Aircraft APU-USA Aircraft Group Corporation

Date: 2025/3/4

I don't know if you have noticed a phenomenon, that is, there is a black hole in the tail of civil airliners. What on earth is this black hole and what is its use? Let's get to know it.
The black hole, known as Auxiliary power unit, or APU for short, is the auxiliary power system on the plane. From the outside of the plane, it looks like a black hole, but there is a lot of mystery inside. In fact, it is a small turbine engine, and now it has become an important device on the aircraft.
Although it is a "little", but its role is not small. It can provide air conditioning and power supply when the main engine is turned off, as well as compressed air and power to start the main engine.
The role in the air is even more important, when the main engine stops, the APU is the key component to restart it. When the engine fails, the APU is also the emergency generator that maintains the operation of some systems, allowing the instruments of the airliner to operate normally.
Do you still remember the movie Captain Sally, which is based on real events? Two minutes after US Airways 1549 took off, it was attacked by birds and both engines stalled. Captain Sally made up his mind and decided to make a forced landing on the Hudson River, and finally avoided the tragedy.
The APU on the plane was responsible for this incident, and the captain activated it in time in case of emergency, providing the necessary emergency power for flight control, instrument display and line protection, so that a passenger was rescued.
APU is the "key" to start the main engine. During take-off, the aircraft can reduce its dependence on airport power supply equipment, provide power for the cabin lighting and air-conditioning system, so that the main engine can use all its power to accelerate and climb on the ground, thus improving take-off performance.
After landing, APU still supplies electric lighting and air conditioning, so that the main engine is turned off early, thus saving fuel and reducing airport noise. This is the role of APU on the plane, it can be said that "the little one has a lot of energy."