Letter | Published:

Stability in Flight

Naturevolume 98page409 (1917) | Download Citation



IN his paper on “Forced Oscillations of a Disturbed Aeroplane” (Aeronautical Journal, October-December, 1916), Dr. Brodetsky shows, on theoretical grounds, that among the chief conditions of safety and stability in windy weather are: (1) a small tail, or small ratio of tail/main-plane, and (2) comparatively small wings, or small ratio of total area/load. In a former paper by Prof. Bryan and Dr. Brodetsky (ibid., April June), the fact that long tails are on the whole disadvantageous is demonstrated. All these conclusions seem to agree well with what we may very easily observe in birds. Those birds the flight of which is what one might call skilful, or agile—that is to say, those which can rapidly dodge and steer, or which do not mind flying in high and shifty winds—are (I should say) all characterised on the whole by small tails and comparatively small and narrow wings. These features are conspicuous in many of our shore birds, sandpipers and the like, and the birds are equally conspicuous for their extraordinary stability, whether against wind or in their own sudden and acute changes of course. Seagulls, solan-geese, albatrosses, and swallows share, more or less, in the same structural characteristics. Powerful or long-continued flight is evidently quite a different thing. Thus the pigeon is a splendid flyer for mere distance, and even for speed; but it goes straight ahead, and its large tail and large rounded wings give it only a moderate stability. In like manner a multitude of little birds, robins and the like, which we are apt to think of as bad or unskilful flyers, turn out to be very good flyers indeed upon their migratory journeys, when all they have to do is to pursue an even course in high and relatively calm regions of the atmosphere, and also (as we may suppose) in carefully selected weather. On the other hand, the really long-tailed birds, such as the magpie and some of the foreign jays, trogons, etc., are all very poor flyers, and are for the most part birds of the sheltered woodlands.

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