The outstanding development in aviation recently, and one of the most significant 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 Guggenheim Fund for the Promotion of Aeronautics, Inc. to announce that the problem of fog-flying, one of aviation's greatest bugbears, had been solved at last.

There has been "blind flying" done in the past but never before in the history of aviation has any pilot taken off, circled, crossed, re-crossed the field, then landed only a short distance away from his starting 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 making the cabin of the plane entirely light-proof. Once seated inside, the flyer, with his co-pilot, Lieut. Benjamin Kelsey, also of Mitchel Field, were completely shut off from any view of the world outside. All they had to depend on were three new flying instruments, developed during the past year in experiments conducted over the full-flight laboratory established by the Fund at Mitchel Field.

The chief factors contributing to the solution of the problem of blind flying consist of a new application of the visual radio beacon, the development of an improved instrument for indicating the longitudinal and lateral position of an airplane, a new directional gyroscope, and a sensitive barometric altimeter, so delicate as to measure the altitude of 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 which indicates longitudinal and lateral position in relation to the ground at all time. He was able to locate the landing field by means of the direction-finding long-distance radio beacon. In addition, another smaller radio beacon had been installed, casting a beam fifteen to twenty miles in either direction, which governs the immediate approach to the field.

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

The sensitive altimeter showed Lieut. Doolittle his altitude and made it possible for him to calculate his landing to a distance of within a few feet from the ground.

Probably the strangest device of all that Lieut. Doolittle has been called upon to test in Mr. Guggenheim's war against fog is a sort of heat cannon that goes forth to combat like a fire-breathing dragon of old. Like the enemies of the dragon, the fog is supposed to curl up and die before the scorching breath of the "hot air artillery" although the fundamental principle behind the device is a great deal more scientific than such an explanation sounds. It is, in brief, based on the known fact that fog forms only in a very narrow temperature zone which lies between the saturation and precipitation points of the atmosphere. If the air grows a little colder the fog turns into rain and falls; if it is warmed very slightly the mist disappears and the air is once more normally clear, although its humidity is very close to the maximum.