Quad-Plane Throttle Dropped Out During Transition

ArduPlane VTOL Plane
1

Was flying a quad-plane the other day and experienced a strange drop in the fixed-wing throttle during the takeoff transition. Here’s a screenshot from the log where I’ve plotted both the fixed-wing throttle output (orange) and the VTOL motor output (blue). And then I’ve circled the “strange” moment in blue.

throttle
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Additionally, here is a link to the flight log so you can take a look at things yourself:

(Ignore the small hop flight at the beginning of the log in QLoiter mode)

Additional things to note:

  • This occurred almost simultaneously with the quad motors shutting off
  • This is after a recent update to 4.4.1
  • This was a fully autonomous flight
  • The waypoint following the transition was set with an altitude of 400 ft. and the aircraft hadn’t reached that altitude yet, so my assumption is that the motor should have remained on so that the aircraft could continue climbing to the desired altitude, but if you look at the altitude it definitely dropped significantly when the motor shut off.

Not sure if this is a possible bug? Or what could have caused this. Any help or thoughts would be appreciated!

Could this be related to this post? QuadPlane VTOL loses altitude during transition from VTOL to Fixed Wing - I know it isn’t the same issue, but could it be caused by the TECS updates that were put in 4.4.1?

2

Throttle is adjusted to control altitude to TECS.hdem.
During the transition, the aircraft is accelerated at full throttle, so high engine power will cause the altitude to exceed TECS.hdem and result in a throttle reduction after the transition is complete.

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Thanks for the reply, that makes sense. Is there a way to tune this so that the drop in throttle isn’t as aggressive? Or so that the transition is a little smoother? In flight it gave us quite the scare because it seemed like the motors had completely died for a split second and we thought it was going to drop.

4

You might consider increasing TECS_CLMB_MAX and decreasing TECS_HDEM_TCONST. This would raise TECS.hdem faster and may keep the throttle higher. However, looking at the source code, it seems there are several other factors that limit the rate of increase of the demanded altitude, so this may not be very effective.

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