TO SWIM a mile and back at two miles an hour takes sixty minutes. But if one swims it down with, and up against, a mile-an-hour current, one mile is made at three miles an hour, taking twenty minutes, and the other at one mile an hour, taking sixty minutes. The time for the round trip is thus increased one third because the slower progress is made over a longer period than the faster progress.
Similarly, when a bomber flies to an objective and back, there is always a net loss in bombing radius if a steady wind exists. The average condition is no more favorable than a steady wind. Bombing radii must therefore be somewhat discounted and, as the fact seems so generally overlooked, it may be interesting to see what the usual effects amount to.
By formula III, we may produce the following table:
According to page 60, Monthly Weather Review, Supplement No. 20, weather at 1,000 meters altitude, the annual average of wind velocities at six well scattered stations in the United States is 22 knots. Taking a 60-knot bomber and assuming a steady wind of 22 knots, the rated bombing radius (making the trip and coming back) must be reduced never less than 7.4 per cent, 10.8 per cent on the average, and possibly as much as 13.5 per cent, depending on the wind’s direction.
The conclusion is that aside from all other margins which prudence suggests, it is unwarranted to undertake two-way non-stop flights with the slower planes without first discounting even the rated endurance something on the order of 10 per cent to allow for possible wind effects of this peculiar though readily understandable nature.