Quadplane landing issue using weathervaning, Quad hover and forward motor simultaneously

I think there might a potential problem with the current quadplane code using both quad and forward motor at the same time whilst in position hold and trying to land.

The issue can be easily replicated in SITL if one increases the wind speed to over 7m/s with weathervaning and forward motor on. At 7m/s the aircraft struggles to descend and at 9m/s wind speed it climbs at a steady pace, despite trying for a landing WP.

I have tried various settings, including max Q_WP_SPEED_DN and Q_ANGLE_MAX, of which the later only helped moderately. I also tried various Q_VFWD_GAIN combinations to the point it would not position hold using both quad and forward motor.

I think the problem is that at those wind speeds the amount of lift generated by the wing (being propelled by the fwd motor) in combination with the minimum quad lift, in particular that of the front quad motors when weathervaning, results in too much lift overall to descend whilst trying to position hold.

From what I can tell when weathervaning with forward motor on the aircraft does not pitch forward significantly. There is a scenario where even if the quad motors would be switched off, and the wind speed is over stall speed of the wings, that the forward motor would not allow a decent without a pitch down attitude. Alternatively if there was no pitch down to descend only reversing the quad motors will make it descend.

Although operating at these wind speeds is less typical, in practice in gusty/windy conditions, we have observed staggered descents because of it. This could potentially be a problem for many user’s who are relying on a quad landing, because if it doesn’t descend in time the aircraft could potentially run out of battery power before landing and crash, or even climb out of range. I have not tried it in RC control modes with position hold, but I’d expect similar behavior.

A potential solution would be to monitor the decent rate and increase the down pitch until Q_WP_SPEED_DN is achieved.

Another related item is that if forward speed is set to less than wind speed it will not position hold in high wind, even more so without fwd motor assistance. Maybe this should be allowed to increase up to FBW Max so that it can maintain position, regardless of speed setpoint. Also I noticed with quadplane in SITL, but haven’t yet tried on a actual quadplane, is that if the quadplane is armed on the ground, activating RTL will result in the quadplane taking off and going to RTL altitude. Maybe not something that should happen in real flights, but maybe only a SITL issue?


Those all sounds like valid bugs, thank you for bringing them to our attention!

experienced the same at high wind 10m/s plus. was only able to land manually.