What is a Ram Air Turbine?

Ram Air Turbines (RATs) are emergency systems that, when deployed by an aircraft, use the force of the airstream to rotate a small propeller which creates electrical or hydraulic power. This emergency backup system offers flight controls the hydraulic power and electricity they need in case of engine loss. When both engines are lost and the electrical supply to the main busbars is cut off, the RAT will deploy in order to provide hydraulic power to the emergency electrical generator (EMER GEN).

Once the RAT is deployed, the EMER GEN supplies a limited amount of power to the most crucial systems on an aircraft, meaning the majority of the screens will be lost. What will remain are the primary flight displays belonging to the captain, while the ECAM will only be displayed on the Engine/Warning Display. The crew is able to review the quick reference handbook which will summarize the systems that are still available. Aside from the primary flight display, the only other systems available will be the number one navigation systems and radio communication on VHF1. Eventually, the EMER GEN disconnects so that the RAT is able to supply hydraulic power. It is important to note that the RAT cannot be retracted in the air once it has been deployed.

On Airbus S320 and A330 aircraft, the emergency electrical configuration occurs when the aircraft loses AC BUS 1 and 2, those of which are normally powered by electrical generators on each engine. When these losses occur, the RAT immediately deploys to offer hydraulic power to that EMER GEN, which then supplies electrical power to vital systems within the aircraft. The emergency electrical configuration reduces the number of available systems, such as the autopilot and flight director. With these systems and screens lost, the crew must manually fly the aircraft in question. Their main priority is to secure the aircraft and establish a safe flight path, and to do this, the crew uses the following protocol: aviate, navigate, and communicate. The term aviate refers to the fact that the aircraft uses primary flight display (PFD) in this situation, and the pilot in the left seat becomes in charge of flight. In terms of navigation, ILS1, VOR1 and GPS1 are all available to help make a safe landing. The VHF1 is the only communication form available at this point, so it is used to declare a mayday.

The ram air turbines on the Airbus A330 provide hydraulic pressure to the green hydraulic system, and in the case of dual engine failure, the RAT will provide for flight controls and the emergency generator. It is possible to manually deploy the RAT, but in the case of a dual engine failure, it will activate automatically. Meanwhile, the Airbus A320 RAT is deployed during a dual engine failure or grave electrical issue to supply power to the engines. These RATs are also able to be deployed manually if needed or automatically with the loss of both engines. They supply electrical power to the essential busses, the equipment required to land the aircraft, and the aircraft must slow down and shed unnecessary busbars to ensure a safe landing.

On August 24th, 2001, an Airbus A330 was flying from Toronto to Lisbon when four hours into the transAtlantic flight, a fuel line which supplied engine number 2 ruptured, causing a fuel leak. The crew was unaware of this development until they received a warning of fuel imbalance between the wings, so they performed a QRH procedure in order to balance it. This caused all fuel to be dumped, resulting in both engines losing power so that the RAT deployed, supplying necessary hydraulic power needed to drive the EMER GEN to achieve safe landing. This example proves the importance of Ram Air Turbines as emergency systems.

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1. mark jones
2. Posted on December 1, 2022
aviation

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