A secondary power unit for an aircraft comprises a gas turbine engine having at least one drive shaft, a twin-load compressor including first and second load compressors both coupled with the drive shaft, a first ram-air intake in fluid communication with the twin-load compressor, and a flow regulating arrangement coupled with the first and second compressors outputs to individually regulate the generated flow of compressed air. The flow regulating arrangement is also adapted to be fluidly communicated with an Air Cycle Machine of an aircraft, and a control system is adapted to feed the flow of compressed air as bleed air to the Air Cycle Machine of an aircraft, both when the aircraft is on ground and in flight. The secondary power unit is capable of avoiding bleed air extraction from the main engines with the aim of reducing fuel consumption.

An engine system includes a gas turbine engine with a first compressor, a first combustor, and a first turbine. The engine system also includes a secondary power unit with a second compressor, a second combustor, a second turbine, a third compressor coupled to the second compressor, and an electric motor-generator, where the secondary power unit is coupled to the gas turbine engine. A controller is operable to determine an operating mode of the engine system, select an input energy source and an output type of the secondary power unit based on the operating mode, control the secondary power unit based on the input energy source and the output type as selected, detect a change in the operating mode of the engine system, and modify the input energy source and/or the output type of the secondary power unit based on the change in the operating mode.

A medium supply system for delivering one or more mediums to an environmental control system of a vehicle includes a manifold arranged in fluid communication with an inlet of the environmental control system, a first medium source for delivering a first medium to the manifold via a first port; a second medium source for delivering a second medium to the manifold via a second port, and a third medium source for delivering a third medium to the manifold via a third port. At least one of a temperature and pressure of each of the first medium, the second medium, and the third medium varies.

An expedited preflight readiness system for aircraft includes a power source having one or more battery modules for storing electrical power. An integrated controller is electrically and communicatively coupled with the power source for monitoring and controlling the power source to provide electrical power to aircraft subsystems. A mobile device is communicatively coupled with the integrated controller for communicating instructions to the integrated controller for initiating preflight readiness of the aircraft and for monitoring preflight readiness. A method for preconditioning an aircraft includes determining a state-of-charge of an APU and activating an environmental control subsystem for preconditioning the aircraft by adjusting a current temperature according to a preconditioning profile based on one or more of a target temperature, a target time, the current temperature, an outside air temperature, an amount of energy, and a state-of-charge of the APU.

Methods and systems for operating an auxiliary power unit (APU) of an aircraft are described. The method comprises obtaining external environment parameters of the aircraft, determining an available output power for the APU as a function of the external environment parameters, and setting an overcurrent protection threshold of the APU to a level associated with the available output power.

A method and system for controlling fresh air flow into a controlled environment are disclosed herein. The method comprises: measuring, using a sensor, a predetermined property in the controlled environment; estimating, by a controller, a number of people inside the controlled environment based on the measured property, and setting, by the controller, a rate of fresh air flow to the controlled environment based at least in part on the estimated number of people inside the controlled environment.

An auxiliary power unit (10) for an aircraft (1) comprises a gas turbine engine comprising an engine core (12). The engine core comprises a core compressor (14) and core turbine (18) coupled by a core shaft (24). The auxiliary power unit further comprises a load spool comprising a load compressor (30), a load turbine (20) and a permanent magnet electric machine (28), each being coupled by a load shaft (26). The load shaft (26) and core shaft (24) are configured to rotate independently of one another.

A distributed auxiliary-power-unit (APU) system for an aircraft includes one or more battery modules for storing electrical power, and a plurality of racks distributed throughout the aircraft for receiving the one or more battery modules to electrically connect with an electrical subsystem of the aircraft. A plurality of hot-swappable racks are adapted to receive the battery modules for electrically and communicatively coupling with the electrical subsystem and an integrated controller. A remote interface is communicatively coupled with the integrated controller for receiving user-input to direct electrical power from the battery modules to one or more subsystems of the aircraft. A number of battery modules installed is based on an amount of electrical power planned for a given flight of the aircraft.

A pressure control system includes an overboard valve in indirect communication with a first enclosed environment and in direct communication with a second enclosed environment. The first environment is suitable for human occupancy and configured to receive pressurized air from an environmental control system. The second environment is configured to receive the pressurized air from the first environment. An inboard valve is configured to supply a discharge of pressurized air from the second environment. An outflow valve is configured to regulate a discharge of air from the first environment to an area outside the first and second environments. A positive pressure relief valve configured to regulate a discharge of air from the first environment. A negative pressure relief valve configured to regulate an ingress of air into the first environment. A control valve is configured to regulator and supply pressurized air from the first environment to a compressor.

An environmental control system of an aircraft includes a compressing device having a compressor configured to receive a first flow of a medium and a turbine configured to receive the first flow of the medium and a distinct second flow of the medium. A dehumidification system is arranged in fluid communication with the turbine. A valve is configured to divert the second flow around the turbine and an inlet port is arranged in fluid communication with the compressor, the turbine, and the dehumidification system.