Yaw control disabling during fast VTOL descents

I fly Pixhawk 2.1 and Ardupilot (latest beta) on a QuadPlane-converted Parkzone Radian.

Recently I’ve been focusing on performing rapid inbound and outbound transitions because it’s super fun.

I found an interesting behavior.
I increased Q_VELZ_MAX (Pilot maximum vertical speed) to 150cm/s (1.5 m/s for us mere mortals :wink:)
The default value is 1m/s.

I found that when I actually command maximum climb or descent, it disables yaw control.
That is, during a rapid climb or descent, it holds current heading no matter how far I deflect the rudder stick.
When I command less than full climb or descent with Q_VELZ_MAX set to 150cm/s, yaw control returns.
If I have Q_VELZ_MAX at the default value of 1m/s I always have yaw control.

Is this a bug or a feature?

When doing inbound transitions from FBWA to Q_HOVER, I would really like to command a rapid descent rate while simultaneously kicking the tail around so I point into the wind.
If I do a crosswind or downwind inbound transition and lose yaw control, then I’m temporarily stuck in a hazardous tail-to-wind condition until I arrest my descent rate.

Any ideas?


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Two of your quad motors would have to decelerate to initiate yaw. If the FC is demanding a rate close to the max performance of your vertical power system it may not have the overhead to continue the climb with less then all 4 motors @ full power. Not sure how the controller deals with that, someone here certainly knows, but that is my guess.