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The North American XP-86 Sabre, in flight over the Mojave Desert. Was it the first to break the so-called sound barrier? (USAF. NASM photo no. A-38492-C)

Mach Match

Did an XP-86 beat Yeager to the punch?

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Editors’ note: October 14, 1947, was a day of undercover celebration at the Muroc Army Air Field in California’s Mojave Desert. Captain Chuck Yeager had broken the so-called sound barrier in the experimental Bell XS-1, and the news was immediately locked away in the vaults of the newly independent U.S. Air Force and the National Advisory Committee for Aeronautics. Although the X-1 program was classified and there were no independent observers, Yeager was able to claim an official record because all airspeed, Mach number, pressure, and temperature data from test flights were tracked, recorded, and documented. Such documentation, like that produced by the Wright brothers, who painstakingly recorded all details of their flights, ensures an unassailable place in history.

But there was another high-speed experimental aircraft flying over the desert that autumn. And although claims that the North American XP-86 achieved Mach 1 are merely anecdotal, Al Blackburn, a former North American test pilot, interviewed eyewitnesses, researched historical accounts, and reconstructed the events of those memorable months in the 1998 book Aces Wild: The Race for Mach 1, from which this excerpt has been adapted.

Going supersonic for the first time is clearly a historic aeronautical event, just as the Wright brothers’ first flights are. But I can never remember which brother did it first. They did it on the same day, and whether it was Wilbur, then Orville, or Orville, then Wilbur, doesn’t seem to matter much. In the supersonic event, was it George Welch, then Chuck Yeager, or Yeager, then Welch? Looking at the record, it could have been Welch by a fortnight or Yeager by four weeks.

The fall of 1947 in California’s Mojave Desert was an incandescent time to be alive—for the crazy-ass pilots who were testing myriad new aircraft and for the lovely, loving, hopeful ladies who attended their safe return. So soon after the war, the prevailing mood was akin to the euphoria of victory but blessed with much smaller casualty lists. Much of the exhilaration centered on a little orange rocketship being sent aloft from Muroc Army Air Field with growing frequency, attched to a B-29 mothership. Everyone knew that this represented a substantial national effort, bringing together the resources of the U.S. Army Air Forces (soon to be renamed the US Air Force), the National Advisory Committee for Aeronautics, and the Bell Aircraft Company to launch the first manned aircraft design solely to fly faster than sound.

The word from the X-1 camp at Muroc was that Army Air Forces Captain Chuck Yeager had come very close to going supersonic on September 12. Surely on the next flight he would push it through. But then the X-1 flights were postponed. Rumors of a seirous pitch control problem drifted out of the Bell camp. There was evidence of a lot of scrambling. Yeager was pressing fellow pilot and engineer Jack Ridley, the one man on the X-1 team in whose hands he’d entrust his life. He wanted Ridley’s assurances that the changes would work—he wanted no more running out of pitch control at Mach .94.

North American test pilot George Welch could only smile as these tales leaked out of traded confiences. His money was on another contender. The first XP-86 aircraft, Army Air Forces serial number PU597, was rolled out of his company’s plant in Los Angeles on August 8. The more involved Welch had gotten in the development of the Sabre, the more he was convinced that he could capture the laurels of the first supersonic flight for North American Aviation.

Welch had joined North American in the middle of 1944, at the height of the war and the peak of demand for North American’s prime product, the P-51 Mustang. He’d been there only a month or two when Fred Borsodi visited from Wright Field and showed his film of shock waves on a Mustang’s wings as it dove at max power straight down from 40,000 feet. Theodore von Kármán, the legendary aerodynamicist from the California Institute of Technology in Pasadena, was at that screening, and observed that when an entire aircraft, not just the air accelerating over the thickest part of the wing, went supersonic, shock waves would be sent to the ground. He theorized that people nearby would hear and feel the passing of that pressure pulse. Listening intently to all this were Ed Horkey, a former student of von Kármán’s and Harrison Storms and Larry Greene, who were leaders in the aerodynamics section of North American’s advance design group. Another observer was George Welch.

Over the next three years, Welch stayed in touch with Horkey, Storms, and Greene as they created the XP-86. And he spent time with Walt Spivak, who had cut out the pieces and put them together on the shop floor. Welch also spent a lot of time in the Sabre’s cockpit at Muroc and observed the flight test crew as they checked out all the systems and instrumentation for this sleek new fighter.

Welch knew that the engineers had carefully reviewed the analytical data and wind tunnel test results the Germans had obtained from their swept-wing designs, and that North American had also run its own wind tunnel tests. Storms told him that they were almost certain that top speed at altitude would be better than Mach 0.9 in level flight. He explained to Welch that at that Mach number, the center of lift would start to move aft on the wing and that he would have to pull back on the stick and start trimming…but very carefully. Changing the angle of the whole stabilizer at that speed and a changing Mach number could get pretty tricky.

“So I’m doing nine-tenths at, say, 35,000 feet and push the nose over into a 25- to 30-degree dive. What then?” Welch asked the designers.

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