What is APU on Airbus A330? (Auxiliary Power Unit)

The Airbus A330, a twin-aisle wide-body aircraft, is known for its reliability, efficiency, and versatility. It has been widely used in both passenger and cargo transportation. One of the key components that contribute to the operational capabilities of the Airbus A330 is the Auxiliary Power Unit, commonly referred to as the APU. In this article, we will explore the significance and functions of the Auxiliary Power Unit on the Airbus A330.

The Importance of the Auxiliary Power Unit

The Auxiliary Power Unit plays a crucial role in the operation of the Airbus A330, providing power in various scenarios. Whether on the ground or during flight, the APU ensures reliable and continuous power supply for critical systems, enhancing the overall performance and safety of the aircraft.

Ground Operations

During pre-flight preparations and on the ground, the APU serves as an independent and self-contained power source. It supplies electrical power to the aircraft, enabling essential systems such as lighting, avionics, and cabin conditioning to function without relying on external power sources. This is particularly important at airports where power availability may be limited or when the aircraft is operating in remote locations where external power supply might not be accessible.

The APU also provides the necessary pneumatic power to start the engines of the Airbus A330. It generates the required airflow and pressure to initiate the ignition sequence in the engines, allowing them to be started even when the main engines are not running. This not only saves fuel but also reduces wear and tear on the main engines, improving their lifespan and overall operational efficiency.

Furthermore, the APU allows for the use of electrical and air conditioning systems while the aircraft is on the ground, ensuring the comfort and convenience of passengers and crew. It maintains a suitable temperature in the cabin, facilitating a pleasant environment for both boarding and disembarking.

In-Flight Operations

The Auxiliary Power Unit continues to play a vital role during the flight of the Airbus A330. While the main engines provide the primary source of power, the APU functions as a backup power generator, ensuring uninterrupted operation of critical systems.

One of the significant functions of the APU during flight is to provide electrical power for essential avionics and flight instruments. It ensures the continuous operation of critical flight systems, including autopilot, navigation equipment, communication devices, and flight control computers. In the event of a failure or power loss in the main engines, the APU can instantly assume the role of the primary power source, preventing any disruptions in the flight operation and allowing the pilots to maintain control of the aircraft.

Moreover, the APU assists in maintaining a suitable cabin environment during flight. It supplies air conditioning and pressurization systems, which are responsible for regulating the temperature, airflow, and pressure within the cabin. This ensures the comfort and well-being of passengers and crew throughout the flight.

In addition, the APU’s pneumatic power capability allows for the operation of various systems that require compressed air, such as the anti-icing system. It prevents the formation of ice on critical surfaces, such as the wings and engine inlets, enhancing the safety of the aircraft during flight in icy or cold conditions.

Technical Specifications of the Auxiliary Power Unit

The Auxiliary Power Unit on the Airbus A330 is a gas turbine engine located at the tail section of the aircraft. It is typically supplied by a separate fuel tank, ensuring an independent fuel source. The APU is capable of delivering electrical power, pneumatic power, and hydraulic power.

The electrical output of the APU ranges from 90 to 120 kVA (Kilovolt-Amperes), providing sufficient power for the aircraft’s electrical systems. The pneumatic output, measured in pounds per square inch (psi), typically ranges from 30 to 50 psi to ensure optimal operation of various systems. Additionally, the APU generates hydraulic power to drive hydraulic pumps, contributing to the operation of the aircraft’s hydraulic systems.

The APU also features an automatic start and shut down system, which can be controlled from the cockpit. It is designed to automatically start when certain conditions are met, such as low electrical power or demand for compressed air. Similarly, it can automatically shut down after a specified period of inactivity or when the main engines are started.

Notably, the APU is equipped with various safety features to ensure its reliable and safe operation. It is capable of self-monitoring, detecting any abnormalities or malfunctions, and initiating appropriate actions, such as an automatic shutdown, to prevent further issues. This contributes to the overall safety and efficiency of the Airbus A330.


The Auxiliary Power Unit (APU) plays a critical role in enhancing the operational capabilities and safety of the Airbus A330. Whether it is providing power during ground operations or serving as a backup power source in-flight, the APU ensures uninterrupted operation of vital systems, contributing to the overall efficiency and reliability of the aircraft. Its ability to generate electrical, pneumatic, and hydraulic power makes it a vital component in enabling the Airbus A330 to perform at its best in various conditions and environments.

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