A theoretical investigation of the longitudinal stability, control and response characteristics of jet-flap aircraft Parts 1 and 2

Abstract

Foreword (1961). Parts I and II of this R. & M. were written as separate Reports in 1958 and 1960. They deal with two stages of an exploratory investigation into the stability, control and response characteristics of jet-flap aircraft, undertaken at a time when the basic aerodynamic theory of the jet-flapped aerofoil was still being developed by such people as Spence, Maskell, Ktichemann and Ross. The aerodynamic assumptions on which the investigation were based were thus necessarily of a tentative and approximate nature. In particular, the incompleteness of the three-dimensional theory, combined with its relative complexity, virtually dictated the use of two-dimensional theoretical lift and moment data as the basis of a tractable stability and control analysis of the generalized nature which was envisaged. Inevitably, therefore, the field of application of the results of these investigations is somewhat restricted, and in any fresh approach to the problem one would certainly hope to proceed from alternative assumptions, based on three-dimensional theory. In Part I, where attention was restricted to considerations of trim, static stability and quasi-steady manoeuvrability, some further simplifying assumptions were made, in particular by neglecting the contributions of thrust and drag forces to the pitching moment of the aircraft about its c.g. However, to ensure self consistency of the dynamic analysis undertaken in Part II, it was found necessary to revise the trim and stability analysis of Part I so as to include the effects of thrust and drag forces. This was done only for the case where the aircraft is trimmed by variation of the jet deflection, although in Part I, trimming by variation of tailplane setting or thrust/weight ratio (throttle setting) had also been considered. Thus although some sections of Part I have effectively been superseded in Part II, much of the earlier Report remains valid as a first approximation which has not, so far, been improved upon. Accordingly it has been thought worth while to publish both Reports in what is substantially their original form, with a few minor amendments and the addition of one or two footnotes, explaining where the analysis or conclusions of Part I need to be modified in the light of Part II. The overall scope of the work is indicated by the summaries for the respective Parts.