FAA Aviation Mechanic Powerplant (AMP)PropellersMedium
A technician inspects a composite propeller blade following a reported lightning strike. Which design feature is specifically built into composite blades to help protect them from lightning strike damage?
- AAn embedded metal mesh or expanded foil layer near the blade surface
- BA mechanical pitch-lock pin near the hub
- CA hollow steel spar running the length of the blade
- DCounterweight arms bolted to the blade shank
Show answer & explanationAnswer & explanation
Correct answer: A. An embedded metal mesh or expanded foil layer near the blade surface
Composite propeller blades typically incorporate a metal mesh or expanded foil layer embedded near the surface to conduct lightning current safely to the hub and airframe, minimizing structural damage. Steel spars, counterweights, and pitch-lock pins serve unrelated structural or governing functions.
Why the other options are wrong
- B. Pitch-lock pins are a governor safety feature, not lightning protection.
- C. Composite blades use composite spars/skins, not hollow steel spars.
- D. Counterweights aid pitch change forces, unrelated to lightning protection.
Composite Blade Lightning Protection
Composite propeller blades include an embedded metal mesh or foil layer that conducts lightning strike current away from the blade to prevent structural damage.
- Metal mesh/foil embedded near surface
- Conducts lightning current to hub/airframe
- Reduces delamination/burn damage risk
- Standard feature on modern composite blades
Memory trick: Mesh catches the lightning like a net, sending it safely to ground.