S 414-020

 (11)
 Close the right thrust reverser half on the applicable engine (AMM 78-31-00/201).

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 ALL  ú ú 01 Page 405 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 AIR-DRIVEN PUMP TURBINE DRIVE - DESCRIPTION AND OPERATION
_________________________________________________________
 1.  General_______
 A.  The air-driven pump turbine drive is used to supply more hydraulic power when the engine-driven pump (EDP) cannot supply sufficient hydraulic power. The turbine drive is also used to supply hydraulic power during an EDP failure. The turbine drive will turn a hydraulic pump to increase hydraulic system pressure.
 B.  There is one turbine drive on the aft side of each engine strut torque box. The turbine drive assembly has these components:
 -Shutoff and speed control valve unit, AMM 29-11-09/401
 -Governor unit and oil pump drive, AMM 29-11-10/401
 -
Turbine drive oil filter, AMM 29-11-14/401

 -
Turbine drive air filter and water separator, AMM 29-11-15/201

 -Acceleration control unit, AMM 29-11-16/401
 -
Electrical component assembly, AMM 29-11-25/401.

 C.  
Operation of the turbine drive is controlled by a three-position switch installed on the P5 overhead panel in the flight compartment. Power is supplied by the 28-volt dc bus No. 1 for the left turbine drive and the 28-volt dc bus No. 4 for the right turbine drive.

 D.  
A hydraulic pump is connected to the turbine drive. The turbine drive will turn the hydraulic pump at 3,200 rpm. The hydraulic pump can supply hydraulic pressure at 2900 psi and 32 gpm.

 2.  Turbine Drive Assembly (Fig. 1)______________________
 A.  The self-contained turbine drive assembly has an axial flow turbine and a control system.
 B.  The axial flow turbine has a turbine rotor assembly, gearbox, and a lubrication system.
 (1)  
The turbine rotor assembly is dynamically balanced and installed as a unit in the gearbox. An overspeed trip actuator is attached to the assembly to prevent damage to the turbine drive.

 (2)  
The turbine rotor assembly, hydraulic pump, and all control components are attached to the gearbox. The turbine drive operating speed of 25,400 rpm is decreased to an accessory pad (hydraulic pump) speed of 3,200 rpm in the gearbox. Two drive gears turn the governor at 5,486 rpm. The oil pump is installed at the bottom of the gearbox. It is connected to the governor by a quill shaft and turns at 5,486 rpm. An oil fill port, drain port, and an oil breather are supplied on the gearbox.

 (3)  
The lubrication system supplies oil to the bearings and gears. The oil pump has inlets at the top and bottom to make sure that a sufficient amount of oil is supplied at high altitudes and during airplane descent. The oil filter has a bypass relief valve which permits the oil to bypass the filter if it becomes clogged.

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 ALL  ú ú 03 Page 1 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

SEE  B 
HYDRAULIC SYSTEM 
PRESSURE LINE 
SEE  A 
OVERSPEED 
TRIP VALVE 
AIR-DRIVEN 
PUMP TURBINE  AIR-DRIVEN 
DRIVE  PUMP 
GOVERNOR UNIT AND 
OIL PUMP DRIVE 
GEARBOX 
OIL BREATHER 
FWD 
A 
ELECTRICAL 
COMPONENT 
ASSEMBLY 
OIL FILL  AIR-DRIVEN 
CAP  PUMP TURBINE 
DRIVE 
AFT LOOKING FORWARD 
NOTE:____  SYSTEM 1 SHOWN; 
SYSTEM 4 SIMILAR.  B 
Air-Driven Pump Turbine Drive 
Figure 1 (Sheet 1) 

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