A line tensioner is disclosed. A winch has a winch drum with at least one groove over which a line is passed. The winch has a line tensioner assembly with a stationary cam surface and a plurality of line tensioners rotating with the winch drum. Each has a line gripping portion and a cam follower. The line gripping portion is brought into and out of contact with the line as the cam follower rides along at least a portion of the cam surface.

The invention relates to a winch automation device comprising: a motor (12) intended to engage a capstan drum (2) of the winch; a supervision member (15) of the motor able to fix the torque applied by the motor to the capstan drum (2); a memory (22) integrating a set of pre-recorded manoeuvres (29, 32, 33), each manoeuvre being associated with at least one limit force (30, 31); means (28) for measuring the force engaged on the winch; and a human-machine interface (26a), connected to the supervision member, and comprising: motor-actuation means (35-37); manoeuvre selection means (34); and at least one display (27) able to convey to a user of the winch information regarding the force engaged on the winch and information regarding the expected limit force for the selected manoeuvre.