Fastest of Them All?

Fast planes of the future will probably look like the Navy's new jet fighter, the Chance Vought XF7U-1, which completed its initial flight tests last week. The new fighter has short, broad wings "swept back" at an angle of 45DEG or better. There is no tail; two stabilizers with rudders are attached to the trailing edges of the wings. Two Westinghouse turbojet engines drive the plane at better than 600 m.p.h.

The XF7U-1's design looks radical, but it has long been foreshadowed by the results of wind-tunnel research. Swept-back wings have two advantages. The air passing over them diagonally (parallel to the plane's motion) acts as if it were passing directly across the wing at right angles to its leading edge. This "short cut" slows the air-stream's apparent speed, and reduces the shockwave difficulties associated with Mach 1 (the speed of sound, 770 m.p.h. at 68DEG F.).

When a plane is flying at Mach 1 or above, shock waves flare back in a "V" from its nose and wing roots like water waves from the bow of a ship. The swept-back wings keep inside the V, and avoid a tangle with the shock wave.

Short, broad wings are good "future practice" in aerodynamics. The NACA (National Advisory Committee for Aeronautics) proved years ago by wind-tunnel tests that the long, graceful wings of bombers are much less efficient above Mach 1 than clumsy-looking "stub" wings. As planes get faster, their wings will probably grow stubbier still until they diminish into something looking like an arrowhead.

How fast will the XF7U-1 go? It is no secret (and the shape itself would be a giveaway) that it was designed to fly considerably faster than Mach 1. Navy Test Pilot Captain F. M. Trapnell, who is putting the XF7U-1 through its paces, said that he has not yet worked it to top speed or top altitude. He expects, however, that it will prove "the fastest of them all."

Captain Trapnell, who passes on all Navy planes, is not much like a moviegoers' idea of a test pilot. He is no daredevil, nor is he "in love with the sky." Like most real-life test pilots, he is middle-aged (46) and matter-of-fact about his profession. He finds all airplanes uncomfortable, and suspects that people were happier riding horses.

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