Apparatus for use on an aircraft

A method of operating an apparatus for use on an aircraft, wherein the apparatus comprises

• a component;
• an actuator arranged to move the component between a first position and a second position, net load from external forces acting on the component tending to drive it towards the first position, wherein the actuator comprises a threaded screw;
• a threaded nut;
• a main prime mover arranged to rotate the screw or the nut in order to impart relative linear motion between the screw and the nut;
• an emergency prime mover arranged to rotate the screw or the nut in order to impart relative linear motion between the screw and the nut;
• a normal control system configured to energize the main prime mover under normal operating conditions so that the main power mover applies torque to the screw or nut acting in opposition to the net load;
• and
• an emergency control system configured to energize the emergency prime mover under emergency operating conditions so that the emergency power mover applies torque to the screw or nut acting in the same sense as the net load thereby driving the component to the first position, wherein
• the emergency control system is configured so that under the normal operating conditions the emergency prime mover is not energized by the emergency control system to apply torque to the screw or nut, the method comprising:
• applying a first torque to the nut or screw with the main prime mover when the component moves from the second position to the first position under normal operating conditions;
• applying a second torque to the nut or screw with the main prime mover when the component moves from the first position to the second position under normal operating conditions;
• and
• applying a third torque to the nut or screw with the emergency prime mover to drive the component from the second position to the first position under emergency operating conditions in which the interface between the nut and the screw has become partially jammed.