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26 October 1958

Pan American World Airways’ Boeing 707-121, N711PA, Clipper America, at Idlewild Airport, New York, 26 October 1958. (Pan American World Airways)

26 October 1958: Pan American World Airways opened the “Jet Age” with the first commercial flight of an American jet airliner. Pan Am’s Boeing 707-121 Clipper America, N711PA, departed New York Idlewild (IDL) on an 8 hour, 41 minute flight to Paris Le Bourget (LBG) with a fuel stop at Gander, Newfoundland (YQX). The distance was 3,634 miles (5,848 kilometers). Aboard were 111 passengers and 11 crewmembers.

The Boeing 707 was developed from the earlier Model 367–80, the “Dash Eighty”. It is a four-engine jet transport with swept wings and tail surfaces. The leading edge of the wings are swept at a 35° angle. The airliner had a flight crew of four: pilot, co-pilot, navigator and flight engineer. The 707-121 is 145 feet, 1 inch (44.221 meters) long with a wing span of 130 feet, 10 inches (39.878 meters). The top of the vertical fin stands 42 feet, 5 inches (12.929 meters) high. The 707 pre-dated the ”wide-body” airliners, having a fuselage width of 12 feet, 4 inches (3.759 meters).

The first versions were powered by four Pratt & Whitney Turbo Wasp JT3C-6 turbojet engines, producing 11,200 pounds of thrust (49,820 kilonewtons), and 13,500 pounds (60.051 kilonewtons) with water injection. This engine was a civil variant of the military J57 series. It was a two-spool axial-flow turbojet engine with a 16-stage compressor and 2 stage turbine. The JT3C-6 was 11 feet, 6.6 inches (3.520 meters) long, 3 feet, 2.9 inches (0.988 meters) in diameter, and weighed 4,235 pounds (1,921 kilograms).

The airliner’s empty weight is 122,533 pounds (55,580 kilograms). Maximum take off weight (MTOW) is 257,000 pounds (116,573 kilograms). At MTOW, the 707 required 11,000 feet (3,352.8 meters) of runway to take off. Its maximum speed is 540 knots (1,000 kilometers per hour). It had a range of 2,800 nautical miles (5,185.6 kilometers).

The Boeing 707 was in production from 1958 to 1979. 1,010 were built. As of 2011, 43 707s were still in service.

Boeing delivered N711PA to Pan American on 17 October 1958. The airliner was named Clipper America,  but was later renamed Clipper Mayflower. It was leased to Avianca (Aerovías Nacionales de Colombia S.A.) from 1960 to 1962. In April 1965 the 707 was upgraded to the –121B standard. This included a change from the turbojet engines to quieter, more powerful and efficient Pratt and Whitney JT3D-1 turbofans, producing 17,000 pounds of thrust. The wings were modified to incorporate changes introduced with the Boeing 720, and a longer tailplane installed. Pan Ayer of Panama purchased Clipper Mayflower 21 February 1975. It was later leased to Türk Hava Yolları, the Turkish national airline, and went on to serve with Air Asia Company Limited (an Air America aircraft service unit) and E-Systems. After 26 years of service, in August 1984 Clipper America was scrapped at Taipei.

Pan American World Airways’ Boeing 707-121, N711PA, Clipper America, arriving at Aéroport de Paris – Le Bourget, Paris, France, 27 October 1958. (Photograph © Jon Proctor. Used with permission.)

© 2016, Bryan R. Swopes

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12 October 1954

North American Aviation’s Chief Engineering Test Pilot, George S. Welch, with the first prototype YF-100A Super Sabre, 52-5754. (U.S. Air Force)

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.

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)

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.

This North American Aviation F-100-1-NA Super Sabre, 52-5761, is from the same production black as the aircraft flown by George Welch, 12 October 1954. (U.S. Air Force)
This North American Aviation F-100-1-NA Super Sabre, 52-5761, is from the same production block as the aircraft flown by George Welch, 12 October 1954. This photograph shows FW-761 with the original short vertical fin of the F-100A. (North American Aviation, Inc.)
North American Aviation F-100A-1-NA Super Sabre  52-5763, sister ship of the airplane flown by George Welch, 12 October 1954. (North American Aviation, Inc.)

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.]

Wreckage of North American Aviation F-100A Super Sabre, 12 October 1954. (U.S. Air Force)
Wreckage of North American Aviation F-100A-1-NA Super Sabre 52-5764, 12 October 1954. (North American Aviation, Inc.)

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.

Scott Crossfield flew the F-100A-5-NA, 52-5778, in flight testing at the NACA High Speed Flight Station, October–December 1954. (NASA)
Test Pilot A. Scott Crossfield flew this F-100A-5-NA, 52-5778, in flight testing at the NACA High Speed Flight Station, October–December 1954. (NASA)

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, it soon developed into an almost completely new airplane. The fuselage incorporated the “area rule,” a narrowing in the fuselage width at the wings to increase transonic performance, similar to the Convair F-102A. The Super Sabre had a 49° 2′ sweep to the leading edges of the wings and horizontal stabilizer. 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.

Following Welch's accident, NACA designed a new vertical fin for the F-100A. Ii was taller but also had a longer chord. This resulted in a 10% increase in area. (NASA E-1573)
Following Welch’s accident, the NACA High Speed Flight Station tested the Super Sabre and designed a new vertical fin for the F-100A. The two F-100As in this photograph are both from the second production block (F-100A-5-NA). 52-5778, on the left, has the new fin, while 52-5773 retains the original short fin. The new fin is taller but also has a longer chord. This resulted in a 10% increase in area. (NASA)

The F-100A had an empty weight of 18,135 pounds (8,226 kilograms), and gross weight of 28,899 pounds (13,108 kilograms). Maximum takeoff weight was 35,600 pounds (16,148 kilograms). It had an internal fuel capacity of 755 gallons (2,858 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. It was rated at  9,700 pounds of thrust (43.148 kilonewtons) for takeoff, and 14,800 pounds (65.834 kilonewtons) with afterburner. Later production aircraft used a J57-P-39 engine. The J57 was a two-spool axial flow turbojet which had a 16-stage compressor, and a 3-stage turbine. (Both had high- and low-pressure stages.) The engine was 15 feet, 3.5 inches (4.661 meters) long, 3 feet, 5.0 inches (1.041 meters) in diameter, and weighed 4,390 pounds (1,991 kilograms).

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, 1,224.9 kilometers per hour, under standard atmospheric conditions.) Its maximum speed was 852 miles per hour (1,371 kilometers per hour) at 35,000 feet (10,668 meters). The service ceiling was 44,900 feet (13,686 meters). Maximum range with external fuel was 1,489 miles (2,396 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.

his is the fifth production F-100A-1-NA Super Sabre, 52-5760, in flight southeast of San Bernardino, California. This fighter is from the same production block as 52-5764, the fighter being tested by George Welch, 12 October 1954. In this photograph, FW-760 has the taller vertical fin that was designed to improve the Super Sabre's controlability. (U.S. Air Force)
This is the fifth production F-100A-1-NA Super Sabre, 52-5760, in flight southeast of San Bernardino, California, 24 June 1955. This fighter is from the same production block as 52-5764, the fighter being tested by George Welch, 12 October 1954. In this photograph, FW-760 has the taller vertical fin that was designed by NACA to improve the Super Sabre’s stability. (North American Aviation, Inc.)

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.

Second Lieutenant Kenneth M. Taylor and Second Lieutenant George S. Welch, 47th Pursuit Squadron, 15th Pursuit Group, the two Curtiss P-40B Warhawk pilots who shot down 8 Japanese aircraft during the attack on Pearl Harbor, Hawaii, 7 December 1941. Both officers were awarded the Distinguished Service Cross. (U.S. Air Force)

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.

George Welch, circa 1943. (Unattributed)
George Welch, circa 1943. (Unattributed)

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.

George S. Welch, now a civilian test pilot forNorth American Aviation, Inc., sits on the canopy rail of a P-51H Mustang, circa 1945. (North American Aviation Inc.)
George S. Welch, now a civilian test pilot for North American Aviation, Inc., sits on the canopy rail of a P-51H Mustang, circa 1945. (North American Aviation Inc.)

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.

© 2016, Bryan R. Swopes

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15 April 1952

The Boeing YB-52 Stratofortress, 49-231, takes off from Boeing Field at 11:09 a.m., 15 April 1952. (Robert F. Dorr Collection)
The Boeing YB-52 Stratofortress, 49-231, takes off from Boeing Field at 11:09 a.m., 15 April 1952. (Robert F. Dorr Collection)

15 April 1952: At 11:09 a.m., Boeing’s Chief of Flight Test, Alvin M. “Tex” Johnston, and Lieutenant Colonel Guy M. Townsend, U.S. Air Force, ran all eight turbojet engines to full power and released the brakes on the YB-52 Stratofortress prototype, 49-231.

With an awesome eight-engine roar, the YB-52 sprang forward, accelerating rapidly, wings curving upward as they accepted the 235,000-pound initial flight gross weight. At V2 (takeoff speed) the airplane lifted off the runway, because of the 6-degree angle of incidence of the wing, and at 11:08 a.m. we were airborne. The initial flight of the YB-52 had begun.

Tex Johnston: Jet-Age Test Pilot, by A.M. “Tex” Johnston with Charles Barton, Smithsonian Books, Washington, D.C., 1992, Chapter 13 at Pages 397–398.

Alvin M. "Tex" Johnston, test pilot, after the first flight of the Boeing XB-52 Stratofortress prototype, 2 October 1952. (LIFE via Jet Pilot Overseas)
Alvin M. “Tex” Johnston, Boeing Chief of Flight Test, after the first flight of the Boeing XB-52 Stratofortress prototype, 2 October 1952. (LIFE via Jet Pilot Overseas)

The YB-52 remained over the Seattle area for approximately 40 minutes while Johnson and Townsend ran through a series of systems checks. When completed, they climbed to 25,000 feet (7,620 meters) and flew the new bomber to Larson Air Force Base at Moses Lake, Washington, where they stayed airborne for continued testing. The Stratofortress finally touched down after 3 hours, 8 minutes—the longest first flight in Boeing’s history at the time. Johnston radioed that the airplane performed exactly as the engineers had predicted.

The YB-52 had actually been ordered as the second of two XB-52s, but modifications and additional equipment installed during building resulted in enough differences to warrant a designation change. The first XB-52, 49-230, would have been the first to fly, but it was damaged during ground testing.

The Boeing XB-52 and YB-52 were prototypes for a very long range strategic bomber. Both were built with a tandem cockpit for the pilot and co-pilot, similar to the earlier B-47 Stratojet. The wings were swept to 35° and mounted high on the fuselage (“shoulder-mounted”). The eight turbojet engines were in in two-engine nacelles mounted on pylons, below and ahead of the wings. This had the effect of preventing the airplane’s center of gravity from being too far aft, and also provided cleaner air flow across the wings. The B-52’s landing gear has four main struts with two wheels, each. They can turn to allow the airplane to face directly into the wind while the landing gear remain aligned with the runway for takeoff and landing. With the landing gear under the fuselage, the wings could be constructed with greater flexibility.

Boeing YB-52 Stratofortress 49-231. (U.S. Air Force)
Boeing YB-52 Stratofortress 49-231. (U.S. Air Force)

The YB-52 was 152 feet, 8 inches (46.533 meters) long with a wingspan of 185 feet, 0 inches (56.388 meters). The prototype’s overall height was 48 feet, 3.6 inches (14.722 meters). The vertical fin could be folded over to the right so that the B-52 could fit into a hangar. The YB-52 had an empty weight of 155,200 pounds (70,398 kilograms) and gross weight of 405,000 pounds (183,705 kilograms).

The YB-52 was powered by eight Pratt & Whitney Turbo Wasp YJ57-P-3 turbojet engines. The J57 was a two-spool, axial-flow turbojet developed from an experimental turboprop engine. It had 16-stage compressor section (9 low- and 7-high-pressure stages), 8 combustors and a 3-stage turbine section (1 high- and 2 low-pressure stages). The YJ57-P-3s were rated at 8,700 pounds of thrust (38.70 kilonewtons), each. The YJ57-P-3 was 183.5 inches (4.661 meters) long, 41.0 inches (1.041 meters) in diameter and weighed 4,390 pounds (1,991 kilograms).

The YB-52 had a cruise speed of 519 miles per hour (835 kilometers per hour) and maximum speed of 611 miles per hour (983 kilometers per hour) at 20,000 feet (6,096 meters). Its range was 7,015 miles (11,290 kilometers).

The two prototypes were unarmed.

The B-52 was produced by Boeing at its plants in Seattle and Wichita from 1952 to 1962, with a total of 744 Stratofortresses built. The last version, the B-52H, entered service with the Strategic Air Command in 1960. The final B-52, B-52H-175-BW Stratofortress 61-0040, was rolled out at Wichita, Kansas, 26 October 1962. This airplane remains in service with the United States Air Force. The newest B-52 in service, 61-0040 is 55 years old and has flown more than 21,000 flight hours.

All previous versions, B-52A through B-52G, have long been retired to The Boneyard and scrapped. Of the 102 Boeing B-52H Stratofortress bombers, 76 are still in the active inventory. One, 61-007, known as Ghost Rider, was recently taken from Davis-Monthan and after an extensive restoration and update, returned to service.

The YB-52 prototype was retired to the National Museum of the United States Air Force in the late 1950s. By the mid-60s it was determined to be excess and was scrapped.

Captain William Magruder (standing) Boeing Chief Test Pilot Alvin M. Johnston (center) and Lieutenant Colonel Guy M. Townsend with the Boeing YB-52 Stratofortress 49-231. (Boeing)
Left to right: Captain William Magruder, Boeing Chief Test Pilot Alvin M. Johnston and Lieutenant Colonel Guy M. Townsend with the Boeing YB-52 Stratofortress, 49-231. (Boeing)

© 2017, Bryan R. Swopes

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