V3.2.1 - No forward speed


I have what was a Cheerson CX-20 with APM 2.8 and Arducopter software v3.2.1 (the most recent it will handle). Until recently it flew perfectly.

When I flew it yesterday it would not fly forward at all. It would loiter, climb and fly backwards but not forwards. Not even a nod in pitch. When commanded, it couldn’t RTL (no forward speed) and in order to get it back I had to reverse it back to me. Reverse speed seemed normal.

  • The accelerometers are calibrated - everything is level and correctly oriented;
  • The R/C is calibrated;
  • The magnetometer is calibrated - and in the correct sense (I can point it at local landmarks in all directions and the Mission Planner map shows perfect correlation);
  • On power-up the ESC beeps are consistent and all motors twitch by the same amount;
  • When given a ‘standard’ flick with a biro [powered-down], each motor turns a similar number of turns;

Because the hardware can’t use v3.3+ I can’t calibrate the ESCs via Mission Planner and, for the CX-20 ESCs, it appears not to be a straightforward thing to do - I reason that in any case the rear motors must be capable of producing more lift as the quad climbs straight up and remains perfectly level; it would be unusual for both motors to go out of kilter at the same time

Looking through the parameter list in Mission Planner I couldn’t see anything that limits forward speed and that might have been erroneously set to zero. I have attached as pdfs* two parameter files (one known good one and the current one). No logs are available via Mission Planner, an error ‘unable to find log index’ (or similar) appears.

It is probably something obvious but I am stumped. I would be grateful for any suggestions before I start changing hardware willy-nilly in a blunderbuss approach to troubleshooting.



*Uploading *.param files isn’t possible.

No forward flight.pdf (263.4 KB)
Know good params.pdf (264.0 KB)