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A
757
MAINTENANCE MANUAL
(2)
The Ram Air Turbine (RAT) is in the fairing aft of the right wheel well, from which it deploys downward into the slipstream. The RAT is extended and retracted by an electric motor. The swing arm, turbine, and pump are all one LRU.
(3)
The hydraulic service panel is aft of the right wheel well. It
provides a central capability to service all three system
reservoirs.
I. Hydraulic System Control Panel (Fig. 8)
(1)
The hydraulic system control panel is on the pilot's overhead panel P5. The panel incorporates the switches and indicators required for normal control and monitoring of the three hydraulic systems.
(2)
Each system has the following switches and indications:
(a)
System pressure, EICAS indicator (AMM 31-41-00)
(b)
System low pressure warning light (amber)
(c)
Primary pump overheat warning light (1 left, 2 center, 1 right) (amber)
(d)
Primary pump ON/OFF switch (1 left, 2 center, 1 right)
(e)
Primary pump low pressure warning light (1 left, 2 center, 1 right) (amber)
(f)
Demand pump low pressure warning light (amber)
(g)
Demand pump control switch
(h)
System quantity low warning light (amber)
(i)
System reservoir quantity, EICAS indicator (AMM 31-41-00)
(j)
System reservoir temperature, EICAS indicator (AMM 31-41-00)
SYSTEM LOW PRESSURE WARNING
SYSTEM LOW QUANTITY WARNING
EDP AND CENTER ACMP ON/OFF SWITCHES
PUMP LOW PRESSURE WARNING
PUMP OVERHEAT WARNING
LEFT AND RIGHT ACMP ON/OFF SWITCHES
PUMP LOW PRESSURE WARNING
PUMP OVERHEAT WARNING
Hydraulic System Control Panel
Figure 8
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757
MAINTENANCE MANUAL
(3)
The primary pump switch/lights are push-on/push-off type. When pushed on, the ON legend is illuminated white. The left and right switches control EDPs. The center switches control ACMPs.
(4)
The demand pump switches are also push-on/push-off switches. The left and right switches control ACMPs.
J. Hydraulic System Controls (Fig. 9)
(1)
Hydraulic Flight Control Panel
(a)
The hydraulic flight control panel on P61 contains three push-on/push-off switch/lights. Each switch controls a shutoff valve that selectively interrupts hydraulic power to the flight controls. The three switches isolate hydraulic power to the left, center, and right hydraulic systems.
(b)
The OFF position of the switch/light illuminates amber when pressed. Isolating hydraulic pressure to the selected areas aids in trouble shooting and allows maintenance without removing all hydraulic power.
(2)
Engine Ignition and Start Control Panel
(a)
The engine ignition and start control panel incorporates the ram air turbine (RAT) switch/light. Pressing the switch starts an electric motor that extends the RAT. The lower part of the switch/light marked UNLKD (unlocked) illuminates amber. The upper part marked PRESS illuminates green when the RAT is generating at least 1000 psi.
(b)
Retraction of the RAT is a ground operation. The turbine blades must be centered before the RAT can be retracted. Retraction is done electrically using a control panel in the right wing aft fairing.
(3)
Stabilizer Trim Hydraulic Power Cutout Switches
(a) Two stabilizer trim cutout switches (center and right) interrupt hydraulic power to stabilizer trim components in the tail. The switches are guarded to the NORM position. Positioning them to CUTOUT closes the cutout valves, which are part of the stabilizer trim control module. This enables trouble shooting and performance of ground maintenance on the stabilizer trim drive hydraulic motors without removing hydraulic system power.
K. Flight Control - Hydraulic Distribution (Fig. 10)
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