Flying Triangle

The public got a good look last week at Britain's spectacular new interceptor, the Gloster GA-5. Photographed for the first time in the air, the bizarre, dartlike R.A.F. plane marks a milestone in aviation: the coming-of-age of the "delta" wing.*

Conceived in the wind tunnels and laboratories of Hitler's Third Reich, the delta wing passed its early years as a kind of aeronautical curiosity, something for designers to toy with when they sketched supersonic planes of the future. Then turbojet and rocket experts began to turn out engines that had enough power to shove a man-carrying airplane up toward the speed of sound. The fantastic troubles of high-speed flight changed from drawing-board theory into tough, practical problems.

Schoolboy's Dart. Airplanes with conventional wings have been known to run into trouble at high speeds. Near the sonic barrier, the turbulent air shoved aside by wings and fuselage offers so much resistance that to go still faster requires extravagant power. Given that power, some straight-winged planes do push through into supersonic flight, e.g., Bell's rocket-powered X-1 (TIME, April 18, 1949). But there are tense moments while they pass through disturbed air.

Aeronautical engineers find it relatively easy to design a fuselage almost unaffected by speed. Wings are harder. Even if wings are satisfactory at high speeds, they still have to fly safely at the low (150-160 m.p.h.) speeds of landing and takeoff. As the engineers continued to study supersonics, they learned to 1) keep the wings as thin as possible in relation to width, 2) keep the wing span small in relation to width and 3) sweep the wings back sharply as they stretch away from the fuselage. These tricks of design, they discovered, add up to a wing like an arrowhead or a schoolboy's paper dart.

Wide & Thin. Once they began to build experimental delta wings (Convair's XF-92 was the first to fly in 1948), airplane manufacturers discovered other advantages of what the designers call "delta configuration." The strain of high-speed flight tends to bend the airframe out of line. Without adding too much weight., the triangular structure can be built stiff enough to eliminate this danger. A relatively thin wing and its short fuselage-have room for fuel tanks, landing gear and auxiliary equipment.

Some designers believe that the wide delta wing is so stable in flight that it does not need the balancing action of a horizontal tail. All the necessary controls except the rudder, they say, can be built into its trailing edge. And a fast-acting electronic auto-pilot can be added to stop the bucking and pitching that have been known to flip a tailless plane into the beginning of a fatal somersault. But the GA-5, as an added measure of safety, carries a small delta tail high on its rakish fin.

Biggest drawback to delta wing planes is their performance at low speeds. To maintain lift during landing and take-off they must hold their noses awkwardly high, limiting the pilot's vision at times when he needs it most. But there are fighters already on the drawing board that will meet this difficulty with adjustable wings.

The tremendous speeds of tomorrow's jet bombers will cut down the precious minutes between the time the bombers are detected by early warning radar and the time a defending plane can climb to altitude. Interceptors that can cruise and fight at more than 1,000 m.p.h. will be a necessity. Planes like the GA-5, each of whose two turbojet engines is more powerful at high speeds than all four piston engines of a World War II Superfort, may be equal to the task. Airmen are hopeful, but they know there is many an agonizing slip between prototype and production fighter.

* There are about half a dozen other delta wing planes, but most of those in the U.S. and Britain are research vehicles. The GA5 is the first to be equipped with twin jets.

This file is automatically generated by a robot program, so reader's discretion is required.