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.

R  **ON A/C 001-049, 101-105, 151-199, 201-210,
 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 a fiberglass fabric/Nomex core sandwich design 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.

R  EFF : 001-049, 101-105, 107-107, 151-199, 49-16-00Page 4 201-210, Config-2 Aug 01/05
 CES  CES  CES

 - 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 core sandwich 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: - 28V DC motor with brake control (basic version), - a limit switch at each end position, - a flap position switch at each end position, - thermal overload protection device. 
R  **ON A/C 107-107, 
R  The air inlet consists of the following major components: 
R R R R R R R  (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. 
R R R R R R R  (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. 

R R R R R  (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 shett metal construction and is acoustically treated with feltmetal along the inlet airstream aft of the lip area. 
R R R  (4) Air Inlet Housing This conventional aluminum structure attached to the air inlet body serves two functions: 
R R R  - provide an attachment for the inlet flap actuator; - serve as maintenance platform for work within the tailcone forward of the APU compartment. 
R R R R R R R R  (5) Air Inlet Actuator This electrically operated linear actuator operates the air inlet flap. Its major components are: - 28V DC motor with brake control (basic version), - a limit switch at each end position, - a flap position switch at each end position, - thermal overload protection device. 
R  **ON A/C 001-049, 101-105, 107-107, 151-199, 201-210,
 C. Air Duct
 The air duct forms the central portion of the air intake system, connecting the air inlet with the APU plenum chamber. It is located completely within the APU compartment and is installed on the access door 316AR. When subject door is opened, the air duct is dislocated from its normal installation position, thus permitting improved access to the APU. The purpose is to duct the airflow to the APU and to reduce aerodynamic noise. In case of APU compartment fire, it retains its shape.
 It consists of 2 major components, which are conventionally joined with brackets and fasteners:
　
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