Mach 1: Assaulting the Barrier

In 1947, no airplane had ever gone faster than the speed of sound.

The Douglas D-558-2 Skyrocket (shown here at Edwards Air Force Base circa May 1949) pushed past Mach 2 on November 20, 1953, beating an advanced X-1 to the record. (US Navy via National Air and Space Museum. Photo SI A-5168-C.)
Air & Space Magazine

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Dismayed by the negativity of the Oklahomans and curious about how much of the claimed damage was boom-caused, the FAA built a small mock village on the White Sands Missile Range in New Mexico and bombarded it in January 1965 with F-104 thunderclaps producing as much as 10 pounds of overpressure per square foot—far more than the Oklahoma test’s levels.

Nothing broke, so the FAA proudly called in the press and did the demo for the TV cameras. Asked to make one more pass (“and get it real low so we can get a good shot…”), the Starfighter pilot got carried away: his 39-pounds-per-square-foot blast turned the town into what could have passed as the set for a spaghetti-Western barfight, with broken glass everywhere. All the FAA could salvage from the PR shambles was the claim that 2,000 chickens hatched from eggs that had been subjected to the sonic booms had a higher fertility rate than those developed in reverent silence.

In 1965 the Air Force made a series of supersonic mock attacks on Chicago with B-58 Hustlers. Among other damages, the entire plaster ceiling of a large conference room in an Evanston church collapsed during one run, and during another a 14-year-old boy took an 11-stitch cut from an exploding pane of glass in his high school classroom. Though sonic booms were sometimes referred to in those days as “the sound of freedom,” 2,520 unimpressed Chicagoans filed damage claims and were paid over $65,000, just over $1,000 per bombing run.

Mach 1 With a Propeller?

“There I was at 40,000 feet,” the young Army Air Forces pilot begins—really—“in the AAF’s latest P-47N with a very specific purpose in mind, mischievous as it was.”

Lieutenant Raymond Hurtienne’s purpose, it turns out, was to break the speed of sound in a propeller-driven aircraft, and he swears he did it, in the spring of 1945, in the skies above Long Island. “I rolled her over, pointed her straight down, retarded throttle, full left trim and full forward stick,” he wrote in a letter to a P-47 pilot’s association. “As the speed increased, control responses became more and more rigid. The airspeed indicator became stuck against the peg at 575 mph. Vapor trails were forming at both wingtips. The stick seemed like concrete. The altimeter was unwinding at a terrific rate. This was it: I had hit Mach 1. There wasn’t another plane in the skies that could touch me.”

That sort of thing seriously griped Herbert O. Fisher, and mischief had nothing to do with it. Herb Fisher, who died last July at the age of 81, made a living diving Republic P-47 Thunderbolts to their absolute maximum controllable airspeed while he was a test pilot for Curtiss-Writght’s propeller division after World War II. He would have been the first to tell you that neither he nor anyone else ever put a World War II piston engine aircraft through the sound barrier. Or, as fellow test pilot Tony LeVier once put it, “Anyone who did ain’t here to tell about it.”

Fisher wore the high-belted pants and tucked-in tie of a man in his 80s, but his eyes were clear, his voice strong, and he had an easy laugh. He chuckled about the radar detector in his big station wagon (New Jersey plates P40P47, for the two airplanes that were his specialty), saying he never drove faster than 60 mph anyway. But once he routinely did 10 times that speed in a P-47—an airplane built for a real-world maximum of a little over 400 mph. Fisher made over 100 high-speed descents from altitudes as high as 38,000 feet and achieved instrument-verified airspeeds of Mach .83 (about 600 mph at that altitude)—but no higher.

“The first time I heard this sort of thing was an Air Force pilot who came out with publicity that he went Mach 1 in a Thunderbolt over Europe,” Fisher groaned. “There’s no way he could have gone Mach 1, but he still believes it. He’s still out there preaching it.”

Other U.S. and British pilots have claimed to have done it as well, recalling flights in Spitfires, P-38s, P-47s, and P-51s. But there is one basic, irrefutable reason why their claims are, as Fisher might have put it, malarkey. A propeller—even one designed to current state-of-the-art standard for maximum efficiency—continues to create thrust up to a point somewhere short of supersonic. At that instant, it suddenly loses efficiency and begins to create not thrust but enormous drag. “It becomes a flat plant,” Fisher said; “a big brake.” One Spitfire pilot, who attained the highest verified speed, Mach .9, achieved by a World War II propeller-driven aircraft, discovered this in a big way when the sudden braking forces became so powerful during a dive that the entire propeller and most of the engine cowling broke off.

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