A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms.
In the aerospace context, a piston refers to a cylindrical component that moves back and forth in a cylinder, typically powered by combustion. It is used in reciprocating engines, such as those found in some small aircraft, helicopters, and some UAVs (Unmanned Aerial Vehicles) to convert the energy from combustion into mechanical energy that can be used to power a propeller or turbine.
Piston engines, also known as reciprocating engines, work by a cycle of four strokes: intake, compression, power, and exhaust. During the intake stroke, the piston moves down, and the intake valve opens, allowing the fuel-air mixture to enter the cylinder. During the compression stroke, the piston moves up, compressing the fuel-air mixture. During the power stroke, the fuel-air mixture is ignited, and the expansion of the combustion gases pushes the piston down. Finally, during the exhaust stroke, the exhaust valve opens, and the combustion gases are expelled from the cylinder.
Examples of aircraft that use piston engines include:
- Cessna 172: A single-engine, four-seat aircraft that is commonly used for training, touring, and personal use.
- Piper PA-28: A family of single-engine, four-seat aircraft that is used for training, touring, and personal use.
- Robinson R22: A single-engine, two-seat helicopter that is commonly used for training and personal use.
- Some UAVs use reciprocating engines as well, such as the Aerovironment Puma AE, a small UAV that is used for reconnaissance, surveillance, and target acquisition.
It's worth noting that Piston engines have been replaced by turbine engines in most commercial aircrafts, but are still used in some general aviation and small aircrafts, and in some UAVs. They are considered cheaper and simpler than turbine engines but they are less efficient, less powerful, and have shorter range.