Subtask 49-31-42-865-056
 B. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s): 1KD, 2KD
 Subtask 49-31-42-790-050
 C. Test
 (1) Start the APU (Ref. TASK 49-00-00-860-005).
 (a) Operate the APU for min. five minutes and examine the joints of the main fuel nozzles and the manifold for leaks.
 NOTE : Leaks are not permitted.
____
 ________

5. Close-up
 Subtask 49-31-42-410-051
 A. Close Access
 (1)
 Make sure that the work area is clean and clear of tool(s) and other items.

 (2)
 Set the LIGHT control switch 11LJ to the off position.

 (3)
 Close the APU access doors 315AL, 316AR (Ref. TASK 52-41-00-410-001).

 (4)
 Remove the access platform(s).

 (5)
 Remove the warning notice(s). Subtask 49-31-42-860-055

 B.
 Aircraft Maintenance Configuration

 (1) De-energize the aircraft electrical circuits
 (Ref. TASK 24-41-00-862-002).

 APU FUEL CONTROL - DESCRIPTION AND OPERATION
____________________________________________

R **ON A/C 001-003, 051-099, 401-499,
 1.
 General

_______ The APU fuel control subsystem operates fully automatically. During APU operation, the FCU, which is governed by the ECB, meters the fuel dependent on the APU load condition. The FDDVA distributes the fuel via both fuel manifolds to the fuel nozzles. During APU start-up/shut-down, the FCU increases/reduces the quantity of fuel delivered to the FDDVA accordingly. During APU start, the FDDVA routs fuel to the combustion chamber via the primary fuel manifold only.

 2.
 Component Location

__________________
 (Ref. Fig. 001)

 -------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA
 | | | | DOOR | REF. -------------------------------------------------------------------------------4005KM2 FUEL CONTROL UNIT (FCU) 315 315AL 49-32-11 4005KM1 FLOW DIVIDER AND DRAIN VALVE 315 315AL 49-32-12
 ASSEMBLY (FDDVA) LOW PRESSURE FUEL FILTER 315 315AL 49-32-13 HIGH PRESSURE FUEL FILTER 315 315AL
 3. System Description
__________________
 (Ref. Fig. 001)

 A. Fuel Control Unit (FCU)
 (1)
 The fuel control unit, together with the FDDVA, schedule the fuel flow to the APU engine. The FCU also supplies high-pressure fuel to the Inlet Guide Vane (IGV) actuator to give the necessary power to position the load compressor IGVs. The FCU has an inlet section, a pump section, and a control and metering section. The inlet section includes:

 -an inlet fuel filter,
 -a fuel-filter bypass valve,
 -an inlet-filter pressure differential-indicator. The pump section includes:
 -
a high-pressure fuel pump,

 -
a high-pressure relief valve,

 -
a high-pressure fuel filter.

 -
a fuel pump seal drain check valve
 The control and metering section includes:

 -an IGV actuator-pressure regulator,
 -
a Torque Motor (TM) metering valve,

 -
a differential pressure regulator,

 -
a pressurizing valve,

 -
a fuel solenoid valve.

 (2)
 The fuel which goes into the FCU passes through the inlet fuel filter to the high-pressure fuel pump. The output from the high-pressure fuel pump goes through the high-pressure filter and then to:

 -
the IGV actuator pressure regulator,

 -
the clevis TM metering valve,

 -
the differential pressure regulator.
 Metered fuel goes through the pressurizing valve, fuel solenoid valve
 and comes out of the discharge port.
 The differential pressure indicator gives a visual indication of a
 clogged filter. The filter bypass valve permits continued operation
 with a clogged filter.

 APU Fuel Control - Component Location
 Figure 001

 CES  B. Flow Divider and Drain Valve Assembly (FDDVA)

 (1)
 The FDDVA together with the FCU, schedule the fuel flow to the APU engine. The FDDVA controls the fuel flow to the primary and the secondary manifolds and drains them at APU shutdown.

 (2)
 The FDDVA has a housing assembly that contains:

 -
a fuel filter element,

 -
a primary drain valve,

 -
a secondary drain valve,

 -
　
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