Sixty-eight years ago this month, the swept-wing XP-86, the initial version of the famed USAF/North America F-86 Sabre, began flight testing at what is now Edwards Air Force Base. The popular Mig Alley legend would be produced in numerous variants and ultimately rack-up a total production run of nearly 10,000 aircraft worldwide.
In the waning days of World War II, the United States Army Air Force (USAAF) issued the requirements for a new high-speed, jet-powered fighter/interceptor aircraft. North American Aviation (NAA) captured the USAAF’s attention with a prototype swept-wing aircraft known as the XP-86. The “X” designation was shorthand for Experimental while the “P” stood for Pursuit.
The XP-86 (later designated as the XF-86 where “F” stood for Fighter) was the first United States fighter to incorporate wing sweep. The key benefit derived from sweeping the wings was to greatly reduce transonic wave drag. Based on aerodynamics data captured from the defeated Third Reich, NAA engineers designed the XF-86 with a wing sweep of 35 degrees.
A drawback to using wing sweep is that low-speed flight characteristics are adversely affected. The principal detrimental effect being a reduction in lift. However, NAA solved this problem by the incorporation of leading edge slats to enhance lift production at low speed.
The XF-86 measured roughly 37-feet both in length and wingspan. Empty weight was some 12,000 lbs. Power was provided by a Chevrolet J35-C-3 turbojet that generated a paltry 3,750 pounds of thrust. Later variants of the Sabre would be powered by jet engines generating nearly 10,000 pounds of thrust.
On Wednesday, 01 October 1947, XF-86 No. 1 took to the air for the first time from Muroc Army Air Field, California. USAAF Major and WW II 16-kill ace George S. “Wheaties” Welch was at the controls of the XF-86. Intestingly, the historical record strongly suggests that Welch exceeded the speed of sound during a dive on that first flight test.
The case of George Welch is an intriguing sub-plot of the F-86 Sabre story. Welch was stationed at Pearl Harbor on 07 December 1941. He was one of the very few American pilots to get in the air and fight the attacking Japanese forces. Numerically overwhelmed, he nontheless splashed four (4) enemy aircraft and lived to fly and fight another day.
Welch served three (3) combat tours in WW II for a total of 348 combat missions. After leaving the service in 1944, he joined North American Aviation as a test pilot. Welch progressed quickly and became NAA’s Chief Test Pilot. This path ultimately led to Welch flight testing the XP-86 Sabre.
Although denied verification in official Air Force records, both oral history and strong circumstantial evidence points to the high likelihood that Welch exceeded Mach 1 at least twice before the Bell XS-1 did so on Tuesday, 14 October 1947.
Incredibly, the first instance of Welch and the XF-86 exceeding Mach 1 was on the occasion of its first flight test! Welch dove the aircraft from 35,000 feet and reportedly generated a weak sonic boom.
The second instance of Mach 1 exceedance reportedly occurred on Tuesday, 14 October 1947. This time Welch dove the XF-86 from 37,000 feet and generated a stronger sonic boom. Apparently, this event took place just before the Bell XS-1, with USAAF Major Charles E. “Chuck” Yeager at the controls, achieved Mach 1.06 later that same morning.
Welch was never officially credited with being the first to achieve supesonic flight. A number of reasons account for this circumstance. First, his aircraft was not instrumented properly to verify flight performance at quasi-supersonic speeds. Additionally, Welch’s aircraft was not tracked by radar.
In addition to the technical reasons cited above, there was political intrigue surrounding Welch’s supersonic dive flights as well. NAA (and thus Welch) had been ordered not to exceed Mach 1 before the rocket-powered Bell XS-1 did so. Perhaps the only concession accorded Welch was that USAF later referred to Yeager’s historic superonic flight as the first time the sound barrier was broken in level flight.
George Welch went on to a distinguished, but all too brief flight test career. On Monday, 25 May 1953, he became the first man to exceed Mach 1 in level flight in a jet-powered production aircraft. That aircraft was the North American F-100 Super Sabre. Welch perished on Tuesday, 12 October 1954 when his YF-100A went out of control and distintegrated during a 7-g pull-up at Mach 1.55.
For its part, the F-86 Sabre ultimately served long and well in the air forces of the United States and a host of other western-friendly nations. Perhaps its greatest claim to fame accrues from the type’s remarkable aerial combat perfromance in the Korean War. Indeed, despite being numerically bested by Soviet-built MIG-15 aircraft, the official record shows that USAF pilots made 792 kills flying the Sabre. Compared with 76 kills made by the opposition, the Sabre registered a phenomenal 10:1 kill ratio.