A retractable landing gear on an aircraft is operated by a landing gear control system 20 having a manually operable lever 26 movable from a first, e.g. gear-down, position to a second, e.g. gear-up position, in response to which a signal (e.g. a gear-up command) is outputted causing the landing gear to move to an up position. The landing gear control system 20 also includes a motor 40 configured to move the lever 26 in dependence on a signal, for example a signal received by a landing gear lever control unit 42 from a take-off detection system 46 which indicates that the aircraft has taken-off. Thus, the lever 26 may be considered as being configured both to be operated by a pilot of the aircraft manually and to be operated by the motor automatically.

A centre seeking actuator having an outer cylinder, a slave cylinder slidably disposed within the outer cylinder, and a rod assembly having a piston slidably disposed within the slave cylinder and a rod extending from the piston to a point outside the outer cylinder. One or more first dynamic seals are arranged to act on a side wall of the rod to inhibit working fluid leaking from the outer cylinder, and one or more second dynamic seals are arranged to act on a sidewall of the slave cylinder to inhibit working fluid leaking from the outer cylinder.

A hybrid actuator, having a central longitudinal axis, may include a housing defining a central cavity. The hybrid actuator may also include a piston disposed within the central cavity, the piston comprising a piston head that divides the central cavity into a pressure chamber and an annular chamber. The piston houses a pump configured to pump fluid through a port defined in the piston head between the annular chamber and the pressure chamber to extend a piston rod of the piston from the central cavity, according to various embodiments.

A hybrid actuator, having a central longitudinal axis, may include a housing defining a central cavity. The hybrid actuator may also include a piston disposed within the central cavity, the piston comprising a piston head that divides the central cavity into a pressure chamber and an annular chamber. The piston houses a pump configured to pump fluid through a port defined in the piston head between the annular chamber and the pressure chamber to extend a piston rod of the piston from the central cavity, according to various embodiments.

Aerial vehicles may be configured to control their attitudes by changing one or more physical attributes. For example, an aerial vehicle may be outfitted with propulsion motors having repositionable mounts by which the motors may be rotated about one or more axes, in order to redirect forces generated by the motors during operation. An aerial vehicle may also be outfitted with one or more other movable objects such as landing gear, antenna and/or engaged payloads, and one or more of such objects may be translated in one or more directions in order to adjust a center of gravity of the aerial vehicle. By varying angles by which forces are supplied to the aerial vehicle, or locations of the center of gravity of the aerial vehicle, a desired attitude of the aerial vehicle may be maintained irrespective of velocity, altitude and/or forces of thrust, lift, weight or drag acting upon the aerial vehicle.

An apparatus for determining a movement direction of a component of a mechanism. The apparatus includes an acoustic emission sensor arranged to detect acoustic emission from the mechanism, and a processor arranged to determine a Doppler shift in a frequency characteristic of the measured acoustic emission and to determine a movement direction of a component of the mechanism on the basis of the determined Doppler shift. A method of determining a movement direction of a component of a mechanism including detecting acoustic emission from the mechanism and determining a Doppler shift in a frequency characteristic of the measured acoustic emission and, determining, based on the Doppler shift in the frequency characteristic, a movement direction of the component of the mechanism.

An apparatus for determining a movement direction of a component of a mechanism. The apparatus includes an acoustic emission sensor arranged to detect acoustic emission from the mechanism, and a processor arranged to determine a Doppler shift in a frequency characteristic of the measured acoustic emission and to determine a movement direction of a component of the mechanism on the basis of the determined Doppler shift. A method of determining a movement direction of a component of a mechanism including detecting acoustic emission from the mechanism and determining a Doppler shift in a frequency characteristic of the measured acoustic emission and, determining, based on the Doppler shift in the frequency characteristic, a movement direction of the component of the mechanism.

An upper side brace for use in landing gear includes a main body having a mounting end configured to be proximal to an aircraft and a lower end configured to be proximal to a lower side brace. The upper side brace further includes an unlock actuator cylinder formed monolithic with the main body and configured to house a piston to form an unlock actuator.

A shock strut may comprise a strut cylinder, a strut piston operatively coupled to the strut cylinder, a shrink piston disposed at least partially within the strut cylinder, and a shrink chamber at least partially defined by the shrink piston. The shrink piston may comprise a shrink piston head, a sleeve extending from the shrink piston head, and a mechanical stop. A hydraulic fluid may be moved into the shrink chamber to compress the shrink piston and the strut piston into the strut cylinder to reduce an overall length of the shock strut.

A shock strut may comprise a strut cylinder, a strut piston operatively coupled to the strut cylinder, a shrink piston disposed at least partially within the strut cylinder, and a shrink chamber at least partially defined by the shrink piston. The shrink piston may comprise a shrink piston head, a sleeve extending from the shrink piston head, and a mechanical stop. A hydraulic fluid may be moved into the shrink chamber to compress the shrink piston and the strut piston into the strut cylinder to reduce an overall length of the shock strut.