In many flight situations an automatic control is used to minimise the deviation of one or two aircraft motion variables from their trim values. The same effect may be brought about, in certain cases, by pilot action. If the control is very strong it may be imagined that the aircraft motion is kinematically constrained in the sense that the controlled motion variables are actually held irrevocably at their trimmed values throughout a disturbance.

More than fifteen years ago Neumark presented an analytical treatment of startling simplicity which dealt with the motion of an aircraft under strict kinematic constraint. By adopting the concept of kinematic constraint and so eliminating one or more variables the motion of the aircraft is described by a simpler set of equations: yet, clearly, the addition of a control system to the aircraft will, in fact, increase the complexity of the complete set of describing equations. However, there is no doubt that Neumark’s theory does give meaningful and useful results.

The analysis described in this paper shows how the motion of a strongly controlled aircraft can be described in terms of simpler sub-systems and indicates that Neumark’s theory appears as the limiting case of infinite control strength. The role of the pilot in applying strong control is placed in the context of the general theory.