In order to reduce the weight of a hybrid propulsion system for a multi-rotor rotary-wing aircraft, the system comprises at least one inverter configured to supply power in parallel to multiple electric motors intended to drive the corresponding propellers of the system.

In order to reduce the weight of a hybrid propulsion system for a multi-rotor rotary-wing aircraft, the system comprises at least one inverter configured to supply power in parallel to multiple electric motors intended to drive the corresponding propellers of the system.

The present disclosure relates to an architecture of a propulsion system of a multi-engine helicopter comprising turboshaft engines connected to a power transmission gearbox, characterized in that it comprises: at least one hybrid turboshaft engine capable of operating in at least one standby mode during a stable cruise flight of the helicopter; at least two systems for controlling each hybrid turboshaft engine, each system comprising an electric machine connected to the hybrid turboshaft engine and suitable for rotating the gas generator thereof, and at least one source of electrical power for the electric machine, each reactivation system being configured such that it can drive the turboshaft engine in at least one operating mode among a plurality of predetermined modes.

The present disclosure relates to an architecture of a propulsion system of a multi-engine helicopter comprising turboshaft engines connected to a power transmission gearbox, characterized in that it comprises: at least one hybrid turboshaft engine capable of operating in at least one standby mode during a stable cruise flight of the helicopter; at least two systems for controlling each hybrid turboshaft engine, each system comprising an electric machine connected to the hybrid turboshaft engine and suitable for rotating the gas generator thereof, and at least one source of electrical power for the electric machine, each reactivation system being configured such that it can drive the turboshaft engine in at least one operating mode among a plurality of predetermined modes.

A propulsion assembly for a rotorcraft includes a raceway having a tapered inner surface and a mast configured to receive the raceway at a raceway receiving station. The mast has a tapered outer surface at the raceway receiving station. The propulsion assembly includes a mast bearing assembly having a plurality of bearings facing the mast to engage the raceway. The tapered inner surface of the raceway is friction welded to the tapered outer surface of the mast at the raceway receiving station to form a tapered friction weld line.

A propulsion assembly for a rotorcraft includes a raceway having a tapered inner surface and a mast configured to receive the raceway at a raceway receiving station. The mast has a tapered outer surface at the raceway receiving station. The propulsion assembly includes a mast bearing assembly having a plurality of bearings facing the mast to engage the raceway. The tapered inner surface of the raceway is friction welded to the tapered outer surface of the mast at the raceway receiving station to form a tapered friction weld line.

A transmission cooling assembly of a helicopter includes: a transmission including a speed change structure that changes the speed of rotation produced by rotational power input from a prime mover and outputs the resulting rotational power and a housing accommodating the speed change structure; a cowl covering at least a part of an outer surface of the housing, with a gap defined between the cowl and the outer surface; and a flow structure that allows external air to flow through the gap.

A transmission cooling assembly of a helicopter includes: a transmission including a speed change structure that changes the speed of rotation produced by rotational power input from a prime mover and outputs the resulting rotational power and a housing accommodating the speed change structure; a cowl covering at least a part of an outer surface of the housing, with a gap defined between the cowl and the outer surface; and a flow structure that allows external air to flow through the gap.

A shaft assembly (which may be a rotor mast for a rotorcraft) may include a shaft body formed with composite material and one or more metal fittings attached to the shaft body. A metal fitting may include an interior opening with a cross-section having a non-circular perimeter (such as an oval or an ellipse). The interior opening may also include contouring, such as a first tapered section in which the fitting converges toward the longitudinal axis of the shaft body and a second tapered section in which the fitting diverges from the longitudinal axis.

A shaft assembly (which may be a rotor mast for a rotorcraft) may include a shaft body formed with composite material and one or more metal fittings attached to the shaft body. A metal fitting may include an interior opening with a cross-section having a non-circular perimeter (such as an oval or an ellipse). The interior opening may also include contouring, such as a first tapered section in which the fitting converges toward the longitudinal axis of the shaft body and a second tapered section in which the fitting diverges from the longitudinal axis.