Aircraft propeller drive system

A method for transmitting power from an intermittent combustion internal combustion engine to a propeller of an aircraft, the propeller being connected to an output shaft, the method comprising:

• driving the output shaft with the engine via a torsion bar, the torsion bar having a first end mechanically operatively connected to the engine and a second end connected to the output shaft, the second end being rotatable relative to the first end about a torsion axis by a torsion angle;
• and
• damping variations of torsion angles of the torsion bar at least for changes of torsion angles outside of a range of torsion angles with a hydraulic damper mechanically operatively connected between the output shaft and the first end of the torsion bar,
• damping variations of torsion angles of the torsion bar at least for changes of torsion angles outside of a range of torsion angles with a hydraulic damper comprising:
• providing a first degree of damping for changes in torsion angles within the range of torsion angles and a second degree of damping for changes torsion angles outside of the range of torsion angles, the second degree of damping being greater than the first degree of damping.