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 B.  When the airplane is on the ground, the RAT can be deployed and retracted with the RAT ground manual switch in the right wheel well. Prior to retracting the RAT, the propellor blades must be moved to align index marks on the hub and strut.
 C.  The RAT consists of a turbine and a hydraulic pump mounted on a hinged strut housing. The turbine consists of a hub with two propellor blades which are driven by the airstream. The RAT is deployed and retracted by the deployment actuator. The actuator retracts with hydraulic pressure and deploys with spring pressure.
 2.  Component Details (Fig. 1)_________________
 A.  RAT Strut
 (1)  
The RAT strut supports the hydraulic pump and turbine. The strut is pivoted at the upper end where it mounts to the airplane. Swivel valves at the top of the strut transfer fluid from the strut to the center hydraulic system. Internal passages in the strut carry fluid between the swivel valves and hydraulic pump.

 (2)  
A spring-loaded blade-lock plunger is mounted at the lower end of the strut. The plunger locks the turbine blades in the correct position for stowing the RAT. The plunger also prevents rotation of the blades until clear of the airplane during deployment. The plunger is actuated by a cable attached to a bracket on the outboard swivel valve. A blade index switch actuated by the plunger stops retraction of the RAT if the plunger does not engage the turbine hub.

 B.  Hydraulic Pump
 (1)  
The hydraulic pump supplies 11.3 gpm at 2140 psi. The pump flow is controlled by the output pressure. At 3025 psi the pump delivery flow is zero.

 (2)  
The pump can be used as a hydraulic motor to drive the turbine for a test of the governor. To back-drive the turbine, a valve in the checkout module reverses the fluid flow from the center hydraulic system. The system pressure is then used as a power source to drive the pump as a motor. In this mode, the pump drives the turbine in the normal direction. Prior to backdriving the turbine, a safety screen is installed which completely encloses the turbine blades for personnel protection. The safety screen must be removed before the RAT is retracted.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

RAT SAFETY VALVE SEE DSEEA
SEE B RAT CHECKOUTRAT ACTUATOR MODULE
CONTROL VALVE SEE E
SEE C FAIRING PANEL
RAT TACHOMETER RAT COMPARTMENT DOOR AND GROUND OUTBOARD WALL ACTUATION MANUAL SWITCH
FWD LINK
SEE F
RIGHT MAIN WHEEL WELL AFT BULKHEAD
A
DEPLOYMENT
ACTUATOR RAT COMPARTMENT ACCESS PANEL (198NZ)
SWIVEL VALVES
PIVOT BOLT (2 PLACES)
STRUT
BLADE LOCK PLUNGER
RAT
COMPARTMENT
DOOR

HYDRAULIC PUMP
TURBINE HUB
TURBINE BLADE
FWD INBD
B

Ram Air Turbine (RAT) System
Figure 1 (Sheet 1)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL

PRESSURE LINE
FROM SAFETY VALVE RIGHT SYSTEM
　
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