During WWII, US developers decided not to use 0.86 centimeter frequency for their “side-looking” aircraft radar because their experimental test models predicted it would have limited range. They chose 1.25 centimeters instead. That turned out to be a major error:
Had it not been for some experiments conducted by British scientists this probably would have remained the general conclusion for some time. What their experiments proved was that the choice of 1.25 centimeters as a radar frequency was a very unfortunate choice indeed, for at frequencies slightly higher (1.8 centimeters) and slightly lower (.86 centimeters), atmospheric attenuation was far less serious than at 1.25 centimeters and other neighboring frequencies. In other words, these experiments proved that the function was not monotonic.
It is not always wise to proceed using almost realistic tests and linear models. Sometimes you just couldn’t have foreseen some variables in the real environment to simulate in experiments. That is why trial-and-error is less costly than it first appears. Much time and cost could have been saved if a range of frequencies was tested at altitude before final selection.
Burton H. Klein, “Policy Issues Involved in the Conduct of Military Development Programs.” Found in Mansfield, Edwin (Ed.). (1968). Defense, Science, and Public Policy. New York, NY, W.W. Norton & Company, pp. 100-101.
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