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Tuesday, September 18, 2012

Aviation Knowledge 2


Today let us talk about aircraft's Auxiliary Power Unit. Ever wondered without the engines running at the gate, how does the aircraft receive electricity for the lighting and also air-con when you are boarding the aircraft?

This is because at the tail section of the aircraft, there is this little magical unit called the APU in short that can provide not only electricity but also compressed air that drives the air-con when the engines are not running.

Auxiliary Power Unit (APU)

After the door is closed and aircraft starts to push back, you will notice the engine will be started at this time and soon after, a flicker of the lights in the cabin will occur. This is the time when the engine's generator kicks in and take over the load from the APU generator to provide electricity. So after the second engine start, normally the APU will be shut down at this time and compressed air will be provided by the engines to sustain the air-con. The APU will be left off until the aircraft reaches its destination and the APU will be turn on again when the aircraft reaches the gate before the engines are shut down.

What happens if the APU is down and not working? How does the aircraft gets electricity and air con at the gate then? There are 2 equipments called the Ground Power Unit and Ground Air Unit which could also be attached to the aircraft to provide both electricity and air-con.

Ground Power Unit

The next time you board an aircraft you will have a better understanding of how the APU works and try spotting the Ground Power Unit too!