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Published online by Cambridge University Press: 14 September 2016
It has been supposed that meteorology must necessarily be of very great importance to aeronautics, and that important as it may be to, say, marine work, the services which it can render to aviation are still greater. It may not be without interest, therefore, to discuss in what ways it can be of most assistance; how an ideal meteorological service might be organised, and how far it is likely to satisfy the demands made upon it. We do not propose to discuss what should be done in the immediate future, since this is complicated by so many considerations, such as the financial outlay which is justified by the existing volume of aerial traffic. But to simplify our question, let us imagine a time when the amount of aerial traffic will be so great that the financial considerations involved would justify any outlay that we are likely to propose. Such a time may be supposed to be many or few years ahead, according as one feels, pessimistic or optimistic, regarding the future of commercial aviation.
Note on page 226 * When dealing with aircraft navigation, we are generally not so much concerned with a change of velocity or direction of the wind alone, but with the result of the two together, or what is known as the “ vector ” change. For example, suppose the wind to be originally west 20 m.p.h. and then change to W.N.W., and to drop by 41/2 m.p.h. to 151/2 m.p.h., the vector change will be 8 m.p.h. to the S.W.; and an aeroplane flying in any direction for an hour after the change of wind and steering on an assumed wind of 20 m.p.h. W. will, at the end of the hour, find itself 8 miles to the S.W. of where it expected to be.
† Once out of ten occasions the “ vector ” change may be expected to exceed about 1.8 times the “ probable ” change, and in once out of 100 occasions about 2.7 times this amount.
Note on page 227 * Where the causes of error are not connected in any way, the error due to many causes together is obtained by finding the square root of the sum of the squares of each error, and not by simple addition.