- Conventional piston-driven aircraft engines are divided into two categories: horizontally opposed and radial engines. Non-piston-driven or jet engines are also divided into two separate categories: turbo shaft and conventional jet engines.
- Horizontally opposed engines are similar in design to a Volkswagen engine. They have a two-piece crankcase separated into two sides and bolted together in the center. They are all primarily air-cooled and use a dry sump scavenge oiling system. They have from two to six cylinders. Except for the very old models, they are all fuel-injected. For safety reasons, the ignition uses two separate systems. It uses two magnetos driven by the flywheel in the rear of the engine. Magnetos produce their own power for the spark to the engine, which eliminates the chance of coil failure. Each mag has its own ignition switch. Both mags operate simultaneously, although one is always redundant. In case of a failure, the opposite mag takes over. There are two sets of wires and spark plugs. The engine uses a gear reduction on the front to operate the propeller.
- Radial engines are used for much higher horsepower and are much more compact for the power they can produce. These engines use a circular crankcase with the pistons extending from the crankcase in a circular fashion. They may have as few as six cylinders to more than 18 cylinders situated in two rows of nine--nine in the front and nine in the rear. They can produce over 3,000 horsepower and were used on all commercial aircraft in their day. They were widely used in military aircraft also. Radial engines also use a dry sump oiling system and fuel injection--usually with a supercharger used for additional altitude.
-
Jet-powered engines are either turbo-shaft or thrust-type engines. The jet engine has been found to be much more reliable and lasts longer than a conventional piston engine. A jet engine produces more power and is capable of operating at much higher altitudes than the conventional engine.
Jet propulsion refers to the action produced by a reaction to the ejection of matter. A jet engine uses a series of fan blades to control the intake and exhaust of the gases. The air enters the front of the engine through the impeller blades and passes through a series of blades as the chamber becomes smaller. This compresses the air to a high pressure. From the compressor, it moves into a combustion chamber where it is mixed with fuel and ignited. The pressure builds tremendously within the combustion chamber, helped along by a turbine, creating resistance to the expulsion of the gases. The gas then moves out of the exhaust at an extremely high velocity as compared to the intake speed, thus providing thrust to propel the aircraft forward. The turbo prop or shaft engine works the same with the exception that the thrust produced turns the rearward turbine. The rearward turbine turns a propeller while the remainder of the exhaust is exited overboard.
