In some examples, a gas turbine engine including a high-pressure (HP) spool assembly including a HP shaft, a HP compressor and HP turbine; a lower pressure (LP) spool assembly including a LP shaft and LP turbine; a motor-generator coupled to the LP shaft; and a controller. The controller is configured to control the motor-generator to operate in a motor mode to apply torque the LP shaft during a starting of the HP spool assembly, and control the motor-generator to operate in a generator mode for a least a period of time following the starting of the HP spool assembly.

In some examples, a gas turbine engine including a high-pressure (HP) spool assembly including a HP shaft, a HP compressor and HP turbine; a lower pressure (LP) spool assembly including a LP shaft and LP turbine; a motor-generator coupled to the LP shaft; and a controller. The controller is configured to control the motor-generator to operate in a motor mode to apply torque the LP shaft during a starting of the HP spool assembly, and control the motor-generator to operate in a generator mode for a least a period of time following the starting of the HP spool assembly.

A tiltrotor aircraft having a propulsion configuration that divorces the engine core power from the thrust fan, using a combined gearbox with a plurality of clutches to couple and decouple one or more rotor systems and one or more thrust fans. The aircraft can be operable for vertical takeoff and landing (VTOL) in a helicopter mode, forward flight in a proprotor mode, and high-speed forward flight in an airplane (jet) mode. The propulsion configuration provides shaft horsepower (SHP) to rotors for VTOL flight, while also providing SHP to the thrust fan for high speed flight. Allowing the rotor and the thrust fan to be clutched on and off, sequentially, enables transition from rotor-borne VTOL flight to wing-borne thrust fan flight, and back.

Method for monitoring the operation of a pair of turboprop engines of an aircraft comprising the steps of: detecting the sound pressure generated by the first or second turboprop engine generating a respective first or second signal x(t); iteratively calculating by means of a function Rx/Ry the similarity between the first/second signal x(t)/y(t) at a time T1 and at a time T2 subsequent to time T1; and storing the degrees of similarity calculated in successive iterations in order to detect situations of normal operation of the engines when the degrees of similarity fall in successive iterations within the interval of a first value and to detect a potential fault situation in the engines when the degrees of similarity depart from this interval.

In accordance with at least one aspect of this disclosure, there is provided a fuel control system for gaseous fuel in an aircraft. The system includes a control module operatively connected to a metering device in a fuel flow conduit, the control module operable to control the flow of fuel through the fuel flow conduit. The control module includes an input line operable to receive a command input indicative of a requested engine state. In embodiments, the control module includes a compressibility logic and machine readable instructions. The machine readable instruction can be configured to cause the control module to control the metering device to achieve the requested engine state based on a compressibility factor input from the compressibility logic.

In accordance with at least one aspect of this disclosure, there is provided a fuel control system for gaseous fuel in an aircraft. The system includes a control module operatively connected to a metering device in a fuel flow conduit, the control module operable to control the flow of fuel through the fuel flow conduit. The control module includes an input line operable to receive a command input indicative of a requested engine state. In embodiments, the control module includes a compressibility logic and machine readable instructions. The machine readable instruction can be configured to cause the control module to control the metering device to achieve the requested engine state based on a compressibility factor input from the compressibility logic.

A hybrid electric propulsion system includes a gas turbine engine having a low speed spool and a high speed spool. The low speed spool includes a low pressure compressor and a low pressure turbine, and the high speed spool includes a high pressure compressor and a high pressure turbine. The hybrid electric propulsion system also includes an energy storage system, an electric motor configured to augment rotational power of the high speed spool, and a controller. The controller is operable to detect a start condition of the gas turbine engine, control power delivery from the energy storage system to the electric motor based on detecting the start condition, and provide a compressor stall margin using a power-assist provided by the electric motor to the high speed spool over a targeted speed range during starting of the gas turbine engine.

A turbomachine for an aircraft extending axially along an axis X comprising a primary flow path in which an air stream flows intended for the combustion chamber and a secondary flow path in which an air stream flows intended for propulsion, the compressor comprising a plurality of first variable bypass valves, a plurality of second variable bypass valves, the turbomachine comprising a first control system configured to control the movement of the plurality of first variable bypass valves and a second control system configured to control the movement of the plurality of second variable bypass valves, the first control system and the second control system being separate.

A turbomachine for an aircraft extending axially along an axis X comprising a primary flow path in which an air stream flows intended for the combustion chamber and a secondary flow path in which an air stream flows intended for propulsion, the compressor comprising a plurality of first variable bypass valves, a plurality of second variable bypass valves, the turbomachine comprising a first control system configured to control the movement of the plurality of first variable bypass valves and a second control system configured to control the movement of the plurality of second variable bypass valves, the first control system and the second control system being separate.

A twin-engine system includes a gas turbine engine comprising a core and a first output shaft drivable by the core. An electric engine has an electric motor configured to drive a second output shaft. A reduction gear box (RGB) has an RGB input drivingly engaged to both the first output shaft and the second output shaft. The RGB has an RGB output to provide rotational output to a rotatable load.