Take – off distance calculator by K.Prakashbalan

S(T/o) = 1.44W2/c*g*S*CL max*[T-D-μ(W-L)]

where, S(T/o) – Take off distance in meter

W – Weight of aircraft in newton

T – Thrust of aircraft in newton

D – Drag of aircraft in newton

L – Lift of aircraft in newton

ρ – ambient density in kg/m^3, g – acceleration due to gravity in m/s^2, S – area in sq. meter, CL max – maximum lift coefficient, µ – friction coefficient etc…


(1) Lift off distance is very sensitive to weight of a/p varying directly as W2. If weight is doubled, ground roll of a/p is quadrupled

(2) S(T/o) increases with an increase in W/S

(3) S(T/o) decreases with an increase in CL max

(4) S(T/o) decreases with an increase in T/W

(5)Ground roll is dependent on ambient density. If we assume that T is proportional to ambient density (i.e.)T ∝ ρ

S(T/o) ∝ 1/ρ2

This is why on hot summer days, when air density is less than that on cooler days, a given a/p requires a longer ground roll. For same reason longer ground rolls are required at airports located at highest altitudes.