What is CSM/G on Airbus A320? (Constant Speed Motor/Generator)

The Constant Speed Motor/Generator (CSM/G) is a critical component of the Airbus A320 aircraft. It plays a crucial role in maintaining the balance and stability of the aircraft’s power system. The CSM/G is responsible for regulating and providing electrical power to various systems on board the aircraft, including the avionics, flight control systems, lighting, and more.

As the name suggests, the CSM/G is designed to operate at a constant speed, which ensures a stable and reliable power supply to the aircraft. It consists of a motor and a generator, combined into a single unit. The motor function of the CSM/G helps propel the aircraft during takeoff, while the generator function provides electrical power to the aircraft’s systems.

How Does the Constant Speed Motor/Generator Work?

The CSM/G operates on a unique principle known as the constant-speed drive system. This system allows the motor and generator to rotate at a constant speed, regardless of the aircraft’s engine speed. This ensures that the electrical power generated by the CSM/G remains stable and uninterrupted, even during changes in engine speed or aircraft load.

When the aircraft’s engines are running, they drive the CSM/G’s motor, which helps propel the aircraft during takeoff. At the same time, the motor also drives the generator, which generates electrical power. This power is then distributed to various systems on the aircraft through electrical buses.

During the cruise phase of the flight, the CSM/G continues to rotate at a constant speed, even if the engines are operating at a different speed. This ensures a stable power supply to the aircraft’s systems and prevents fluctuations or interruptions in the electrical power.

The Importance of the Constant Speed Motor/Generator on the Airbus A320

The CSM/G plays a vital role in ensuring the safe and efficient operation of the Airbus A320 aircraft. Its constant speed operation allows for consistent electrical power supply to critical systems, such as flight controls, navigation, and communication systems. This helps maintain the stability and control of the aircraft during all phases of flight.

Additionally, the CSM/G contributes to the overall fuel efficiency of the aircraft. By providing a stable power supply, it reduces the need for additional power generation or backup systems, resulting in lower fuel consumption. This not only reduces operating costs for airlines but also helps limit the environmental impact of the aircraft.

Furthermore, the CSM/G enhances the reliability and resilience of the aircraft’s electrical system. Its constant speed operation ensures uninterrupted power supply, even in the event of engine failures or other electrical system malfunctions. This redundancy and backup capability are essential for the safety and continued operation of the aircraft.


The Constant Speed Motor/Generator (CSM/G) is a critical component of the Airbus A320 aircraft, providing a constant speed power supply to various systems on board. Its unique design and operation ensure stability, reliability, and fuel efficiency for the aircraft. The CSM/G’s importance in maintaining the safe and efficient operation of the aircraft cannot be overstated.

For More: What is BSCU on Airbus A320? (Brake Steering Control Unit)