Electro hydrostatic actuator

An electro hydrostatic actuator comprising:

• a hydraulic pump driven by an electric motor to supply hydraulic fluid to a hydraulic actuator, the pump comprising:
• an inlet and an outlet for the hydraulic fluid and an active flow path configured therebetween such that, in an active mode of operation when the pump is driven by the electric motor, hydraulic fluid is actively drawn in through the inlet and exhausted out through the outlet;
• and
• a bypass flow path configured to open between the inlet and outlet such that, in a damping mode of operation when the pump is not driven by the electric motor, hydraulic fluid is able to pass through the pump along the bypass flow path between the inlet and outlet;
• wherein the hydraulic pump is a rotary piston pump comprising a pump barrel driven to rotate by a motor shaft and the pump further comprises:
• a bypass port plate positioned at the base of the pump barrel and driven to rotate by the motor shaft;
• wherein in the damping mode of operation the pump barrel and the bypass port plate are configured to axially separate to form the bypass flow path through a gap between the pump barrel and the bypass port plate created by the separation of the pump barrel and the bypass port plate.