2. Description
___________
 (Ref. Fig. 001)

 A. Single-Stage Centrifugal Compressor
 The compressor section includes:

 -a single-stage, 8:1 pressure ratio, machined titanium, centrifugal impeller,
 -single-stage, radial-inflow, diffuser vanes,

 -axial de-swirl vanes.
 The housing of the centrifugal compressor will contain the debris should
 a compressor hub failure occur.

 B. Combustor Assembly The combustor assembly is the point in the engine where compressed air and fuel are mixed and ignited. The combustor assembly is made of high-temperture resistant steel alloy and has an inner combuster chamber assembly. The forward end of the combuster housing assembly attaches to the engine power section turbine casing and the aft end attaches to the engine exhaust casing, turbine ring support and containment shield. The main fuel nozzles and pilot fuel nozzles are installed around the circumference of the combustor housing assembly. The main fuel manifold and pilot fuel manifold connect to the respective nozzles. A combuster drain valve is installed in the bottom, centre of the combustor housing assembly (Ref 49-30-00). Two igniters are also installed in the combustor housing assembly (Ref 49-40-00).

 APU Power Section Figure 001 
R  EFF :  106-106, 108-149, 211-299, 301-399,  Page 249-21-00 Config-3 Aug 01/05
 CES 

 C. Two Stage Axial Flow Turbine
 The turbine consists of:

 -
the first stage nozzle guide vanes (22),

 -
the first stage turbine wheel with inserted blades (37),

 -
the second stage nozzle guide vanes (26),

 -
the second stage turbine wheel with inserted blades (31). The turbine rear shaft is supported by a roller bearing mounted in a flexible cage. A stainless steel diffuser guides the exhaust gas to the exhaust muffler. Insulation mats, installed around the exhaust muffler, prevent high surface temperatures in the APU tailpipe.

 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 main and pilot fuel injectors provide the air and fuel mixture for combustion. Additional air enters through holes along the combustion chamber and through secondary tubes. This additional air helps to contain the flame envelope, prevent torching of the combustion-chamber walls and completes the combustion process. The hot gas discharges from the combustion chamber and flows through the 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,
 -necessary controls and accessories for the APU engine operation. A logic program in the ECB 59KD prevents engine compressor surge. The fuel flow is limited as a function of inlet temperature, inlet pressure and speed.

 POWER SECTION - REMOVAL/INSTALLATION
____________________________________ TASK 49-21-00-920-007 Discard Life Limited Parts of the APU Power Section in accordance with OEM
 Recommendation (131-9(A))
 1.
 Reason for the Job

__________________
 Refer to the MPD TASK: 492100-B5

 2.
 Job Set-up Information

______________________
 A. Referenced Information
 -------------------------------------------------------------------------------REFERENCE DESIGNATION -------------------------------------------------------------------------------
49-11-11-000-004 Removal of the Power Plant (APU) (131-9(A)) 49-11-11-400-004 Installation of the Power Plant (APU) (131-9(A)) EM 49-22-00
 3. Job Set-up
__________ Subtask 49-21-00-010-054
 A. Remove the APU (Ref. TASK 49-11-11-000-004).
 4. Procedure
_________ Subtask 49-21-00-020-054
 A. Remove and discard the life limited parts that follow:
 -Engine Compressor Impeller;
 -First Stage Turbine Disc;
 -Second Stage Turbine Disc;
 -Turbine Shaft.
 (Ref. EM 49-22-00)

R  EFF : 001-049, 101-105, 107-107, 151-199, 49-21-00Page 401 201-210, Aug 01/05
 CES  Subtask 49-21-00-420-054

 B. Install the new life limited parts that follow:
 -Engine Compressor Impeller;
 -First Stage Turbine Disc;
 -Second Stage Turbine Disc;
 -Turbine Shaft.
 (Ref. EM 49-22-00)
　
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