As the tail of aircraft is down, the axis of rotation is inclined. The down-going blade produces greater thrust as it is at higher angle of attack than the up-going blade. This causes asymmetric loading and aircraft making the aircraft tending to yaw.
One of the “left-turning tendencies” of aircraft with a propeller, in which the loading of a propeller disc produces more thrust on one side than the other. If the nose of the aircraft points up relative to the oncoming wind, the downward-moving blade creates greater thrust than the upward-going blade, as the former is at a higher angle of attack than the latter. Assuming that the engine is turning clock-wise as viewed from the rear (as is the case in the majority of single-engine propeller aircraft), the aircraft will tend to turn left. Also known as asymmetric propeller loading