29-11-08
 ALL  ú ú 02 Page 5 ú Feb 10/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 (5)  
When the control switch is put in the ON position, the turbine drive will operate continuously. The operation of the turbine drive is the same as the run-on-demand mode (control switch in the AUTO position). The turbine assembly will get to 70 percent of its output speed in 1 second in this run-continuous mode.

 (6)  
Advisory and status messages (HYD PRESS DEM 1 or 4) are displayed on the main EICAS screen. The message will show if the turbine drive is put in the OFF position, or the hydraulic pressure is less than 1400 psi when the turbine drive is in operation.

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 29-11-08
 ALL  ú ú 01 Page 6 ú Feb 10/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 AIR-DRIVEN PUMP TURBINE DRIVE - MAINTENANCE PRACTICES
_____________________________________________________
 1.  General_______
 A.  This procedure has two tasks. To set the overspeed trip valve and to perform a visual inspection of the Air-Driven Pump Turbine Drive magnetic plug.
 B.  If the overspeed trip valve moves to the overspeed position, you must set the valve before the turbine drive for the air-driven pump (ADP) can operate again. After you correctly set the overspeed trip valve, you will see approximately 0.08 inch more of the shiny sleeve in the two slots of the overspeed trip valve.
 C.  An overspeed trip usually shows a malfunction in the turbine drive unit. An overspeed can occur if the speed control valve becomes caught in the open position. An overspeed can also occur if the governor has a malfunction or from the vibration of a defective bearing.
 D.  If the overspeed trip valve moves to the overspeed position, you must do a check of the oil level in the turbine drive of the ADP. Operation with no oil can cause damage to the bearings in the turbine drive. The vibration of a defective bearing can cause the overspeed trip valve to move to the overspeed position. If there are signs that the turbine drive operated with no oil or if the oil level is very low, you must replace the turbine drive.
 E.  The overspeed trip valve is on the lower right side of the ADP turbine drive. You can get access to the valve through the right fairing door on the trailing edge of the strut.
 F.  The visual Inspection of the Air-Driven Pump Turbine Drive magnetic plug is done to determine if the turbine drive should be replaced.
 TASK 29-11-08-822-001
 2.  Set the Overspeed Trip Valve (Fig. 201)____________________________
 A.  Special Tools and Equipment
 (1)
ME60B00158 Air-Driven Hydraulic Pump Muffler

 B.  
Standard Tools and Equipment

 (1)
Wood Dowel - 1/4 inch in diameter, 3 inches in length

 C.  
References

 (1)
AMM 24-22-00/201, Manual Control

 (2)
AMM 36-00-00/201, Pneumatic System

 (3)
AMM 54-62-00/201, Nacelle Strut Access Panels

 D.  
Access

 (1)  
Location Zone
 454 System 1 - Strut Aft Fairing
 484 System 4 - Strut Aft Fairing

 (2)  
Access Panel 454A Trailing Edge Fairing Door, RH - System 1 484A Trailing Edge Fairing Door, RH - System 4

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 29-11-08
 ALL  ú ú 01 Page 201 ú Oct 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL

SLOT (2 LOCATIONS)OVERSPEED SEE A TRIP VALVE SEE C
RESET PLUG
FWD 
B 
OVERSPEED 
TRIP VALVE 
SEE  B 
TURBINE DRIVE AIR-DRIVEN PUMP  (2 LOCATIONS) SLOT 

A (EXAMPLE)  FWD  OVERSPEED TRIP VALVE  C  SLEEVE SHINY 
Figure 201 Turbine Drive Overspeed Reset 

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