AIR INTAKE SYSTEM - DESCRIPTION AND OPERATION
_____________________________________________
 1. General
_______
 The air intake system provides ambient air of sufficient quantity and
 quality to the APU. Its major components are:

 -a diverter,
 -
an air inlet (including actuator-driven flap),

 -
an air duct.
 The main function of the air intake system is:

 -provide sufficient mass flow to the APU plenum chamber,
 -minimization of pressure loss and flow distortion (thus also reducing the danger of APU surge),
 -noise reduction,
 -reduce the potential for foreign object ingestion,
 -
prevent exhaust (from APU and main engines) from re-entering the inlet,

 -
prevent the ingestion of fluids existing externally,

 -
prevent the accumulation of flammable fluids in the intake system.

 2. Component Location
__________________
 (Ref. Fig. 001)

 -------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA | | | | DOOR | REF. -------------------------------------------------------------------------------DIVERTER - FIXED 311/ 314AR 49-16-41 312 AIR INLET 313/ 314AR 49-16-42 314 FLAP - AIR INLET 313/ 314AR 49-16-43 314 NOSE - AIR INLET 313/ 314AR 49-16-44 314 4015KM ACTUATOR - AIR INLET FLAP 313/ 314AR 49-16-51 314 AIR DUCT 315/ 315AL/ 49-16-45 316 316AR DIFFUSOR - AIR DUCT 315/ 315AL/ 49-16-45 316 316AR ELBOW - AIR DUCT 315/ 315AL/ 49-16-45 316 316AR

 Air Intake System - Component Location Figure 001 (SHEET 1)

R EFF : 106-106, 108-149, 211-299, 301-399, 49-16-00Page 2 Config-3 Aug 01/05
 CES

 Air Intake System - Component Location Figure 001 (SHEET 2)

R EFF : 106-106, 108-149, 211-299, 301-399, 49-16-00Page 3 Config-3 Aug 01/05
 CES

 3. System Description__________________ (Ref. Fig. 001)
 A. Fixed Diverter This item, being installed just forward of the tailcone at the bottom the rear fuselage, serves two purposes:
 (1)
 Its primary purpose is to improve the ram air recovery during in-flight APU operation. This is accomplished by positioning the inlet some 50mm into the airstream, thus the lowest energy portion of the aerodynamic boundary layer is prevented from entering the air inlet.

 (2)
 Its secondary purpose is to divert any fluids (such as oil, hydraulic or de-icing fluid, fuel or water), which might be migrating aft along the fuselage during flight. They are thus prevented from entering the air inlet.

 B. Air Inlet The air inlet assembly is installed as a unit in a cutout in the bottom of the tailcone just forward of the APU compartment, positioned by 4 bolts. The interface to the air duct is attached to the APU compartment forward firewall. The inlet airstream area up to approximately 150mm (6in) forward of the interface to the APU compartment is covered with a CRES face sheet to serve as an extension of the APU compartment fireproof area. A fireproof gasket is used to join the air inlet assembly to the APU compartment firewall. The air inlet consists of the following major components:
 (1)
 Air Inlet Body This is essentially a U-shaped component, forming both side walls as well as the the rear portion of the upper wall. It is of a fiberglass fabric/aluminum core sandwich design. The upper wall is acoustically treated with feltmetal. Rails, which extend into the airstream, are incorporated along the side walls in order to prevent the ingression of fluids flowing along the tailcone outer surface.

 (2)
 Air Inlet Flap It is of an aluminium alloy machined part without acoustic treatment. The flap is hinged at the forward end of the air inlet body and is operated by an attached actuator. It serves two purposes:

 -
to close the air inlet when the APU is not in operation.

 -
to form the forward portion of the upper wall when the APU is in operation.

 (3)
 Air Inlet Nose This item forms the lower wall of the air intake and is permanently installed in the air inlet body. It is of a CRES skin/aluminum sheet metal construction and is acoustically treated with feltmetal along the inlet airstream aft of the lip area.

 (4)
 Air Inlet Housing This conventional aluminum structure attached to the air inlet body serves two functions:

 -provide an attachment for the inlet flap actuator;
 -serve as maintenance platform for work within the tailcone forward of the APU compartment.

 (5)
 Air Inlet actuator This electrically operated linear actuator operates the air inlet flap. Its major components are:
　
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