With cruciform missiles it is usual to express overall aerodynamic forces and moments in terms of aileron, elevator and rudder angles. It is shown that an alternative formulation in terms of individual control angles is both more general and more revealing.

The fundamental assumption is that the overall coefficients can be expressed sufficiently accurately as the sum of independent control effects and of the mutual interference between adjacent controls. This assumption has been found to be valid over quite wide regions of supersonic Mach number, body incidence and control deflection for some typical cruciform rear control missiles. In principle the method applies at all speeds and to all types of layout, but it seems likely to be less widely applicable at subsonic and transonic speeds and to moving wing and canard layouts. The region of applicability is ultimately a matter of experimental investigation for each missile.

This new approach gives a clearer understanding of cross-coupling effects, simplifies and improves the accuracy of a mathematical model of the aerodynamic characteristics, and facilitates the interpolation of wind tunnel test measurements. These measurements are made on configurations with two adjacent controls deflected and the other two controls either always undeflected or always removed. The test programme can be matched more easily to the aerodynamic characteristics, and the testing time is much the same or significantly less than for a comparable programme involving combinations of aileron, elevator and rudder settings. Greater demands on experimental accuracy are imposed, however.

There is considerable scope for research work in investigating the applicability of the new technique to various types of missile layouts and to assessing the relative merits of having the two dummy controls undeflected or removed.