Abstract: An inlet door assembly for reducing air pressure loss and enhancing performance of an auxiliary power unit (APU) contained within an aircraft housing is provided. The inlet door assembly includes a duct and a diffuser. The duct, which is configured to be movably coupled to an aircraft and to move between open and closed positions, has a flow passage extending therethrough. Air external to the aircraft flows through the duct while it is in the open position, but not while it is in the closed position. The diffuser is coupled to the duct and configured to move therewith. The diffuser has a passage extending therethrough that is in fluid communication with the duct flow passage, and is configured to diffuse the air that flows therethrough.

Abstract: An auxiliary power unit (APU) compartment air inlet system seals, via one or more inlet doors driven by a single actuator, an APU compartment, and isolates the APU inlet and cooling system inlets from each other. The system includes either one or two inlet doors, depending on the number of ram air inlets formed in the APU compartment. In either instance, however, a single actuator is used to move the inlet door(s) between open and closed positions.

Abstract: The present invention provides a fireproof mounting system that is configured to couple an auxiliary power unit (“APU”) to a support structure, where the APU includes a case flange having a plurality of spaced apart fastener openings formed therethrough. The mount system comprises a rib and a receptacle. The rib has a portion configured to extend substantially parallel to at least a portion of the case flange, and includes a plurality of openings formed therethrough and disposed in a pattern such that at least selected ones correspond to one or more of the case flange fastener openings. The receptacle is integrally formed on the rib and having an outer surface and a funnel-shaped inner surface. The rib and the receptacle comprise fireproof material.

Abstract: A fireproof mount adapter is provided that is configured to couple a case flange of an auxiliary power unit to a stud adapter, the case flange having a plurality of spaced apart fastener openings formed therethrough. The mount adapter comprises a first rib and a mount plate. The first rib has a portion configured to extend substantially parallel to at least a portion of the case flange and includes a plurality of openings formed therethrough. The openings are disposed in a pattern such that at least selected ones correspond to one or more of the case flange fastener openings. The mount plate has a first side integrally formed on the first rib, a second side, and a plurality of apertures extending therebetween. The first rib and the mount plate comprise fireproof material.

Abstract: A muffler system is provided for use with an auxiliary power unit. In one embodiment, and by way of example only, the system includes an outer can, an annular baffle, and a tube. The outer can has a sidewall including a forward end, an aft end, and a cavity extending therebetween. The sidewall is disposed about a first longitudinal axis, and the cavity has a first cross-sectional area and a smaller second cross-sectional area. The annular baffle is coupled to and extends radially inward from the outer can sidewall and has an opening that is disposed about a second longitudinal axis that is non-coincident with the first longitudinal axis. The tube extends through the annular baffle opening and is spaced apart from the annular baffle to define a radial gap therebetween, comprises acoustic material, and has a length and a substantially uniform cross-sectional area along the length.