Abstract: A variable K factor energy absorber for an aircraft arresting system has a movable control element which is moved into different positions to adjust the K factor. The movement of the control element is programmed during payout of the arresting system in accordance with the speed of the arrested aircraft. The speed is sensed by a pump driven by the arresting gear tape reel. The program is provided by a cam (also driven by the tape reel through a reduction gear). The control element is moved by a hydraulic drive actuated by an electrical shifting switch, which is triggered when the detected speed of the arrested aircraft exceeds the predetermined speed established by a cam during initial and final phases of payout. The control element is thereby moved from an initial low K to an intermediate K position during the initial phase of payout if the predetermined speed established by the cam is exceeded.