Principles of Flight - Thrust (1)

Thrust is the last force to cover. It is the forward-moving force and parallel to the flight path. Such force is produced by the engines. 

Below are some common types of engines used by different aircraft.

PISTON ENGINE (4-STROKE ENGINE)

  

Piston engine is commonly used in small aircraft. The above diagram shows the key parts inside a piston engine. The crankshaft at the bottom is connected to the propeller which spins and produces thrust. A completed cycle of a piston engine includes 4 strokes.

Intake: The inlet valve is opened to allow fuel-air mixture to be drawn into the combustion chamber. The piston is moved downward by the connecting rod.

Compression: The inlet valve is closed and the piston is moved upward to compress the fuel-air mixture inside the chamber.

Power/Combustion: The spark plugs ignite the mixture resulting a high temperature and pressure. Air expands which pushes the piston down again. 

Exhaust: The exhaust valve is opened and the piston is moved upward again to expel all gases from the engine.