engine in accordance with the amount of power requested. The computing system allows the maximum
engine performance available without exceeding operating limits. The fuel then flows through tubing to
the right and left fuel manifolds and the eight fuel nozzles in the combustors.
8.10.
INTERNAL COOLING AND PRESSURIZATION
Ninth stage air passes through holes in the compressor rotor rear hub, down through the
inside of the rotor, and out through holes in the front hub. This air is used to pressurize the main
bearing seals and to cool hot parts of the engine.
8.11.
INLET GUIDE VANE ANTI-ICING SYSTEM
To prevent icing of the compressor inlet surfaces, an anti-icing air system is installed in the
engine. Compressor bleed air is carried forward to the inlet case by an external tube on the left side of
the engine. Air flow through this tube is controlled by a solenoid-operated valve. When icing
conditions are encountered, the anti-ice switch in the cockpit is turned on to deenergize the solenoid
which allows the valve to open and hot anti-icing air to pass forward.
Anti-icing air enters the compressor inlet outer case through the anti-icing air boss and into
the cavity formed by the compressor-inlet outer case and the IGV outer, shroud. The air then passes
through the hollow inlet-vanes and through openings in the inner shroud to the bullet nose cone.
The air passes through the bullet nose cone and is ejected out through louvers into the air-
stream.
8.12.
LUBRICATION SYSTEM
The engine lubrication system is illustrated in figure 8.10. Oil from the tank is fed to the
inlet of the pressure section of the main oil pump. The pressure oil is then directed through the main
oil filter, through the fuel oil cooler if cooling is required, and to the bearings. The oil passes through
external tubing to the No. 1 and 2 bearing compartments. Oil to the No. 3 bearing compartment is
supplied by an internal tube that connects with No. 2 bearing supply. Pressure oil flows through an
external tube to the free turbine accessory drive gearbox. An internal line carries oil from this connector
to the No. 4 and 5 bearings. Pressure oil flow is maintained by metering orifices, thus providing a
relatively constant oil flow at
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