3.
Tighten sleeved jamnut on adjustment screw.
4.
Repeat steps 4) thru 10) and 14) thru 20)a)3. until valve is adjusted correctly.
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b) On airplanes with configuration 2 rate adjusting screw (Fig. 504, View 3).
1.
Loosen jamnut on rate control adjustment screw.
2.
Turn adjustment screw clockwise to increase opening time.
NOTE: Adjustment can only be made in a clockwise direction. If adjusting screw is turned in too far, it will be necessary to back adjustment screw all the way out. The sleeve will come out with it. Manually slide sleeve (interference fit) on screw restrictor so that more of the adjusting slot is visible. Install the screw and sleeve. Adjust again, turning screw clockwise.
3.
Tighten jamnut on adjustment screw.
4.
Repeat steps 4) thru 10) and 14) thru 20)b)3. until valve is adjusted correctly.
21) If bleed load control thermostat temperature limit was not met in step 14), replace the load thermostat (AMM 49-52-32/401) and adjust the load control thermostat (AMM 49-52-32/501).
(e)
Disconnect Gas Turbine Engine Tester from Engine 1) Check that BATTERY switch is OFF and placard. 2) Repeat steps 2.A.(6)(h) thru 2.A.(6)(n).
(f)
Restore Airplane to Normal Configuration
1) Install lower shroud.
a) Position lower shroud against upper shroud and close shroud latches.
CAUTION: MAINTAIN A MINIMUM CLEARANCE OF 0.18 INCH BETWEEN ENGINE PLUMBING, FIRE DETECTOR, CLAMPS AND INSIDE SURFACE OF LOWER SHROUD.
CAUTION: EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
2) Disengage APU compartment access door support rods and stow rods. Close and latch access door.
3) Remove placard from BATTERY switch.
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G00108G00180
Bleed Air Valve Adjustment 563
49-21-01 Figure 504 (Sheet 1) Aug 15/79
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563 Bleed Air Valve Adjustments
Aug 15/79 Figure 504 (Sheet 2) 49-21-01
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APU FUEL SYSTEM - DESCRIPTION AND OPERATION
1. General
A. The APU fuel system supplies fuel from the airplane fuel system to the APU and automatically meters the flow rate to match speed and loading requirements. The system consists of a fuel control unit, a fuel solenoid valve, a fuel atomizer, an APU control thermostat, a low pressure fuel filter, a fuel heater and a fuel sensing flow control, and various lines connecting the components (Fig. 1).
B. The fuel control unit supplies and regulates the fuel flow to the fuel atomizer. The regulated fuel flow controls the acceleration of the engine during the starting operation. When a load is applied to the APU, the fuel control unit meters the fuel flow to maintain a near constant speed and a safe operating temperature of the unit.
2. APU Fuel Valve
A. The APU fuel valve connects the APU fuel system to the airplane fuel tank No. 1. The valve is located on the rear spar of the left wing and controlled through the APU master switch. For description and operation of the valve, refer to Chapter 28, Engine Fuel Feed System.
3. Low Pressure Fuel Filter
A. The low pressure fuel filter protects the fuel control unit from contamination with dirt in fuel. The filter is a full-flow type with a replaceable filter element. A bypass valve in the filter allows unfiltered fuel to be delivered to the fuel control unit when the filter element becomes clogged. The bypass valve opens when the pressure differential across the filter is approximately 14 psi. The filter is installed on the fuel control unit (Fig. 1).
4. Fuel Control Unit
A. The fuel control unit regulates the fuel flow to the combustion chamber. It consists of an engine-driven fuel pump, a fuel filter, an acceleration limiter valve, a flyweight governor, a sleeve-type fuel bypass valve, two relief valves, fuel inlet and outlet ports, drive shaft seal drain line, and a control air connection. The fuel control unit is mounted on the accessory drive section (Fig. 1). It is driven by the accessory drive gear train at approximately 10% engine rpm.
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B. The engine-driven fuel pump is a gear-type positive displacement high pressure pump. The pump housing contains a spring-loaded ball-type pressure relief valve which allows fuel to return to the pump inlet if excessive fuel pressure is built up in the fuel control unit. The high pressure fuel filter is a micronic fuel filter located downstream of the pump outlet port and filters all fuel passing from the pump to the governor.
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