The commonly accepted practice of resolving a velocity V at incidence α into components V sin Λ parallel to the leading edge and V cos Λ normal to the leading edge at incidence α sec Λ is only approximately true and the exact method of resolution is developed here.

In dealing with the aerodynamics of swept-back wings the free stream velocity may be resolved into a constant component parallel to the leading edge and a variable component normal to the leading edge. This is only possible if the constant percentage chord lines are all parallel to the leading edge, that is there is no taper, thickness taper or twist on the wing. This note gives the exact form and the small angle approximations of the velocity components and of the incidence of the component normal to the leading edge.