks like a throttle scaling issue, as seen here

I have submitted a pull request but is yet to be merged,

If your using a pixhawk1 there is a compiled version with the fix you could try.

Interesting that it started suddenly, upping the D gains in particular seem to bring it on, I have found there is a wide range of gains that work.

Defiantly use EKF3