Landing Ground Roll

This formula estimates how far an aircraft will travel along the runway after touchdown before it comes to a stop, assuming its deceleration is roughly constant. It comes from the constant-acceleration kinematics relation v^2 = u^2 + 2as, applied with final speed v = 0 and initial speed u = Vtd, then rearranged to solve for distance. Because it uses the average deceleration, it is a simplified model that captures the main effect of braking, drag, and reverse thrust without tracking each one separately.

Use this when you need a quick estimate of landing distance during runway planning, performance analysis, or safety margin checks. It is especially useful in problems that give touchdown speed and an average braking/deceleration value rather than detailed time-varying forces.

• Using cruise speed or approach speed instead of touchdown speed
• Forgetting that the deceleration goes in the denominator, so stronger braking means a shorter roll
• Mixing up units, such as using km/h for speed and m/s² for deceleration without converting