Flying Teakettle

Since the summer of 1941 hardy British countrymen, inured to many a shock of World War II, have been startled out of their wits on various occasions by the swift and noisy visitations of a friendly but seemingly insane aircraft.

It would pop into sight with a squealing shriek that sent some groundlings dashing for shelter, sure that a heavy bomb was screaming down near by. As it whisked overhead the sound changed to something like "a giant whistling teakettle on the boil." It disappeared over the far horizon before you could say "knife." After a while, neighborhood people got used to it, even gave it a nickname: "The Squirt."

Last week the mystery was cleared up. A joint statement by the R.A.F. and U.S. Army Air Forces announced that the Allies have developed a radically new type of fighter aircraft which flies without a propeller. It is driven entirely by jet propulsion. Work on the design was started in 1933 by ace British designer Frank Whittle, now an R.A.F. group captain. It took him four years to lick the engine problem, four more before a plane actually flew.

Generals Fly. In July 1941, plans and a completed engine were turned over to the U.S., and American engineers went to work. General Electric, experienced in building turbines and turbosuperchargers, was assigned to produce the engines, Bell Aircraft to build the planes. The first flight of an American model was made on Oct. i, 1942, by lean, studious Robert M. Stanley, Bell test pilot.

Since then hundreds of flights have been made, all without mishap, and some of the more seasoned necks of the Air Forces have been risked in the propellerless ships -- among them those of 51 -year-old Lieut. General William E. Keprter, U.S. fighter commander in Britain; Brigadier General B. W. Chidlaw, 43, Materiel Division chief.

The Allies' announcement of this not-so-secret weapon was scarcely surprising. The basic principles of jet propulsion have been known for at least 30 years, and experiments of this type have been carried on by the major European powers.

The Italians had a workable jet aircraft three years ago, flew it over Milan by daylight and completed one cross-country flight from Milan to Rome; the Germans were reported working on a similar plane. Nothing more has been heard of either.

General Silence. Having announced their jet plane, the Allies relapsed into discreet silence on details. About all that could be learned was that the present model has two engines and has been mistaken in the air for a twin-tailed P-38 Lightning. Imaginative press dispatches promptly dubbed the aircraft a rocket plane, which it is not.

British expert G. Geoffrey Smith, whose authoritative work, Gas Turbines and, Jet Propulsion for Aircraft, will soon be published in the U.S. by Aerosphere, Inc., makes this distinction: a rocket carries its own combustion mixture, including oxygen; a jet-propulsion device has fuel but draws oxygen for combustion from the surrounding atmosphere.

What makes the jet-propulsion plane fly is the extreme pressure built up within the mechanism by air compression and burning fuel. This pressure is exhausted to the rear through the jet opening, thus exerts a powerful forward reaction, or thrust, on the plane.

U.S. jet planes will soon go into production, and pilots undoubtedly will be trained for them. Whether the development will move fast enough for them to play a part in this war no man can say. But for aviation in the future, jet propulsion undoubtedly has dazzling possibilities of speed, lightness and fuel economy. One problem a propellerless plane solves automatically is that of supersonic speeds at propeller tips; engineers have discovered that a propeller encounters "compressibility burble" and loses its effect on the air when the blade tips whirl at a speed approaching that of sound, about 750 m.p.h. at sea level.

This is one trouble that limits present airplane speed to around 450 m.p.h. A jet-propulsion ship might conceivably lift the speed ceiling another 250 to 300 m.p.h. Then the plane's surfaces would develop their own burbles and science would have to go to work again.

But last week's final word on the jet plane came from its designer, slight, dark, publicity-shy Group Captain Whittle: "I am completely embarrassed. Damn it, I wish I had been a doctor."

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