A method is presented for quick calculation of the frequency of cross-wind components which limit the landing of aircraft on runway layouts at aerodromes ánd for deriving the best runway layouts for a site with a known or deducible wind distribution. The method depends on some initial study of the relevant wind rose but an exact solution is obtained by the application of the empirically derived formula nv = Ce–bv2 where nv denotes the percentage of time that a wind exceeds a velocity v and C and b are constants for a given site. This formula was originally verified only for the British Isles but later it has been found to be valid elsewhere where there is a wide range of wind speeds. Allowance can be made in the calculations for bad weather, e.g. dense smoke or low cloud approaching the aerodrome from certain directions, for use of one end only of a runway and for a permissible tail wind component.

The paper was originally issued in 1944. The method described has not been changed and the description is only slightly modified. The chief changes are the substitution of numerical integration using Meteor computer instead of the original planimeter measurement of curves and the introduction of the ‘bisector’ correction. Certain details of the calculation notably four-figure tables of L(i) (eqn (5)) and of the bisector correction, a complete example of the method, the way to remove ‘bias’ in wind summaries and the derivation of the bisector correction are given in a duplicated Addendum to this paper which is available on request from the Institute.