main EICAS.

 (b)  
Set the AUTO SELECT switch on the CPCS selector panel to the A position. 1) Make sure that the LDG ALT value is 14000 |50 MAN on the

 main EICAS.

 (c)  
Turn the LDG ALT knob on the CPCS selector panel counterclockwise. Stop when the LDG ALT value is approximately equal to the present field altitude on the main EICAS.

 (d)  
Push the LDG ALT button on the CPCS selector panel.

 L. Do the Forward Overboard Valve Control Test
 S 715-051
 (1)
Make sure that the forward overboard valve is in the open position.

 S 715-052

 (2)  
Make sure that the valve operates at takeoff:

 (a)  Open 6H19 PROBE HEAT ENG 1 and 6H23 PROBE HEAT ENG 3 circuit breakers on the P6 Main Power Distribution Panel.
 CAUTION: OPEN THE ENGINE PROBE HEAT CIRCUIT BREAKERS BEFORE YOU DO
_______ THE SUBSEQUENT STEP. FAILURE TO OPEN THESE CIRCUIT BREAKERS CAN RESULT IN DAMAGE TO THE ENGINE PT2/TT2 PROBES.
 (b)  AIRPLANES WITH ROLLS ROYCE ENGINES; Hold the S2 switch on the engine 1 and 3 N3 speed cards (in the electrical systems card file) to the TEST position.
 NOTE: The lockout speed card switch actuator can be used to
____ hold the switch to the TEST position.
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747-400 MAINTENANCE MANUAL
 (c)  AIRPLANES WITH GENERAL ELECTRIC ENGINES; Hold the S2 switch on the engine 1 and 3 N2 speed cards (in the electrical systems card file) to the TEST position.
 NOTE: The lockout speed card switch actuator can be used to
____ hold the switch to the TEST position.
 (d)  Make sure that the forward overboard valve closes.
 S 715-077
 (3)  Make sure that the valve operates at the aft cargo fire bottles arm:
 (a)  
Push the CARGO FIRE AFT switch on the P5 Overhead Panel to the ARMED position.

 (b)  
Make sure that the forward overboard valve opens.

 (c)  
Puch the CARGO FIRE AFT switch to the off position.

 (d)  
Make sure that the forward overboard valve closes.

 S 715-059
 (4)  Make sure that the valve operates during landing:
 (a)  
AIRPLANES WITH ROLLS ROYCE ENGINES; Release the engine 1 and 3 N3 speed switches so that they return to the NORM position.

 (b)  
AIRPLANES WITH GENERAL ELECTRIC ENGINES; Release the engine 1 and 3 N3 speed switches so that they return to the NORM position.

 (c)  
Make sure that the forward overboard valve opens.

 S 865-060
 (5)  
Close 6H19 PROBE HEAT ENG 1 and 6H23 PROBE HEAT ENG 3 circuit breakers on the P6 Main Power Distribution Panel.

 S 865-063

 (6)  
Remove the electrical power, if it is not necessary
 (AMM 24-22-00/201).

 TASK 21-31-00-705-065
 5. Operational Check of the Outflow Valve and Manual Mode Control
______________________________________________________________
 NOTE: This is a scheduled maintenance task.
____
 A. References
 (1)  AMM 24-22-00/201, Manual Control
 B. Access
 (1)  Location Zone
 221/222, Control Cabin

 C. Do the Test
 S 865-066
 (1)  Supply electrical power (AMM 24-22-00/201).
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747-400 MAINTENANCE MANUAL
 S 715-067
 (2)  Make sure that the left outflow valve operates in manual mode:
 (a)  
Monitor the left and right outflow valve position indicators on the EICAS ECS synoptic page. 1) Make sure that both indicators point to the full open

 position. 2) Make sure that AUTO shows below each indicator.

 (b)  
Push the MAN L switch on the CPCS selector panel to ON. 1) Make sure that the EICAS advisory message OUTFLOW VLV L shows.
　
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