AERONAUTICS: Blind Flying Accomplished

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Totally blind flying, solely by the aid of navigating instruments, became an accomplished fact for the first time last week. Lieutenant James Harold ("Jimmy") Doolittle, 33, "best Army Flyer," did it, at Mitchel Field, L. I. Thereby he completed eleven months' experiments for which the Daniel Guggenheim Fund for the Promotion of Aeronautics borrowed him from the Army Air Corps, and which presaged the highest safety in flying through no matter what weather.

Blind flying, where nothing of the ground or horizon can be seen, is the terror of aviation. At the speed of plane flight (100 m.p.h., usually) a pilot loses his sense of balance. At night or in fog, where he cannot orient himself against ground objects, he flies to one side, his wings tilt, the plane goes up, down or, happily, level. He does not know. His instruments go "hay wire." He is helpless. In terror he may try to guide himself. Generally that is useless. Experienced professional pilots, particularly on the night mail routes, often set their planes at neutral, take their hands off the controls, fold their arms and apathetically wait to get out of the fog, or to crash.

Three new instruments developed† during the eleven months' work made Lieutenant Doolittle's work possible. Those instruments: 1) Visual radio direction finder consisted of two reeds vibrating in consonance with a new short range radio beacon at Mitchel Field. When the plane is directly in the path of the beacon, the reeds vibrate uniformly. When the plane is off course, one reed fibrillates faster than the other. The closer the plane is to the beacon, the more intense the vibration. 2) Artificial horizon showed instantly at what angle the plane was flying in relation to the ground, whether and how the wings were tilted, whether the nose was up, down or level, and to what degree. 3) Barometric altimeter showed to within a very few feet how far above the ground of a particular field, in this case Mitchel Field, the plane was at all times. Because the action of this altimeter depends upon barometric pressure, a variable factor, a ground crew was obliged to radiophone Lieut. Doolittle air pressure conditions. In development are more independent instruments, the sonic altimeter by Dr. Elmer Sperry and the radio altimeter by General Electric Co. They will sensitively record the time and therefore the distance which a sound or radio impulse travels from a plane to the ground and back.