Abstract: A tape threading arm mechanical linkage undergoes significant variations in mechanical advantage through its motion. In order to compensate for the drastic changes in the mechanical advantage of the tape threading arm, the operation of the tape threading arm is divided up into a plurality of control segments. Each segment represents a portion of the tape threading path wherein the mechanical advantage of the tape threading arm remains fairly constant. A control memory stores data indicative of various control parameters that are required to regulate the operation of the tape threading arm motor to maintain the tape speed throughout this segment of the tape threading path at a constant velocity. In addition, the measured velocity of the magnetic tape as it is removed from the file reel is used to compute the difference between the predicted operation of the tape threading arm and the measured operation of the tape threading arm.