There is provided an actuator for use in a thrust reverser of an aircraft, comprising a screw shaft and a nut translatable along the shaft between a retracted position and an extended position, a tine component comprising tine fingers formed with projections that are configured to engage formations on the nut when the nut occupies its retracted position to secure the nut against axial movement, and a movable lock member engageable with the tine fingers to restrict radial movement of the tine fingers in a first position, the lock member movable between the first position and a second position in which the lock member does not restrict radial movement of the tine fingers. The lock member is movable between the first position and the second position by means of an electromagnetic actuator.