The takeoff distance consists of two parts, the ground run, and the distance from where the vehicle leaves the ground to until it reaches 50 ft (or 15 m). The sum of these two distances is considered the takeoff distance. (Note: sometimes a 35 ft altitude is used). The takeoff distance is generally calculated for maximum weight in a standard atmosphere. In addition, usually the worst case scenario is also calculated which is maximum weight, high altitude, and a standard “hot” day. Of immediate concern here is the calculation of the ground roll. In order to calculate the ground roll, we need to write the equations of motion for the vehicle as it moves down the runway. A free-body diagram of the vehicle is
shown to the right. The forces that act on it are the aerodynamic forces of lift and drag (L and D), the thrust force (T),
the ground normal force (R) and the ground friction force (R), where is the coefficient of rolling friction. We can
now write the equations of motion along the runway and perpendicular to it.
Read next