Page 17 D633W101-BEJ Sep 05/2002
RAM AIR TURBINE SYSTEM -RAT CHECKOUT MODULE -PHYSICAL DESCRIPTION
* MOTOR.
A lever controls the position of the valve. The valve is spring-loaded to the FLIGHT position.
In the FLIGHT position, the valve lets RAT pump pressure go to the center hydraulic system. In the MOTOR position, the valve permits center hydraulic system pressure to backdrive the RAT during ground operational tests.
Start-Up Quantity Bypass Fuse
The start-up quantity bypass fuse lets hydraulic fluid from the RAT pump go to the center system return during RAT start-up. This keeps the RAT unloaded during start-up to permit a faster RAT spin-up.
Filters and Check Valves
Two filters clean RAT case drain and pressure hydraulic flow.
The five check valves control the direction of the hydraulic flow.
Pressure Relief Valve
The pressure relief valve supplies over-pressure protection to the RAT system. The pressure relief valve starts to open at 3700-3900 psi.
Pressure Transducer
The pressure transducer sends RAT output pressure data to the HYDIM cards.
Thermal Bleed Orifice
The thermal bleed orifice lets approximately 0.3 gpm of hydraulic fluid through the RAT pump when the center hydraulic system is pressurized. This keeps the RAT hydraulic pump warm to reduce thermal shock when the RAT is extended.
EFFECTIVITY BEJ ALL 29-20-00
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D633W101-BEJ Sep 05/2002
RAM AIR TURBINE SYSTEM -RAT CHECKOUT MODULE -PHYSICAL DESCRIPTION
EFFECTIVITY BEJ ALL 29-20-00
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D633W101-BEJ Jan 05/2002
777 AIRCRAFT MAINTENANCE MANUAL
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Page 20 D633W101-BEJ Jan 05/2002
RAM AIR TURBINE SYSTEM -EXTENSION -FUNCTIONAL DESCRIPTION
General
A switch on the P5 overhead panel permits manual RAT extension. The HYDIM cards or the ELMS can automatically extend the RAT.
The extend signal supplies power to either or both of the solenoids on the RAT actuator. This unlocks the RAT and permits the spring in the actuator to extend the RAT.
As the RAT gets near the fully extended position, the blade lock pin releases the turbine. The airstream turns the RAT.
Power Sources
These sources can energize the RAT actuator solenoids:
*
APU battery bus
*
Hot battery bus
*
Captain’s flight instrument bus.
HYDIM Auto-Extension
The HYDIM cards CL and CR independently control the automatic RAT extension.
CR extends the RAT for these conditions:
*
Airplane is in the air mode
*
Airspeed or ground speed is more than 80 knots
EFFECTIVITY
BEJ ALL
* Both engines are below idle rpm and center hydraulic system pressure is low or (L,C, and R hydraulic system pressures are low).
CL automatic extension conditions are almost the same as CR. CL extends the RAT for these conditions:
*
Airplane is in the air mode
*
Airspeed or ground speed is more than 80 knots
*
Both engines are below idle rpm and center hydraulic system pump pressures are low or (left and right systems and center system pump pressures are low).
Both CL and CR energize one of the solenoids to unlock the RAT actuator.
ELMS Auto-Extension
The ELMS energizes the other solenoid on the RAT actuator to extend the RAT for these conditions:
*
Airplane in the air mode
*
Airplane not in the ground mode
*
Left and right transfer buses have lost electrical power for 15 seconds.
Manual Extension
The RAT manual switch on the hydraulic/RAT panel energizes both the solenoids on the RAT actuator to extend the RAT.
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RAM AIR TURBINE SYSTEM -EXTENSION -FUNCTIONAL DESCRIPTION
Indication
The RAT stowed switch in the RAT compartment sends a not-stowed signal to HYDIM CL when the RAT is not in the stowed position.
HYDIM CL turns on the RAT switch UNLKD light and sends a signal to the AIMS to show the RAT UNLOCKED advisory message.
EFFECTIVITY BEJ ALL 29-20-00
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