A method of starting an aircraft having at least a first starter/generator (S/G) and a second S/G using at least one inverter/converter and at least one of an AC power source and a first DC power source, the method includes selectively starting at least one of the first S/G or second S/G in an AC start mode and in a DC start mode.

A turbofan engine includes a first spool including a first turbine and a second spool including a second turbine. A superposition gear system includes a plurality of intermediate gears engaged to a sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. A second tower shaft is engaged to drive the sun gear. A starter is selectively coupled to the sun gear through a starter clutch. A first electric motor and a second electric motor are coupled to the superposition gear system and are operable to input power into a corresponding one of the first and second spools.

A turbofan engine includes a first spool including a first turbine and a second spool including a second turbine. A superposition gear system includes a plurality of intermediate gears engaged to a sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. A second tower shaft is engaged to drive the sun gear. A starter is selectively coupled to the sun gear through a starter clutch. A first electric motor and a second electric motor are coupled to the superposition gear system and are operable to input power into a corresponding one of the first and second spools.

An aircraft turbine engine includes a gas generator and a fan arranged upstream from the gas generator and configured to generate a main gas flow, one portion of which flows in a flow path of the gas generator to form a primary flow, and another portion of which flows in a flow path around the gas generator to form a secondary flow. The gas generator has a low-pressure body with a rotor driving the fan and a low-pressure compressor situated upstream from an intermediate housing. The turbine engine also includes an electric machine, mounted coaxially downstream from the fan and upstream from the intermediate housing. An intermediate shaft is driven by the rotor of the low-pressure body and drives rotors of the electric machine and of the low-pressure compressor.

An aircraft turbine engine includes a gas generator and a fan arranged upstream from the gas generator and configured to generate a main gas flow, one portion of which flows in a flow path of the gas generator to form a primary flow, and another portion of which flows in a flow path around the gas generator to form a secondary flow. The gas generator has a low-pressure body with a rotor driving the fan and a low-pressure compressor situated upstream from an intermediate housing. The turbine engine also includes an electric machine, mounted coaxially downstream from the fan and upstream from the intermediate housing. An intermediate shaft is driven by the rotor of the low-pressure body and drives rotors of the electric machine and of the low-pressure compressor.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

A gas turbine engine for an aircraft and a method of operating a gas turbine engine on an aircraft. Embodiments disclosed include a gas turbine engine for an aircraft including: an engine core has a turbine, a compressor, and a core shaft; a fan located upstream of the engine core, the fan has a plurality of fan blades; a nacelle surrounding the engine core and defining a bypass duct and bypass exhaust nozzle; and a gearbox that receives an input from the core shaft and outputs drive to the fan wherein the gas turbine engine is configured such that a jet velocity ratio of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core at idle conditions is greater by a factor of 2 or more than the jet velocity ratio at maximum take-off conditions.

An aircraft starting and generating system includes a starter/generator and an inverter/converter/controller that is connected to the starter/generator and that generates AC power to drive the starter/generator in a start mode for starting a prime mover of the aircraft, and that converts AC power, obtained from the starter/generator after the prime mover have been started, to DC power in a generate mode of the starter/generator. A four leg inverter is coupled with the DC power output and has an inverter/converter/controller (ICC) with a four leg MOSFET-based bridge configuration that drives the starter/generator in a start mode for starting a prime mover of the aircraft, and converts DC power to AC power in a generate mode of the starter/generator. A four leg bridge gate driver is configured to drive the four leg MOSFET-based bridge using pulse width modulation (PWM) during start and generate mode.

An aircraft starting and generating system includes a starter/generator and an inverter/converter/controller that is connected to the starter/generator and that generates AC power to drive the starter/generator in a start mode for starting a prime mover of the aircraft, and that converts AC power, obtained from the starter/generator after the prime mover have been started, to DC power in a generate mode of the starter/generator. A four leg inverter is coupled with the DC power output and has an inverter/converter/controller (ICC) with a four leg MOSFET-based bridge configuration that drives the starter/generator in a start mode for starting a prime mover of the aircraft, and converts DC power to AC power in a generate mode of the starter/generator. A four leg bridge gate driver is configured to drive the four leg MOSFET-based bridge using pulse width modulation (PWM) during start and generate mode.