Air Start Service Equipment

An air start unit is a power source used to give the primary rotation to start big engines. This system is used to start large diesel and gas turbine engines. Diesel engines have very high compression rations to offer reliable and complete ignition of the fuel without spark plugs. A powerful electronic starter is enough to start this large engine. While starting the engine, compressed air is admitted to any cylinder that  has a piston just over the top dead center, that is used to forcing it downward. Once the engine starts to turn, the air start valve on the next cylinder in line opens to continue the rotation. 

Another method of air starting an engine is by using compressed gas to drive a fluid motor in place of an electronic motor. They can be used to start large sized engines and if more starting power is needed, two or more motors can be used. An air starter on a turbine engine would typically consist of a radial inward flow turbine or axial flow turbine, which is connected to the high pressure compressor spool through the accessory gearbox. Compressed gas is provided to the system by bleed air from the aircraft’s compressor situated on ground support equipment. 

In comparison of, electric starters, air starters have a higher power to weight ratio. The wiring of electric starters can become very hot if it takes longer than expected to start the engine. On the other hand air starters can run as long as their air supply lasts. Turbine starters are very simple and they are a natural fit for turbine engines. They are comprehensively used on big turbofan engines used on commercial and military aircraft.

So, these are the airstart unit equipments and their functions.