Piston engine mainly by the crankshaft, connecting rod, piston, cylinder, sub-gas institutions and casing and other components. The front of the engine has a gear unit to reduce the speed of the output shaft. Most engines are equipped with turbochargers at the rear of the casing to improve engine altitude performance. According to the cylinder cooling method The engine is divided into liquid and air-cooled two. Early aircraft flight speed is very low, the use of liquid-cooled engine. With the increase in flight speed, you can use high-speed air direct cooling cylinder, air-cooled engine was widely used. The engine is divided into star and inline by cylinder. Star engine cylinder to the crankshaft as the center along the casing was radially uniform arrangement, a single row and double row and other forms. Inline engine cylinder along the casing before and after the arrangement, there are on the cylinder, I-shaped, V-shaped arrangement, to star and V-type more. Sometimes according to the different ways of fuel and engine will be divided into carburetor and direct injection of two, including a wide range of direct oiling applications.