-Radial expansion of approx. 6mm in diameter: This leads to central positioning of the muffler assembly because of its assymetrical installation position at ambient temperature.
 -Fwd. axial expansion: This leads to a reduction of the distance between the muffler assembly and the APU. This is taken up externally by compression of the bellows; Internally by forward displacement of the sealing ring along its contact surface on the hot nozzle assembly.
 -Aft. axial expansion:

 APU Exhaust Muffler Assembly - Major Components
 Figure 002 (SHEET 1)

 CES

 APU Exhaust Muffler Assembly - Major Components
 Figure 002 (SHEET 2)

 CES

 This leads to a somewhat further extension of the muffler assembly into
 the airstream and an increase in compression of the access fairing seal.

 EXHAUST SYSTEM - DESCRIPTION AND OPERATION
__________________________________________
 1. General
_______ The APU exhaust system ducts the APU exhaust gases overboard. Its secondary function is to decrease the exhaust noise level. To keep aerodynamic losses during APU operation to a minimum, the duct has a sufficiently large diameter. The exhaust system discharge is positioned at the very aft end of the aircraft, where a low pressure area is generated during flight. This design makes sure that exhaust gases does not re-enter the APU air intake system.
 All components in contact with exhaust gases are made of corrosion resistant materials. All components exposed to high temperatures are made of fireproof or fire resistant materials. A flexible connection allows for relative movement between the APU and the muffler assembly and allows for any vibrations and inertia loads during operation. Drainage provisions are incorporated into the muffler assembly. One ventilation louver each at the top and the bottom of the muffler compartment limits the structure temperature to 110 deg. C max. The muffler assembly surface temperature does not exceed 232 deg. C.
 2. Component Location
__________________
 (Ref. Fig. 001)

 -------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA | | | | DOOR | REF. -------------------------------------------------------------------------------
EXHAUST MUFFLER BODY  315/ 315AL/ 49-81-41 316/ 316AR/ 317 317AL
 HOT NOZZLE ASSEMBLY 315/ 315AL/ 49-81-42 316 316AR BELLOWS 315/ 315AL/ 49-81-42 316 316AR V-CLAMP INSULATION SEGMENTS 315/ 315AL/ 49-81-41 316 316AR

R  EFF : 001-049, 101-105, 107-107, 151-199, 49-81-00Page 1 201-210, Config-2 Aug 01/05
 CES

 APU Exhaust Muffler - Component Location Figure 001 (SHEET 1)

R  EFF : 001-049, 101-105, 107-107, 151-199, 49-81-00Page 2 201-210, Config-2 Aug 01/05
 CES

 APU Exhaust Muffler - Component Location Figure 001 (SHEET 2)

R  EFF : 001-049, 101-105, 107-107, 151-199, 49-81-00Page 3 201-210, Config-2 Aug 01/05
 CES

 3. System/Component Description____________________________ (Ref. Fig. 001, 002)
 A. Major Components
 (1) Exhaust Muffler Body
 (a)
 Muffler Substructure This is a riveted corrosion resistant steel (CRES) structure, made of frames, an outer tube and provisions for external seals and insulation segments. It has the function of:

 -
the load carrying structure of the complete muffler assembly,

 -
the muffler resonator,

 -attaching the muffler assembly to the rails in the tailcone muffler compartment.

 (b)
 Tail Pipe Assembly The central part is made of feltmetal (sound attenuation CRES sheet metal). The end pieces are made of solid CRES sheet metal. The aft tube section is welded to the muffler substructure. The central tube section is put in from the front and positioned against the aft tube section. The forward tube section, which has a provision for the piston ring, is then put in and riveted to the muffler substructure. The feltmetal tube section is captured between the end sections with sufficient space to allow for thermal expansion.

 (c)
 Insulation Covers The complete exterior surface of the muffler is covered with 2 large insulation blankets and several small insulation segments. These are held in position with lockwire fastened to the buttons on the insulation components. The function of these is to reduce the muffler assembly surface temperature to a maximum of 232 deg. C for all ambient temperatures or APU operating conditions.

 (d)
 Piston ring This component is riveted in a recess on the inner liner forward-tube-section. It is in continuous contact with the hot nozzle assembly. Thus it seals the clearance between these assemblies and allows for relative movement between them.
　
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