Hi experts,
I’ve been working on a 2.9KG 4+1 Quadplane with 2 elevons and no rudder design, as shown below:
The details of my build are as follows:
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Wingspan: 1130mm.
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Wing Area: 31dm2.
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Wing Propulsion: 13 Inch pusher propeller.
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Battery: 6S Li-Ion.
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The COG for wing mode is about 60mm from the leading edge (Marked in red in the image), which is recommended, but for VTOL mode, the drone is front-heavy due to the battery.
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Using Arduplane 4.6.3.
I’ve tuned the VTOL mode, and it flies really well and stable. I’ve tried Qloiter multiple times, and it performs amazingly. No vibrations or oscillations whatsoever.
Next, I went to try the forward flight.
I took off in QLOITER and switched to CRUISE mode at a decent altitude.
(Using CRUISE mode since I have a spring-centered throttle on my RC, and I’m not confident in using it for FBWA, as it might cause a stall in case I leave it during flight).
So, upon entering CRUISE mode, I noticed that the pusher started rotating, and the drone started moving forward and gaining speed.
After reaching around 17m/s, the VTOL motors started spooling down (I could hear), but the drone started rolling left and yawed left, all uncommanded. I immediately switched to QLOITER in order to prevent any crash. It rolled to around -40 degrees, all uncommanded.
The next day, I went again for the test. This time, I increased the PID Roll gains and reduced the throttle skew, thinking that it might help, but got the same result. When the VTOL motors spooled down, it again rolled to around -35 degrees, all uncommanded.
My pusher prop is rotating clockwise (when seen from the back), so can the left roll be a result of counter torque produced by it? I’m thinking that as long as the VTOL motors are active, they counter the torque, but when the VTOL motors spool down, the torque rolls the body?
What else can cause this?
Here are the flight logs from my test flights:
Please help.
Thanks
Divyanshu
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