We have had some issues with transitioning from Fixedwing to VTOL flight when QRTL is activated facing away from the home location and or too close to the home location. The plane banks hard but then banks back and looses control which is only recovered by switching to QHover.
We have had two of three flights fail in this configuration. Here is a log with a successful turn and an unsuccessful turn and an included video of the log showing the failure.
Any ideas? Thanks!
This is a known limitation of QRTL. It likes to be heading directly to home before it gets close enough for the VTOL motors to kick in. So it wants a bit of room to do the turn towards home in fixed wing flight.
However, it should not “loose control”, I would expect it to be a bit un-gracefull, but once it does come to a stop it should make its way back to home in VTOL flight before landing.
You could use fixed VTOL approach QRTL mode Return to Launch — Plane documentation but you will need to set a large RTL radius so there is room to make final the turn towards home.
I hope we can improve this behavior in a future release.
Regardless of any fundamental limitations of Q_RTL_MODE 3, after reviewing your LOG, I have a few comments to make about the flight and the settings you’re using to fly the MFE Fighter:
Fortunately, the flight never really got out of control at any point, even though it came close. But this wasn’t due to Arduplane’s control behavior, but rather to problematic settings and poor PID values, especially for pitch.
Roll and target roll after the third RTL don’t actually look that bad:
Pitch regulation, on the other hand, is significantly worse:
Furthermore, you’re flying with an airspeed sensor that’s giving fairly inaccurate readings:
The actual airspeed was likely at least 22 m/s, not 19 m/s. I estimate the wind speed at 4–5 m/s.
Your WP_LOITE_RAD is 60 meters. With that radius, at 22 m/s you’d need a bank angle of about 41° to follow the turn. However, people often forget that waypoints and loiter circles don’t move with the wind—they’re fixed points on the ground. With a 5 m/s wind, when circling, you’re already flying at 27 m/s over ground at the end of the downwind leg. To follow a 60-meter radius, you’d need a bank angle of 52°. Arduplane normally stops at 45°. So you’re already making it physically impossible to stay on course.
In fact, this is what your flight looks like (actual roll versus target roll)
I also fly an MFE Fighter, but with a WP_LOITER_RAD of 150 meters.
Above all, I strongly recommend that you adjust the airspeed sensor correctly.
I hope you have many great flights with the beautiful MFE Fighter.
Rolf
