(1)
The air/oil heat exchanger includes one housing to fill the engine oil system. The oil inlet and outlet ports are installed on the upper aft side of the heat exchanger. Engine oil is flowed into two semi-cylindrical heads at the top of the unit and is collected and returned at the bottom in two semi-cylindrical chambers. A relief (bypass) valve, nominally set at 50 psid (345 kPad), is installed between the inlet and outlet ports to bypass the oil in cold engine start conditions. The air/oil heat exchanger uses fan discharge air which is ducted from the 2.5 bleed valve duct and modulated by the air/oil heat exchanger valve.
B.
The air/oil heat exchanger valve, which is installed just forward of and directly attached to the air/oil heat exchanger, modulates fan discharge air to the air/oil heat exchanger at high oil heat conditions during engine idle and low power operation.
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79-21-00
ALL ú ú N01 Page 7 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
C. The valve includes four main subassemblies housed in one body: dual butterfly valves installed on a single driveshaft, a fuel pressure-driven actuator, a dual rotary variable transformer (RVT), and a dual-coil torque motor. Valve operation is done by an input signal from the electronic engine control (EEC) to the torque motor. The torque motor modulates pressures which act upon each side of the actuator piston, thus causing a change in the actuator position. Movement of the actuator turns the two butterfly valves through a connecting link. The butterfly valve angular position is measured by the RVT installed on the end of the butterfly valve drive shaft.
D. The valve is made to fail-safe open if failure of an electrical or fuel pressure signal occurs.
7. Last Chance Oil Strainers (Fig. 1)
_________________________
A. The final component the oil goes through before it goes to the bearings or gearboxes are the last chance oil strainers, which prevent large particle contaminants from entering and clogging the oil nozzles or bearing compartments.
B. There are four last chance oil strainers installed as follows:
(1)
Strainer 1 - installed on the No. 1, 1.5, and 2 bearing oil pressure line installed at the 9 o'clock position on the forward HPC case
(2)
Strainer 2 - installed on the angle and main gearbox oil pressure outlet fitting on the fuel/oil cooler
(3)
Strainer 3 - installed on the No. 3 bearing oil pressure line at the
9:30 o'clock position on the diffuser case
(4) Strainer 4 - installed on the No. 4 bearing oil pressure line at the
11:30 o'clock position on the turbine exhaust case
8. Lubrication and Scavenge Oil Pump (Fig. 1)
_________________________________
A. The lubrication and scavenge oil pump is installed on the aft face of the main gearbox and is driven by the main gearbox. The lubrication and scavenge oil pump is a non-pressure regulated, gear type pump which includes six stages: one main lubrication pump stage and five scavenge pump stages; one each for the No. 1, 1.5, and 2 bearing compartment, No. 3 bearing compartment, No. 4 bearing compartment, angle gearbox, and the main gearbox.
B. The lubrication and scavenge oil pump supplies engine oil for lubrication and scavenge functions of the engine bearing compartments and the angle and main gearboxes.
9. Magnetic Chip Detector (Fig. 1)
______________________
A. There are six magnetic chip detectors (MCD) installed as follows:
(1)
Four MCD's installed on the scavenge inlet ports of the lubrication and scavenge oil pump
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