An air intake system comprising an air duct suitable for providing airflow to the inside of an aircraft, preferably to an auxiliary power unit; an inlet arranged at one end of the air duct; a skin surrounding the inlet; a plurality of slots arranged on the skin; a driving arrangement, a flap door connected to the driving arrangement, and a plurality of fins connected to the driving means. The driving arrangement is configured for moving the flap door between at least two positions, the positions being a closed position wherein the flap door closes the inlet, and an opened position wherein the flap door is driven away from the closed position. The driving arrangement is also configured for moving the plurality of fins such that the plurality of fins protrudes through the slots.

A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

An inlet door state control system for an auxiliary power unit (APU) includes an inlet door configured to allow air into an inlet of the APU. The system also includes an actuator configured to open the inlet door. The system also includes an APU threshold switch connected to the actuator, the APU threshold switch configured to automatically change from an open position to a closed position when a predetermined APU operating condition is met. In the system, the actuator opens the inlet door when the APU threshold switch is in the closed position.

A method and apparatus are presented. An active flow control system comprises a flow control valve, a manifold, and a temperature control system. The flow control valve is configured to control a flow of air into the manifold. The manifold is operatively connected to a number of actuators. The temperature control system is configured to heat at least a portion of the flow of air.

An airplane has main propulsion engines and a first fuel supply for the main propulsion engines. The airplane further has an auxiliary propulsion engine and a second fuel supply for the auxiliary propulsion engine, this second fuel supply being separate from the first fuel supply. The auxiliary propulsion engine can be switched on independently from the main propulsion engines. Such airplane has increased safety, since it will be possible to maintain flight, particularly when at high altitude, even if all main propulsion engines have failed.

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.

An aircraft including a combustion engine with a combustion chamber an injection device for injecting fuel in the combustion chamber and an air separation device adapted to separate air into an oxygen-enriched gas mix and an nitrogen-enriched gas mix, wherein the oxygen-enriched gas mix is injected into the combustion chamber with the fuel while the nitrogen-enriched gas mix is used to inert at least some portions of the aircraft in the environment of said combustion engine.

An aircraft auxiliary power unit is equipped with a charging compressor. A method determines a surge parameter indicative of a risk that the charging compressor will display the phenomenon known as surge. A method and a system control a relief valve of this charging compressor. The method for determining the surge parameter includes calculating this surge parameter Ppomp as being the sum of a first term T1 and of a second term T2, the first term T1 being calculated on the basis of a first pressure P1 measured downstream of a diffuser of the charging compressor, and of a second pressure P2 measured upstream of the diffuser, the second term T2 being calculated on the basis of a third pressure P3 measured upstream of the diffuser and of an ambient pressure Psamb indicative of a pressure of an ambient environment.

An aircraft including a combustion engine with a combustion chamber an injection device for injecting fuel in the combustion chamber and an air separation device adapted to separate air into an oxygen-enriched gas mix and an nitrogen-enriched gas mix, wherein the oxygen-enriched gas mix is injected into the combustion chamber with the fuel while the nitrogen-enriched gas mix is used to inert at least some portions of the aircraft in the environment of said combustion engine.