Longitudinal motions of aircraft involving high angles of attack

Abstract

After a general introduction to the longitudinal motion of aircraft over an extended range of angle of attack there follows a wide-ranging investigation of various aspects of the low-speed-deceleration manoeuvre with excursion to very high angles of attack in the case of failure to recover. The entry into such flight conditions of two distinct types of aircraft--one with a wing of moderately large aspect-ratio and having a high tailplane, the other a tailless slender aircraft--is considered in some detail by examining the effect of various inputs on the motion. In Part I some attention is paid to the factors influencing the ease with which control of the aircraft may be regained, particularly in cases in which normal recovery has only been achieved by forceful recovery action and those in which the aircraft only recovers after an excursion to extreme angles of attack. The possibility of recovery depends on the general nature of the motion under the action of markedly non-linear aerodynamic forces and moments. For aircraft having pitching-moment characteristics like those of the subject aircraft three types of motion can follow an attempt at recovery. There can be a reduction to two or even one as outlined in Appendix A. The problem of the stability of these motions in the broad sense is investigated. Examination of the allied single degree-of-freedom motion in pitch provides much insight into the more general problem, whilst phase-plane and similar three-dimensional plots prove useful means of displaying and interpreting results. The effect of varying the aircraft characteristics is examined. Various forms and levels of damping are considered as well as the more evident effects of the centre-of-gravity position and the inertia-in-pitch of the aircraft.