Aeroplane

Annotation

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. The range of speed variation of a steady atmospheric wind is roughly proportional to the mean speed of the wind, and positive and negative speed fluctuations of 25 per cent. Of the mean speed, with occasional speed excursions of 35 per cent., are to be expected, so that a steady wind of a mean speed of 20 miles per hour will probably have a speed range of 13 miles per hour to 27 miles per hour. A steady wind also has fluctuations of direction, although no definite connection appears to exist between the speed and the direction fluctuations. Low surface winds are usually Of a gusty nature, chiefly due to the eddy motion created by obstacles.