Have you ever heard about APU? It’s an auxiliary generator commonly found on large aircrafts to run their electrical systems even with engines are switched off.
Having been trained in the Aeronautical Construction sector, I personally found it interesting to expand the application and the use of two devices frequently found in the aeronautical sphere which are APU and GPU
APU
Auxiliary Power Unit.
The use of APU has been banned in many airports due to the noise they generate once activated. Imagine all the operators approaching the aircraft for the various activities, using ramps, unloading luggage, assistance services, and for many hours they must be near an APU in operation!
GPU, Ground Power Unit is in effect an electric generator. . It is used in airports to power an Airplane or a Helicopter when it is stationed on the ground with the engines turned off.
It is characterized by a range of voltages, currents and frequencies that are not used in other applications 28VDC o 115VAC, 400Hz depending on the type of aircraft
Why using the GPU
Keeping the engine running on an airplane has very important costs even when it does not produce the necessary energy for take-off.
To understand the difference between the consumption of a diesel-powered GPU and the engine of an airplane, a Boeing 757 for instance, powered by Kerosene, we consider that the latter will consume in 1 hour what the GPU will consume in 24 hours. Approximately 270 liters
I'm starting the APU. When a generator set saves lives
US Airways Flight 1549 - 15: 27: 21.3 HOT-1 “I'm starting the APU”
An APU produced by Honeywell has contributed with Captain Sullenberger's intrepidity in saving the lives of US Airways Flight 1549, which with both engines in failure, made an emergency landing on the Hudson River.
The 131-9A Auxiliary Power Unit (APU), friendly called U9A, is installed in the tail section of the Airbus A320.
After both engines got stuck due to the impact with a flock of Geese, U9A intervened by feeding the on board devices to temporarily hold in position the flight controls, displays and other sensitive and necessary equipment on the fly.
Had it not been for the APU, Captain Sullenberger could not have landed in the Hudson River at the lowest possible speed and saved all those lives.