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.
12 October 1954: North American Aviation Chief Engineering Test Pilot George S. Welch, testing the ninth production F-100A-1-NA Super Sabre, serial number 52-5764, made a planned 7.3 G pullout from a Mach 1.55 dive to verify the aircraft’s design limits.
A Boeing B-47 Stratojet crew flying at 25,000 feet (7,620 meters) reported that Welch’s F-100 winged over and began a rapid descent, passing within four miles (6.4 kilometers) of their position and diving at a very high speed. The aircraft appeared to be under control but then suddenly disintegrated.
The Super Sabre had encountered Inertial Roll Coupling. It went out of control and then disintegrated. Its nose folded over the windshield, crushing Welch in his seat. The vertical fin broke away. The ejection seat fired but because of the supersonic speeds the parachute was shredded.
Welch was still alive when rescue teams arrived. He died while being flown to a hospital by helicopter.
Inertial roll coupling led to the death of test pilot Mel Apt when his rocket-powered airplane, the Bell X-2, went out of control at Mach 3.2 It nearly killed Chuck Yeager when he lost control of the Bell X-1B at Mach 2.4. It is a complex phenomenon which I will briefly attempt to explain:
To increase maximum speed of transonic and supersonic airplanes during the late 1940s and early 1950s, their wings and tail surfaces were made smaller in order to decrease aerodynamic drag. At the same time, the fuselage became longer and the placement of engines, armament, landing gear, fuel, etc., within the fuselage concentrated the airplane’s mass near its center. While the gyroscopic effects of the turbojet engine contributed some degree of longitudinal stability, the torque effect made rolls to the left occur more easily, but with a higher rate than a roll to the right. The resistance to a change in attitude—inertia—decreased at the same time that the control surfaces’ ability to control the airplanes’ attitude also decreased. The airplanes became unstable.
When George Welch tried to pull the F-100 out of its supersonic dive, the airplane’s speed began to decrease as the angle of attack increased. The wings’ ability to stabilize the natural roll instability of the fuselage’s concentrated mass was lessened, and the ailerons could not provide sufficient control to counteract this rolling tendency. The low vertical fin of the original F-100A did not provide adequate directional stability. The Super Sabre rolled and then yawed, entering a side slip. This caused the Super Sabre to pitch down and it was suddenly out of control in all three axes. The physical forces exceeded the strength of the aircraft structure and it came apart.¹
[Aerodynamicists and Aeronautical Engineers: Your corrective comments are welcome.]
Following the death of George Welch, NACA High Speed Flight Station research test pilot Albert Scott Crossfield spent three months conducting flight tests of the F-100A, demonstrating its inertial roll coupling characteristics using three different vertical fins. F-100A-5-NA 52-5778 was Crossfield’s test aircraft.
The North American Aviation F-100 Super Sabre was designed as a supersonic day fighter. Initially intended as an improved F-86D and F-86E, the “Sabre 45” soon developed into an almost completely new airplane. The Super Sabre had a 49° 2′ sweep to the leading edges of the wings and horizontal stabilizer. The total wing area was 385.2 square feet (35.79 square meters). The wings had an angle of incidence of 0°, with no twist or dihedral. The ailerons were placed inboard on the wings and there were no flaps, resulting in a high stall speed in landing configuration. The horizontal stabilizer was moved to the bottom of the fuselage to keep it out of the turbulence created by the wings at high angles of attack. The F-100A had a distinctively shorter vertical fin than the YF-100A. The upper segment of the vertical fin was swept 49° 43′.
There were two service test prototypes, designated YF-100A, followed by the production F-100A series. The first ten production aircraft (all of the Block 1 variants) were used in the flight testing program.
The F-100A Super Sabre was 47 feet, 1¼ inches (14.357 meters) long with a wingspan of 36 feet, 6 inches (11.125 meters). With the shorter vertical fin, the initial F-100As had an overall height of 13 feet, 4 inches (4.064 meters), 11 inches (27.9 centimeters) less than the YF-100A.
The F-100A had an empty weight of 18,135 pounds (8,226 kilograms), and its maximum takeoff weight was 28,971 pounds (13,141 kilograms). It had an internal fuel capacity of 744 gallons (2,816 liters) and could carry two 275 gallon (1,041 liter) external fuel tanks.
The early F-100As were powered by a Pratt & Whitney Turbo Wasp J57-P-7 afterburning turbojet engine. The J57 was a two-spool axial-flow turbojet which had a 16-stage compressor section (9 low- and 7 high-pressure stages) and a 3-stage turbine (2 high- and 1 low-pressure stages). Its continuous power rating was 8,000 pounds of thrust (35.586 kilonewtons). The Military Power rating was 9,700 pounds (43.148 kilonewtons) (30-minute limit). Maximum power was 14,800 pounds (43.148 kilonewtons) with afterburner (5-minute limit). The engine was 20 feet, 9.7 inches (6.342 meters) long, 3 feet, 3.9 inches (1.014 meters) in diameter, and weighed 5,075 pounds (2,303 kilograms). Later production aircraft used a J57-P-39 engine.
The Super Sabre was the first U.S. Air Force fighter capable of supersonic speed in level flight. It could reach 760 miles per hour (1,223 kilometers) at Sea Level. (Mach 1 is 761.1 miles per hour at Sea Level, 1,224.9 kilometers per hour, under Standard Atmospheric Conditions.) The maximum speed of the F-100A was 759 knots (873 miles per hour/1,406 kilometers per hour)—Mach 1.32—at 35,000 feet (10,668 meters). Its service ceiling was 47,500 feet (14,478 meters). The fighter’s combat radius was 402 nautical miles (463 statute miles/745 kilometers). The maximum ferry range with external fuel was 1,124 nautical miles (1,493 statute miles/2,082 kilometers).
The F-100 was armed with four M-39 20 mm autocannons, capable of firing at a rate of 1,500 rounds per minute. The ammunition capacity of the F-100 was 200 rounds per gun.
North American Aviation built 199 F-100A Super Sabres at its Inglewood, California, plant before production shifted to the F-100C fighter bomber variant. Approximately 25% of all F-100As were lost in accidents.
George Welch was born George Lewis Schwartz, Jr., in Wilmington, Delaware, 10 May 1918. He was the first of two sons of George Lewis Schwartz, a chemist at the Dupont Experimental Station in Wilmington, and Julia Welch Schwartz. 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 University, Indiana, and enlisted in the Army Air Corps in 1939. Welch graduated from pilot training at Kelly Field, Texas, and on 4 October 1940, was commissioned as a second lieutenant, U.S. Army Air Corps.
George S. Welch is best remembered as one of the heroes of Pearl Harbor. He, along with Second Lieutenant Kenneth M. Taylor, were the only two fighter pilots to get airborne from Haleiwa Auxiliary Airfield 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. Taylor also shot down four Japanese airplanes. For this action, Lieutenant General Henry H. “Hap” Arnold recommended the Medal of Honor, but because Lieutenants Welch and Taylor had taken off without orders, an officer in their chain of command refused to endorse the nomination. Both fighter pilots were awarded the Distinguished Service Cross.
During the War, 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. In addition to the Distinguished Service Cross, George Welch was awarded the Silver Star, the Distinguished Flying Cross with two oak leaf clusters (three awards), the Air Medal with one oak leaf cluster (two awards), the Presidential Unit Citation with two oak leaf clusters (three awards), American Defense Service medal with one service star, American Campaign Medal, Asiatic-Pacific Campaign Medal with one silver and one bronze star (six campaigns), and the World War II Victory Medal.
Welch received the nickname, “Wheaties,” because he was the first military officer to be featured on a box of Wheaties cereal. (Wheaties, “The Breakfast of Champions,” was a toasted wheat bran cereal produced by General Mills. It normally featured champion athletes on its distinctive orange-colored boxes.)
Suffering from malaria, George Welch was out of combat and recuperating in Australia. There he met Miss Janette Alice Williams and they were soon married. Welch returned to the United States with his new wife. They had a son, Giles, born in October 1947. Their home was in Brentwood, California.
North American Aviation approached General Arnold to recommend a fighter pilot who could bring his combat experience to testing new fighters. Welch was one of two that General Arnold suggested. The general authorized Welch’s release from active duty so that he could join North American. Welch held the rank of major, Air Reserve, from 13 November 1944 to 1 April 1953.
Welch went on to test fly the North American P-51H Mustang, FJ-1 Fury, F-86 Sabre and F-100 Super Sabre.
George Welch made the first flight of the XP-86 prototype, 1 October 1947. There is some evidence that on that flight, and during a subsequent flight on 14 October, Welch exceeded the speed of sound while in a dive. It has been said that during the Korean War, while teaching U.S. Air Force pilots how to best use the F-86 Sabre, he shot down several enemy MiG-15 jet fighters.
George S. Welch is buried at the Arlington National Cemetery, Section 6, Site 8578-D.
¹ Recommended: Coupling Dynamics in Aircraft: A Historical Perspective, by Richard E. Day, Dryden Flight Research Center, Edwards AFB, California. NASA Special Publications 532, 1997.
25 May 1953: North American Aviation Chief Test Pilot George S. Welch took the YF-100A Super Sabre, U.S. Air Force serial number 52-5754, for its first flight at Edwards Air Force Base. The airplane reached Mach 1.03.
Development of the Super Sabre began with an effort to increase the speed of the F-86D and F-86E Sabre fighters. The wings had more sweep and the airfoil sections were thinner. A much more powerful engine would be needed to achieve supersonic speed in level flight. As design work on the “Sabre 45” proceeded, the airplane evolved to a completely new design. Initially designated XF-100, continued refinements resulted in the first two aircraft being redesignated YF-100A.
The two YF-100As, 52-5754 and 52-5755, were 47 feet, 11¼ inches (14.611 meters) long with a wingspan of 36 feet, 7 inches (11.151 meters) and height of 16 feet, 3 inches (4.953 meters). The wings were swept to 45° at 25% chord, and had 0° angle of incidence and 0° dihedral. The ailerons were placed inboard on the wings to eliminate their twisting effects at high speed. The airplane had no flaps. The pre-production prototypes weighed 18,135 pounds (8,226 kilograms) empty, and had a gross weight of 24,789 pounds (11,244 kilograms).
The new air superiority fighter was powered by a Pratt & Whitney Turbo Wasp J57-P-7 engine. The J57 was a two-spool axial-flow turbojet which had a 16-stage compressor section (9 low- and 7 high-pressure stages) and a 3-stage turbine (2 high- and 1 low-pressure stages). The J57-P-7 had a Maximum Continuous Power rating of 8,000 pounds of thrust (35.586 kilonewtons) at 5,875 r.p.m., N1, and 9550 r.p.m., N2. The engine’s Military Power rating was 9,700 pounds thrust (43.148 kilonewtons) at 6,275 r.p.m./9,900 r.p.m., for 30 minutes; and 14,800 pounds thrust (65.834 kilonewtons) at 6,275 r.p.m./9,900 r.p.m. with afterburner, limited to five minutes. The engine was 20 feet, 9.7 inches (6.342 meters) long, 3 feet, 3.9 inches (1.014 meters) in diameter, and weighed 5,075 pounds (2,303 kilograms). Later production aircraft used a J57-P-39 engine, which had the same ratings.
The YF-100A had a maximum speed of 660 miles per hour (1,062 kilometers per hour) at 43,350 feet (13,213 meters). The service ceiling was 52,600 feet (16,033 meters). Range with internal fuel was 422 miles (679 kilometers).
During testing, 52-5754 reached Mach 1.44 in a dive. On 29 October 1953, Colonel Frank K. Everest set a world speed record of 1,215.298 kilometers per hour (755.151 miles per hour) with 754.¹
In service with the United States Air Force, the Super Sabre’s mission changed from air superiority fighter to fighter bomber. It was used extensively during the Vietnam War. North American Aviation, Inc., built 2,294 single and tandem-seat Super Sabres between 1954 and 1959.
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 the War, 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.
26 April 1948: At Muroc Field (now known as Edwards Air Force Base), in the high desert of southern California, North American Aviation test pilot George Welch put the prototype XP-86 Sabre, 45-59597, into a 40° dive and broke the Sound Barrier. It is only the second U.S. aircraft to fly supersonic. The first was the Bell X-1, piloted by Chuck Yeager, only a few months earlier.
Or, maybe not.
In his book, Aces Wild: The Race For Mach 1, fellow North American Aviation test pilot Albert W. Blackburn makes the case that George Welch had taken the prototype XP-86 Sabre supersonic on its first flight, 1 October 1947, and that he had done so three times before Chuck Yeager first broke the Sound Barrier with the Bell X-1 rocketplane, 14 October 1947. Blackburn described two runs through the NACA radar theodolite with speeds of Mach 1.02 and 1.04 on 13 November 1947.
Mr. Blackburn speculates—convincingly, in my opinion—that Secretary of the Air Force W. Stuart Symington, Jr., ordered that Welch’s excursions beyond Mach 1 were to remain secret. However, during a radio interview, British test pilot Wing Commander Roland Prosper (“Bee”) Beamont, C.B.E, D.S.O. and Bar, D.F.C. and Bar, stated that he had flown through the Sound Barrier in the number two XP-86 Sabre prototype (45-59598). Once that news became public, the U.S. Air Force released a statement that George Welch had flown beyond Mach 1 earlier, but gave the date as 26 April 1948.
It wasn’t long after the first flight of the XP-86 on October 1, 1947, that Welch dropped into Horkey’s [Edward J. Horkey, an aerodynamicist at North American Aviation] office at the Inglewood plant. He wanted to talk about his recent flight and some “funny” readings in the airspeed indicator. He had made a straight-out climb to more than 35,000 feet. Then, turning back toward Muroc Dry Lake, he began a full-power, fairly steep descent.
“I started at about 290 knots,” Welch was explaining to Horkey. “In no time I’m at 350. I’m still going down, and I’m still accelerating but the airspeed indicator seems stuck like there’s some kind of obstruction in the pitot tube. I push over a little steeper and by this time I’m through 30,000 feet. All of a sudden, the airspeed indicator flips to 410 knots. The aircraft feels fine, no funny noises, no vibration. Wanted to roll off to the left, but no big deal. Still, I leveled out at about 25,000 and came back on the power. The airspeed flicked back to 390. What do you think?”
“. . . You may be running into some Mach effects. . . .”
— Aces Wild: The Race For Mach 1, by Al Blackburn, Scholarly Resources Inc., Wilmington, Delaware, 1999, at Pages 147–148.
The “funny” reading of the airspeed indicator became known as the “Mach jump.” George Welch was the first to describe it.
The Sabre became a legendary jet fighter during the Korean War. 9,860 were built by North American, as well as by licensees in Canada, Australia and Japan.
George Welch had been recommended for the Medal of Honor for his actions as a P-40 Warhawk fighter pilot in Hawaii, December 7, 1941. He was killed while testing a North American Aviation F-100A Super Sabre, 12 October 1954.
22 December 1949: North American Aviation, Inc., test pilot George S. Welch made the first flight of the YF-86D Sabre, 50-577 (c/n 164-1, at Edwards Air Force Base, in the high desert of southern California.
Based on the F-86A day fighter, the F-86D (originally designated YF-95) was a radar-equipped, rocket-armed, all-weather interceptor. Its first flight took place only nine years after the first flight of North American’s prototype NA-73X, which would become the famous P-51 Mustang fighter of World War II. This was an amazing jump in technology in just a few years.
The interceptor was intended to be an improved variant of the F-86A Sabre day fighter. During development, though, so many changes became necessary that the F-86D shared only about 25% of its parts of the F-86A. Essentially an new airplane, the Air Force assigned it the designation YF-95. It would revert to the F-86D designation before it actually flew.
The first YF-86D (still identified as YF-95) was rolled out at North American’s Inglewood plant in September 1949. In late November it was partially disassembled to be transported by truck to Edwards Air Force Base, about 120 miles (193 kilometers) away. The airplane was then reassembled and ground tested to prepare it for flight.
The first two test aircraft carried no armament or fire control/radar system and retained the sliding canopy of the F-86A. This would be replaced with a hinged “clamshell” canopy in production models. The airplane was 40 feet, 3.1 inches (12.271 meters) long with a wingspan of 37 feet, 1 inch (11.294 meters) and overall height of 15 feet, 0 inches (4.572 meters). Its empty weight was 12,470 pounds (5,656 kilograms) and maximum takeoff weight was 18,483 pounds (8,384 kilograms).
The service test aircraft and early production airplanes were powered by a General Electric J47-GE-17 single-shaft axial-flow turbojet engine, producing 5,425 pounds of thrust (24.132 kilonewtons) at 7,950 r.p.m., or 7,500 pounds (33.362 kilonewtons) with afterburner. This engine was equipped with an electronic fuel control system which substantially reduced the pilot’s workload. The engine had a 12-stage compressor, 8 combustion chambers, and single-stage turbine. It was 226.0 inches (5.740 meters) long, 39.75 inches (1.010 meters) in diameters, and weighed 3,000 pounds (1,361 kilograms).
The first production aircraft, F-86D-1-NA Sabre, had a maximum speed of 614 knots (707 miles per hour/1,137 kilometers per hour) at Sea Level, and 539 knots (620 miles per hour/998 kilometers per hour)at 40,000 feet (12,192 meters). From a standing start, the interceptor could climb to 40,000 feet in 5 minutes, 54 seconds with a full combat load. The service ceiling was 54,000 feet (16,460 meters).
The F-86D Sabre carried no guns. Instead, its armament consisted of twenty-four 2.75-inch (70 millimeter) Folding Fin Aerial Rockets (FFAR) with explosive warheads, carried in a retractable tray in the airplane’s belly. A Hughes electronic fire control computer was used to calculate an interception path and determine the firing point for the unguided rockets.
The single-seat F-86D Sabre was nearly 50 knots faster than the contemporary twin-engine Northrop F-89 Scorpion and Lockheed F-94 Starfire, both of which carried a two-man crew. North American Aviation built 2,504 F-86D Sabres, and these equipped nearly two-thirds of the Air Defense Command interceptor squadrons.
After the Air Force service test program was completed, 50-577 was transferred to the National Advisory Committee on Aeronautics (NACA) Ames Aeronautical Laboratory at Moffett Field, California, and designated NACA 149. It was used as a variable stability aircraft for flight testing various control configurations for feel, sensitivity and response.
NACA 149 remained at Ames from 26 June 1952 to 15 February 1960.