A method of operating a twin engine helicopter power plant, the power plant comprising: two turboshaft engines each having an engine shaft with a turbine at a distal end and a one-way clutch at a proximal end; a gear box having an input driven by the one way clutch of each engine and an output driving a helicopter rotor; a bypass clutch disposed between the proximal end of each engine shaft and the input of the gear box; and power plant management system controls for activating the bypass clutch; the method comprising: detecting when a rotary speed of an associated engine shaft is less than a rotary speed of the gear box input; activating the bypass clutch to drive the associated engine shaft using the rotation of the gear box input; and starting an associated engine by injecting fuel when the bypass clutch is activated.

A vertical take-off and landing aircraft including a wing structure including a wing, a rotor operatively supported by the wing, and a hybrid power system configured to drive the rotor, the hybrid power system including a first power system and a second power system, wherein a first energy source for the first power system is different than a second energy source for the second power system.

An aircraft power plant has a hybrid propulsion system having an electric motor, a combustion engine, an output shaft drivingly connectable to a thrust generator, a compressor, and a transmission having a first transmission drive path and a second transmission drive path, the combustion engine and the output shaft in driving engagement with the first transmission drive path, the electric motor selectively drivingly engageable to the compressor via either the first drive path or via the second drive path.

An aircraft power plant has a hybrid propulsion system having an electric motor, a combustion engine, an output shaft drivingly connectable to a thrust generator, a compressor, and a transmission having a first transmission drive path and a second transmission drive path, the combustion engine and the output shaft in driving engagement with the first transmission drive path, the electric motor selectively drivingly engageable to the compressor via either the first drive path or via the second drive path.

A propulsion system for a tiltrotor aircraft includes an engine supported by the airframe and a fixed gearbox operably coupled to the engine. Inboard and outboard tip ribs extend above the wing and define slots. Inboard and outboard bearing cartridges are received in respective slots. The inboard and outboard bearing cartridges respectively include inboard and outboard bearing assemblies. A pylon assembly is rotatably coupled between the inboard and outboard bearing assemblies. The pylon assembly includes a spindle gearbox having an input gear, a mast operably coupled to the input gear and a proprotor assembly operable to rotate with the mast. The spindle gearbox is rotatable about a conversion axis to selectively operate the tiltrotor aircraft between helicopter and airplane modes. A common shaft, rotatable about the conversion axis, is configured to transfer torque from an output gear of the fixed gearbox to the input gear of the spindle gearbox.

An interconnect drive system for an aircraft has a driveline and clutch control system. The driveline comprises a shaft for each propulsion assembly, each shaft for transferring torque to and from the associated propulsion assembly, and a clutch operably coupling the shafts and configured for selective engagement. The clutch is capable of transferring a first amount of torque between the shafts while engaged and a second amount of torque between the shafts while disengaged. The system also has a clutch control system, comprising a computer operably connected to the clutch for controlling operation of the clutch and sensors for sensing torque applied to the driveline, output from the sensors being communicated to the computer. The computer commands operation of the clutch in response to the output from the sensors, the clutch being commanded to disengage to relieve a transient torque imbalance in the driveline.

An aircraft propulsion system includes at least one hybrid-electric power plant for delivering power to an air mover for propelling an aircraft. The at least one hybrid-electric power plant includes a first thermal engine and an electrical motor arranged in a parallel drive configuration or in an in-line drive configuration. The aircraft propulsion system includes a second thermal engine operatively connected to the electrical motor to power the electrical motor. A method for providing propulsion to an aircraft includes delivering power to an air mover for propelling the aircraft with at least one hybrid-electric power plant. The at least one hybrid-electric power plant includes a first thermal engine and an electrical motor arranged in a parallel drive configuration or in an in-line drive configuration. The method includes powering the electrical motor with a second thermal engine.

An aircraft propulsion system includes at least one hybrid-electric power plant for delivering power to an air mover for propelling an aircraft. The at least one hybrid-electric power plant includes a first thermal engine and an electrical motor arranged in a parallel drive configuration or in an in-line drive configuration. The aircraft propulsion system includes a second thermal engine operatively connected to the electrical motor to power the electrical motor. A method for providing propulsion to an aircraft includes delivering power to an air mover for propelling the aircraft with at least one hybrid-electric power plant. The at least one hybrid-electric power plant includes a first thermal engine and an electrical motor arranged in a parallel drive configuration or in an in-line drive configuration. The method includes powering the electrical motor with a second thermal engine.

A method of managing a loss of power from a power plant having three engines. During a monitoring step, each engine is monitored in order to detect whether the engine is suffering a loss of power. During a verification step, it is determined whether the power plant is overpowered. During a signalling step, a first alert is generated when an engine has lost power but the power plant is in fact overpowered, and a second alert different from the first alert is generated when an engine has lost power and the power plant is not overpowered.

A method of managing a loss of power from a power plant having three engines. During a monitoring step, each engine is monitored in order to detect whether the engine is suffering a loss of power. During a verification step, it is determined whether the power plant is overpowered. During a signalling step, a first alert is generated when an engine has lost power but the power plant is in fact overpowered, and a second alert different from the first alert is generated when an engine has lost power and the power plant is not overpowered.