RAT Hydraulic Pump
The RAT hydraulic pump is a two-stage pressure-compensated pump. It attaches to the aft face of the governor-generator assembly.
The pump flow rate is 10 gpm at 2850 psi.
RAT Strut
The trunnion mounted strut assembly attaches the governor-generator and hydraulic pump to the airplane. Electric and hydraulic lines are in the strut.
RAT Blade Lock Pin and Blade Locked Switch
The RAT blade lock pin behind the turbine locks the turbine blades in a vertical position when the RAT is more than 9 degrees from the extended position. This keeps the blades from turning until they are clear of the structure of the airplane. It also keeps the blades from causing damage to the airplane during retraction.
The RAT blade locked switch closes when the blade lock pin locks the turbine. This switch keeps the RAT from retracting more than 15 degrees unless the blades are locked by the blade index pin.
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RAM AIR TURBINE SYSTEM -RAT ASSEMBLY
RAT Strut Angle Switch
The RAT strut angle switch at the top of the RAT strut permits initial RAT retraction. The switch is closed between 0 and 15 degrees of the RAT extended position. It opens when the RAT is 15 degrees from the extended position to change retraction control to the RAT blade locked switch.
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777 AIRCRAFT MAINTENANCE MANUAL
RAM AIR TURBINE SYSTEM -RAT ASSEMBLY
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RAM AIR TURBINE SYSTEM -RAT ACTUATOR AND STOWED SWITCH
Purpose
The RAT actuator extends and retracts the ram air turbine assembly.
The RAT stowed switch gets RAT stowed position input for flight deck indication.
Physical Description
The RAT actuator is a spring-loaded hydraulic actuator. An internal spring extends the RAT. Hydraulic pressure retracts the RAT.
An internal mechanical lock keeps the actuator in the retracted position.
Two solenoids on the actuator unlock the actuator to extend the RAT.
Location
The RAT actuator and RAT stowed switch are in the RAT compartment aft of the right wheel well.
Functional Description
To extend the RAT, one or both solenoids are energized by a signal from any of these:
* HYDIM cards
*
ELMS
*
RAT manual switch.
This unlocks the actuator and the internal spring extends the RAT.
To retract the RAT, center system hydraulic pressure goes to the retract side of the RAT actuator. The RAT retracts and the internal lock keeps the actuator in the retracted position.
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RAM AIR TURBINE SYSTEM -RAT ACTUATOR AND STOWED SWITCH
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RAM AIR TURBINE SYSTEM -RAT CHECKOUT MODULE -INTRODUCTION
Purpose
The RAT checkout module controls the flow of hydraulic fluid to and from the RAT pump during RAT operation and during ground operational tests.
The RAT checkout module also controls the hydraulic flow to and from the RAT actuator during the RAT retraction.
Location
The RAT checkout module is on the aft bulkhead of the right wheel well. You access the RAT checkout module on the ground with the main landing gear doors open.
Physical Description
Eight hydraulic tubes of different sizes and locations connect to the RAT checkout module. Three of these are the center hydraulic system supply, pressure and return lines. Three hydraulic lines connect the RAT checkout module to the RAT pump for pump supply, pressure and case drain. Two hydraulic lines connect the RAT checkout module to the RAT actuator for RAT retraction and extension.
Two electrical connectors connect to the RAT checkout module. One connector is for the RAT pressure transducer and the other for the RAT stow valve switch and RAT module solenoid valve.
The RAT checkout module components visible from outside the module (some of which are LRUs) are these:
*
Pressure transducer (LRU)
*
Pressure and case drain filters (LRUs)
*
Start-up quantity bypass fuse (LRU)
*
RAT module solenoid valve (LRU)
*
RAT stow valve
*
RAT motoring valve.
Pressure Transducer
The pressure transducer measures the RAT pump output pressure and sends the data to a HYDIM card.
Pressure and Case Drain Filters
The two filters clean the RAT case drain and pressure hydraulic flow from the RAT pump. The filters are different sizes and replaceable cartridge type.
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