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ENG START/RAT CONTROL PNL
Ram Air Turbine Schematic
Figure 2 (Sheet 1)
A
B
C
D
EFG
A
757
MAINTENANCE MANUAL
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A
757
MAINTENANCE MANUAL
CLOSEDCLOSECENTER
A
NORMAL
SYSTEMHYD
M
FROM CENTER
HYD RESERVOIR
BOPEN
C(FROM SH 1) P
D FROM RATEF
OPEN DEPLOYMENT
BACK DRIVE
RAM AIR TURBINE RETRACTSW (SH 1)
CONTROL VALVE RAT HYDLOCK
PRESS D
RAT UNLOCKED (Y)
RAT (W) RIGHT
HYD
SYSTEM
L/R EICAS CMPTR
DEPLOY
RAT MECH
RAT SAFETY
EXT/HYD
VALVE
RETRACT ACT RAT CHECK OUT MODULE
E<14.5`
FG LAMPTEST
>15`
RAT STRUT INDEXOVER
15 DEG SWITCH
RAT MUST
BE RUNNING
R
>13.5`
L
LOCKED
SPEED
GOVG FREQUENCY
L
SWITCHING
UNLOCKEDSPEED
LOGIC
RAT BLADE INDEX13 DEG SWITCH RAT TACH IND RATPUMP TACHOMETERSUPPLY
GENERATOR
RETURN
PRESSURE RAM AIR TURBINE
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Ram Air Turbine Schematic
Figure 2 (Sheet 2)
A
757
MAINTENANCE MANUAL
(c)
The RAT can also be deployed with the RAT deployment switch on the pilot's overhead panel P5. This switch energizes the manual deploy solenoid to unlock the deployment actuator.
(d)
When unlocked, the actuator deploys the RAT by spring force. The blade-lock plunger unlocks the turbine hub as the RAT deploys. The stowed limit switch moves to the not-stowed position and turns on the RAT UNLOCKED light on the pilot's overhead panel P5. A RAT UNLOCKED message also appears on the EICAS display. The force of the airstream rotates the turbine blades to drive the hydraulic pump. A governor in the hub varies the pitch of the blades to control turbine speed.
(e)
Fluid is supplied to the hydraulic pump from the reserve supply outlet on the center system reservoir. The reserve supply outlet draws fluid from the bottom of the reservoir to allow use of a reserve amount of fluid retained there for use only by the RAT pump, by a standpipe on the ACMP supply outlet. Pressure and case drain flow from the pump enters the center system through filters in the checkout module. Pump pressure closes the checkout module pressure switch and turns on the RAT pressure light on panel P5.
(2) Ground Deployment
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