In a piston engine, pressure from the explosions drives pistons back and forth. In a rotary engine, the pressure drives a triangular rotor in a path around the inside of the chamber. As the rotor moves, it takes in air and fuel and compresses it. Spark plugs ignite the compressed fuel-and-air mixture, creating an explosion. The force of the explosion keeps the rotor moving. As it continues on the path, the rotor releases the exhaust and begins the cycle again.

To look at each individual stroke in the cycle, click on the button at the top of the frame.

Rotary engines have fewer moving parts that piston engines, so they are generally more reliable, and they operate more smoothly. But they are also less fuel-efficient as a rule, and they emit more pollution. A few aircraft, mostly experimental are now fitted with a Wankel engine.