Abstract: An APU has a gas turbine engine and a starter generator to be selectively driven by the gas turbine engine. A sensor senses windmilling of components associated with the starter generator. A lock feature limits rotation within the starter generator when windmilling is sensed. A method of operation is also disclosed.

Abstract: An APU has a gas turbine engine and a starter generator to be selectively driven by the gas turbine engine. A sensor senses windmilling of components associated with the starter generator. A lock feature limits rotation within the starter generator when windmilling is sensed. A method of operation is also disclosed.

Abstract: An APU has a gas turbine engine and a starter generator to be selectively driven by the gas turbine engine. A sensor senses windmilling of components associated with the starter generator. A lock feature limits rotation within the starter generator when windmilling is sensed. A method of operation is also disclosed.

Abstract: An anti-surge mechanism has a duct for tapping compressed air and delivering that air into an exhaust flow. A selectively open valve allows the tapped air to flow into the exhaust flow through a plurality of holes. The holes are sized to tune a frequency of a sound created by the tapped air to a frequency range outside of normal human hearing. A gas turbine engine is also disclosed.

Abstract: An assembly for use with a power-producing unit includes an annular case, a hub positioned radially inward of the case, a fluidic flow path defined between the case and the hub, a plurality of support tubes each extending between the case and the hub, and a flow modifying structure positioned on an exterior surface of at least a first one of the support tubes and configured to reduce vortex shedding of a passing fluid.

Abstract: An assembly for reducing compressor noise includes a compressor and an acoustic shield. The compressor has a rotor with a plurality of blades mounted thereto. Additionally, the compressor has one or more bleed slots therein. The acoustic shield is disposed adjacent to the one more bleed slots and spaced at a distance therefrom.

Abstract: A heat exchanger has a first passage to be connected to a source of fuel. The heat exchanger has an outlet to communicate the fuel downstream. A second passage connects to a source of air. The air passes adjacent to the first passage to heat fuel in the first passage. A jet pump is positioned downstream of the second passage to receive air from the second passage. The jet pump includes a tap connected to a housing compartment to drain fluid from the compartment. A method is also disclosed.

Abstract: A system and method are provided for determining the health of an engine. The method includes a plurality of standard noise spectra collected from engines with known defects. A noise spectrum of the engine being monitored is sensed and compared to the plurality of standard noise spectra from the engines with known defects. From the comparison, a type and a degree of defect is identified based upon the comparison.

Abstract: An example auxiliary power unit air inlet assembly includes a noise attenuating component disposed within a conduit. The conduit is configured to communicate a first flow of fluid to an auxiliary power unit. A second flow of fluid is communicated to the noise attenuating component. The second flow of fluid limits formation of ice in the conduit. The first flow of fluid is different than the second flow of fluid.

Abstract: A shaft includes a shoulder that transitions the shaft from a first diameter to a second diameter. The shaft includes a groove that is disposed immediately adjacent to and/or is formed in an inner radial portion of the shoulder. The groove acts to produce uniform deflection of the shoulder in an axial direction with respect to a centerline axis of the shaft.

Abstract: An example auxiliary power unit (APU) exhaust silencer includes cooling features to protect the outer skin and other components from heat generated by gases passing through an exhaust duct. Cooling air flow through a cooling air passage in thermal contact with the exhaust silencer carries heat away from other nearby components and the aircraft skin.

Abstract: An exhaust silencer assembly includes an exhaust duct and an exhaust silencer. The exhaust silencer is disposed about the exhaust duct and has a plurality of solid baffles and at least one perforated baffle The exhaust silencer assembly is disposed downstream of an auxiliary power unit and at least partially attenuates the downstream noise of the combustion gases that result from operation of the auxiliary power unit. In one embodiment, at least one of the plurality of solid baffles is disposed to extend axially between generally radially extending solid baffles, perforated baffle(s), or partially perforated baffles. The axially extending solid baffle allows for cavity depth variation in the silencer to optimize tuning of particular frequencies from the auxiliary power unit.

Abstract: An assembly for use with a power-producing unit includes an annular case, a hub positioned radially inward of the case, a fluidic flow path defined between the case and the hub, a plurality of support tubes each extending between the case and the hub, and a flow modifying structure positioned on an exterior surface of at least a first one of the support tubes and configured to reduce vortex shedding of a passing fluid.

Abstract: A shaft includes a shoulder that transitions the shaft from a first diameter to a second diameter. The shaft includes a groove that is disposed immediately adjacent to and/or is formed in an inner radial portion of the shoulder. The groove acts to produce uniform deflection of the shoulder in an axial direction with respect to a centerline axis of the shaft.

Abstract: An exhaust silencer assembly for use with an auxiliary power unit includes an eductor and a discharge pipe. The eductor is disposed downstream of the auxiliary power unit and has an entrance opening at a forward axial end thereof. The entrance opening is configured to receive exhaust airflow from the auxiliary power unit. The discharge pipe extends from the auxiliary power unit and communicates with the exhaust silencer assembly downstream of the entrance opening of the eductor.

Abstract: An assembly for reducing compressor noise includes a compressor and an acoustic shield. The compressor has a rotor with a plurality of blades mounted thereto. Additionally, the compressor has one or more bleed slots therein. The acoustic shield is disposed adjacent to the one more bleed slots and spaced at a distance therefrom.

Abstract: A method for cooling a gas turbine engine includes supplying power to a motor to generate mechanical motion and translating the mechanical motion of the motor to a shaft of the gas turbine engine to rotate a compressor stage and a turbine stage after the engine has been shutdown to circulate air within the engine and cool engine components. A system for preventing hot soakback in an auxiliary power unit includes a starter motor, a compressor, a turbine, a shaft connected to at least one stage of the compressor and at least one stage of the turbine, a gearbox for connecting the starter motor to the shaft, a temperature sensor and a controller. The controller receives information from the temperature sensor and instructs the starter motor to rotate and drive the shaft when the temperature sensor senses a temperature above a low limit temperature threshold.

Abstract: An exhaust duct system for a gas turbine engine that mounts within a tail cone of an aircraft, comprises an exhaust exit that exits one side of the tail cone offset from the axial centerline of the tail cone and an exhaust duct that couples the engine to the offset exhaust exit, with a straight section of the exhaust duct extending from the exhaust exit for a length that corresponds to at least one diameter of the exhaust duct.

Abstract: An exhaust silencer assembly for use with an auxiliary power unit includes an eductor and a discharge pipe. The eductor is disposed downstream of the auxiliary power unit and has an entrance opening at a forward axial end thereof. The entrance opening is configured to receive exhaust airflow from the auxiliary power unit. The discharge pipe extends from the auxiliary power unit and communicates with the exhaust silencer assembly downstream of the entrance opening of the eductor.

Abstract: A system and method are provided for determining the health of an engine. The method includes a plurality of standard noise spectra collected from engines with known defects. A noise spectrum of the engine being monitored is sensed and compared to the plurality of standard noise spectra from the engines with known defects. From the comparison, a type and a degree of defect is identified based upon the comparison.