Center biased actuator

An aircraft landing gear assembly including a center biased actuator arranged to bias a first part of the assembly to assume a predetermined position relative to the second part a second part of the assembly, the assembly being arranged, in use, to force the actuator to assume the first condition when in a first state and having a second state in which the actuator moves the first part of the assembly to assume the predetermined position relative to the second part, wherein the first part comprises a bogie beam and the second part comprises a main strut, the center biased actuator comprising:

• an outer cylinder;
• a slave cylinder arranged to be linearly transposed within the outer cylinder;
• a rod assembly having a piston arranged to be linearly transposed within the slave cylinder and a rod extending from the outer cylinder;
• one or more first dynamic seals arranged to act on a sidewall of the rod to inhibit hydraulic fluid leaking from the outer cylinder;
• one or more second dynamic seals arranged to act on a sidewall of the slave cylinder or an inner surface of the outer cylinder to inhibit hydraulic fluid leaking from the outer cylinder;
• and
• a gas chamber comprising a sealed expandable chamber containing gas, the expandable chamber being arranged to act on hydraulic fluid within the center biased actuator to bias the center biased actuator to assume an intermediate condition which lies between a compressed condition and an extended condition, wherein the expandable chamber comprises an elastic vessel, a metal bellows, or a bladder.

A center biased actuator comprising:

• an outer cylinder;
• a slave cylinder arranged to be linearly transposed within the outer cylinder;
• a rod assembly having a piston arranged to be linearly transposed within the slave cylinder and a rod extending from the outer cylinder;
• one or more first dynamic seals arranged to act on a sidewall of the rod to inhibit hydraulic fluid leaking from the outer cylinder;
• one or more second dynamic seals arranged to act on a sidewall of the slave cylinder or an inner surface of the outer cylinder to inhibit hydraulic fluid leaking from the outer cylinder;
• a gas chamber comprising an unvented expandable chamber containing gas, the expandable chamber being arranged to act on hydraulic fluid within the center biased actuator to bias the center biased actuator to assume an intermediate condition which lies between a compressed condition and an extended condition;
• and
• wherein the expandable chamber comprises an elastic vessel, a metal bellows or a bladder.