Encountered Two Flight Controller Issues While Building a Tailsitter UAV

I’m working on a tailsitter VTOL UAV as shown in the diagram. It is equipped with two motors on the wings and a single two-stroke engine at the rear for propulsion. I’m facing some challenges with flight control and seeking advice. Here’s how I plan to allocate power:

  1. Before takeoff, the motors are off, and the internal combustion engine is idling.
  2. During vertical takeoff, the electric motors start and accelerate until they generate the required lift for upward motion, while the internal combustion engine continues to idle. Control and stabilization of the aircraft are assisted by elevons.
  3. Once the aircraft reaches a certain desired altitude, it transitions from the vertical takeoff attitude to horizontal flight.
  4. During level flight, the internal combustion engine throttle increases, and the electric motors are turned off, with thrust provided solely by the internal combustion engine. The aircraft maintains a cruising state until the mission is completed.
  5. When a landing is required, the electric motors start, and the internal combustion engine goes back to idling. The aircraft transitions from horizontal flight to vertical mode, with lift generated solely by the electric motors.
  6. The aircraft then initiates a vertical landing, controlled by both the electric motors and hybrid control surfaces.

I intend to use the PX4 flight controller for this aircraft, and I realize that modifications to the airframe and mixers may be necessary. However, I have two main concerns:

  1. I’ve noticed that there will be a period during flight where both the electric motors and the internal combustion engine are operational simultaneously, which could pose challenges for torque balance in the aircraft.
  2. I haven’t yet figured out how to implement the power switching during the transition to level flight.

Could someone provide suggestions for addressing these two issues?