The RAT, located on the top of the fuselage, is an integral part of the hydraulic No. 2 system and supplies hydraulic power to the flying controls if an engine failure occurs.

The RAT is automatically extended whenever the No.2 system pressure falls below 103 bar. Indication that the RAT is functioning is given by the HYD 2 pressure gauge cycling between 160 and 210 bar as control column demands are made. When operating, the RAT pump recharges both its own and the No. 2 system flying controls accumulator.

The output of the RAT pump is dependent on airspeed. At sea level the pump develops maximum output at speeds in excess of 130 knots. At 105 knots the output is reduced to 75% of maximum.

Once the hydraulic No. 2 system is available and repressurised, the HYD 2 RESET button can be used to retract the RAT.

During engine shutdown, the RAT extends when No. 2 system pressure falls to 103 bar. When pressure has dissipated the RAT is retracted automatically by spring action and its bay doors close.

See page 25 of the manual for more information.