It would be possible to write a paper conforming, literally, to the above title in very few words by simply describing the behaviour of the crescent wing in various circumstances. Such treatment, however, would avoid what is really the prime question of all, namely, why is the crescent wing used? What is the attraction of this layout? The answer to that question is performance. One essential characteristic of the crescent wing is thus its performance characteristic.

Therefore, in this paper, the matter will be introduced from a performance angle and an attempt will be made to show, in general terms, why there should be a performance gain from the crescent layout. Having established the case, the aerodynamic and aeroelastic characteristics will be considered in some detail so that, with these properties explained, the way will be clear to consider a performance comparison in greater detail and thus gain a fuller appreciation of the situation.