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T10035 RIGHT SLEEVE LVDT M7198 ELECTRONIC ENGINE CONTROL
Thrust Reverser Indicating Smplified Schematic - Eng 1 Figure 2 (Sheet 2)
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
(1) Indication System for the Thrust Reverser Position
(a)
When reverse thrust is selected, hydraulic pressure is provided to the hydraulic actuators. The hydraulic pressure unlocks the locking hydraulic actuators from the stowed position and causes the actuators to translate the thrust reverser sleeve aft.
(b)
The target mounted on the lockout lever for the locking actuator moves away from the proximity sensor for the actuator lock as the actuator translates the sleeve. This target far condition generates a logic 0 output from the proximity sensors.
(c)
The deploy proximity sensors are in a target far condition (logic 0) when the thrust reverser is stowed or in transit. This will change to a target near condition (logic 1) as the actuator drives the feedback screw target toward the deploy proximity sensor as the reverser reaches the fully deployed position.
(d)
Output from all four proximity sensors is directed to two OR gates. Each OR gate has four inputs; two normal logic and two reverse logic. The normal logic inputs retain the logic of its inputs, a logic 1 remains logic 1 and logic 0 remains logic 0. The reverse logic input reverses the input; a logic 1 input changes to logic 0 and logic 0 changes to logic 1.
(e)
For the condition where the thrust reverser is in transit to the fully deployed or stowed position, the proximity sensors output is logic 0 (target far). Both OR gates output logic 1 to an AND gate. The AND gate produces a logic 1 output resulting in a REV amber EICAS message.
(f)
For the condition where the thrust reverser is fully deployed, the output from the proximity sensors for the actuator lock is logic 0 (target far) while the deploy proximity sensors output is logic 1 (target near). Outputs from one OR gate is logic 1 while the other outputs logic 0. The AND gate output from these inputs is logic 0 which will not produce any EICAS message. The output from both deploy proximity sensors is directed to an AND gate. Therefore, when the thrust reverser is fully deployed, the logic 1 output from this AND gate produces a REV green EICAS message.
(g)
For the condition where the thrust reverser is stowed, the output from the proximity sensors for the actuator lock is logic 1 (target near) while the deploy proximity sensors is logic 0 (target far). Outputs from one OR gate is logic 0 while the other outputs logic 1. The AND gate output from these inputs is logic 0 which will not produce any EICAS message. The output from both deploy proximity sensors is logic 0 which does not produce an EICAS message.
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(2) Fault Indication System of the Isolation Valve for the Thrust Reverser
(a)
Moving the reverse thrust levers aft provides power to the thrust reverser solenoid and the T/R HYD ISOL VLV relays. The solenoid causes the isolation valve to pressurize the reverser hydraulic system which actuates the valve pressure switch. The T/R HYD ISOL VLV relay energizes to the deploy position. With the air/gnd relays in the gnd position, the T/R ISOL DETECT relay remains energized which prevents EICAS messages.
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