Hydraulic actuator including a multi-head piston for hydraulic gearing

A hydraulic actuator system of an aircraft, the actuator system comprising:

• a hydraulic actuator having a housing with a piston having a piston shaft with a piston head attached thereto and arranged within the housing;
• wherein the piston head divides in internal volume of the housing into an extend cavity and a retract cavity, wherein the extend cavity is configured to be connected to a low pressure fluid source;
• a pressure selector unit fluidly connected to the retract cavity and configured to be connected to the low pressure fluid source and to a high pressure fluid source, wherein the pressure selector unit selectively connects the low pressure fluid source or the high pressure fluid source to the extend or retract the piston, respectively, wherein the pressure selector unit includes:
• a first solenoid having a first solenoid high pressure input configured to be connected to the high pressure fluid source, a first solenoid low pressure input configured to be connected to the low pressure fluid source and a first solenoid output;
• a second solenoid having a second solenoid high pressure input configured to be connected to the high pressure fluid source, a second solenoid low pressure input configured to be connected to the low pressure fluid source, and a second solenoid output;
• and
• a third solenoid having a third solenoid first input connected to the first solenoid output, a third solenoid second input connected to the second solenoid output, and a third solenoid output connected to the retract cavity;
• a controller that can cause each of the first, second and third solenoids to be in either an energized or deenergized state and determine if the third solenoid has failed, wherein when the third solenoid has failed it will be in either a normal state or an energized state;
• wherein the controller is configured to cause the first solenoid to control fluid flow to the actuator when the third solenoid fails in the normal state and to cause the second solenoid to control fluid flow to the actuator when the third solenoid fails in the energized state.