Health monitoring based on blade tip trajectory

A propeller health monitoring system for an aircraft comprising;

• an aircraft having one or more propellers, each of the one or more propellers comprising:
• a hub having an axis of rotation;
• and
• a plurality of propeller blades, each of the plurality of propeller blades comprising:
• a blade body having a hub end and a tip end;
• and a light source mounted in or on the blade body, the light source being able to emit a light beam from the tip end of the propeller blade in a direction which radiates outwardly from the propeller hub;
• wherein the system further comprises:
• one or more receptors mounted to a fuselage or a nacelle of the aircraft, each receptor having a sensor surface which is able to detect a position for each light beam crossing over the sensor surface as the propeller rotates, such that the receptor generates a signal that is indicative of the position as a measure of blade tip trajectory for each passing propeller blade;
• and
• a processing unit which analyses the signals from the receptor to determine health of the propeller blades of the one or more propellers based on where the beams of light from the propeller blades have crossed over the sensor surface in the forward or aft direction of the aircraft.