H29488
Oil Tank Drain Valve Installation 500
79-11-21Page 402 Figure 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Nov 15/67
ENGINE OIL DISTRIBUTION SYSTEM - DESCRIPTION AND OPERATION
P&W 79-00 page 1 Dec 15/62
1. General
A. The engine oil distribution system is a self-contained high pressure design consisting of a pressure system which supplies lubrication to the main engine bearings and to the accessory drives, and a scavenge system by which oil is withdrawn from the bearing compartments, and from the accessories, and then returned to the oil tank. A breather system connecting the individual bearing compartments, the accessory drive gearbox, and the oil tank completes the oil distribution system. (See figure 1.) For a complete description of the internal engine oil system refer to chapter 72-00 "ENGINE - DESCRIPTION.”
2. Oil Pressure System
A. Oil flows by gravity from the oil tank to the engine driven pump, located inside the accessory drive gearbox housing. Pressure oil from the pump flows through an oil filter to a fuel cooled oil cooler. From this unit it passes to the various engine bearings. Bypass valves are provided in the filter and in the oil cooler. These valves open and allow oil to continue flowing through the system in the event that either unit becomes clogged. An adjustable pressure regulating valve, installed in the accessory drive gearbox on the pressure side of the pump, maintains system pressure and flow by bypassing oil back to the pump inlet.
3. Scavenge Oil System
A. Four scavenge pumps return oil from the bearing cavities to a sump in the accessory drive gearbox. The scavenge stage of the engine driven pump then returns the oil to the tank. A deaerator in the tank separates the air from the returning oil, thus minimizing foaming.
4. Oil Breather System
A. An oil breather system connects the engine bearing cavities, the accessory drive gearbox, and the oil storage tank. This system controls the pressures in the accessory drive gearbox and main bearing cavities, thereby ensuring adequate oil flow and preventing scavenge pump cavitation during engine operation.
B. Oil droplets and vapor are removed from the breather airstream by a centrifugal separator located in the accessory drive gearbox. After passing through the separator unit the breather air is exhausted overboard through a vent pipe.
500
Apr 15/66 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 79-21-0 Page 1
H27713
Engine External Oil Distribution 542
79-21-0 Figure 1 Feb 1/76
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5. Fuel Coolant Oil Cooler
A. The fuel-oil cooler is of the full flow type with a pressure bypass feature. The cooler is mounted on the lower left side of the front compressor case. It consists of a housing containing a removable core composed of more than 200 soda straw-like tubes through which fuel passes; a series of baffles within the core which direct the flow of oil around the tubes; and a bypass valve which permits oil flow to the main bearing compartments in the event of core clogging.
B. The oil leaves the oil pressure pump in the gearbox and flows to the fuel oil cooler. The oil flows through the cooler directed by baffles to flow around the tubes through which fuel flows. Heat from the oil is transferred through the tube walls to the fuel. If the cooler becomes clogged, the oil bypass valve opens to permit the continuous flow of oil. Oil leaves the cooler and flows through the oil pressure tubing to the main bearing compartments.
500
Apr 15/66 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 79-21-0 Page 3
ENGINE OIL DISTRIBUTION - MAINTENANCE PRACTICES
1. General
A. This section provides instructions for performing the oil breather pressure test.
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