Abstract: Auxiliary power systems, aircraft including the same, and related methods are disclosed herein. In one embodiment, the aircraft includes an airframe and an auxiliary power system that includes an auxiliary power unit (APU), an APU controller, and a bleed air temperature (BAT) sensor. The APU defines a bleed air outlet and is configured to regulate a BAT of a bleed air flow generated by the auxiliary power unit. The BAT sensor is positioned at a remote BAT location that is outside the bleed air outlet of the APU. In another embodiment, the auxiliary power system includes an APU configured to generate a bleed air flow, an APU controller configured to receive and transmit signals, and a BAT sensor suite configured to measure the BAT of the bleed air flow and to generate a BAT signal that is based, at least in part, on the BAT.

Abstract: Auxiliary power systems, aircraft including the same, and related methods are disclosed herein. In one embodiment, the aircraft includes an airframe and an auxiliary power system that includes an auxiliary power unit (APU), an APU controller, and a bleed air temperature (BAT) sensor. The APU defines a bleed air outlet and is configured to regulate a BAT of a bleed air flow generated by the auxiliary power unit. The BAT sensor is positioned at a remote BAT location that is outside the bleed air outlet of the APU. In another embodiment, the auxiliary power system includes an APU configured to generate a bleed air flow, an APU controller configured to receive and transmit signals, and a BAT sensor suite configured to measure the BAT of the bleed air flow and to generate a BAT signal that is based, at least in part, on the BAT.

Abstract: Auxiliary power systems, aircraft including the same, and related methods. An auxiliary power system comprises an auxiliary power unit (APU) controller and an APU with an air intake, a powerhead, and a load compressor stage. The load compressor stage includes a flow regulator assembly, a load compressor, and a bleed air temperature (BAT) sensor for generating a BAT signal. The APU controller regulates a flow rate of a load compressor airflow through the load compressor based on the BAT signal. A method of utilizing an auxiliary power system includes compressing a load compressor airflow to generate a bleed air flow, measuring the BAT with a BAT sensor, generating a BAT signal based on the BAT, transmitting the BAT signal to an APU controller, generating a flow regulator command with the APU controller, transmitting the flow regulator command to a flow regulator assembly, and controlling a flow regulator assembly.

Abstract: Systems and methods for cooling bleed air from an aircraft engine are described. An example system includes a housing to bifurcate airflow exiting a fan of an engine fan system, a pre-cooler assembly disposed within the housing to remove heat from the bleed air, and an inlet duct within the housing to direct the airflow to the pre-cooler assembly. The example system also includes at least one diverter duct within the housing and coupled to the inlet duct to divert the airflow around the pre-cooler assembly. The at least one diverter duct includes an exit directing the airflow into a fan duct of the engine fan system. The example system also includes at least one valve to control an amount of airflow through the inlet duct and an amount of airflow through the at least one diverter duct.

Abstract: Auxiliary power systems, aircraft including the same, and related methods. An auxiliary power system comprises an auxiliary power unit (APU) controller and an APU with an air intake, a powerhead, and a load compressor stage. The load compressor stage includes a flow regulator assembly, a load compressor, and a bleed air temperature (BAT) sensor for generating a BAT signal. The APU controller regulates a flow rate of a load compressor airflow through the load compressor based on the BAT signal. A method of utilizing an auxiliary power system includes compressing a load compressor airflow to generate a bleed air flow, measuring the BAT with a BAT sensor, generating a BAT signal based on the BAT, transmitting the BAT signal to an APU controller, generating a flow regulator command with the APU controller, transmitting the flow regulator command to a flow regulator assembly, and controlling a flow regulator assembly.

Abstract: Auxiliary power unit inlet apparatus and methods are disclosed. An example apparatus includes an aircraft including a fuselage, the fuselage including an air inlet including a first sub-inlet and a second sub-inlet separated from the first sub-inlet; and a door coupled along the air inlet to enable air to separably flow into the first sub-inlet and the second sub-inlet, the door to deter the air from flowing between the first sub-inlet and the second sub-inlet.

Abstract: Systems and methods for cooling bleed air from an aircraft engine are described. An example system includes a housing to bifurcate airflow exiting a fan of an engine fan system, a pre-cooler assembly disposed within the housing to remove heat from the bleed air, and an inlet duct within the housing to direct the airflow to the pre-cooler assembly. The example system also includes at least one diverter duct within the housing and coupled to the inlet duct to divert the airflow around the pre-cooler assembly. The at least one diverter duct includes an exit directing the airflow into a fan duct of the engine fan system. The example system also includes at least one valve to control an amount of airflow through the inlet duct and an amount of airflow through the at least one diverter duct.

Abstract: Pre-cooler inlet ducts that utilize active flow-control and systems and methods including the same are disclosed herein. The systems include a pre-cooler inlet duct for a jet engine that is configured to receive a pre-cooler air stream and to direct the pre-cooler air stream into a heat exchanger. The pre-cooler inlet duct includes a flow-directing surface, which defines at least a portion of the pre-cooler inlet duct, and an active flow-control device. The active flow-control device is located to modify a boundary layer fluid flow within a boundary layer adjacent the flow-directing surface to resist separation of the boundary layer from the flow-directing surface when the pre-cooler air stream flows through the pre-cooler inlet duct. The methods include methods of resisting boundary layer separation in the pre-cooler inlet duct by flowing the pre-cooler air stream across the flow-directing surface and modifying the boundary layer with the active flow-control device.

Abstract: Thrust recovery outflow valves for aircraft are disclosed. An example thrust recovery outflow valve includes a flow control member having a first aerodynamic surface and a second aerodynamic surface to define at least a portion of a fluid flow passageway between an inlet and an outlet of the thrust recovery outflow valve. A first portion of the first aerodynamic surface and a first portion of the second aerodynamic surface provides a converging profile between the inlet and a throat of the fluid flow passageway. A second portion of the first aerodynamic surface and a second portion of the second aerodynamic surface provides a diverging profile between the throat and the outlet of the fluid flow passageway. The fluid flow passageway is positioned at a small angle relative to an outer surface of an aircraft to enable fluid exiting the fluid flow passageway to provide a thrust recovery vector oriented substantially parallel to the outer surface of the aircraft and opposite a direction of drag.

Abstract: A turbine engine nozzle can include a primary outer wall extending from an engine core area to an annular wall terminus that surrounds an engine tail cone, to form a core nozzle. The turbine engine nozzle also includes a single engine core cowl extending from the engine core area to an annular cowl terminus to form a core compartment vent nozzle. The core compartment vent nozzle exhausts air from a core compartment in a trailing edge between the single engine core cowl and the primary outer wall.

Abstract: In one aspect a propulsion system comprises an engine and a drive assembly coupled to the engine, comprising a first driveshaft rotatable in a first direction about a first axis, a first fan coupled to the first driveshaft to rotate in the first direction, and a clutch assembly to selectively disengage the first fan from the first driveshaft. Other aspects may be described.

Abstract: Systems and methods provide for the mitigation of vibrational forces acting on a horizontal stabilizer of an aircraft. According to one aspect, a damper is coupled to a front portion of a horizontal stabilizer to dampen vibrations in a first degree of freedom, with another damper coupled to a mounting point of the horizontal stabilizer to dampen vibrations in a second degree of freedom. The dampers may be passive, operating independently to mitigate vibrational forces, or active, applying a mitigating force to the horizontal stabilizer based on real-time or estimated vibration states.

Abstract: An apparatus comprises a leading edge of an inlet. The leading edge of the inlet is positioned relative to a direction of air flow such that a total pressure of air along the leading edge of the inlet is equalized within selected tolerances.

Abstract: A method and apparatus for supplying air to a precooler. Air flow is created through a fan duct in an engine system. A first portion of the air flow is directed into a first inlet of an inlet system to feed a first half of the precooler. A second portion of the air flow is directed through the fan duct into a second inlet of the inlet system to feed a second half of the precooler.

Abstract: Thrust recovery outflow valves for aircraft are disclosed. An example thrust recovery outflow valve includes a flow control member having a first aerodynamic surface and a second aerodynamic surface to define at least a portion of a fluid flow passageway between an inlet and an outlet of the thrust recovery outflow valve. A first portion of the first aerodynamic surface and a first portion of the second aerodynamic surface provides a converging profile between the inlet and a throat of the fluid flow passageway. A second portion of the first aerodynamic surface and a second portion of the second aerodynamic surface provides a diverging profile between the throat and the outlet of the fluid flow passageway. The fluid flow passageway is positioned at a small angle relative to an outer surface of an aircraft to enable fluid exiting the fluid flow passageway to provide a thrust recovery vector oriented substantially parallel to the outer surface of the aircraft and opposite a direction of drag.

Abstract: Auxiliary power unit inlet apparatus and methods are disclosed. An example apparatus includes an aircraft including a fuselage, the fuselage including an air inlet including a first sub-inlet and a second sub-inlet separated from the first sub-inlet; and a door coupled along the air inlet to enable air to separably flow into the first sub-inlet and the second sub-inlet, the door to deter the air from flowing between the first sub-inlet and the second sub-inlet.

Abstract: Auxiliary power unit inlet apparatus and methods are disclosed. An example apparatus includes an air inlet for an aircraft including a first air flow path and a second air flow path. The first air flow path is immediately adjacent the second air flow path. The first air flow path is at least partially separated from the second air flow path by a first panel. The example apparatus includes a door hingably coupled adjacent the air inlet. The door includes a second panel extending from an interior surface of the door to substantially prevent air from flowing across the interior surface between the first air flow path and the second air flow path.

Abstract: A turbine engine nozzle can include a primary outer wall extending from an engine core area to an annular wall terminus that surrounds an engine tail cone, to form a core nozzle. The turbine engine nozzle also includes a single engine core cowl extending from the engine core area to an annular cowl terminus to form a core compartment vent nozzle. The core compartment vent nozzle exhausts air from a core compartment in a trailing edge between the single engine core cowl and the primary outer wall.

Abstract: Systems and methods provide for the mitigation of vibrational forces acting on a horizontal stabilizer of an aircraft. According to one aspect, a damper is coupled to a front portion of a horizontal stabilizer to dampen vibrations in a first degree of freedom, with another damper coupled to a mounting point of the horizontal stabilizer to dampen vibrations in a second degree of freedom. The dampers may be passive, operating independently to mitigate vibrational forces, or active, applying a mitigating force to the horizontal stabilizer based on real-time or estimated vibration states.

Abstract: Pre-cooler inlet ducts that utilize active flow-control and systems and methods including the same are disclosed herein. The systems include a pre-cooler inlet duct for a jet engine that is configured to receive a pre-cooler air stream and to direct the pre-cooler air stream into a heat exchanger. The pre-cooler inlet duct includes a flow-directing surface, which defines at least a portion of the pre-cooler inlet duct, and an active flow-control device. The active flow-control device is located to modify a boundary layer fluid flow within a boundary layer adjacent the flow-directing surface to resist separation of the boundary layer from the flow-directing surface when the pre-cooler air stream flows through the pre-cooler inlet duct. The methods include methods of resisting boundary layer separation in the pre-cooler inlet duct by flowing the pre-cooler air stream across the flow-directing surface and modifying the boundary layer with the active flow-control device.