14 October 1947: Twenty minutes before Captain Charles E. (“Chuck”) Yeager broke the sound barrier with a Bell X-1 rocketplane, North American Aviation Chief Test Pilot George S. Welch put the swept-wing XP-86 prototype, serial number 45-59597, into a shallow dive from 37,000 feet (11,278 meters) and accelerated. In direct violation of orders from the Secretary of the Air Force to not do so, Welch broke the “sound barrier.”
Witnesses on the ground heard the distinctive “B-BOOM” double-shock as the aircraft exceeded the speed of sound. Welch was the first to observe “Mach jump” as the airspeed indicator momentarily indicated higher due to the compression of air in front of the aircraft.
Estimates are that the XP-86 reached Mach 1.02–1.04 on this flight.
3 October 1967: The 188th flight of the X-15 Program was the 53rd for the Number 2 aircraft, 56-6671. It had been extensively modified by North American Aviation to an X-15A-2 configuration following a landing accident which had occurred 9 November 1962. The fuselage was lengthened 28 inches (0.711 meters) to accommodate a liquid hydrogen fuel tank for a scramjet engine that would be added to the ventral fin, a new tank for additional hydrogen peroxide to generate steam for the rocket engine turbo pump, and external propellant tanks to allow the rocketplane to reach higher speeds and altitudes. The entire surface of the X-15 was covered with an ablative coating to protect the metal structure from the extreme heat it would encounter on this flight.
Minor issues delayed the takeoff but finally, after they were corrected, and with Pete Knight in the X-15’s cockpit, it was carried aloft under the right wing of Balls 8, a Boeing NB-52B Stratofortress, 52-008.
At 45,000 feet (13,716 meters) over Mud Lake, Nevada, the X-15 was droppeded at 14:31:50.9 local time. Knight fired the Reaction Motors XLR99-RM-1 rocket engine and began to climb and accelerate. After 60 seconds, the ammonia and liquid oxygen propellants in the external tanks was exhausted, so the the tanks were jettisoned to eliminate their weight and aerodynamic drag.
The X-15A-2 climbed to 102,100 feet (31,120 meters) and Pete Knight leveled off, still accelerating. After 140.7 seconds of engine burn, Knight shut the XLR99 down. He noticed that thrust seemed to decrease gradually and the X-15 continued to accelerate to 6,630 feet per second (2,021 meters per second), or Mach 6.72.
Shock waves from the dummy scramjet mounted on the ventral fin impinged on the fin’s leading edge and the lower fuselage, raising surface temperatures to 2,700 °F. (1,482 °C.) The Inconel X structure started to melt and burn through.
Pete Knight entered the high key over Rogers Dry Lake at 55,000 feet (16,764 meters) and Mach 2.2, higher and faster than normal. As he circled to line up for Runway One Eight, drag from the scramjet caused the X-15 to descend faster and this set him up for a perfect approach and landing. Because of heat damage, the scramjet broke loose and fell away from the X-15.
Knight touched down after an 8 minute, 17.0 second flight. His 4,520 mile per hour (7,274 kilometers per hour) maximum speed is a record that still stands.
The X-15A-2 suffered considerable damage from this hypersonic flight. It was returned to North American for repairs, but before they were completed, the X-15 Program came to an end. This was 56-6671’s last flight. It was sent to the National Museum of the United States Air Force where it is part of the permanent collection.
In a ceremony at the White House, President Lyndon B. Johnson presented the Harmon International Trophy to Major William J. Knight.
1 October 1947: After three years development in which 801,386 engineering hours and 340,594 drafting hours had been expended, the first prototype North American Aviation XP-86 (company designation NA-140), serial number 45-59597, was ready for its first flight at Muroc Dry Lake in the high desert, north of Los Angeles, California.
Completed at North American’s Inglewood plant on 8 August 1947, it was trucked to Muroc in mid-September. It was reassembled, everything was checked out, and after a few taxi tests, company test pilot George S. Welch took off for a initial familiarization flight. Chief Test Pilot Bob Chilton flew chase in an XP-82 Twin Mustang with a company photographer on board. The duration of the first flight was 1 hour, 18 minutes.
During this first flight, George Welch climbed to 35,000 feet (10,668 meters):
“In a little more than ten minutes he had reached 35,000 feet. Leveling out, the test pilot smiled as he watched the indicated airspeed accelerate to 320 knots. He estimated that should be 0.90 Mach number. . . Rolling into a 40 degree dive, he turned west. . . The airspeed indicator seemed to be stuck at about 350 knots. The Sabre was behaving just fine. Then at 29,000 feet, there was a little wing roll. Correcting the roll, George pushed into a steeper dive. The airspeed indicator suddenly jumped to 410 knots and continued to rise. At 25,000 feet, he pulled the Sabre into level flight and reduced power. The wing rocked again and the airspeed jumped back to 390.”
—Aces Wild: The Race for Mach 1, by Al Blackburn, Scholarly Resources Inc., Wilmington, Delaware, 1998, at Chapter 5, Pages 144–145.
George Welch was the first to report instrument readings that would be referred to as “Mach jump.” It has been argued that George Welch flew the XP-86 beyond Mach 1 during this flight, breaking the “sound barrier” two weeks before Chuck Yeager did with the Bell X-1 rocketplane. During flight testing, it was firmly established that the XP-86 could reach Mach 1.02–1.04 in a dive, so it is certainly possible that he did so on the Sabre’s first flight.
The XP-86 was unlike any airplane before it. It was the first airplane with a swept wing. After analyzing test data from the Messerschmitt Me 262, North American’s engineers designed a wing with a 35° degree sweepback to its leading edge. The wing tapered toward the tips, and its thickness also decreased from the root to the tip. In order to create a very strong but very thin wing, it was built with a two-layered aluminum skin, instead of ribs and spars, with each layer separated by “hat” sections. The wing sweep allowed high speed shock waves to form without stalling the entire wing.
The wing also incorporated leading edge “slats” which were airfoil sections that automatically extended below 290 knots, smoothing the air flow over the wing’s upper surface and creating more lift at slow speeds. Above that speed, aerodynamic forces closed the slats, decreasing drag and allowing for higher speeds. Effectively, the wing could change its shape in flight.
The XP-86 prototypes were 37 feet, 6½ inches (11.443 meters) long with a wingspan of 37 feet, 1–7/16 inches (11.314 meters) and overall height of 14 feet, 9 inches (4.496 meters). The empty weight was 9,730 pounds (4,413.5 kilograms), gross weight, 13,395 pounds (6,075.9 kilograms) and maximum takeoff weight was 16,438 pounds (7,456.2 kilograms).
The XP-86 was initially powered by a General Electric-designed, Chevrolet-built J35-C-3 turbojet which produced 4,000 pounds of thrust. This was soon changed to an Allison J35-A-5. Performance testing was conducted with the Allison engine installed. The J35 was a single-spool, axial-flow turbojet engine with an 11-stage compressor and single-stage turbine. The J35-A-5 was rated at 4,000 pounds of thrust (17.79 kilonewtons) at 7,700 r.p.m. (static thrust, Sea Level). The engine was 14 feet, 0.0 inches (4.267 meters) long, 3 feet, 4.0 inches (1.016 meters) in diameter and weighed 2,400 pounds (1,089 kilograms).
The maximum speed of the XP-86 at Sea Level was 0.787 Mach (599 miles per hour, 964 kilometers per hour), 0.854 Mach (618 miles per hour, 995 kilometers per hour) at 14,000 feet (4,267 meters) and 575 miles per hour (925 kilometers per hour) at 35,000 feet (10,668 meters)—0.875 Mach.
The prototype fighter was able to take off at 125 miles per hour (201 kilometers per hour) in just 3,020 feet (920.5 meters) of runway. It could climb to 30,000 feet (9,144 meters) in 12.1 minutes and had a service ceiling of 41,300 feet (12,588 meters).
XP-86 45-59597 was expended as a target during nuclear weapons tests. On 25 May 1953, it was 1,850 feet from ground zero of Upshot Knothole Grable. The only part still intact was the engine, which was thrown 500 feet.
George Welch was born George Lewis Schwartz, in Wilmington, Delaware, 10 May 1918. His parents changed his surname to Welch, his mother’s maiden name, so that he would not be effected by the anti-German prejudice that was widespread in America following World War I. He studied mechanical engineering at Purdue, and enlisted in the Army Air Corps in 1939.
George S. Welch is best remembered as one of the heroes of Pearl Harbor. He was one of only two fighter pilots to get airborne during the Japanese surprise attack on Hawaii, 7 December 1941. Flying a Curtiss P-40B Warhawk, he shot down three Aichi D3A “Val” dive bombers and one Mitsubishi A6M2 Zero fighter. For this action, Lieutenant General H.H. “Hap” Arnold recommended the Medal of Honor, but because Lieutenant Welch had taken off without orders, an officer in his chain of command refused to endorse the nomination. He received the Distinguished Service Cross.
During World War II, George Welch flew the Bell P-39 Airacobra and Lockheed P-38 Lightning on 348 combat missions. He had 16 confirmed aerial victories over Japanese airplanes and rose to the rank of Major.
Suffering from malaria, George Welch was out of combat, and when North American Aviation approached him to test the new P-51H Mustang, General Arnold authorized his resignation. Welch test flew the P-51, FJ-1 Fury, F-86 Sabre and F-100 Super Sabre. He was killed 12 October 1954 when his F-100A Super Sabre came apart in a 7 G pull up from a Mach 1.5 dive.
After testing, the North American Aviation XP-86 was approved for production as the F-86A. It became operational in 1949. The first squadron to fly the F-86 held a naming contest and from 78 suggestions, the name “Sabre” was chosen. The F-86 Sabre was in production until 1955 at North American’s Inglewood, California, and Columbus, Ohio, plants. It was also built under license by Canadair, Ltd., Sain-Laurent, Quebec, Canada; the Commonwealth Aircraft Corporation, Port Melbourne, Victoria, Australia; and Mitsubishi Heavy Industries at Nagoya, Aichi Prefecture, Japan. A total of 9,860 Sabres were built. They served with the United States Air Force until 1970.
XP-86 45-59597 was expended in nuclear weapons tests, Operation Snapper Easy and Snapper Fox, at the Nevada Test Site, Frenchman’s Flat, Nevada, in May 1952. The second and third prototypes, 45-59598 and 45-59599, met similar fates.
21 September 1964: The first prototype North American Aviation XB-70A-1-NA Valkyrie, serial number 62-0001, flown by Chief Test Pilot Alvin S. White and Colonel Joseph F. Cotton, U.S. Air Force, made its first flight from Air Force Plant 42, Palmdale, California, to Edwards Air Force Base.
Originally a prototype Mach 3 strategic bomber, 62-0001 (also known as AV-1) and it’s sister ship, XB-70A-2-NA, 62-0207, (AV-2), were built and used by the Air Force and NASA as high-speed research aircraft. The third Valkyrie, XB-70B-NA 62-0208 (AV-3), was never completed.
The B-70 was designed as a high-altitude Mach 3 strategic bomber armed with thermonuclear bombs. The XB-70A is 196 feet, 6 inches (59.893 meters) long with a wingspan of 105 feet (32.004 meters) and an overall height of 30 feet, 8 inches (9.347 meters). It weighs 231,215 pounds (104,877 kilograms) empty and has a maximum takeoff weight of 534,792 pounds (242,578 kilograms).
The XB-70’s delta wing had a total area of 6,297 square feet (585.01 square meters). it had a sweep of 58.0° at 25% chord. The angle of incidence was 0° and the wing incorporated 3.0° negative twist. There was no dihedral. (The second XB-70 had 5° dihedral.) The outer wing panels could be lowered as much as 60° to increase longitudinal stability in high speed flight.
The XB-70A was powered by six General Electric YJ93-GE-3 single-spool, axial-flow turbojet engines, which used an 11-stage compressor and two-stage turbine. The engine required a special heat-resistant JP-6 fuel. It had a maximum continuous power rating of 28,000 pounds of thrust (124.55 kilonewtons) at 6,825 r.p.m. The YJ93-GE-3 was 19 feet, 8.3 inches (6.002 meters) long, 4 feet, 6.15 inches (1.375 meters) in diameter, and weighed 5,220 pounds (2,368 kilograms).
The XB-70A had a maximum speed of Mach 3.1 (2,056 miles per hour, or 3,309 kilometers per hour). At 35,000 feet (10,668 meters), it could reach Mach 1.90 (1,254 miles per hour, or 2,018 kilometers per hour), and at its service ceiling of 75,550 feet (23,012 meters), it had a maximum speed of Mach 3.00 (1,982 miles per hour, or 3,190 kilometers per hour). The planned combat range for the production bomber was 3,419 miles (5,502 kilometers) with a maximum range of 4,290 miles (6,904 kilometers).
North American Aviation XB-70A Valkyrie 62-0001 made 83 flights with a total of 160 hours, 16 minutes flight time. 62-0001 is on display at the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio.