What is APU on Airbus A320? (Auxiliary Power Unit)

The Auxiliary Power Unit (APU) plays a crucial role in the overall operation of an Airbus A320 aircraft. This small but powerful device is responsible for providing electrical power and compressed air to various systems on the aircraft, both on the ground and in flight. The APU is a self-contained unit located at the tail of the aircraft, and it serves as an independent source of power to ensure that essential functions can be performed even when the main engines are not running. Let’s dive deeper into the functionalities and significance of the Auxiliary Power Unit on the Airbus A320.

Functionality of the Auxiliary Power Unit

The Auxiliary Power Unit on the Airbus A320 is essentially a small gas turbine engine, similar to the main engines but with a lower power output. It is typically used during ground operations to power the aircraft while it is stationary, such as when preparing for departure or after landing. Additionally, the APU provides backup power in case of emergencies, and it allows for the operation of essential aircraft systems when the main engines are not running, such as during engine start-up or in the event of engine failure.

One of the primary functions of the APU is to supply electrical power to the aircraft’s electrical systems. This includes lighting, avionics, and communication systems, among others. The electrical power generated by the APU is essential for maintaining the functionality of these systems, both on the ground and in flight. It ensures that critical instruments and equipment are operational, contributing to the overall safety and efficiency of the aircraft.

In addition to electrical power, the APU also provides compressed air to various systems on the aircraft. This includes air conditioning, pressurization, and engine starting. The compressed air is used to operate the air conditioning packs, which cool and condition the air inside the cabin and cockpit. It also helps maintain the desired pressure inside the aircraft, ensuring a comfortable and safe environment for passengers and crew.

Significance of the Auxiliary Power Unit

The Auxiliary Power Unit is a critical component of the Airbus A320, offering several advantages that enhance the overall functionality and safety of the aircraft. Firstly, it provides an independent source of electrical power. This autonomy is crucial during ground operations, where relying solely on external power sources may not always be feasible or reliable. Having an onboard power supply ensures that the aircraft can maintain its essential systems and functions, even in remote or challenging environments.

The APU also enables quicker and more efficient engine starts. By providing compressed air to the engines, the APU assists in spinning the engine turbines, allowing for a faster ignition process. This reduces the time required for engine start-up, which is particularly important during ground operations, where expediency is vital for maintaining flight schedules. Additionally, in the event of an engine failure, the APU can provide the necessary power to operate critical systems, giving the pilots more control and flexibility in navigating the situation.

Furthermore, the APU contributes to fuel efficiency and cost savings. Instead of running the main engines for all electrical and air supply needs, the APU can handle these requirements at a much lower fuel consumption rate. This significantly reduces fuel consumption during ground operations, as well as on short flights or during taxiing on the runway. By optimizing fuel usage, the APU supports a greener and more sustainable aviation industry.


The Auxiliary Power Unit (APU) is an integral part of the Airbus A320 aircraft, providing essential electrical power and compressed air to the various systems on board. Its functionalities, such as supplying power during ground operations and backup power in emergencies, enhance the overall safety, efficiency, and autonomy of the aircraft. The APU also supports quicker engine starts, contributes to fuel efficiency, and reduces operational costs. This compact but powerful device plays a significant role in ensuring the smooth operation of the Airbus A320, contributing to a superior flying experience for passengers and crew alike.

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