(2)  
71-11-04/201, Fan Cowl Panels

 (3)  
71-11-06/201, Core Cowl Panels

 (4)  
78-31-00/201, Thrust Reverser System

 B. Access
 (1)  
Location Zone
 412 Engine 1 - HPC Case 10:00 o'clock
 422 Engine 2 - HPC Case 10:00 o'clock
 432 Engine 3 - HPC Case 10:00 o'clock
 442 Engine 4 - HPC Case 10:00 o'clock

 (2)  
Access Panel
 415 Left Thrust Reverser Half - Engine 1
 425 Left Thrust Reverser Half - Engine 2
 435 Left Thrust Reverser Half - Engine 3
 445 Left Thrust Reverser Half - Engine 4

 C. Prepare to Activate the PRV
 S 862-008
 (1) Release the pressure in the pneumatic system (Ref 36-00-00/201).
 S 042-022
 WARNING: DO THE DEACTIVATION PROCEDURE FOR THE THRUST REVERSER TO
_______ PREVENT THE OPERATION OF THE THRUST REVERSER. ACCIDENTAL OPERATION OF THE THRUST REVERSER CAN CAUSE INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT.
 (2)  Do the deactivation procedure for the thrust reverser for ground maintenance (Ref 78-31-00/201).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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747-400
MAINTENANCE MANUAL

 S 012-023
 (3)  
Open the left fan cowl panel (Ref 71-11-04/201).

 S 012-024

 (4)  
Open the left core cowl panel (Ref 71-11-06/201).

 S 012-025
 WARNING: OBEY THE INSTRUCTIONS IN THE PROCEDURE TO OPEN THE THRUST
_______ REVERSERS. IF YOU DO NOT OBEY THE INSTRUCTIONS WHEN YOU OPEN THE THRUST REVERSERS, INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR.
 (5)  
Open the left thrust reverser (Ref 78-31-00/201).

 D.
Activate the PRV

 S 442-010
 (1)
Remove the positioning screw from the switch actuating lever.

 S 012-013

 (2)  
Replace the C-seal if it is damaged.

 S 442-014

 (3)  
Install the positioning screw with the C-seal in the actuator cap.

 (a)
Tighten the screw to 15-25 pound-inches (1.7-2.8 N.m).

 E.
Put the Airplane Back to Its Usual Condition

 S 412-012
 WARNING: OBEY THE INSTRUCTIONS IN THE PROCEDURE TO CLOSE THE THRUST
_______ REVERSERS. IF YOU DO NOT OBEY THE INSTRUCTIONS WHEN YOU CLOSE THE THRUST REVERSERS, INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR.
 (1)  
Close the left thrust reverser (Ref 78-31-00/201).

 S 412-026

 (2)  
Close the left core cowl panel (Ref 71-11-06/201).

 (3)  
Close the left fan cowl panel (Ref 71-11-04/201).

 S 442-028

 (4)  
Do the activation procedure for the thrust reverser (Ref
 78-31-00/201).

 S 412-027
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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747-400 MAINTENANCE MANUAL
 PRESSURE REGULATING VALVE (PRV) - REMOVAL/INSTALLATION
______________________________________________________
 1.  General_______
 A.  This procedure contains two tasks. The first task removes the pressure regulating valve. The second task installs the pressure regulating valve. The second task also contains a test for the installation of the pressure regulating valve.
 B.  The pressure regulating valve (PRV) is found near the high pressure compressor (HPC). It is at the 10:00 o'clock position. It is necessary to open the left half of the thrust reverser to get access to the PRV. The installation is the same for each engine.
 TASK 36-11-19-004-036
 2.  Remove the PRV (Fig. 401)______________
 A.  References
 (1)  
AMM 20-11-28/401, Lockwire

 (2)  
24-22-00/201, Manual Control
　
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