A Review of Some Stalling Research With an Appendix on Wing Sections and their Stalling Characteristics

Abstract

Over a period of years a considerable amount of stalling research on various aeroplanes was completed at the Royal Aircraft Establishment and it was considered desirable that the main results should be summarised and reviewed. The report includes a general discussion of the effect on stalling b~haviour of wing section, plan form, washout, flaps, nacelles, gills, slipstream, antomatic wing-tip slots and Hudson-type slits. The important part that is played by the longitudinal trim and stability at incidences near the stall is emphasised. The relation between wing sections and their stalling characteristics is discussed and it is shown that the stalling characteristics can be broadly predicted from an examination of the form of the wing-section upper-surface pressure distribution at high incidences. The results indicate that vicious stalling behaviou) can be avoided by the use of wing sections towards the tip of fairly high camber (3 to 4 per cent.) and moderate thickness (>12 per cent.). For some types of aeroplanes there are, however, serious objections to the use of high camber towards the tips ; the designer is then advised to avoid wing sections which experiments and theory indicate have particularly bad stalling characteristics. The worst tip thickness for stalling appears to be in the region of 9 per cent. High taper tends to worsen the stalling behaviour and it is advisable to consider taper ratios greater than 2:1 only in conjunction with wing-tip sections having good stalling characteristics. The use of part-span flaps does not appear to cause any marked deterioration in stalling behaviour, and frequently it improves the behaviour ; but there is some evidence, though not yet conclusive, that the use of full-span flaps may be accompanied by an appreciable worsening in stalling behaviour. Attention is drawn to the advisability of examining the flow at high incidences in the neighbourhood of the tail-plane of an aeroplane in the design stage, with a view to assessing its probable stalling behaviour ; in particular, the possibilities of designing for some stall warning can then be examined.