AERONAUTICS: Caterpillars

"If you need one and haven't got one, you'll never need one again."—Air Corps Proverb.

The chronicle of the Caterpillar Club appears this week in a new book Jump! by Don Glassman,graduate of the University of Missouri, journalist. A "Caterpillar" is a flyer who has dropped over the side of a disabled or lost plane—like a butterfly wriggling out of its cocoon—and swung down through space to safety with parachute mushrooming over his head.

A parachute is a hollow hemisphere of strong, light silk or cotton, diameter varying from 22 ft. to 28 ft., with shroud lines running from the rim of the fabric to a harness worn around the body of the jumper. The parachute idea is credited to Leonardo da Vinci, mathematician and scientist as well as painter and sculptor, in 1495 (in his tome Codex Atlanticus).

Not until after the War, in January 1919, when Major E. L. Hoffman assumed charge of parachute research at McCook Field, Dayton, Ohio, did the modern development of the chute really begin. Within a few months he produced the first successful "free-type" chute, to be worn on the back and opened by the wearer as he falls clear of his machine. It was followed by the seat-type, now in general use, first tested by Leslie Irvin, who jumped merely to prove that man does not lose control of his faculties in falling unhindered through space.

When a man goes over the side of his disabled airplane, from deep in his consciousness comes the reflex which makes him pull the rip cord, located over his heart, and open up his life saver. Psychologically it is almost impossible to forget to pull. Three hundred feet of altitude is the safe minimum in which the chute can be used, although jumps of less height are on record. The highest jump on record is one of better than 24,000 ft. At that height, the jumper had to have oxygen for breathing. The longest delayed jump was from a height of 11,000 ft. The experimenter pulled his rip cord at 2,000 ft. The cloth chute opened with a report that was heard for miles around. His body had been falling at 20 m. p. h., the maximum speed that a man's body attains in a free fall.

When a parachute opens, the hemisphere offers such air resistance to gravity that descent is checked to about 16 ft. per second. This amounts to a force equal to that of jumping from a ten-foot fence, often sufficient to sprain an ankle. Chutes can be partially guided when the jumper wishes to avoid landing in a clump of trees or a pond, by pulling the shroud lines on the side toward which he wants to go. In a high wind, if the jumper does not unharness himself before he lands, as he must do when landing on water, he will be dragged over the ground, bashed and banged.