RAT Deployment and Stowage

Question

In this question, it states that the ram air turbine (RAT) deploys automatically on Airbus aircraft when there is a dual engine failure. Is there a way to stow the RAT in case systems are recovered and the RAT is no longer needed while the aircraft is airborne or does it have to be stowed by ground personnel? Are there differences between Boeing and Airbus aircraft insofar as deployment and stowage are concerned?

Answer 1

The RAT is typically deployed using a spring loaded lever and cannot be stowed in flight. See this question for more details on deployment: How do Ram Air Turbines get deployed?

There is no fundamental difference between the implementations of Airbus, Boeing or Bombardier. I will quote some relevant sections of a few flight manuals here:

• Airbus A320:

  Ram Air Turbine (RAT)

  A drop-out RAT coupled to a hydraulic pump allows the blue system to function if electrical power is lost or both engines fail. The RAT deploys automatically if AC BUS 1 and AC BUS 2 are both lost. It can be deployed manually from the overhead panel. It can be stowed when the aircraft is on the ground.

  ^{(Airbus A320 FCOM - Hydraulic Description, italic emphasis mine)}

• Boeing 777:

  Ram Air Turbine (RAT)

  The RAT, when deployed, provides hydraulic power only to the primary flight control components connected to the center hydraulic system. The RAT provides hydraulic and electrical power throughout the flight envelope. In flight, the RAT deploys automatically if:

  • both engines are failed and center system pressure is low, or
  • both AC transfer busses are unpowered, or
  • all three hydraulic system pressures are low

  The RAT can be deployed manually by pushing the RAM AIR TURBINE switch. The hot battery or APU battery bus must be powered. The RAT is deployed by a compressed spring. Once deployed, the RAT cannot be stowed in flight.

  ^{(Boeing 777 FCOMv2 - 13.20.3 Hydraulics - System Description, italic emphasis mine)}

• Bombardier CRJ:

  Air Driven Generator (ADG)

  In the event of a complete AC power failure in flight, the ADG will automatically deploy and supply emergency AC power to the ADG bus and to the AC essential bus. If the automatic deploy function fails, the ADG can be deployed manually by pulling the ADG manual release handle on the ADG CONTROL control panel at the rear of the center console. [...]

  The ADG cannot be restowed in flight. It is restowed manually, on the ground, by maintenance personnel.

  ^{(Bombardier CRJ FCOM - Electrical - AC Electrical System, italic emphasis mine)}

To stow the A320 RAT on the ground, the blue hydraulic system must be pressurized (via the electric pump) and the RAT EXTN SOL1 circuit breaker must be pulled. The RAT control panel is on the blue ground service panel. The RAT is stowed with STOW switch like this:

^{(YouTube: AIRBUS A320 RAM AIR TURBINE EXTENTION)}