Preventing abnormal fan blade deflection or fan flutter with retroreflectors

A processor-implemented method for preventing abnormal fan blade deflection or fan flutter in an engine, the method comprising:

• emitting radiant flux from an optical emitting source towards a retroreflector when the retroreflector is disposed on a fan blade of the engine and the engine is operating;
• receiving an incident radiant flux from the retroreflector by an optical receiver, wherein the optical receiver is separate from the optical emitting source, the optical emitting source and the optical receiver disposed in a pylon supporting the engine;
• determining a deflection value of the fan blade based on the incident radiant flux received by the optical receiver;
• determining whether the deflection value is greater than or equal to a threshold for deflection of the fan blade to identify the abnormal fan blade deflection or fan flutter;
• and
• selectively changing a state of the engine when the abnormal fan blade deflection or fan flutter is identified.

An aircraft including a system for preventing abnormal fan blade deflection or fan flutter in an engine of the aircraft, the aircraft comprising:

• a fan blade;
• an electronics housing disposed on the aircraft, the electronics housing including an optical emitting source configured to provide radiant flux and an optical receiver, wherein the optical receiver is separate from the optical emitting source;
• a retroreflector on the fan blade of the engine, the fan blade including only a single retroreflector;
• a processor;
• and
• a memory, including instructions stored thereon, which, when executed by the processor cause the system to:
• emit the radiant flux from the optical emitting source towards the retroreflector when the retroreflector is disposed on the fan blade and the engine is operating;
• receive an incident radiant flux from the retroreflector by the optical receiver;
• determine a deflection value of the fan blade based on the incident radiant flux received by the optical receiver;
• determine whether the deflection value is greater than or equal to a threshold for deflection of the fan blade to identify the abnormal fan blade deflection or fan flutter;
• and
• selectively change a state of the engine when the abnormal fan blade deflection or fan flutter is identified.