The disclosure describes a clutch assembly that includes a first clutch element coupled to an input shaft and including a first clutch element friction surface; a second clutch element coupled to an output shaft, and a brake clutch coupled to a stationary component. The second clutch element includes a first friction surface configured to engage the first clutch element friction surface and a second friction surface opposite the first friction surface. The second clutch element is configured to move relative to the first clutch element to engage and disengage the first friction surface and the first clutch element friction surface. The brake clutch includes a brake clutch friction surface configured to engage the second friction surface of the second clutch element when the first clutch element and the second clutch element are disengaged.

The disclosure describes a clutch assembly that includes a first clutch element coupled to an input shaft and including a first clutch element friction surface; a second clutch element coupled to an output shaft, and a brake clutch coupled to a stationary component. The second clutch element includes a first friction surface configured to engage the first clutch element friction surface and a second friction surface opposite the first friction surface. The second clutch element is configured to move relative to the first clutch element to engage and disengage the first friction surface and the first clutch element friction surface. The brake clutch includes a brake clutch friction surface configured to engage the second friction surface of the second clutch element when the first clutch element and the second clutch element are disengaged.

A clutch has an inner race, an outer race spaced from the inner race and forming a radial cavity between the races, and a plurality of sprags disposed in the radial cavity. The sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both races, and a sprag cage retains the sprags at a uniform spacing within the radial cavity. When the clutch is at a first temperature, a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged. When the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

A clutch has an inner race, an outer race spaced from the inner race and forming a radial cavity between the races, and a plurality of sprags disposed in the radial cavity. The sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both races, and a sprag cage retains the sprags at a uniform spacing within the radial cavity. When the clutch is at a first temperature, a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged. When the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

A mechanical system for transmitting rotary motion between firstly at least one inlet wheel driven in rotation by at least one engine, each inlet wheel being suitable for being driven in rotation by a corresponding dedicated engine, and secondly at least two distinct driven shafts of an accessory box, the at least one engine serving to drive rotation of one of the at least two driven shafts in isolation, or to drive the at least two driven shafts simultaneously, jointly with at least one aircraft rotor, the mechanical system including a selective rotary drive member that is movable axially between two distinct drive positions.

A mechanical system for transmitting rotary motion between firstly at least one inlet wheel driven in rotation by at least one engine, each inlet wheel being suitable for being driven in rotation by a corresponding dedicated engine, and secondly at least two distinct driven shafts of an accessory box, the at least one engine serving to drive rotation of one of the at least two driven shafts in isolation, or to drive the at least two driven shafts simultaneously, jointly with at least one aircraft rotor, the mechanical system including a selective rotary drive member that is movable axially between two distinct drive positions.

Described is a sensor-less motor reversal (“SLMR”) apparatus that aids the reversal of motor rotation of a bidirectional motor, such as a brushless DC motor of an aerial vehicle. The SLMR includes an RPM dependent clutch that is rotated by a drive shaft of the motor and that engages an engageable shaft of the SLMR apparatus during a low RPM range of the motor during which indirect measurement of the RPM of the motor through a back-EMF of the motor is unreliable. As the engageable shaft increases in RPM, energy is stored by an energy storage mechanism of the SLMR. As the RPM of the motor decreases as part of a motor reversal, the energy stored by the energy storage mechanism is discharged and aids in the transition of the reversal of the motor from positive to negative, or negative to positive. As described, the SLMR apparatus is stateless.

Aspects of the technology relate to propulsion systems for high altitude, long duration balloons, such as balloons that operate in the stratosphere for weeks, months or longer. A propeller assembly is used to provide lateral directional adjustments, which allows the balloon to spend more time over a desired region, reduce the return time to the desired region, reduce fleet overprovisioning, and increases the safety case by additional controls and avoidance abilities. A control assembly manages operation of the propeller assembly, including setting the pointing direction, speed of rotation and determining when to turn on the propeller and for how long. The propulsion system including the control and propeller assemblies is rotatable around a connection member of the balloon. Such rotation is independently adjustable from any rotation of the balloon's payload. The propeller blades may be made of plastic, which reduces weight and cost while providing sufficient speed at stratospheric altitudes.

An electric power generating apparatus for use in an aircraft is an electric power generating apparatus connected through an emergency cut-off device to a gear box such that the gear box can transmit power to the electric power generating apparatus, the gear box being configured to decrease speed of rotational power of an aircraft engine. The electric power generating apparatus includes: a manual transmission configured to change the speed of the rotational power transmitted from the emergency cut-off device and including a plurality of gear stages; and an electric power generator to which the rotational power which has been changed in speed by the manual transmission is transmitted.

An electric power generating apparatus for use in an aircraft is an electric power generating apparatus connected through an emergency cut-off device to a gear box such that the gear box can transmit power to the electric power generating apparatus, the gear box being configured to decrease speed of rotational power of an aircraft engine. The electric power generating apparatus includes: a manual transmission configured to change the speed of the rotational power transmitted from the emergency cut-off device and including a plurality of gear stages; and an electric power generator to which the rotational power which has been changed in speed by the manual transmission is transmitted.