Major William J. Knight, United States Air Force, with the North American Aviation X-15A-2, 56-6671. (U.S. Air Force)
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.
North American Aviation X-15A-2 56-6671 is carried to launch altitude under the right wing of the Boeing NB-52B Stratofortress 52-008. The scramjet is attached to the ventral fin. (U.S. Air Force)North American Aviation X-15A-2 56-6671 immediately after being released from the mothership, Boeing NB-52B Stratofortress 52-008, Balls 8, over Mud Lake, Nevada, 3 October 1967. The steam trail is hydrogen peroxide used to power the rocket engine turbopump. (U.S. Air Force)The X-15A-2’s XLR99-RM-1 rocket engine ignites after release from the mothership, Balls 8, 3 October 1967. (U.S. Air Force)
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.
Firefighters cool down the ventral fin of the North American Aviation X-15A-2 56-6671 after its final landing on Rogers Dry Lake, 3 October 1967.(U.S. Air Force)
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.
The Harmon International Trophy at the Smithsonian Institution National Air and Space Museum. (NASM)
North American Aviation test pilot George S. Welch, flying the first of three XP-86 prototypes, serial number 45-59597. (North American Aviation, Inc.)
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.
Recently completed, the first prototype XP-86, 45-59597, waits inside the North American Aviation plant at Inglewood, California, 14 August 1947. (North American Aviation, Inc.)
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.
North American Aviation Model NA-140, the first XP-86 prototype, 45-59597, at Muroc AAF, 1947. (U.S. Air Force)
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.
Cutaway illustration of the XP-86. The speed brake configuation was not used for production aircraft. (North American Aviation, Inc.)
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.
This photograph of the XP-86 shows the 35° wing sweep. Test pilot George S. Welch, wearing his distinctive orange helmet, in the cockpit of the prototype XP-86. (North American Aviation, Inc.)
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).
North American Aviation XP-86 45-59597. (Ray Wagner Collection, San Diego Air & Space Museum Archives, Catalog #: 16_002950)
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 three North American Aviation XP-86 prototypes. Front to back, 45-59598, 45-59597 and 45-59599. (National Archives and Records Administration)
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).
The end of XP-86 45-59597 at Frenchman Flats, 1953.
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.
Upshot Knothole Grable (National Nuclear Security Administration CIC 0315864)George S. Welch, North American Aviation test pilot, wearing his orange flight helmet. An F-86 Sabre is in the background. (San Diego Air and Space Museum Photo Archives)
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.
An early production aircraft, North American Aviation P-86A-1-NA Sabre 47-630 (s/n 151-38457). (North American Aviation, Inc./Chicago Tribune)
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.
The first of two North American Aviation XT-28 prototypes, 48-1371, lands at Edwards Air Force Base 3 February 1950. (U.S. Air Force)
26 September 1949: At Vultee Field, a private industrial airport in Downey, California, North American Aviation test pilot Jean LeRoy (“Skip”) Ziegler ¹ took the first of two prototype military flight trainers, the XT-28 (NAA Model 159–2), U.S. Air Force serial number 49-1371, for its first flight. The 45-minute flight was two weeks ahead of schedule.
The Long Beach Press-Telegram reported:
New Training Plane Tested
LOS ANGELES, Sept 27. (AP) The Air Force’s first postwar training plane—North American’s T-28—has tried her wings and found they work very well.
The company announced that the twin cockpit craft—designed to train pilots for advanced high speed fighters and bombers—flew 45 minutes yesterday. Said test pilot Skip Ziegler, “It handles more like a fighter than a trainer.” He termed the flight, “completely satisfactory.”
The T-28 has a ceiling of 29,800 feet and can move 288 miles an hour. The T-6, present Air Force trainer, ceilings at 22,000 and travels 205 m.p.h. top.
One of the two North American Aviation XSN2J-1 prototypes in flight of the Southern California shoreline, circa 1946. (North American Aviation, Inc./San Diego Air & Space Museum Archives, Catalog #: 00033269)
The XT-28 was developed from an earlier North American Aviation project for the United States Navy. In 1946, NAA proposed their Model 142, as a replacement for the World War II SNJ/T-6 Texan, a trainer which had also been built by North American, and used by both the Navy and the U.S. Army Air Forces. The Navy designated the proposed airplane XSN2J-1. Two were built and assigned Bureau of Aeronautics serial numbers (“Bu. No.”) 121449 and 121450. 121449 was the first to fly, 15 February 1947.
The Navy tested both aircraft, but did not order them into production.
One of the two North American Aviation XSN2J-1 prototypes during testing at NATC Patuxent River, Maryland, October 1948. The prototype is armed with with five-inch air-to-surface rockets. (National Archives and Records Administration)
A year later, NAA made a similar proposal to the United States Air Force. The Air Force wanted a trainer to transition pilots into turbojet-powered aircraft. Similar to the XSN2J-1, the XBT-28 was changed to tricycle landing gear, a first for a miltiary trainer. The prototype’s two cockpits were laid out very similar to the new, swept-wing North American XP-86 Sabre. The Air Force ordered the airplane into production as the T-28A. The first T-28A arrived at Eglin Air Force Base, Florida, 15 June 1950, where it would tested for suitability as a flight trainer.
Prototype North American Aviation XBT-28. (T-28 Trojan Foundation)
The North American Aviation T-28 Trojan is an all-metal, two-place airplane with retractable tricycle landing gear. The dual cockpits are arranged in tandem. The T-28A was used by the United States Air Force as a primary training aircraft, while the more powerful T-28B and T-28C were employed by the U.S. Navy. The airplane was noted for its stability and handling qualities, its easy recovery from stalls and spins, and its excellent visibility.
Initially, the T-28 was built at North American Aviation’s Downey Division, in Downey, California, which at the time was primarily a farming community about 13 miles (21 kilometers) south of downtown Los Angeles, California. Production was shifted to North America’s Columbus Division in Columbus, Ohio.
North American Aviation T-28A Trojan internal arrangement. (U.S. Air Force)
The XT-28 and production T-28As were 32.0 feet (9.754) long with a wingspan of 40.6 feet (12.375 meters), and overall height of 12.7 feet (3.871 meters). The wing had an angle of incidence of 2° with 3° of negative twist, and 8° dihedral. The total wing area was 268.0 square feet (24.9 square meters). The vertical fin was offset 1° to the left of the airplane’s centerline. The prototype and early production T-28As had an empty weight of had an empty weight of 6,909 pounds (2,998 kilograms). This was increased in later aircraft to 7,282 pounds (3,303 kilograms). The Maximum Takeoff Weight (MTOW) was 7,751 pounds (3,516 kilograms).² The two prototypes had a belly-mounted speed brake. All T-28As had provisions for this installation.
North American Aviation XT-28 three-view illustration with dimensions. (U.S. Air Force)
The XT-28 and production T-28A were powered by an air-cooled, supercharged, 1,301.868 cubic inch (21.334 liter) Wright Aeronautical Division Cyclone 7 R-1300-1 (853C7BA1) 7-cylinder radial engine with a compression ratio of 6.2:1. This engine required 91/98 octane aviation gasoline. It was rated at 700 horsepower at 2,400 r.p.m., and 800 horsepower at 2,600. r.p.m. for takeoff. The engine also produced some jet thrust from its exhaust system. The engine thrust line was angled downward 5° from fuselage reference line. The R-1300-1 drove a two blade, 10 foot, 0 inch (3.048 meters) diameter Aeroproducts hydraulic variable pitch propeller through 0.5625:1 gear reduction. The engine was 4 feet, 1.12 inches (1.248 meters) long, 4 feet, 2.45 inches (1.281 meters) in diameter, and weighed 1,065 pounds, (483 kilograms).
The XT-28 had a maximum fuel capacity of 125 gallons (473 liters), carried in two wing tanks. Two additional tanks were added to later production T-28As, increasing the capacity to 177 gallons (670 liters).
The T-28A had a cruise speed of 165 knots (190 miles per hour/306 kilometers per hour, and maximum speed of 247 knots (284 miles per hour/457 kilometers per hour) at 5,800 feet (1,768 meters). VNE varied from 190 knots (219 miles per hour/352 kilometers per hour) at 25,000 feet (7,620 meters) with external load, to 340 knots (391 miles per hour/630 kilometers per hour) at Sea Level, clean. The airplane’s best power off glide speed was 105 knots (120 miles per hour/194 kilometers per hour).
The T-28A could climb at a maximum rate of 1,870 feet per minute (9.5 meters per second). Its service ceiling was 24,000 feet (7,315 meters). The maximum range was 720 nautical miles (829 statute miles/1333 kilometers) in early production models, or 880 nautical miles (1,013 statute miles/1,630 kilometers) in aircraft with increased fuel capacity.
For training purposes, the T-28A could be armed with one detachable gun pod under each wing. Each pod contained a .50-caliber AN-M3 Browning Aircraft Machine Gun. These had a rate of fire of approximately 1,100 rounds per minute. Each gun was supplied with 100 rounds of ammunition. The trainer could also be equipped with a removable bomb rack for a 100-pound (45 kilogram) bomb. Three 2.25 inch (5.7 centimeters) Sub-Caliber Aerial Rocket (SCAR)—Rocket, 2.25-Inch Practice—rockets could be carried on pylons mounted to hardpoints under each wing.
The first production North American T-28A Trojan, 49-1494 (North American serial number 159-1), at the National Museum of the United States Air Force. Delivered to Wright-Patterson AFB, this aircraft was used as a static test airframe. (U.S. Air Force 050322-F-1234P-020)
A total of 1,948 T-28s were built from 1950 to 1957. 1,194 of these were T-28As. The Air Force retired its T-28As by 1959. Many USAF T-28As were pulled from storage at Davis-Monthan Air Force Base, Tucson, Arizona, and were converted to the T-28D configuration for combat operations during the Vietnam War. Others were converted to the AT-28D attack variant, which included an ejection seat.
North American Aviation test pilot Robert A. (“Bob”) Hoover, with a U.S. Navy T-28B Trojan, circa 1953. (National Museum of Naval Aviation)
XT-28 48-1371 was sent to “The Boneyard” at Davis-Monthan Air Force Base near Tucson, Arizona, 23 January 1961, and to reclamation, 18 June 1965. In 1974, it was observed, disassembled, at the Hamilton Aviation Company yard in Tucson. (Hamilton produced modified T-28s: the military T-28R-1, and the civilian T-28R-2 Nomair.)
¹ For biographical information about Skip Ziegler, please see “This Day in Aviation” for 12 Nay 1953 at: https://www.thisdayinaviation.com/12-may-1953/
North American Aviation P-51B Mustang fighter in the Full-Scale Tunnel, NACA Langley Memorial Aeronautical Laboratory, Hampton, Virginia, 23 September 1943. (NASA)Drag test of North American Aviation P-51B-1-NA Mustang 43-12105 in the NACA Full-Scale Tunnel. (NASA)
North American Aviation XB70A-1-NA 62-0001 takes off for the first time, 21 September 1964. (U.S. Air Force)
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.
Colonel Joseph F. Cotton, USAF, and Alvin S. White, North American Aviation, with an XB-70A Valkyrie. (Autographed photograph courtesy of Neil Corbett, TEST & RESEARCH PILOTS, FLIGHT TEST ENGINEERS)
62-0001 was the first of three prototype Mach 3+ strategic bombers. (The third prototype, XB-70B 62-0208, was not completed.) The Valkyrie utilized the most advanced technology available. Materials and manufacturing techniques had to be developed specifically to build this airplane. It is a large delta wing airplane with a forward canard and two vertical fins. The outer 20 feet (6.096 meters) of each wing could be lowered to a 25° or 65° angle for high speed flight. Although this did provide additional directional stability, it actually helped increase the compression lift, which supported up to 35% of the airplane’s weight in flight.
The XB-70A is 185 feet, 10 inches (56.642 meters) long with a wingspan of 105 feet (32.004 meters) and overall height of 30 feet, 9 inches (9.373 meters). The delta wing had 0° angle of incidence and 0° dihedral. (The second XB-70A had 5° dihedral.) The wing has 3.0° negative twist. At 25% chord, the wing has 58.0° sweepback. Total wing area is 6,297 square feet (585 square meters). The Valkyrie has a empty weight of 231,215 pounds (104,877 kilograms), and maximum takeoff weight (MTOW) of 521,056 pounds (2236,347 kilograms).
It is powered by six General Electric YJ93-GE-3 turbojet engines. The J93 is an afterburning single-shaft axial-flow turbojet with an 11-stage compressor section and two-stage turbine. It has a Normal Power rating of 17,700 pounds of thrust (78.73 kilonewtons), 19,900 pounds (88.52 kilonewtons), Military, and 28,000 pounds (124.55 kilonewtons) Maximum. (All ratings are continuous, at 6,825 r.p.m.) The YJ93-GE-3 is 236.3 inches (6.002 meters) long, 54.15 inches (1.375 meters) in diameter, and weighs 5,220 pounds (2,368 kilograms).
A Boeing B-52 Stratofortress flies formation with North American Aviation XB-70A Valkyrie 62-0001, approaching the runway at Edwards Air Force Base, California. (U.S. Air Force)
The maximum speed achieved was Mach 3.08 (1,787 knots/2,056 miles per hour, or 3,309 kilometers per hour) at 73,000 feet (22,250 meters), 12 April 1966. Its mission maximum speed is 1,721 knots (1,980 miles per hour/3,187 kilometers per hour) at 79,050 feet (29,094 meters). The XB-70A has a rate of climb of 33,000 feet per minute (168 meters per second). The service ceiling is 79,000 feet (24,079 meters).
North American Aviation XB-70A Valkyrie 62-0001 lost approximately 15% of its paint during its third test flight, 12 October 1964—its first supersonic flight. United States Air Force)
The Valkyrie has a maximum fuel capacity of 43,646 gallons (165,218 liters) JP-5 or JP-6, carried in 11 tanks throughout the fuselage and wings. It also carries 42.4 gallons (161 liters) of engine oil. The maximum range is 2,969 nautical miles (3,417 statute miles/5,499 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.
North American Aviation XB-70A-1-NA Valkyrie 62-0001 just before landing at Runway 4 Right, Edwards Air Force Base, ending of its first flight, 21 September 1964. A Piasecki HH-21B rescue helicopter hovers over the adjacent taxiway. (U.S. Air Force)
