(2)
The PCAs continue to move in the commanded direction as long as the control lever is displaced from neutral. When more than one PCA is used on a single surface, movement is synchronized by adjustment of the control linkage. All control surfaces are moved by hydraulic power input to the PCAs. There is no reversion to manual movement.
E. Hydraulic Power Systems - Introduction (Fig. 4)
(1)
Three independent hydraulic systems are installed. System tubing is color coded for easy identification. The left is red, the center is blue, and the right is green. Each hydraulic system provides power for all essential flight control systems.
(2)
Three types of hydraulic pumps are used: Engine Driven Pumps (EDPs), Alternating Current Motor Pumps (ACMPs), and Ram Air Turbine (RAT). The EDPs are in the left and right systems. The ACMPs are in all three systems. The RAT is in the center system.
(3)
Other equipment and components for each system includes independent pressurized reservoirs, filters for each pump, and associated valves, gages, and sensors. Rated pressure of each system is 3000 psi. Fluid used is fire resistant BMS 3-11 Type IV, which is purple in color.
(4)
Components of the left system are in the hydraulic bay of the left engine strut. Components of the center system are in the right wheel well. Components of the right system are in the hydraulic bay of the right engine strut.
(5)
The system also uses a Power Transfer Unit (PTU) to drive the landing gear, flaps, and slats, which are normally driven by the left system. The PTU consists of a hydraulic motor, powered by the right system, which drives a hydraulic pump connected to the left system.
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Power Control Actuator Reaction
Figure 3
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LEFT SYSTEM
COLOR CODE - RED ONE EDP ONE ACMP RIGHT SYSTEM
COLOR CODE - GREEN ONE EDP ONE ACMP
CENTER SYSTEM
COLOR CODE - BLUE ONE RAT TWO ACMP'S
LEGEND:
ENGINE DRIVEN HYDRAULIC PUMP - EDP ALTERNATING CURRENT MOTOR PUMP - ACMP RAM AIR TURBINE - RAT
Hydraulic Power Systems - Introduction
Figure 4
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F. Hydraulic System - Simplified (Fig. 5)
(1) The left, center, and right hydraulic systems provide power for primary flight control systems: ailerons, rudder, elevators, flight spoilers, and autopilot. The right and center hydraulic systems provide power for the stabilizer trim system, and elevator feel (computer and actuator). The left and right hydraulic systems provide power for the thrust reversers, brakes, high lift devices, landing gear actuation, and nose gear steering. The right hydraulic system provides power for the ground spoilers.
(a)
Each system uses primary and demand pumps. Primary pumps run continuously. Demand pumps run when required.
(b)
The left and right systems use EDPs as the primary pumps. The center system uses two ACMPs as primary pumps.
(c)
The left and right systems use ACMPs as demand pumps which start when system pressure is low.
(d)
The center system has a RAT for emergency use if both engines fail in flight. The RAT provides hydraulic power for stabilizer trim, autopilot, ailerons, rudder, elevators, elevator feel, and spoilers.
(e)
All hydraulic systems have system pressure and temperature sensors. Each pump's pressure is monitored by an independent sensor. Check valves on each pumps output and return lines allow each system to maintain pressure when some of the pumps in the system are not operating. The left and right EDPs have fluid supply shut-off valves.
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