At the Barrier

The airplane speed record returned to the U.S. last week after almost ten years in Europe. Veteran Army Test Pilot Colonel Albert Boyd, 40, made four three-kilometer (1.86 mi.) runs, with and against a light breeze, in a jet-propelled Lockheed P-80R over Muroc Dry Lake, Calif. His average speed: 623.8 m.p.h., only 7.8 m.p.h. faster than Britain's record, hung up in 1946.

That thin sliver of extra speed cost enormous effort. The P-80R, though designed as a practical military airplane rather than a souped-up racing job, is a refinement of Lockheed's P-80 (Shooting Star). It has a thinner, broader wing, a smaller canopy than the original model. Its Allison 400 turbojet engine develops a take-off thrust of 4,600 Ibs. Half of this tremendous power is soaked up in attaining the last 70 m.p.h.

From that point upward, says Lockheed's Designer Clarence Johnson, "the drag curve is almost vertical." No matter how much power is applied, the P-80R will fly only a little faster.

Horse-&-Buggy Rules. Last week's speed test was flown under the antiquated rules set up by the Federation Aeronautique Internationale in the days when airplanes were made of sticks and cloth and wire. To establish an official speed record, a plane must stay below 75 meters (246 ft.) over the measured course, and it cannot rise above 1,312 ft. on the turns beyond. Such low-level flying is hampering and hazardous for modern, high-speed jet planes.

Future speed tests will probably be flown at high altitudes. Even under liberalized conditions, few designers think that conventional planes will fly much faster than the P-80R, which is already pushing against that invisible sky barrier, the speed of sound. The next major speed increase will come, most airmen think, when a radically different plane breaks through the barrier and runs at supersonic speed, as V-2 rockets do.

Mach .81. Modern test pilots and designers do not measure a fast plane's speed in miles per hour, but in "Mach numbers." Mach 1 is the speed of sound in the air through which the plane is passing. In the warm air near the ground it is about 765 m.p.h., but it falls (to about 650 m.p.h. at 40,000 ft.) in the cold air of high altitudes. Well below these speeds, the "sonic barrier" makes itself felt, jamming an airplane's controls, destroying the lift of its wings. The P-80R got up to Mach .81 last week over the hot, sun-baked desert. If it had flown at 20,000 ft., it would have met less resistance from the thin upper air but it might have run into "compressibility effects" when it came too close to the cold-slowed speed of sound.

Designer Johnson believes that Mach 1 will be reached (and probably surpassed simultaneously) in about three years. He is sure that neither the P-80R nor any similar airplane can ever fly that fast.

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