Typically, general aviation aircraft are powered by propellers and internal combustion piston engines (similar to those used in the automobile industry). The basic working principles are as follows: the air in the surroundings enters the engine, it is mixed with fuel and burned, thereby releasing a tremendous amount of energy in the mix (air and fuel) that is employed in increasing its energy (heat and molecular movement). This mix at high speed is exhausted to move a piston that is attached to a crankshaft, which in turn acts rotating a propeller.
The process of combustion in the engine provides very little thrust. Rather, the thrust is produced by the propeller due to aerodynamics. Propellers have various (two, three, or four) blades with an airfoil shape. The propeller acts as a rotating wing, creating a lift force due to its motion in the air. The aerodynamics of blades, i.e., the aerodynamics of helicopters, are slightly different than those studied in Chapter 3, and lay beyond the scope of this course. Nevertheless, the same principles apply: the engine rotates the propeller, causing a significant change in pressure across the propeller blades, and finally producing a net balance of forwards lift force.