This model represents a towing rope that can be used to connect a tug aircraft to another aircraft that is being towed. This model is modified from the Modelica Standard Library SpringDamperParallel model and thus works as line force with a linear spring and linear damper in parallel with the given spring constant (c) and damping constant (d) parameters. However, the force acting on the tugAircraft frame is constrained to ≤ 0, whereas the force acting on the towedAircraft frame is constrained to ≥ 0, i.e. the rope slackens and no force is applied when the distance between the frames is less than the unstretched length (sUnstretched), albeit the slackening of the rope is not visualized in the animation.

The other modification includes adding a condition for the releasing of the rope. The rope is released, meaning that no forces are any longer applied, after the input Boolean signal for the release condition (uDetach) rises from false to true for the first time. The release condition may rise and fall multiple times, for example, when it is set to a certain flight altitude as in the GliderTow example, but obviously the rope will not get reattached any longer after the first rise of uDetach. This model also outputs a Boolean signal referring to the detachment status of the rope (yDetach) and  real signal referring to the time passed from start of the simulation until the rope release (yDetachTime).