Function of the Lubrication System

The components that make up a piston engine are subjected to high loads, high temperatures, and high speeds. The component parts are generally made of metals, and as the moving parts of the engine slide against each other, there is a resistance to their movement. This is called Friction.

The Friction will increase as the load, temperature and speed increases, the movement of the components also produces Wear which is the loss or destruction of the metal components. Both Friction and Wear can be reduced by preventing the moving surfaces coming into contact by separating them with a material/substance which has lower frictional properties than the component parts. This is referred to as a Lubricant.

The oil can be forced between the moving parts, called Pressure Lubrication or the components can be Splash Lubricated.

The Primary task of the lubrication system of the engine is to Reduce Friction and component Wear. Secondary is the task of Cooling. The flow of oil through the engine helps to dissipate the heat away from the internal components of the engine.

As the oil flows through the engine it also carries away the by-products of the combustion process and cleans the engine. The internal metal components are protected against Corrosion by the oil, which also acts as a Hydraulic Medium reducing the shock loads between crankshaft and bearing and so reducing vibration. The oil can provide the power source for the operation of a hydraulic variable pitch propeller.

The oil system can be used to give an indication of the power being developed by the engine, and its condition. The oil system’s use as an Indicating Medium is of great importance to the pilot as it can give an early warning of mechanical failure or loss of power.

It should be remembered that an increase in Friction will cause an increase in Friction Horsepower, and therefore a reduction in the Brake Horse Power developed by the engine.

The Reduction in Friction and Wear by the lubricant is of prime importance, but the secondary functions of Cooling, Cleaning, Protection, Hydraulic and Indicating Mediums should not be ignored.

The purpose of engine oil in a piston engine is cooling, lubrication of the engine and disposal of fine abrasion.