Abstract: A lockable actuator has lock segments that move into recesses inside a piston to enable the piston to move. The lock segments may also move radially outwardly from the recesses in the piston to engage a bevel edge of a cylinder housing assembly to lock the piston. Lock rams having ramps force the lock segments radially outwardly into engagement with the bevel edge of the cylinder housing assembly.

Abstract: A redundant seal assembly for an aircraft shock absorber comprises a changeover unit and dual dynamic seals for sealing a fluid chamber formed between an inner member and an outer member of the shock absorber. The first dynamic seal functions as a primary seal, and the second dynamic seal functions as a backup seal in the initial operation of the shock absorber. A fluid passage is formed from the fluid chamber to the first dynamic seal. The changeover unit has a spool provided in the fluid passage. The spool has a channel that forms pat of the fluid passage. A changeover activator is movable to open and close the fluid passage at the spool to apply or remove the fluid pressure on or from the first dynamic seal so as to change over the functionality as the primary seal between the first dynamic seal and the second dynamic seal.