AIRCRAFT ENGINE

What is under the hood of the aircraft?

There are several different types of aircraft engines, from reciprocating, turboprop, turbojet and even turbofans. In general aviation, you will typically find horizontally opposed engines and radial engines. Radial engines are found in vintage aircraft.

Radial engine Horizontally Opposed

Today, there are three general aviation engine manufacturers which build reciprocating (or piston) engines. Reciprocating simply means the back-and-forth movement of the pistons. The two biggest and widely used manufacturers are Lycoming, Continental, and now the Rotax engine. Rotax is the newest of the three and is generally found in light sport aircraft (LSA).

The most commonly used engine is the Lycoming O-360 series. It is found in most Cessna 172’s, Piper Aircraft, Mooney Aircraft, Beechcraft, homebuilt aircraft and the list goes on.

These engines that are used in smaller aircraft are designed with the following, (engine only):

Lycoming and Continental are air-cooled or liquid cooled.
- Rotax engines are partially water (liquid) cooled, using a radiator.
Horizontally opposed cylinders, usually four or six cylinders.
Direct drive to the propeller, meaning no gears.

Both engine manufacturers, Lycoming and Continental, are totally different, but use the same two different types of fuel systems. A few of them are used in training aircraft.

Fuel System types:

O – Opposed cylinders
IO – Fuel injected, instead of carbureted
T – Turbocharged
AE – Aerobatic
LIO – Left handed crankshaft (used on multi-engine aircraft)

The numbers represent the size of the cylinder bore and stroke in cubic-inches. For example, the 360 family of engines has a 361 cubic inch bore.

As a private pilot, you only need to be familiar with the fuel and cylinder type, but still good to know.

Engine Components:

The parts of spark ignition four-stroke reciprocating engine remains the most common design used in GA aircraft. The main parts are broken down:

Crankcase and accessory housing
Cylinders

The crankcase and the cylinders are attached to each other. Inside of the two pieces are:

Crankshaft
Connecting Rods
Piston

Attached to the outside of cylinder are:

Intake valve
Exhaust valve
Spark plug

NOTE: Keep in mind the engine, with no added accessories it is just called the engine. When the accessories are added to the engine it becomes known as the power plant, a few accessories would be: