-8 hours at 20 DEG.C (68.00 DEG.F)
 -6 hours at 60 DEG.C (140.00 DEG.F)
 -15 minutes at 80 DEG.C (176.00 DEG.F)
 -10 minutes at 100 DEG.C (212.00 DEG.F)
 5. Close-up
________ Subtask 49-20-00-865-080
 A. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s): 1KD, 2KD
 Subtask 49-20-00-410-065
 B. Close Access
 (1)
 Make sure that the work area is clean and clear of tool(s) and other items.

 (2)
 Set the light switch 11LJ to off.

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

 (4)
 Remove the access platform(s). Subtask 49-20-00-860-061

 C.
 Aircraft Maintenance Configuration

 (1)
 Pressurize the reservoirs of the hydraulic systems.
 (Ref. TASK 29-14-00-614-002).

 (2)
 De-energize the ground service network
 (Ref. TASK 24-41-00-862-002).

 (3)
 Remove the warning notice(s).

 POWER SECTION - DESCRIPTION AND OPERATION
_________________________________________

R **ON A/C 001-003, 051-099, 401-499,
 1. General
_______ The power section of the Auxiliary Power Unit (APU) supplies shaft power to drive:
 -a load compressor,
 -
an accessory gearbox,

 -
an electrical generator.
 It is a single-shaft assembly with:

 -
a single-stage centrifugal compressor,

 -
a single-stage, radial-inflow turbine,

 -
a reverse-flow, annular combustion-chamber. The single main shaft of the assembly is held with two bearings. The first bearing is a roller bearing which is installed directly aft of the accessory gearbox. A second bearing, which is of the ball type, is installed between the centrifugal compressor and the turbine. The power section compressor and the turbine wheel are given full hub containment. If a rotor hub or disc failure occurs, the debris is contained.

 2. Description
___________ R
 A. Single-Stage Centrifugal Compressor
 The compressor section includes:

 -a single-stage, 6 : 1 pressure ratio, machined titanium, centrifugal impeller,
 -single-stage, radial-inflow, diffuser vanes,

 -axial de-swirl vanes.
 The centrifugal compressor is less likely to suffer blade or disc failure
 than an axial flow compressor. The housing of the centrifugal compressor
 will contain the debris should a compressor hub failure occur.

 B. Reverse-Flow Annular Combustion-Chamber The combustion chamber is of a reverse-flow annular design. It is installed inside the turbine plenum and consists of an inner and outer shell. Holes and slots along the surface of both these shells permit the correct amount of air to enter and form the flame pattern and cool the walls.

 C. Single-Stage Radial-Inflow Turbine
 The single-stage, radial-inflow turbine includes:

 -cooled nozzle guide vanes,
 -
a rotor,

 -
a diffuser exhaust pipe, which includes a diffuser nozzle and seven

 radial vanes. The turbine operates on a high cyclic (stop-start) life. A necessary property of the turbine is long life. The component is made from a high temperature nickel-based alloy. The turbine is provided with full hub containment, which will contain all the debris should a turbine hub or disc failure occur. Insulation mats, installed around the exhaust muffler, prevent high surface temperatures in the APU tailpipe section.
 3. Operation
_________ The Fuel Control Unit (FCU), and the Electronic Control Box (ECB) 59KD, control the optimal air and fuel flow. This is necessary for the operation of the power section module. After the APU starts, air moves through the plenum chamber to the compressor of the power section. It then passes into the primary zone of the reverse-flow annular combustion-chamber. The atomizers spray fuel into the combustion-chamber where it is mixed with the air to produce combustion. Additional air enters through holes along the combustion chamber. This additional air helps to contain the flame envelope, prevent torching of the combustion-chamber walls and complete the combustion process. The hot gas discharges from the combustion chamber and flows through the single-stage radial-inflow turbine. The hot gas expands across the turbine where its energy is converted to mechanical power. This power is used to drive the:
 -direct-drive load compressor,
 -APU generator,
　
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