A drive shaft body extends between axial ends and has an outer peripheral surface with undulations extending between relatively greater and smaller outer diameters. The undulations extend along a non-zero angle relative to a circumferential direction defined relative to a drive axis of the drive shaft. The undulations extend along a spiral. The drive shaft body is formed of a fiber-reinforced composite material.

According to an aspect, a computer-implemented method for water volume estimation includes detecting water based at least in part on sensor-based data; determining a volume of water based at least in part on the sensor-based data; determining a location at the water for an aircraft to retrieve water via a water retrieving apparatus; and translating the location of the water into pilot inputs to guide the aircraft to the water.

According to an aspect, a computer-implemented method for water volume estimation includes detecting water based at least in part on sensor-based data; determining a volume of water based at least in part on the sensor-based data; determining a location at the water for an aircraft to retrieve water via a water retrieving apparatus; and translating the location of the water into pilot inputs to guide the aircraft to the water.

A variable guide vane assembly has: variable guide vanes having airfoils extending from inner ends to outer ends, the variable guide vanes pivotable about respective spanwise axes between one or more open positions and a closed position, in the closed position, trailing edge regions of the airfoils sealingly engage leading edge regions of adjacent ones of the airfoils to block an air flow; an outer wall extending around the central axis, the outer ends of the variable guide vanes pivotably engaged to the outer wall; and an inner wall extending around the central axis, the inner ends of the variable guide vanes pivotably engaged to the inner wall, the inner wall defining inner faces distributed about the central axis, a shape of the inner faces complementary to a shape of the inner ends of the airfoils to form a seal when the variable guide vanes are in the closed position.

A variable guide vane assembly has: variable guide vanes having airfoils extending from inner ends to outer ends, the variable guide vanes pivotable about respective spanwise axes between one or more open positions and a closed position, in the closed position, trailing edge regions of the airfoils sealingly engage leading edge regions of adjacent ones of the airfoils to block an air flow; an outer wall extending around the central axis, the outer ends of the variable guide vanes pivotably engaged to the outer wall; and an inner wall extending around the central axis, the inner ends of the variable guide vanes pivotably engaged to the inner wall, the inner wall defining inner faces distributed about the central axis, a shape of the inner faces complementary to a shape of the inner ends of the airfoils to form a seal when the variable guide vanes are in the closed position.

A hybrid propulsion system with controllers and a drive shaft of a helicopter with a main rotor connected to a gearbox which can keep a flight attitude set by a pilot stable. It includes a pilot controller, a combustion engine and an electric motor, both of which act directly on the drive shaft. The VM is connected to a VM controller, and the EM is connected to an EM controller. One torque sensor and one tachometer are each arranged on the drive shaft, wherein during operation both the VM controller and the EM controller are able to receive values for the current speed and the current torque. Specified values for speed and torque, in which the VM can attain its optimum efficiency, are stored in memory and can be retrieved by the EM controller, wherein the first value can also be retrieved by the VM controller.

A hybrid propulsion system with controllers and a drive shaft of a helicopter with a main rotor connected to a gearbox which can keep a flight attitude set by a pilot stable. It includes a pilot controller, a combustion engine and an electric motor, both of which act directly on the drive shaft. The VM is connected to a VM controller, and the EM is connected to an EM controller. One torque sensor and one tachometer are each arranged on the drive shaft, wherein during operation both the VM controller and the EM controller are able to receive values for the current speed and the current torque. Specified values for speed and torque, in which the VM can attain its optimum efficiency, are stored in memory and can be retrieved by the EM controller, wherein the first value can also be retrieved by the VM controller.

A brake for an aircraft includes a housing, a shaft defining an axis (X) and extending into the housing, a floating brake disk on the shaft, the brake disk fixed for rotation with the shaft and arranged to be axially movable within the housing, a static brake pad arranged on a first side of the floating brake disk, a movable brake pad arranged on a second, opposite, side of the floating brake disk and biasing means for moving the movable brake pad relative to the housing to press the movable brake pad against the floating brake disk. The biasing means press the floating brake disk against the static brake pad to apply braking force to the floating brake disk. The brake also includes a thermal fuse in thermal contact with the static brake pad. The thermal fuse has a fusing temperature, T, above which the thermal fuse fuses.

An easily inspected shaft assembly is provided and includes a shaft, a sleeve receptive of a portion of the shaft and an optically activatable layer including first and second sections disposed on respective exterior surfaces of the shaft and the sleeve, respectively, such that the first and second sections move relative to one another as the shaft and the sleeve move relative to one another.

In an asymmetric operating regime, a first engine is operating in an active mode to provide motive power to an aircraft while a second engine is operating in a standby mode and de-clutched from a gearbox of the aircraft. In response to an emergency exit request, the second engine’s speed is increased, at a maximum permissible rate, to a re-clutching speed while increasing the first engine’s power output at a maximum permissible rate. When the re-clutching speed is reached, the second engine’s power output is increased at a maximum permissible rate. In response to a normal exit request, the second engine’s speed is increased to the re-clutching speed at a rate lower than the maximum permissible rate. When the re-clutching speed is reached, the second engine’s power output is increased at a rate lower than the maximum permissible rate.