(2)
Alternate Hydraulic Pressure Source
(a) The thrust reverser alternate hydraulic power source consists of a line connection to the standby hydraulic power system (Ref Chapter 29, Standby Hydraulic System).
C. When reverse thrust operation is selected, reverse thrust lever input is transmitted to the thrust reverser control cam, through the engine thrust shaft, by direct cable connection. The control cam, through the rocker arm, positions the control valve to route pressurized hydraulic fluid to either the stow or deploy ports as selected by the reverser thrust lever. The push-pull cable and follow-up controls provide thrust shaft lockout while the thrust reverser is in transit between thrust positions.
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2. Thrust Reverser Controls
A. Thrust Reverser Control Valve
(1) The thrust reverser control valve provides directional control for routing pressurized hydraulic fluid through the deploy or stow ports, as selected by the reverse thrust lever in the control cabin (Fig. 1). The control valve is actuated by the thrust reverser control cam on the engine thrust shaft (Fig. 1). When reverse or forward thrust is selected at the control stand, thrust shaft rotation repositions the control valve, and pressurized hydraulic fluid is routed through the valve to the appropriate port. The control valve is mounted to the engine control drum-and-shaft assembly support bracket at the wing front spar above the engine.
B. Thrust Reverser Control Cam
(1) The thrust reverser control cam transmits position input to the thrust reverser control valve from the thrust levers (Fig. 1). The control cam is splined to the engine thrust shaft at the drum-and-shaft assembly at the wing front spar and is located beneath the start and thrust quadrants on the shaft. When the forward or reverse thrust levers are operated, the thrust shaft is rotated and the control cam positions the control valve through a rocker arm.
C. Thrust Reverser Follow-up Controls
(1)
The thrust reverser follow-up controls consist of a shaft installation on which are installed the thrust reverser follow-up cam, control valve rocker arm, and a follow-up crank (Fig. 1). The shaft installation is supported between two flanges on the bracket that supports the engine controls drum-and-shaft installation at the wing front spar. The follow-up cam and follow-up crank are splined to opposite ends of the shaft. The rocker arm is supported by bearings on the shaft and is connected to the control valve piston. The follow-up crank is connected to the thrust reverser push-pull control.
(2)
The rocker arm transmits thrust reverser control cam rotation to the control valve, repositioning it to the selected thrust position (Fig. 1). The thrust reverser follow-up cam and crank transmit thrust reverser deflector door position indication from the thrust reverser push-pull control to the thrust shaft to lock out application of increased thrust until the deflector doors have reached the selected thrust position.
(3)
Maintenance practices for the thrust reverser follow-up controls shaft installation are covered in Chapter 76.
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D. Thrust Reverser Push-Pull Cable
(1) The thrust reverser push-pull cable transmits deflector door position to the engine thrust shaft to provide lockout of the shaft at a low thrust setting when the thrust reverser is in transit between thrust positions (Fig. 3). The push-pull cable is connected at one end to the guide carriage on the thrust reverser and at the opposite end to the thrust reverser follow-up controls at the engine control drum-and-shaft assembly (Fig. 1). The cable installation includes a push-pull cable, a pushrod, an idler link and a feedback control lever. The push-pull cable consists of two cable subassemblies joined at a quick-disconnect and enclosed in a conduit. The quick-disconnect facilitates removal and installation of the engine. A telescopic assembly is located at both ends of the cable. The forward telescopic assembly of the push-pull cable terminates the cable near the forward end of the engine firewall. The telescopic assembly rod end is connected at its rod end fitting to the idler link. The idler link is suspended at its pivot point from the engine firewall. The pushrod is also connected to the idler link and runs forward between the engine mounts to the thrust reverser follow-up shaft where it is connected to the follow-up crank. The cable runs in the conduit along the underside of the engine firewall to the thrust reverser. At the thrust reverser, the cable is connected to the lower arm of the feedback control lever. The upper arm of the feedback control lever is connected to the guide carriage through a feedback control rod. The quick-disconnect in the cable and conduit is located near the aft end of the cable in the engine midfairing area just forward of the thrust reverser tailpipe extension.
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