Systems and methods for operating an engine in a multi-engine rotorcraft are described herein. A first parameter indicative of torque of a first engine is obtained. A decrease of the first parameter is detected. In response to detecting the decrease of the first parameter, an autorotation of the rotorcraft is accommodated, A second parameter indicative of torque of a second engine of the rotorcraft is assessed while accommodating the autorotation. If the second parameter has not decreased, a shaft shear of the first engine is identified and accommodating of the autorotation is ended. If the second parameter has decreased, the accommodating is maintained.

A method for controlling an aircraft capable of hovering is described, comprising a first engine; a second engine; at least one rotor; and a transmission interposed between the first and second engine and the rotor; the transmission comprises a first and a second inlet connected respectively to a first outlet member of the first engine and to a second outlet member of the second engine; the method comprises step i) of placing the in a first configuration, in which the first and second engine make available a first and a second power value; or in a second configuration, in which the first engine (makes available a third power value greater than the first power value to the first inlet, and the second engine delivers a nil power value to the second inlet; the method also comprises, characterised in that it comprises the steps of ii) detecting a series of parameters associated with the operating conditions of the aircraft; and iii) enabling the transition of the aircraft from the first configuration to the second configuration, when the parameters assume respective first values.

The present disclosure provides methods and systems for operating a multi-engine rotorcraft. The method comprises driving a rotor of the rotorcraft with a first engine while a second engine is de-clutched from a transmission clutch system that couples the rotor and the second engine, instructing the second engine to accelerate to a re-clutching speed, and controlling an output shaft speed of the second engine during acceleration of the second engine to the re-clutching speed by applying a damping function to a speed control loop of the second engine.

The present disclosure provides methods and systems for operating a multi-engine rotorcraft. The method comprises driving a rotor of the rotorcraft with a first engine while a second engine is de-clutched from a transmission clutch system that couples the rotor and the second engine, instructing the second engine to accelerate to a re-clutching speed, and controlling an output shaft speed of the second engine during acceleration of the second engine to the re-clutching speed by applying a damping function to a speed control loop of the second engine.

An aircraft propulsion system includes a fan section that includes a fan shaft that is rotatable about a fan axis. The fan shaft includes a fan gear. The aircraft propulsion system also includes a boost turbine engine that includes a first output shaft that includes a first gear that is coupled to the fan gear. The boost turbine engine has a first maximum power capacity. The aircraft propulsion system further includes a cruise gas turbine engine that includes a second output shaft that includes a second gear that is coupled to the fan gear. The cruise turbine engine has a second maximum power capacity that is less than the first maximum power capacity of the boost turbine engine. The fan section produces a thrust that corresponds to power input through the fan gear from the boost turbine engine and the cruise turbine engine.

A combined cycle power generation system for an aircraft includes fuel cell and supercritical CO.sub.2 cycles. The fuel cell cycle includes a compressor and turbine disposed on a first shaft, a fuel cell in fluid communication with the compressor and a fuel source, and a combustor in fluid communication with the fuel cell and the turbine. The combustor is configured to combust partially spent fuel from the fuel cell and produce combustion exhaust gas for delivery to the turbine. The supercritical CO.sub.2 cycle includes a compressor and turbine disposed on a second shaft, a supercritical CO.sub.2 fluid circuit in thermal communication with the combustor and configured to deliver CO.sub.2 to the turbine and compressor, and a heat exchanger in thermal communication with the supercritical CO.sub.2 fluid circuit and a source of cooling fluid. A mechanical linkage is configured to transfer power from the second shaft to the first shaft.

A combined cycle power generation system for an aircraft includes fuel cell and supercritical CO.sub.2 cycles. The fuel cell cycle includes a compressor and turbine disposed on a first shaft, a fuel cell in fluid communication with the compressor and a fuel source, and a combustor in fluid communication with the fuel cell and the turbine. The combustor is configured to combust partially spent fuel from the fuel cell and produce combustion exhaust gas for delivery to the turbine. The supercritical CO.sub.2 cycle includes a compressor and turbine disposed on a second shaft, a supercritical CO.sub.2 fluid circuit in thermal communication with the combustor and configured to deliver CO.sub.2 to the turbine and compressor, and a heat exchanger in thermal communication with the supercritical CO.sub.2 fluid circuit and a source of cooling fluid. A mechanical linkage is configured to transfer power from the second shaft to the first shaft.

A gas turbine engine includes a first spool of a primary flow path and a second spool of a secondary flow path. The second spool is nonconcentric with the first spool. The second spool includes a boost compressor and a load compressor in fluid communication with an inlet plenum. An inlet duct assembly and an outlet duct assembly place the secondary flow path in communication with the primary flow path. The gas turbine includes a controller operable to vary open areas of variable inlet guide vanes to control a flow division between the boost compressor and the load compressor.

A gas turbine engine includes a first spool of a primary flow path and a second spool of a secondary flow path. The second spool is nonconcentric with the first spool. The second spool includes a boost compressor and a load compressor in fluid communication with an inlet plenum. An inlet duct assembly and an outlet duct assembly place the secondary flow path in communication with the primary flow path. The gas turbine includes a controller operable to vary open areas of variable inlet guide vanes to control a flow division between the boost compressor and the load compressor.

An aircraft engine, has: a low-pressure compressor and a high-pressure compressor located downstream of the low-pressure compressor; a gaspath valve upstream of the high-pressure compressor, the gaspath valve movable between an open configuration and a closed configuration; and a bypass flow path having in flow series a bypass inlet, a bypass valve, and a bypass outlet, the bypass inlet fluidly communicating with the gaspath upstream of at least one stage of the low-pressure compressor, the bypass valve having an open configuration in which the bypass valve allows a bypass flow and a closed configuration in which the bypass valve blocks the bypass flow, the bypass outlet fluidly communicating with the bypass inlet via the bypass valve and with the gaspath at a location in the gaspath fluidly downstream of the gaspath valve, downstream of the low-pressure compressor, and upstream of the high-pressure compressor.