A wing (9) having a base section (11) and a tip section (13) pivotably connected to the base section (11) such that the tip section (13) is pivotable between a deployed position and a stowed position in which the spanwise length of the wing (9) is smaller than in the deployed position. The wing arrangement also has an actuating arrangement (19) including a linear hydraulic actuator (21) coupled between the base section (11) and the tip section (13) such that it is operable to selectively move the tip section (13) between the deployed position and the stowed position, a first and a second hydraulic connection portion (79a, 79b) connected to the linear hydraulic actuator (21) such that they are in fluid communication with different chamber sections (27a, 27b) of a cylinder (25) of the linear hydraulic actuator (21), and a first hydraulic subsystem (81a) and a second hydraulic subsystem (81b).

A method of operating a fail-fixed hydraulic actuator system is provided. The method includes providing an actuator in an initial position, electromechanically operating a valve assembly to hydraulically drive actuator movement and halting the hydraulic driving of the actuator movement by the valve assembly.

A method of operating a fail-fixed hydraulic actuator system is provided. The method includes providing an actuator in an initial position, electromechanically operating a valve assembly to hydraulically drive actuator movement and halting the hydraulic driving of the actuator movement by the valve assembly.

A cylinder acceleration mechanism includes a buffer tank that supplies and discharges oil to and from a bottom-side line that is connected to a bottom-side chamber of an actuating cylinder, and an inversion lever having an intermediate fulcrum as a rotation axis. The buffer tank includes a buffer chamber with a variable capacity achieved by a seal lid moving back and forth inside of a case, and extends and reduces a length of a coupling rod provided to the seal lid and projects from the case. A bottom-side branching line branched from the bottom-side line is connected to the buffer chamber. The actuating rod of the actuating cylinder and the coupling rod of the buffer tank are coupled to respective ends of the inversion lever. The actuating rod and the coupling rod extend and retract alternately with respect to each other as the inversion lever turns.

A cylinder acceleration mechanism includes a buffer tank that supplies and discharges oil to and from a bottom-side line that is connected to a bottom-side chamber of an actuating cylinder, and an inversion lever having an intermediate fulcrum as a rotation axis. The buffer tank includes a buffer chamber with a variable capacity achieved by a seal lid moving back and forth inside of a case, and extends and reduces a length of a coupling rod provided to the seal lid and projects from the case. A bottom-side branching line branched from the bottom-side line is connected to the buffer chamber. The actuating rod of the actuating cylinder and the coupling rod of the buffer tank are coupled to respective ends of the inversion lever. The actuating rod and the coupling rod extend and retract alternately with respect to each other as the inversion lever turns.

The invention relates to a control apparatus for a hydraulic variable-pitch propeller (12) of an aircraft, land vehicle or water vehicle, comprising: a hydraulic oil feed line (24); a control line (16) which can be connected to the variable-pitch propeller (12); a pressure generating device (73) which is connected to the hydraulic oil feed line (24) and provides hydraulic oil with a basic pressure; a servo valve (78) which is arranged downstream of the pressure generating device (73), the input pressure to which servo valve is the basic pressure and the output pressure from which servo valve during normal operation defines a control pressure in the control line (16) and which servo valve is connected to a controller (28) which delivers a control signal for changing the control pressure; and pressure reducing means which are arranged downstream of the servo valve (78) and upstream of the control line (16), which are mechanically actuated and which, in the event of a failure of the servo valve (78), change the control pressure in the control line (16).

A hydraulic actuator includes a hydraulic cylinder; a piston within the hydraulic cylinder and movable in response to movement of hydraulic fluid in a hydraulic circuit coupled to the hydraulic cylinder; a synchronisation connection for receiving an input from a simultaneous transmission line; and a valve for controlling the flow of hydraulic fluid in the hydraulic circuit. The valve is a rotary valve comprising: a first valve section arranged to rotate in either a first rotational direction or a second rotational direction in response to input from the simultaneous transmission line in order to open a hydraulic flow path to the cylinder and urge the piston to move along the hydraulic cylinder in a corresponding first linear direction or second linear direction; and a second valve section arranged to rotate in either the first or second rotational direction.

A method of operating a fail-fixed hydraulic actuator system is provided. The method includes providing an actuator in an initial position, electromechanically operating a valve assembly to hydraulically drive actuator movement and halting the hydraulic driving of the actuator movement by the valve assembly.

An actuator synchronization system comprising a control valve in fluid communication with a plurality of actuators; each of the actuators comprising an input member moveable by the control valve, a main valve moveable from a null to an off-null position, an output member moveable from a first to a second output position, and a feedback linkage and a drive link configured such that selective movement of the input member causes movement of the valve from the null to the off-null position and movement of the output member to the second output position causes movement of the valve member from the off-null to the null position; and a mechanical connector between each of the input members or drive links of the actuators configured such that rotational motion of each of the respective drive links is synchronized.

An actuator synchronization system comprising a control valve in fluid communication with a plurality of actuators; each of the actuators comprising an input member moveable by the control valve, a main valve moveable from a null to an off-null position, an output member moveable from a first to a second output position, and a feedback linkage and a drive link configured such that selective movement of the input member causes movement of the valve from the null to the off-null position and movement of the output member to the second output position causes movement of the valve member from the off-null to the null position; and a mechanical connector between each of the input members or drive links of the actuators configured such that rotational motion of each of the respective drive links is synchronized.