Try VTOL without gps or compass?

Does anyone know if you can fly a non-vectored tailsitter in Qstabilize and FBWA without a GPS and without a compass?


After note: I’ve had two successful hover flights with my plank dual motor tailsitter, and two crash flights where one motor would just totally overpower the other motor at take off. My hypothesis: it’s using the much drifted yaw angle to correct itself resulting in its going towards a way off “level” yaw angle.