Abstract: 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.

Abstract: A method of verifying operation of an aircraft in a pre-defined flight mode includes operating the aircraft in a first flight mode, commanding the aircraft to transition to a second flight mode, evaluating a plurality of motor performance parameters, and based on values of the plurality of motor performance parameters, determining whether the aircraft has successfully transitioned to the second flight mode.

Abstract: A method of verifying operation of an aircraft in a pre-defined flight mode includes operating the aircraft in a first flight mode, commanding the aircraft to transition to a second flight mode, evaluating a plurality of motor performance parameters, and based on values of the plurality of motor performance parameters, determining whether the aircraft has successfully transitioned to the second flight mode.

Abstract: A blade-pitch change mechanism includes a motor comprising a rotating motor shaft and a housing, a solenoid coupled to a first end of the rotating motor shaft and to the housing, and a hub coupled with a second end of the rotating motor shaft. The hub includes a cylindrical puck having formed therein a gated castellated groove and connected to the second end of the rotating motor shaft and a cylindrical blade-pitch hub selectively couplable with the cylindrical puck via a plurality of drive pins and having formed therein a blade-pitch adjustment groove.

Abstract: An exemplary aircraft includes a turbine engine having a gas generator spool and a power spool, the power spool operational to drive a rotor, a first generator coupled to the gas generator spool, and a controller operable to increase a load on the gas generator spool when the gas generator spool is on a speed limit thereby increasing a speed limit margin in order to increase power available from the turbine engine.

Abstract: 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.

Abstract: An exemplary aircraft includes a turbine engine having a gas generator spool and a power spool, the power spool operational to drive a rotor, a first generator coupled to the gas generator spool, and a controller operable to increase a load on the gas generator spool when the gas generator spool is on a speed limit thereby increasing a speed limit margin in order to increase power available from the turbine engine.

Abstract: A hybrid propulsion system for a tiltrotor aircraft comprises one or more engines that provide thrust whenever the tiltrotor aircraft is in a first forward flight mode, one or more electrical or hydraulic power sources, and two or more pylon assemblies. Each pylon assembly houses one or more electric or hydraulic motors connected to the one or more electrical or hydraulic power sources and a proprotor. All or part of each pylon assembly is rotatable. The proprotors provide lift whenever the tiltrotor aircraft is in a vertical takeoff and landing mode and a hover mode, and provide thrust whenever the tiltrotor aircraft is in a second forward flight mode.

Abstract: A modular tandem tiltrotor aircraft in which the tiltrotor assemblies are operably coupled at the forward and aft ends of the fuselage of the aircraft is disclosed. The modular tandem tiltrotor assemblies are capable of rotating between a vertical lift position and a horizontal flight position. The modular tandem tiltrotor aircraft can be structurally more efficient and lower drag than a conventional tiltrotor, has better control authority and lifting capacity than hybrid-quads and tail-sitters, and has more range than a helicopter or multi-rotor. The modular tandem tiltrotor aircraft can orbit and search over a broad area, or can hover for long periods, depending on the application. Instead of providing a multi-function tandem tiltrotor aircraft that is generally suited for all applications, but not optimized for any, the modular tandem tiltrotor aircraft allows for customized configuration to optimize the aircraft for a particular application.

Abstract: An exemplary convertible engine includes an engine housing forming a fan duct extending from a fan inlet to an exhaust; a fan positioned in the fan duct proximate the fan inlet; an engine core located in the fan duct aft of the fan, the engine core coupled to the fan by a fan shaft; a drive shaft mechanically coupled to the engine core and extending exterior of the engine housing; and a dedicated core inflow duct coupled to the core and having a core inlet to capture and direct air into the engine core. An inlet barrier filter may be located in the dedicated core inflow duct. The core inlet may be located inside of the fan duct or exterior to the fan duct. A gearbox may be operationally connected to the fan shaft and may be located inside of the fan duct.

Abstract: 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.