RAT CHECKOUT MODULE
E
FWDFAIRING PANEL
RAT TACHOMETER AND
GROUND CHECKOUT MODULE
F
Ram Air Turbine (RAT) System
Figure 1 (Sheet 2)
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29-21-00
ALL ú ú 01 Page 3 ú Jun 15/83
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
C. Turbine
(1)
The turbine consists of a hub with two propellor blades. The hub is connected to the hydraulic pump by a driveshaft. The blades are attached to a mechanical governor in the hub. The governor varies the blade pitch angle to control the turbine speed.
D.
Deployment Actuator
(1)
The deployment actuator is a hydraulic cylinder attached to airplane structure and to the RAT strut. The actuator moves the strut between the deployed and retracted positions. Right hydraulic system pressure drives the actuator to the retracted position where it is held by an internal mechanical lock. The actuator is driven to the deployed position by springs which compress during retraction. The actuator is unlocked by either of two solenoids, one for manual deployment and one for automatic deployment. Hydraulic fluid from the actuator flows into the right system return line as the RAT deploys.
E.
Actuator Control Valve
(1)
The control valve connects the deployment actuator to either the right system return line or to the RAT safety valve. The valve is on the fuselage skin inside the aft right wing/body fairing. The two-position valve is operated by a 28-volt dc motor which is controlled by the RAT ground manual switch. The actuator pressure port is normally connected to the right system return line. For deployment or retraction with the RAT ground manual switch, the actuator pressure port is connected to the RAT safety valve.
F.
Safety Valve
(1)
The safety valve is on the aft wall of the right main wheel well. The valve is a three-position valve operated by two 28-volt dc solenoids. The valve solenoids are controlled by the RAT ground manual switch. In the retraction position, the valve connects right system pressure to the deployment actuator pressure port. In the deployment position, the valve connects the actuator pressure port to the right system return line. In the off position, the valve blocks flow from the actuator pressure port to stop actuator movement.
G.
Checkout Module
(1)
The checkout module is on the aft wall of the right main wheel. The module contains a back-drive valve, filters, pressure switch, check valves, and a volumetric fuse cartridge valve. The module is used to check the operation of the RAT with the airplane on the ground.
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