A method of extracting work from a convertible gas turbine engine having a core flowpath and a bypass flowpath. The method comprises operating the convertible gas turbine engine at a first volumetric flow rate through the core flowpath and a second volumetric flow rate through the bypass flowpath to produce a first work output of the convertible gas turbine engine; extracting the first work output via an unshrouded fan and a shaft at a first fan to shaft extraction ratio; altering the second volumetric flowrate through the bypass flowpath while maintaining the first work output; and extracting the first work output via an unshrouded fan and a shaft at a second fan to shaft extraction ratio.

An engine includes a first power source configured to drive a first power input, a power output, and a transmission engaged with the first power input and the power output. The transmission includes an epicyclic gear train engaged with the first power input and selectively engageable with the power output. A brake is engageable in a drive condition with the epicyclic gear train to transfer power from the first power input to the power output. The brake in a start condition is disengageable to decouple the first power input from the power output. A start assist motor associated with a second power source is engaged with the transmission to rotate the power output.

The present disclosure provides methods and systems for controlling a propeller-driven aircraft powered by at least one gas turbine engine. A thrust change is obtained corresponding to a difference between an actual thrust and a desired thrust for an engine. When the thrust change is greater than a pre-determined threshold, a setting change to one or more control input(s) of the engine is determined. One or more commands are output to cause the setting change of the control input(s).

Systems and methods for controlling a gas turbine engine and a propeller are described herein. A target output power for the engine and a target speed for the propeller are received. A measurements of at least one engine parameter and a measurement of at least one propeller parameter are received. At least one engine control command is generated based on the target output power, the measurement of the at least one engine parameter and at least one model of the engine. At least one propeller control command is generated based on the target speed, the measurement of the at least one propeller parameter and the at least one model of the propeller. The at least one engine control command is output for controlling an operation of the engine accordingly and the at least one propeller control command is output for controlling an operation of the propeller accordingly.

A method of extracting work from a convertible gas turbine engine having a core flowpath and a bypass flowpath. The method comprises operating the convertible gas turbine engine at a first volumetric flow rate through the core flowpath and a second volumetric flow rate through the bypass flowpath to produce a first work output of the convertible gas turbine engine; extracting the first work output via an unshrouded fan and a shaft at a first fan to shaft extraction ratio; altering the second volumetric flowrate through the bypass flowpath while maintaining the first work output; and extracting the first work output via an unshrouded fan and a shaft at a second fan to shaft extraction ratio.

Systems and methods are disclosed for controlling the pitch angle of a propeller and rotor assembly that selectively limit the pitch angle according to a selected mode of operation. The system comprises a fine stop collar defining a primary channel, an oil transfer bearing (OTB) extending across the fine stop collar, and an actuator piston engaged with a propeller blade crankshaft to vary propeller blade pitch, wherein the annular piston is positioned about the OTB in fluid communication with the primary channel.

Systems and methods are provided for an air-driven augmentor fan equipped aircraft propulsor. The augmentor fan may increase the effective bypass ratio of the aircraft propulsor and reduce fuel consumption and carbon emissions of the aircraft. The augmentor fan may be driven by air energized by a ducted fan powered by the core engine of the aircraft propulsor. The energized air may be received by an inlet, flowed through a flow path, and exhausted out the outlet to drive the augmentor fan. The exhausted energized air may impart a torque on the augmentor fan or blades of the augmentor fan. One or more of the inlet, flow path, or outlet may be variable in size to control the volume of air flowed through the flow path.

Systems and methods include providing an aircraft with a fuselage and a convertible engine disposed within the fuselage. The convertible engine is operable as a turbofan engine in a thrust mode and a turboshaft engine in a shaft power mode. The convertible engine includes a housing, an engine core having a low pressure turbine shaft, and a bypass fan system. The bypass fan system includes a bypass fan having a fan clutch. The fan clutch selectively couples at least a portion of the bypass fan to the low pressure turbine shaft when the convertible engine is operated in the thrust mode and decouples at least a portion of the bypass fan from the low pressure turbine shaft when the convertible engine is operated in the shaft power mode.

Systems and methods include providing an aircraft with a fuselage and a convertible engine disposed within the fuselage. The convertible engine is operable as a turbofan engine in a thrust mode and a turboshaft engine in a shaft power mode. The convertible engine includes a housing, an engine core having a low pressure turbine shaft, and a bypass fan system. The bypass fan system includes a bypass fan having a fan clutch. The fan clutch selectively couples at least a portion of the bypass fan to the low pressure turbine shaft when the convertible engine is operated in the thrust mode and decouples at least a portion of the bypass fan from the low pressure turbine shaft when the convertible engine is operated in the shaft power mode.

A propeller shaft assembly for an aircraft engine includes a shaft having a bore extending through the shaft at a front end thereof, the front end of the shaft having an outer surface facing radially outwardly from the shaft and an inner surface spaced apart from the outer surface and facing radially inwardly to the bore. The shaft has a front flange extending radially outwardly on the outer surface, the front flange having a base merging with the outer surface of the shaft. A sleeve is coupled to the shaft within the bore by an interference fit between the sleeve and the shaft, at least part of the sleeve axially aligned with the front flange. The sleeve axially extends from a front to a rear sleeve end, the rear sleeve end axially offset from the engine side surface of the front flange at the base of the front flange.