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In 1999, Al Blackburn wrote a book, Aces Wild: The Race for Mach 1, and from it an article for the Smithsonian Air and Space magazine. Both are clearly the culmination of a lot of research into a fascinating subject, and I don’t want to steal his work, so what follows is a summary of a few points of the interesting story he pieced together – that the X-1 might not have been the first aircraft to break the sound barrier.

In the 40s and 50s the air around Muroc Field was filled with all manner of experimental aircraft, the X-1, of course, but others, such as the Convair XF-92, the Lockheed XF-90, the Northrop XB-35 and XB-49. These aircraft were more closely aligned to production needs than the X-1 or the D-558 Phase I and II. There was another fighter in that air too, the North American XP-86 Sabre.

The Sabre was an experimental version of a plane that was desined for production. Built in LA it was moved to Muroc Field for flight testing. Unlike the X-1, the Sabre was jet powered and fully capable of all aspects of fighter operation.

A couple of months into it’s flight test program and the XP-86 was already at Mach 0.9. The air and ground crews for many of the aircraft at Muroc would kick back at a watering-hole called Pancho’s. Enevitably stories would be swapped, or things would be read into the mood of the different teams. From this XP-86 test pilot, George Welch, deduced the X-1 team was having issues approaching the last few fractions of a Mach on the way to supersonic.

Welch had found the XP-86 to fly very well approaching the magic Mach number. He’d also heard breaking Mach 1 would generate a boom that could be heard on the ground. So Welch hatched a plan, he asked his girlfriend at Pancho’s (a bar on the edge of Muroc Field) to listen for the boom while he flew overhead.

On 1st October 1947, he climb to 35,000ft, turned off the recording instruments, pulled up the gear, and dived towards Pancho’s. The airspeed indicator stuck at 350kts then jumped to 410 and climbed to 450kts before he pulled out and returned to the planned tests.

After the flight, his girlfriend confirmed that a boom had occurred, and engineers confirmed that the airspeed indicator would be affected as the supersonic shockwave moved over the airspeed probe. Welch was convinced he’d gone supersonic, but had no hard evidence. Meanwhile the X-1 program was inching closer to an instrumented Mach 1.

On 13th October, Welch’s bosses insisted the next two Sabre flights were done with the gear down.The aircraft had been having problems with the landing gear, but Welch believed that the Air Force didn’t want anything to disturb they’re carefully planned X-1 program’s triumphant breaking of the sound barrier. He was also a fighter pilot, so being second wasn’t in his blood.

On the 14th, Welch’s chase pilot, Bob Chilton, suggested Welch lag the relaying his test result over the radio to give him time to execute an unplanned supersonic dive. Welch took up the idea and executed a dive towards Pancho’s while relaying the results of his previous test.

Welch was on the ground heading to debriefing when he heard a distant boom. 10:30am, the X-1’s record setting effort. Twenty minutes after he’d dived at Pancho’s.

Apparently some people remarked it was strange to hear two booms, since X-1 could only fly for a few minutes and it took two days to prep it for flight, but no-one questioned it further.

In the following weeks booms were often heard over Muroc Field and eventually high precision radar was used to verify the XP-86’s performance – Mach 1.02 and 1.04 on it’s two attempts. It has to be said though that a more powerful engine had been fitted by this point. According to Welch’s flight log by February ’48 he had repeated such dive tests more than 20 times, though again, there is no record of the results.

In a short time the X-1 assured itself of it superiority by pushing to even higher speeds. Either way the sound barrier had been broken by visionaries, people who got things done, fantastic machines, and pilots who risked their lives to prove barriers were there to be broken.

The X-1 and XP-86 were different aircraft with different objectives. One had a mass of documented test results, the other anecdotal evidence. The USAF and Bell had backed one solution and had the clout to manipulate events to organize their success, a success that would further their funding and development goals. North American had an equal amount to gain from making the Mach 1 claim, but they wouldn’t want to bite the Air Force-hand that fed it. And they had no data to support any claim, so it could be wishful thinking.

What do you think?



(Images courtesy of Wikipedia)

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