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The secondary airflow goes around (bypasses) the core of the engine. The secondary airflow makes approximately 80 percent of the forward thrust. The thrust reverser system also uses secondary airflow for reverse thrust.
Low Pressure Rotor System (N1)
The LP rotor system is a seven-stage low pressure compressor (LPC) connected to a seven-stage low pressure turbine (LPT). A coupling connects the LPT drive shaft to the LPC.
The first stage of the LPC is the fan. The next six stages are numbered 1.1, 1.3, 1.6, 2, 3, and 4. This keeps the stage identification common with earlier PW4000 engines.
High Pressure Rotor System (N2)
The HP rotor system is an eleven-stage high pressure compressor (HPC) connected to a two-stage high pressure turbine (HPT). A coupling connects the HPT drive shaft to the HPC.
The HPC stages are numbered 5 to 15. The HPC has variable stator vanes in the first four stages.
EFFECTIVITY BEJ ALL  72-00-00 
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D633W101-BEJ  Sep 05/2003 

PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

ENGINE -GENERAL DESCRIPTION -1

EFFECTIVITY BEJ ALL  72-00-00 
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D633W101-BEJ  Sep 05/2003 

ENGINE -GENERAL DESCRIPTION -2

Main Engine Bearings
Five main engine bearings hold the N1 shaft and the N2 shafts. Numbers identify the engine bearings. The oil pump supplies lubricating oil to the bearings and pulls oil out of the bearing compartments.
The number 1 ball bearing holds the front of the N1 shaft. It is the thrust bearing for the N1 shaft.
The number 1.5 bearing is a roller bearing and holds only radial loads for the N1 shaft. The number 2 ball bearing holds the front of the N2 shaft. It is the thrust bearing for the N2 shaft.
The number 3 roller bearing holds the rear of the N2 shaft.
The number 4 roller bearing holds the rear of the N1 shaft.
Accessory Drives
There are three gearboxes on the engine:
*
Internal

*
Angle

*
Main.

The internal and angle gearboxes transfer energy from the N2 shaft to the main gearbox. The main gearbox holds and turns the engine accessories.
The N2 shaft turns the tower shaft through the internal gearbox. The tower shaft turns the lay shaft through the angle gearbox. The lay shaft turns the main gearbox.
Training Information Point
You remove the no. 4 bearing compartment cover to inspect the compartment and bearing. You must remove the exhaust plug (not shown) before you can remove the cover.
EFFECTIVITY BEJ ALL  72-00-00 
Page 8 
D633W101-BEJ  Sep 05/2003 

PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

ENGINE -GENERAL DESCRIPTION -2

EFFECTIVITY BEJ ALL  72-00-00 
Page 9 
D633W101-BEJ  Sep 05/2003 
　
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