What is RAT on Boeing 777? (Ram Air Turbine)

When it comes to aviation, every aircraft is designed with caution and careful thought put into its systems and components. The Boeing 777, a popular wide-body airliner, is no exception. One of the crucial components of the Boeing 777 is the Ram Air Turbine (RAT). The RAT plays a vital role in ensuring the safety and functionality of the aircraft in emergency situations. In this article, we will delve deeper into what the Ram Air Turbine is and how it contributes to the overall performance of the Boeing 777.

The Importance of the Ram Air Turbine

The Ram Air Turbine (RAT) is a small yet powerful hydraulic device installed on the Boeing 777 aircraft. Its primary purpose is to supply emergency power to essential aircraft systems when other sources of power, such as the engines or auxiliary power units, are unavailable or fail. In critical situations, the RAT can be a lifesaver, providing vital power to important functions that are necessary for the safe operation of the aircraft.

Powered by the aircraft’s forward movement, the Ram Air Turbine operates based on the principle of ram air pressure. As the aircraft flies through the air, the RAT is deployed and harnesses the force of the oncoming air to generate hydraulic pressure. This pressure is then used to drive a hydraulic pump, which in turn powers systems like the flight controls, crucial avionics, and landing gear, among others. Essentially, the RAT acts as a backup power source, ensuring that essential functions can still operate even in the absence of primary electrical or hydraulic power.

Activation and Performance of the Ram Air Turbine

The Ram Air Turbine on the Boeing 777 is designed to automatically deploy when certain conditions are met. These conditions typically include an engine failure, a total loss of electrical power, or the failure of primary hydraulic systems. Once activated, the RAT extends from its stowed position under the fuselage of the aircraft and begins generating hydraulic power to sustain critical systems.

During its deployment, the Ram Air Turbine can produce a significant amount of power. For instance, it is capable of delivering up to 6,000 pounds of hydraulic pressure per square inch. This hydraulic pressure allows the RAT-driven pump to supply the necessary power to various flight controls, including the primary flight control surfaces like the ailerons, elevators, and rudder. Additionally, it ensures that the landing gear can be extended and retracted, which is crucial during takeoff and landing procedures.

Furthermore, the Ram Air Turbine also serves an essential function in providing power to the aircraft’s avionics systems. These systems include flight instruments, navigation equipment, and communication tools. The backup power supplied by the RAT ensures that pilots can maintain situational awareness and communication with air traffic control even in emergency situations where the primary power sources are unavailable.


The Ram Air Turbine (RAT) is a critical component of the Boeing 777 aircraft, providing emergency power to essential systems when other power sources fail. Its deployment and operation are automatic, ensuring that critical functions like flight controls, landing gear, and avionics can still be powered even in dire situations. The RAT’s ability to generate hydraulic pressure and supply power to various components makes it an indispensable safety feature of the Boeing 777. By understanding the role and functionality of the Ram Air Turbine, we can appreciate the engineering and design considerations that go into ensuring the safety and reliability of modern aircraft.

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