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In Rostov started production of the most load-lifting rotary-wing car The Russian holding «Helicopt[...]
Reducing trailing vortex (induced) drag
We have already seen that trailing vortex drag is dependent on the aspect ratio. In fact, the drag coefficient due to trailing vortex drag is proportional to 1/(aspect ratio). The use of high aspect ratios, however, incurs penalties in terms of structural weight. Furthermore, high aspect ratio wings are unsuitable for aircraft that have to perform rapid manoeuvres, and for supersonic aircraft. Therefore, various attempts have been made to find other means of reducing trailing vortex drag.
Improving spanwise lift distribution
Most airliners use a fuselage with a circular cross-section, and this shape produces virtually no lift. It is therefore impossible to produce a true elliptical lift distribution across the whole span. There is always a dip in the distribution at the fuselage, as shown in Fig. 4.11(a). Many modern combat aircraft such as the MiG-29 (Fig. 4.12) overcome this problem by using a cambered fuselage of non-circular cross-section, which generates lift, as in Fig. 4.11(b).
