Which rotorcraft type has rotors that rotate by air rather than being engine-driven after start?

• A. Gyroplane
• B. Gyrodyne
• C. Helicopter
• D. Heliport

Answer: (A)

Autorotation is the key idea. In a gyroplane, the rotor is not powered by the engine once you’re in flight—the rotor spins because of the forward airspeed as air flows up through the blades. The engine may provide forward thrust with a propeller, but it doesn’t drive the rotor during flight, so the rotor is turned by air instead. This is what distinguishes a gyroplane from a helicopter (engine-driven rotor throughout flight) or a gyrodyne (the rotor is driven for takeoff/landing and uses other means for forward flight). A gyroplane is the rotorcraft whose rotors rotate by air after start.