Astounding Stories of Super-Science April 1930

  SAFE FLYING IN FOGS

  The outstanding development in aviation recently, and one of the mostsignificant so far in aviation history was the "blind" flight of Lieut.James H. Doolittle, daredevil of the Army Air Corps, at Mitchel Field,L. I., which led Harry P. Guggenheim, President of the Daniel GuggenheimFund for the Promotion of Aeronautics, Inc. to announce that the problemof fog-flying, one of aviation's greatest bugbears, had been solved atlast.

  There has been "blind flying" done in the past but never before in thehistory of aviation has any pilot taken off, circled, crossed,re-crossed the field, then landed only a short distance away from hisstarting point while flying under conditions resembling the densest fog,as Lieut. "Jimmy" Doolittle has done, in his Wright-motored "Husky"training-plane. It was something uncanny to contemplate.

  The "dense fog" was produced artificially by the simple device of makingthe cabin of the plane entirely light-proof. Once seated inside, theflyer, with his co-pilot, Lieut. Benjamin Kelsey, also of Mitchel Field,were completely shut off from any view of the world outside. All theyhad to depend on were three new flying instruments, developed during thepast year in experiments conducted over the full-flight laboratoryestablished by the Fund at Mitchel Field.

  The chief factors contributing to the solution of the problem of blindflying consist of a new application of the visual radio beacon, thedevelopment of an improved instrument for indicating the longitudinaland lateral position of an airplane, a new directional gyroscope, and asensitive barometric altimeter, so delicate as to measure the altitudeof an airplane within a few feet of the ground.

  Thus, instead of relying on the natural horizon for stability, Lieut.Doolittle uses an "artificial horizon" on the small instrument whichindicates longitudinal and lateral position in relation to the ground atall time. He was able to locate the landing field by means of thedirection-finding long-distance radio beacon. In addition, anothersmaller radio beacon had been installed, casting a beam fifteen totwenty miles in either direction, which governs the immediate approachto the field.

  To locate the landing field the pilot watches two vibrating reeds, tunedto the radio beacon, on a virtual radio receiver on his instrumentboard. If he turns to the right or left of his course the right or leftreed, respectively, begins doing a sort of St. Vitus dance. If the reedsare in equilibrium the pilot knows it is clear sailing straight to hisfield.

  The sensitive altimeter showed Lieut. Doolittle his altitude and made itpossible for him to calculate his landing to a distance of within a fewfeet from the ground.

  Probably the strangest device of all that Lieut. Doolittle has beencalled upon to test in Mr. Guggenheim's war against fog is a sort ofheat cannon that goes forth to combat like a fire-breathing dragon ofold. Like the enemies of the dragon, the fog is supposed to curl up anddie before the scorching breath of the "hot air artillery" although thefundamental principle behind the device is a great deal more scientificthan such an explanation sounds. It is, in brief, based on the knownfact that fog forms only in a very narrow temperature zone which liesbetween the saturation and precipitation points of the atmosphere. Ifthe air grows a little colder the fog turns into rain and falls; if itis warmed very slightly the mist disappears and the air is once morenormally clear, although its humidity is very close to the maximum.