Douglas X-3 49-2892. Rogers Dry Lake is in the background. (NASA)
20 October 1952: At Edwards Air Force Base, California, Douglas Aircraft Company test pilot William Barton (“Bill”) Bridgeman made the first test flight of the X-3 twin-engine supersonic research airplane. During a high-speed taxi test five days earlier, Bridgeman and the X-3 had briefly been airborne for approximately one mile over the dry lake bed, but on this flight he spent approximately 20 minutes familiarizing himself with the new airplane.
William Barton “Bill” Bridgeman, 1916–1968. (Loomis Dean/LIFE Magazine)
Bill Bridgeman had been a Naval Aviator during World War II, flying the Consolidated PBY Catalina and PB4Y (B-24) Liberator long range bombers with Bombing Squadron 109 (VB-109), “The Reluctant Raiders.”
Bridgeman stayed in the Navy for two years after the war, then he flew for Trans-Pacific Air Lines in the Hawaiian Islands and Southwest Airlines in San Francisco, before joining Douglas Aircraft Co. as a production test pilot. He checked out new AD Skyraiders as they came off the assembly line at El Segundo, California. He soon was asked to take over test flying the D-558-2 Skyrocket test program at Muroc Air Force Base (now, Edwards AFB.) With the Skyrocket, he flew higher—79,494 feet (24,230 meters)—and faster—Mach 1.88—than any pilot had up to that time.
Douglas X-3 parked on Rogers Dry Lake, 1956 (NASA)
The Douglas X-3, serial number 49-2892, was built for the Air Force and NACA to explore flight in the Mach 1 to Mach 2 range. It was radically shaped, with a needle-sharp nose, very long thin fuselage and small straight wings. The X-3 was 66 feet, 9 inches (20.345 meters) long, with a wing span of just 22 feet, 8.25 inches (6.915 meters). The overall height was 12 feet, 6.3 inches (3.818 meters). The X-3 had an empty weight of 16,120 pounds (7,312 kilograms) and maximum takeoff weight of 23,840 pounds (10,814 kilograms).
It was to have been powered by two Westinghouse J46 engines, but when those were unsatisfactory, two Westinghouse XJ34-WE-17 engines were substituted. This was an axial flow turbojet with an 11-stage compressor and 2-stage turbine. It was rated at 3,370 pounds (14.99 kilonewtons) of thrust, and 4,900 pounds (21.80 kilonewtons) with afterburner. The XJ34-WE-17 was 14 feet, 9.0 inches (4.496 meters) long, 2 feet, 1.0 inch (0.635 meters) in diameter and weighed 1,698 pounds (770 kilograms).
The X-3 had a maximum speed of 706 miles per hour (1,136 kilometers per hour) and a service ceiling of 38,000 feet (11,582 meters).
This view of the Douglas X-3 shows its very small wings and tail surfaces. (NASA)
The X-3 was very underpowered with the J34 engines and could just reach Mach 1 in a shallow dive. Its highest speed, Mach 1.208, required a 30° dive. The research airplane was therefore never able to be used in flight testing in the supersonic speed range for which it was designed. Because of its design characteristics, though, it became useful in exploring stability and control problems encountered in the transonic range.
Two X-3 aircraft had been ordered from Douglas, but only one completed.
In addition to Bill Bridgeman, the Douglas X-3 was flown by Air Force test pilots Major Chuck Yeager and Lieutenant Colonel Frank Everest, and NACA High Speed Flight Station research pilot Joseph A. Walker.
NACA flight testing began in August 1954. On the tenth flight, 27 October, Joe Walker put the X-3 into abrupt left aileron rolls at 30,000 feet (9,144 meters), first at 0.92 Mach and then at Mach 1.05. Both times, the aircraft violently yawed to the right and then pitched down.
This was a new and little understood condition called inertial roll coupling. It was a result of the aircraft’s mass being concentrated within its fuselage, the torque reactions and gyroscopic effect of the turbojet engines and the inability of the wings and control surfaces to stabilize the airplane and overcome its rolling tendency. (Just two weeks earlier, North American Aviation’s Chief Test Pilot George S. Welch had been killed when the F-100A Super Sabre that he was testing also encountered inertial roll coupling and disintegrated.) A post-flight inspection found that the X-3 had reached its maximum design load. The X-3 was grounded for the next 11 months.
Joe Walker resumed flight testing the X-3 in 1955. It’s last flight was 23 May 1956. After the flight test program came to an end, the X-3 was turned over to the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio.
Douglas X-3 49-2892 at the National Museum of the United States Air Force. (NASM)
Eugène Welferinger à bord de l’Antoinette IV : [photographie de presse] / [Agence Rol]19 October 1908: From the grounds of the Château de Bagatelle, Paris, France, Eugène Welferinger (1872–1936) made the first flight of the Société d’aviation Antoinette monoplane, the Antoinette IV.
A single-place, single-engine airplane, the Antoinette IV was one the first successful monoplanes. American Machinist described it as a “purely racing machine.”
The airplane and its V-8 engine were designed by Léon Levavasseur. It was modified a number of times, as was its sister ship, the Antoinette V.
“Left front view of Société Antoinette ‘Antoinette IV’ on the ground. This version is of ‘Antoinette IV’ is fitted with two large in-line wheels, substantial mid-wing skids, and a paddle-type propeller. Designer Léon Levavasseur stands at left (bearded man wearing dark vest and cap). Issy-les-Moulineaux, Paris, France, November 1908.” (M. Rol & Cie, 4 Rue Richer, Paris/Library of Congress)
Augustus Post, Secretary of the Aero Club of America, wrote in the weekly technical publication, American Machinist:
M. Levavasseur considered that the monoplane offered the advantages of simplicity of form, natural stability, and was easier to construct; that is to say, that the thrust of the motor required for flight was less under the same conditions of speed and weight.
The “Antoinette” is particularly interesting on account of the manner in which the problems have been studied and the great amount of thought that has been given to them. The machine is perhaps without question the most finely finished of those in its class, shows the most careful workmanship in its most minute detail, and presents more new and original features than any of the other machines which may be compared with it. It also provides a comfortable cockpit for the aviator, a distinct advantage in long and trying flights.
—American Machinist, Hill Publishing Company, New York, 7 October 1909, Page 608 at Column 2
Antoinette IV, right front quarter view. (Phototeque chronorama)Antoinette IV, front view. (Geneanet)
The Antoinette IV was approximately 11,50 mètres (37.72966 feet) long with a wingspan of 14,80 mètres (48.55643 feet). The leading edge was swept aft 3°. They had a chord of 3 meters (9.8 feet) at the root, tapering to 2 meters (6.6 feet) at the tip. The wing had an angle of incidence of 4° with 6° dihedral. The total surface area was 34 square meters (366 square feet). The weight of the Antoinette IV was 460 kilograms (1,014 pounds) with one hour of fuel. It was capable of reaching 120 kilometers per hour (75 miles per hour).
Antoinette IV in an early configuration. (La Phototeque de Chonorama)
The airplane was described in contemporary reports as “beautiful” and often mentioned was the very narrow triangular cross section of its fuselage. Different configurations of landing gear were tried, with combinations of skids and wheels, wheels in tandem, and side-by-side. Directional control was created through “wing-warping” as had been used by the Wright Brothers. This was later modified to an aileron system. The tail surfaces were cruciform, with two triangular rudders located above and below the triangular elevator. Flight controls were four hand wheels and two pedals which connected to the control surfaces by cables.
An unidentified Antoinette employee with Hubert Latham (center) and Léon Levavasseur (right), The airplane is the Antoinette IV. (Librairie Militaire Guérin Mourmelon, via Old Machine Press)
As originally built, the Antoinette IV was powered by a steam-cooled, normally-aspirated, 7.274 liter (443.861 cubic inch displacement) Antoinette 8V 90° overhead valve V-8 engine which produced approximately 45–50 chaval-vapeur (44.4–49.3 horsepower) at 1,400 r.p.m. This engine was considerably smaller and lighter than Levavasseur’s previous V-8s. Because the compression ratio was increased, the aluminum cylinder heads were replaced with forged steel heads. Carburetors were used instead of direct injection, which was prone to clogging. The 8V was a direct-drive engine which turned a propeller with two aluminum blades which were riveted to a steel tube that attached to the engine’s output shaft. The propeller had a diameter of 2.20 meters (7 feet, 2.6 inches). The V-8 engine was 0.750 meters (2 feet, 5.5 inches inches) long, 0.600 meters (1 foot, 11.6 inches) wide and (0.600 meters (1 foot, 11.6 inches) high. It weighed 60 kilograms (132 pounds), dry, and 85 kilograms (187 pounds) in running order.
Two-view drawing of an early configuration of Léon Levavasseur’s Antoinette Monoplane. (Flight, Vol. I, No. 43, 23 October 1909, at Page 663)
The engine sold for ₣12,500 (approximately $2,451 U.S. dollars) with delivery expected in 10 months. Antoinette airplanes could be purchased for ₣25,000, or about $4,902 U.S. dollars.
On 19 July 1909, Arthur Louis Hubert Latham, who had been taught to fly by Welféringer, attempted to fly the Antoinette IV across the English Channel, but an engine failure forced it down about 8 miles (13 kilometers) off the French coast.
Hubert Latham is rescued from the English Channel by the crew of the French torpedo boat destroyer, Harpon, 19 July 1909. (hydroretro)
The airplane remained afloat and Latham was rescued by the French torpedo boat destroyer FS Harpon, but the airplane was severely damaged during the recovery.
Léon Lavavasseur, circa 1905. (National Aviation Museum/CORBIS)
Léon Levavasseur was a French engineer, born 8 January 1863 near Cherbourg, France. He invented the 90° V-8 engine, which he patented in 1902. He specialized in lightweight engines, using components designed to be only as strong as was required by their specific use. He developed direct fuel injection and evaporative cooling for internal combustion engines.
Mlle. Antoinette Gastambide, namesake of the Antoinette IV and the company that built it. (L’Aérophile)
His company, Société d’aviation Antoinette, and its products, were named for the daughter of his business partner, Jules Gastambide. The company initially produced lightweight engines for other airplane builders, but began to construct complete airplanes in 1906. Both Levavasseur and Gastambide left Antoinette in 1909 following a disagreement with the board of directors, but they returned five months later. The company failed in 1911.
Levavasseur was appointed Chevalier de la légion d’honneur in 1909.
Léon Levavasseur died in Paris, France, 26 February 1922, at the age of 59 years.
Recommended: An excellent article about Léon Levavasseur’s Antoinette engines can be found at Old Machine Press:
Rockwell International B-1B Lancer 82-0001 takes off for the first time at Air Force Plant 42, Palmdale, California. (U.S. Air Force)
18 October 1984: The first production Rockwell International B-1B Lancer, serial number 82-0001, a supersonic four-engine strategic bomber with variable sweep wings, made its first flight from Air Force Plant 42, Palmdale, California.
Rockwell test pilot Mervyn Leroy Evenson (Colonel, U.S.Air Force, retired) was the aircraft commander, with co-pilot Lieutenant Colonel Leroy Benjamin Schroeder; Major S.A. Henry, Offensive Systems Officer; Captain D.E. Hamilton, Defensive Systems Officer.
Rockwell International B-1B takeoff on Oct. 25, 1986. Note the lit afterburners. (U.S. Air Force)
After 3 hours, 20 minutes, the B-1B landed at Edwards Air Force Base where it would enter a flight test program.
Rockwell B-1B 82-0001 parked at the Rockwell International Corp. facility, Palmdale, California, 3 September 1984. (MSGT Mike Dial, U.S. Air Force)
The Rockwell International B-1B Lancer is a supersonic intercontinental bomber capable of performing strategic or tactical missions. It is operated by a flight crew of four.
The B-1B is 147 feet, 2.61 inches (44.8719 meters) long, with the wing span varying from 86 feet, 8.00 inches (26.4160 meters) at 67.5° sweep to 136 feet, 8.17 inches (41.6603 meters) at when fully extended to 15° sweep. It is 33 feet, 7.26 inches (10.2428 meters) high to the top of the vertical fin. The bomber’s empty weight is approximately 180,500 pounds (81,873 kilograms). Its maximum weight in flight is 477,000 pounds (216,634 kilograms). The internal payload is up to 75,000 pounds (34,019 kilograms).
The bomber is powered by four General Electric F101-GE-102 turbofan engines, mounted in two-engine nacelles under the wing roots. These are rated at 17,390 pounds of thrust (17.355 kilonewtons) and produce 30,780 pounds (136.916 kilonewtons) with “augmentation.” The engine has two fan stages, a 9-stage axial-flow compressor and a 3-stage turbine. The F101-GE-102 is 15 feet, 0.7 inches (4.590 meters) long, 4 feet, 7.2 inches (1.402 meters) in diameter and weighs 4,460 pounds (2,023 kilograms).
Rockwell International B-1B Lancer. (U.S. Air Force)
“The Bone” has a maximum speed of Mach 1.2 at Sea Level (913 miles per hour, or 1,470 kilometers per hour). The service ceiling is “over 30,000 feet” (9,144 meters). The Lancer’s maximum range is “intercontinental, unrefueled.”
It can carry up to 84 Mk.82 500-pound (226.8 kilogram) bombs, 24 Mk.84 2,000-pound (907.2 kilogram) bombs or other weapons in three weapons bays. The B-1B was built with the capability to carry 24 B61 thermonuclear bombs, though, since 2007, the fleet no longer has this capability.
A Rockwell B-1B Lancer drops Mk. 82 bombs from its three weapons bays. (U.S. Air Force)
100 B-1B Lancers were built between 1983 and 1988. As of September 2021, 45 B-1B bombers remained the active Air Force inventory. The Air Force plans upgrades to the aircraft and to keep it in service until 2033.
To comply with the START weapons treaty, B-1B 82-0001 was scrapped at Ellsworth Air Force Base, South Dakota, in the mid-1990s.
A Rockwell International B-1B Lancer in flight. (U.S. Air Force)
First flight, Sikorsky YUH-60A 73-21650 at Stratford, Connecticut, 17 October 1974. (Sikorsky, a Lockheed Martin Company)
17 October 1974: Sikorsky Chief Pilot James R. (Dick) Wright and project chief test pilot John Dixson made the first flight of the prototype YUH-60A, 73-21650, at the company’s Stratford, Connecticut, facility. This helicopter was the first of three prototypes.
Early flight testing revealed excessive vertical vibrations associated with the main rotor. Extensive engineering and flight testing determined that this was caused by air flow upward through the rotor system and around the transmission and engine cowlings. The purpose of the low-mounted main rotor was to aid in fitting inside transport aircraft with minimal disassembly. It was necessary to increase the height of the mast and reshape the cowlings to achieve an acceptable level of vibration.
After eight months of testing, the U.S. Army selected the YUH-60A for production over its competitor, the Boeing Vertol YUH-61A. In keeping with the Army’s tradition of naming helicopters after Native Americans, the new helicopter was named Black Hawk, who was a 17th Century leader of the Sauk (or Sac) people.
Sikorsky YUH-60A 73-21650 at roll-out, 28 June 1974, with low main rotor, large-area tail rotor pylon and swept stabilator. (Sikorsky, a Lockheed Martin Company)
The Sikorsky Model S-70 (YUH-60A) was designed to meet the requirements of the U.S. Army Utility Tactical Transport Aircraft System (UTTAS). It had a 3-man crew and could carry an 11-man rifle squad. The helicopter could be transported by a Lockheed C-130 Hercules.
The three UTTAS prototypes were 63 feet, 6 inches (19.355 meters) long, with rotors turning. The span of the horizontal stabilizer was 15 feet, 0 inches (4.572 meters). The prototypes’ overall height was 16 feet, 10 inches (5.131 meters).
The three Sikorsky YUH-60A UTTAS prototypes. A fourth prototype, an S-70, was built and retained by Sikorsky for internal research and development and demonstrations. (Vertical Flight Society)
The YUH-60A had an empty weight of 11,182 pounds (5,072 kilograms) and gross weight of 16,750 pounds (7,598 kilograms). The helicopter had a structural load factor of 3.5 Gs. With 1,829 pounds (830 kilograms) of fuel, it had an endurance of 2 hours, 18 minutes.
The YUH-60A had a four-blade fully-articulated main rotor with elastomeric bearings. It had a diameter of 52 feet, 0 inches (15.850 meters). During flight testing, the diameter was increased to 52 feet, 4 inches (15.951 meters), and finally to 52 feet, 8 inches (16.053 meters). The blades were built with titanium spars and used two different airfoils and a non-linear twist (resulting in a net -16.4°). The outer 20 inches (0.508 meters) were swept aft 20°. These characteristics improved the helicopter’s maximum speed and hover performance. The main rotor turned counterclockwise, as seen from above (the advancing blade is on the right) at 258 r.p.m. The blade tip speed was 728 feet per second (222 meters per second). During flight testing it was decided to change the main transmission gear reduction ratio in order to operate the engines at a slightly increased r.p.m. At the higher r.p.m., the engines produced an additional 50 horsepower, each.
Sikorsky YUH-60A 73-21650 (c/n 70-001), right profile. In this photograph, the prototype has been modified closer to the production variant. The rotor mast is taller, the vertical fin has been decreased in size, a variable-pitch stabilator has replaced the fixed horizontal stabilizer, the engine cowlings have been redesigned, and the crew side window is the two-piece version. (U.S. Army Aviation Museum)
The four-bladed bearingless tail rotor was positioned on the right side of the tail rotor pylon in a tractor configuration. The tail rotor diameter was 11 feet (3.353 meters), and turned 1,214 r.p.m., rotating clockwise as seen from the helicopter’s left (the advancing was blade below the axis of rotation). The blade tip speed was 699 feet per second (213 meters per second). The tail rotor blades had -18° of twist. Because the Black Hawk’s engines are behind the transmission, the aircraft’s center of gravity (c.g.) is also aft. The tail rotor plane is inclined 20° to the left to provide approximately 400 pounds of lift (1.78 kilonewtons) to offset the rearward c.g.
Cutaway illustration of the T700-GE-700 turboshaft engine. (Global Security)
Power was supplied by two General Electric T700-GE-700 modular turboshaft engines, rated at 1,622 shaft horsepower at 20,900 r.p.m. Np, at Sea Level under standard atmospheric conditions. The T700 has a 5-stage axial-flow, 1-stage centrifugal-flow compressor, with a 2-stage axial-flow gas producer and 2-stage axial-flow power turbine. The T700 is 3 feet, 11 inches (1.194 meters) long, 2 feet, 1 inch (0.635 meters) in diameter and weighs 437 pounds (198 kilograms). The helicopter’s main transmission was designed for 2,828 horsepower. The engines are derated to the transmission limit.
The YUH-60A had a cruise speed of 147 knots (169 miles per hour/272 kilometers per hour) at 4,000 feet (1,219 meters) and 95 °F. (35 °C.). It could climb at 450 feet per minute (2.29 meters per second) at the same altitude and air temperature.
Sikorsky YUH-60A prototype, 73-21650, late configuration. (Vertical Flight Society)
While operating with an Army crew on the night of 9 August 1976, YUH-60A 73-21650 developed a significant vibration. An emergency landing was made. Because of darkness and mist, the pilots thought they were landing in a corn field, but it was actually a pine tree plantation. The helicopter’s rotors cut down more than 40 trees with trunk diameters up to 5 inches (12.7 centimeters).
Close inspection by Army and Sikorsky personnel found that the only visible damage was to the four main and four tail-rotor blades other than nicks and dents to the airframe that were of no structural concern. All gearboxes and engines turned freely, and all flight controls responded properly. ¹ The blades were replaced on-site and the helicopter was flown out the following day.
73-21650 crashed into the Housatonic River near the Stratford plant at 9:10 a.m., Friday, 19 May 1978, killing all three Sikorsky employees on board, pilots Albert M. King, Jr., John J. Pasquarello, and flight engineer John Marshall.
During routine maintenance an airspeed sensor for the all-flying tailplane had been disconnected. As the Black Hawk transitioned from hover to forward flight, the all-flying tailplane remained in the hover position and forced the helicopter’s nose to pitch down to the point that recovery was impossible.
A Sikorsky YUH-60A and Boeing Vertol YUH-61A hover for the camera. (U.S. Army)
The Black Hawk has been in production since 1978. More than 4,000 of the helicopters have been built and the type has been continuously improved. The current production model is the UH-60M.
Sikorsky is a Lockheed Martin Company.
A Sikorsky UH-60M Black Hawk in flight. (Sikorsky, a Lockheed Martin Company)Sikorsky’s UH-60M Black Hawk for the U.S. Army, seen here in the Military Hangar at Sikorsky Aircraft in Stratford, Connecticut, 20 February 2008. (Sikorsky, a Lockheed Martin Company)
¹ Black Hawk: The Story of a World Class Helicopter, by Ray D. Leoni, American Institute of Aeronautics and Astronautics, Reston, Virginia, 2007, Chapter 8 at Page 173.
The Boeing XB-15 takes off on its first flight, Boeing Field, 15 October 1937. (U.S. Air Force)
15 October 1937: Test pilot Edmund Turney (“Eddie”) Allen, a consulting engineer to Boeing, and Major John D. Korkille, Air Corps, United States Army, made the first flight of the prototype Boeing XB-15, 35-277, at Boeing Field, Seattle, Washington. Major Corkille reported that the airplane “handled easily and maneuvered readily.”
The flight deck of the Boeing XB-15. The radio operator’s station is on the left, and the navigator’s on the right. (The Boeing Company)
The Boeing Model 294, designated XB-15 by the Air Corps, was an experimental airplane designed to determine if a bomber with a 5,000 mile (8,047 kilometers) range was possible. It was designed at the same time as the Model 299 (XB-17), which had the advantage of lessons learned by the XB-15 design team. The XB-15 was larger and more complex than the XB-17 and took longer to complete. It first flew more than two years after the prototype B-17.
The Boeing Model 294 (XB-15) at Boeing Field, Seattle, Washington. The prototype bomber was rolled out for engine tests, 27 September 1937. (The Boeing Company)
Designers had planned to use an experimental 3,421.19-cubic-inch-displacement (56.063 liter) liquid-cooled, supercharged and turbosupercharged Allison V-3420 twenty-four cylinder, four-bank “double V” engine which produced a maximum of 2,885 horsepower at 3,000 r.p.m. The engine was not available in time, however, and four air-cooled Pratt & Whitney R-1830 (Twin Wasp) engines were used instead. With one-third the horsepower, this substitution left the experimental bomber hopelessly underpowered as a combat aircraft.
Boeing XB-15 35-277. (U.S. Air Force)Boeing XB-15 35-277. (U.S. Air Force)Boeing XB-15 35-277. (U.S. Air Force)
The XB-15 was a very large four-engine mid-wing monoplane with retractable landing gear. It was of aluminum monocoque construction with fabric-covered flight control surfaces. The XB-15 had a ten-man crew which worked in shifts on long duration flights.
Boeing XB-15 35-277
The prototype bomber was 87 feet, 7 inches (26.695 meters) long with a wingspan of 149 feet (45.415 meters) and overall height of 18 feet, 1 inch (5.512 meters). The airplane had an empty weight of 37,709 pounds (17,105 kilograms) and maximum takeoff weight of 70,706 pounds (32,072 kilograms)—later increased to 92,000 pounds (41,730 kilograms).
As built, the XB-15 was powered by four air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engines, rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engines turned three-bladed controllable-pitch propellers through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).
These gave the experimental airplane a maximum speed of 197 miles per hour (317 kilometers per hour) at 5,000 feet (1,524 meters) and a cruise speed of 152 miles per hour (245 kilometers per hour) at 6,000 feet (1,829 meters). The service ceiling was 18,900 feet (5,761 meters) and maximum range was 5,130 miles (8,256 kilometers).
The Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit. (U.S. Air Force)
The bomber could carry a maximum of 12,000 pounds (5,443 kilograms) of bombs in its internal bomb bay, and was armed with three .30-caliber and three .50-caliber machine guns for defense.
Only one XB-15 was built. During World War II it was converted to a transport and redesignated XC-105. In 1945 it was stripped and abandoned at Albrook Field, Territory of the Canal Zone, Panama.
The XB-15 set several Fédération Aéronautique Internationale (FAI) world records: On 30 July 1939, the XB-15 carried 14,135 kilograms (31,162 pounds) to an altitude of 2,000 meters (6,562 feet) over Fairfield, Ohio.¹ The same flight set a second record by carrying 10,000 kilograms (22,046 pounds) to an altitude of 8,228 feet (2,508 meters).² On 2 August 1939, the XB-15 set a World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram Payload, at an average speed of 267.67 kilometers per hour (166.32 miles per hour).³
