Hi everyone! 
I’m working on a custom drone build called the “Winged Quad” and I’m struggling to find the right flight mode in ArduPilot. I’d love to get some input from people who’ve dealt with unconventional VTOL geometries.
My weird concept
It’s a quadcopter with fixed wings angled at 45° (see diagram attached). The idea is simple: in forward flight, the wings generate lift and improve efficiency/endurance. The motors are permanently fixed : no tilt servos, no moving parts! It’s a lot like what RcTestFlight tried to do 3 years ago.
Quad mode sucks
In Loiter or Auto, when the drone reaches cruise speed and pitches backward to stop accelerating, the wings brutally generate lift. Arducopter doesn’t know about the wings, so it perceives the unexpected climb as an error and corrects downward : it kills the airspeed, which kills the lift, which causes a drop, and the cycle repeats.
This leads to pitch oscillations at cruise speed that I haven’t found a clean way to tune out.
Tailsitter might work
My next thought was Tailsitter (CopterMotor, no control surfaces), but the fit isn’t perfect either. A standard tailsitter assumes cruise happens around 90° pitch with motors pointing fully forward. Here, cruise equilibrium is at 45° where lift and thrust balance with the wing angle.
Q_TAILSIT_ANGLE set to 45 looks like it could work, handing off to the FW controller at exactly that pitch, but I’m unsure whether the fixed-wing controller will behave sensibly when “cruise” is declared at 45° rather than near-horizontal, and whether back-transition will be stable. I feel like this could end deep in the ground.
My questions
Has anyone built a similar fixed-45° geometry and found a reliable ArduPilot setup?
Is there a smarter way to tell ArduPilot “the wings provide lift above X m/s” without switching to a full tailsitter or QuadPlane setup?
Thanks a lot in advance, I would be happy to share more details or parameters!!