(d)  
Make sure that the left and right manifold duct pressures become stable at a pressure greater than 20 psig.

 (e)  
The duct pressures must agree (| 5 psi).

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A
747-400 MAINTENANCE MANUAL
 S 715-142
 CAUTION:_______ MAKE SURE THAT THE PARKING BRAKES FOR THE LANDING GEARS HAVE
 BEEN SET, GROUND LOCKS HAVE BEEN INSTALLED ON THE NOSE AND MAIN
 LANDING GEARS AND CHOCKS HAVE BEEN PLACED IN FRONT AND AFT OF
 THE NOSE AND MAIN LANDING GEAR TIRES BEFORE YOU INCREASE ENGINE
 SPEED DURING POWER PLANT OPERATION TO PREVENT AIRCRAFT MOVEMENT
 (AMM 71-00-00/201).

 (22) While you monitor Engine N1 and the ENG DUCT PRESS on the auxiliary EICAS display, slowly increase engine power until the ENG DUCT PRESS decreases significantly (i.e., by more than 20 psig).
 NOTE: The sudden decrease in pressure occurs when the high
____ pressure shutoff valve (HPSOV) closes.
 (a)  
Make sure that the ENG DUCT PRESSURE is 57-72 psig before the HPSOV closes and is 15-30 psig after the HPSOV closes.

 (b)  
Make sure that N1 is 45-60 percent when the HPSOV closes.

 S 865-167
 (23)
 Slowly reduce the engine power until the HPSOV opens.

 (a)  
Make sure that the ENG DUCT PRESSURE is 57-70 psig after the HPSOV opens.

 NOTE: Allow the ENG DUCT PRESSURE to stabilize before you
____ record the values.
 (b)  
Make sure that N1 is 45-60 percent when the HPSOV opens.

 (c)  
Make sure that the MANIFOLD DUCT PRESSURE is 32 to 43 psi.

 NOTE: Allow the MANIFOLD DUCT PRESSURES to stabilize
____ before you record the values.
 (d)  Make sure that the PRECOOLER OUT TEMP is around 138-182 °C (280-360 °F) after the HPSOV opens.
 NOTE: Allow the PRECOOLER OUT TEMP to stabilize before you
____ record the values.
 S 865-144
 (24) Reduce the applicable engine power to ground idle.
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747-400 MAINTENANCE MANUAL
 S 865-145
 (25)
 Shutdown the applicable engine (AMM 71-00-00/201).

 S 865-146

 (26)
 Do this test on the other engines, if necessary.

 TASK 36-11-00-745-073
 3.  Ground Tests - Pneumatic System_______________________________
 A. General
 (1)  
These bleed system ground tests are available in the form of a built-in-test to check the operational status of the engine bleed air supply system and to diagnose system faults with the use of the Central Maintenance Computer System (CMCS).

 (a)  
Bleed System Electrical Ground Test This test performs electrical checks of the entire bleed system. The engine must not be in operation, but the APU or the ground cart may be in use. Input signals (which do not need pneumatic power to operate) to the ASCTU are monitored for proper values.

 (b)  
Bleed System APU Ground Test This test performs the engine X (where engine X is the selected engine) bleed system test with the selected engine X not in operation. Pneumatic air must be supplied by the APU or by a ground cart for this test. Valve positions, pressures and other signals to the ASCTU are monitored for proper values while the selected engine X bleed system is pressurized.

 (c)  
Bleed System Engine Ground Test This test performs the engine X (where engine X is the selected engine) bleed system test with the selected engine X in operation. Valve positions, pressures and other signals to the ASCTU are monitored for proper values while the selected engine X bleed system is pressurized.

 B. References
 (1)  AMM 24-22-00/201, Manual Control
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