What is EDP on Boeing 777? (Engine Driven Pump)

The Boeing 777 aircraft is powered by two high-bypass turbofan engines, which generate the necessary thrust for flight. These engines are complex machines, relying on various components to function smoothly and efficiently. One such component is the Engine Driven Pump, commonly abbreviated as EDP. The EDP plays a crucial role in the aircraft’s hydraulic system, ensuring the proper functioning of vital systems such as landing gear, brakes, and flight controls.

The Importance of the Engine Driven Pump

To understand the significance of the Engine Driven Pump, we must first grasp the basics of the hydraulic system on the Boeing 777. This aircraft utilizes a hydraulic system composed of three independent systems: the primary system, the alternate system, and the standby system. These systems are responsible for different functions, ensuring redundancy and maintaining the overall safety of the aircraft.

The primary hydraulic system, which is powered by the engine-driven pumps, is the main source of hydraulic power for the aircraft. It operates under normal conditions and enables the precise control of various flight control surfaces, such as ailerons, elevators, and rudder. Additionally, it powers important mechanisms like the landing gear and brakes, ensuring their reliable operation during takeoff and landing.

In the event of an engine failure or other hydraulic system malfunction, the secondary hydraulic system, also known as the alternate system, engages. This system relies on an electric motor-driven pump to generate hydraulic power, providing a backup in case of primary system failure. The standby hydraulic system acts as yet another backup, utilizing a hand pump to create hydraulic pressure in case both the primary and alternate systems are compromised.

The Engine Driven Pump plays a critical role in the overall operation of the hydraulic system. It is responsible for providing the necessary hydraulic pressure to power the primary system, ensuring the smooth movement of flight control surfaces and the operation of vital components. Without the EDP’s continuous supply of hydraulic power, the aircraft’s maneuverability and safety would be severely compromised.

The Functioning of the Engine Driven Pump

Now that we understand the importance of the Engine Driven Pump, let’s delve into its functioning. The EDP is typically located within the aircraft’s engine nacelle, which houses the engine and various auxiliary components. It is directly driven by the engine’s accessory gearbox, drawing power from the rotation of the engine itself. This mechanical drive ensures a constant and reliable supply of hydraulic power, unaffected by electrical or other external factors.

The Engine Driven Pump consists of several essential components, including an impeller, a shaft, a housing, and various valves. As the engine rotates, the impeller within the pump starts spinning rapidly, creating a vacuum that draws hydraulic fluid into the pump. The fluid then flows through a series of valves and passages, which increase its pressure before it is distributed to the various parts of the hydraulic system.

The EDP is designed to operate within specific pressure and flow rate limits, ensuring the hydraulic system receives the optimal supply of power. Additionally, the pump incorporates various protective features to prevent damage or failure. For instance, if the pressure exceeds the specified limit, a relief valve opens, allowing excess fluid to bypass the pump and maintain safe operating conditions.

The reliability and efficiency of the Engine Driven Pump are crucial not only for normal flight operations but also in emergency situations. For example, during an engine failure, the EDP continues to operate, providing hydraulic power to the primary system. This ensures that the aircraft can maintain control and execute critical maneuvers even with one engine out of operation.


The Engine Driven Pump is an integral component of the Boeing 777’s hydraulic system, supplying hydraulic power essential for the reliable operation of flight control surfaces, landing gear, and brakes. Its mechanical drive, driven by the engine’s rotation, ensures a continuous and consistent supply of hydraulic pressure. With redundant hydraulic systems, including the primary, alternate, and standby systems, the EDP provides a vital layer of safety and functionality to the aircraft.

Understanding the role and functioning of the Engine Driven Pump on the Boeing 777 enhances our appreciation for the complex systems that enable safe and efficient air travel. This critical component exemplifies the engineering marvels that go into building an aircraft capable of crossing continents and connecting the world.

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