Tiltrotor Transition failure from Q_Loiter to FBWA

[VUAS (Mathew Herbert)]

Hi All.

I am setting up our first Tiltrotor system ( quad plane with front two motors tilting weighing in at 4.5kg) and we are getting a strange issue when we attempt to transition to FBWA from Q_Loiter.

For context we have a quadplane 4 + 1 variant of the same aircraft and that has been flying well since day 1 and we have a smaller vtol tricopter with tilting front motors that is working just fine so this one has us scratching heads.

The behaviour is as follows:

Climb to 20m hit FBWA and aircraft accelerates fine for the first second or so then tops out at 8 m/s and does not complete the transition (we have had to abort each attempt as the aircraft was getting to far away. It seems like it is hitting some kind of limit at 8 m/s as the motors see to spool down a little from peak.

I’m pretty sure we are just missing something and I am hoping some ideas as to what it could be.

Aircraft is running a Cube Orange+ with a Here4, airspeed sensor, Mauch power supply and 15 inch props.

Link to Logs. Thanks in advance!

[Rolf]

Could the pitot tube be obstructed? There is a significant divergence between airspeed and ground speed. Or did you make the transition with a strong tailwind?

[VUAS (Mathew Herbert)]

Its not obstructed (tested on ground getting peaks airspeeds of above 20m/s) and we took off into wind. We did have the pitot tube in the wing when we first saw this behaviour and have since moved it (and changed the sensor and tube). I hadn’t graphed it since the first instance and since we changed the sensor I figured it was unlikely to be the problem but seeing this would indicate that maybe I am incorrect in that assumption. It is certainly somthing to go on thanks!