C.  
The upper EICAS display in the flight compartment gives the following messages for the applicable engine; REV amber to indicate the reverser is no longer stowed and is in transit to the deployed position. REV green indicates the reverser is fully deployed.

 D.  
Each proximity sensor is driven by a periodic pulse, generated in the PSEU. The pulse is used to measure the inductance of the sensor such that with the target near, the inductance increases. For target far, the inductance decreases.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
SEE  A 
FEEDBACK LVDT FOR THE THRUST REVERSER  SENSOR PROXIMITY ACTUATOR 
SCREW FEEDBACK  LOCK LEVER 

TARGET
DEPLOY
PROXIMITY
SENSOR

FWD
CENTER LOCKING HYDRAULIC ACTUATOR
A
Proximity Sensor Description Figure 1
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
E.  When a specific inductance is measured, the PSEU proximity channel output changes state. The output is represented as follows; target near equals logic zero (0), target far equals logic one (1). The PSEU output is processed through OR gates, supplying a normal or reverse logic to an AND gate. An AND gate logic 1 generates an EICAS display message.
 3.  Fault Indicating System of the Isolation Valve for the Thrust Reverser______________________________________________________________________ (Fig. 1)
 A.  The fault indication circuit for the isolation valve consists of a pressure switch (S1683, S1684, S1685, S1686) mounted on the isolation valve, hyd isolation valve relay (R7375, R7376, R7377, R7378) controlled by the reverser control system. Two air/gnd relays, a disagree relay (R7371, R7372, R7373, R7374) controlled by one air/gnd relay, and an isolation detect relay complete the circuit.
 B.  De-energizing of the isolation detect relay (R7367, R7368, R7369, R7370) provides a ground to the EICAS which after a two second time delay illuminates the ENG REV DISAGREE EICAS warning and ENG REV DISAGREE maintenance messages.
 C.  The ENG REV DISAGREE EICAS warning indicates that a failure in the control system for the thrust reverser may result in a reverser deployment if the reverse thrust lever is actuated in flight, or that a reverser may not deploy when commmanded on the ground.
 4.  Linear Variable Differential Transformer (LVDT) for the Position Feedback of____________________________________________________________________________ the Thrust Reverser (Fig. 1)___________________
 A.  Movement of the thrust reverser actuators and translating sleeves is transmitted electrically to Electronic Engine Control (EEC) by four LVDTs. The Electronic Engine Control uses reverser position to determine interlock actuator command for the thrust lever and maximum allowable engine thrust when reverser is in a non-commanded position.
 B.  One LVDT (T10033,T10035) is located on each center locking hydraulic actuator. The LVDT has a primary (Ch A) and secondary (Ch B) feedback channel to each EEC and receives its excitation signal from each EEC. The actuator feedback rod operates the LVDT. Further information on the EEC/thrust reverser feedback LVDT operation can be found in Fuel Control System (Ref 73-21-00/001).
 C.  The feedback rod on the center actuators retracts as the actuators extend. The rod travels 3.5 inches for 21.75 inches of piston travel. The feedback rod extends and retracts utilizing the same acme screw nut mechanism as the rotary flexshafts.
 5.  Operation
_________
 A.  Functional Description (Fig. 2)
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