Aviation glossary
Piston engine
A reciprocating internal-combustion engine — in helicopters typically an air-cooled flat four or six. Powers the Robinson R22, R44 and Guimbal Cabri G2.
The piston engine is the usual choice for light helicopters up to about 300 hp. In the Cabri G2 it is a modified Lycoming O-360-J2A (145 hp); the Robinson R22 uses a Lycoming O-320 derated to 131 hp. Advantages are low purchase and operating cost and easier maintenance; drawbacks are higher weight per horsepower, sensitivity to fuel quality (AVGAS 100LL) and reduced performance at altitude compared with a turbine. The pilot usually manages the piston engine directly with the throttle; on the Cabri G2 an automatic correlator takes over much of that work. The turbine (turboshaft) alternative is covered on the Safran Arrius 2D page.