What type of motors are used in helicopters?

Answer 1

Hemi

If you mean model helicopters, in most cases, they use small permanent magnet DC motors for both the tail rotor and the main rotor. Some more sophisticated models use a 'brushless DC motor' which is actually a three phase permanent magnet motor, and a compact electronic variable frequency AC inverter for speed control.

If you mean REAL helicopters........

Smaller helicopters commonly have 'flat-four' or 'flat-six' piston-type aircraft engines, mounted with the crankshaft vertical. They have a clutch that engages to drive the 'wing' (the top rotor) and the tail rotor once the engine has started, and the clutch can be disengaged to allow the helicopter to 'auto-rotate' if the engine fails in flight. There is also a 6:1 gearbox in the drive train, as the 'wing' rotates at about 450 RPM, but the engine runs at about 2700 RPM at full speed. Older helicopters had 9 or 18 cylinder radial aircraft engines to drive the spinning bits. The engine - clutch - gearbox system is usually mounted directly behind the cabin, often in line with the rotor vertical main shaft, behind the cockpit.

Larger helicopters have one or two turbine engines - these develop more horsepower per pound and per cubic foot than piston engines, and spin at 10,000 plus RPM. While they have fewer moving bits and don't need high-octane petrol, they need more care to keep them reliable and are a bit more delicate internally. Turbine engines are small enough that they can be mounted in the top structure of the helicopter, increasing cabin space.

Turbine engines can usually be identified by the awful howling noise they make, or if they aren't howling, by the huge exhaust pipe (6 - 10 inches in diameter).