Tag Archives: Boeing Airplane Company

2 August 1939

August 2, 2024AviationA.C. Brandt, Adolph Cattarius, Boeing Airplane Company, Boeing XB-15, Caleb Vance Haynes, Daniel L. Spicer, FAI, Fédération Aéronautique Internationale, James E. Sands, Kill Devil Hills, Pratt & Whitney R-1830-11, Pratt & Whitney Twin Wasp S1B3-G, Walter G. Bryte Jr., William D. Old, World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram PayloadBryan Swopes

Major Caleb V. Haynes, U.S. Army Air Corps, with Captain William D. Old; Walter G. Bryte, Jr.; A.C. Brandt; Master Sergeant Adolph Catarius; Technical Sergeant Daniel L. spice; Staff Sergeant James E. Sands, the distance record-setting crew of the Boeing XB-15 35-277. (FAI) — The speed-distance record-setting crew of the Boeing XB-15 experimental long range bomber, left to right: Major Caleb V. Haynes, U.S. Army Air Corps, with Captain William D. Old; Walter G. Bryte, Jr.; A.C. Brandt; Master Sergeant Adolph Cattarius; Technical Sergeant Daniel L. Spicer; Staff Sergeant James E. Sands. (FAI)

2 August 1939: The Boeing Model 294, designated by the U.S. Army Air Corps as the XB-15, serial number 35-277, flown by a crew led by Major Caleb Vance Haynes, set a Fédération Aéronautique Internationale (FAI) World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram Payload, when they flew the experimental long range heavy bomber a distance of 3,109 miles at an average speed of 267.67 kilometers per hour (166.32 miles per hour) while carrying a payload of 2,000 kilograms (4,409.25 pounds).¹

The other members of the XB-15 crew were Captain William D. Old, Walter G. Bryte, Jr., A.C. Brandt, Master Sergeant Adolph Cattarius, Staff Sergeant William J. Heldt, Technical Sergeant Daniel L. Spicer and Staff Sergeant James E. Sands.

The Boeing XB-15, 35-277, flies past teh Wright Brothers memorial at the kill Devil Hills, Kitty Hawk, North Carolina. (U.S. Air Force) — The Boeing XB-15, 35-277, flies past the Wright Brothers National Memorial at the Kill Devil Hills, Kitty Hawk, North Carolina. (U.S. Air Force)

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 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, circa 1937. (The Boeing Company)

Designers had planned to use an experimental 3,421.194-cubic-inch-displacement (56.063 liter) liquid-cooled, supercharged and turbosupercharged Allison V-3420 twenty-four cylinder, four-bank “double V” engine. It 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. (The Douglas XB-19 was retrofitted with V-3420s in 1942, and re-designated XB-19A.)

Boeing XB-15 at NACA Langley Memorial Aeronautical Laboratory, 13 September 1938. (NASA)

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.

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).

The XB-15’s wings used a symmetrical airfoil and were very highly tapered (4:1 from root to tip). They had an angle of incidence of 4½° and 4½° dihedral. The total area was 2,780 square feet (258.271 square meters). A contemporary aeronautical publication wrote, “The airfoil provides constant center of pressure, minimum profile drag with flaps up and high maximum lift with flaps down.” The XB-15’s wings were adapted by Boeing for the Model 314 Clipper flying boat.

Boeing XB-15 in flight. (U.S. Air Force)050406-F-1234P-053

As built, the XB-15 was equipped with four air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney R-1830-11 (Twin Wasp S1B3-G) two-row 14-cylinder radial engines with a compression ratio of 6.7:1. The R-1830-11 was rated at 850 horsepower at 2,450 r.p.m. and 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. They 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).

The experimental airplane had a cruise speed of 152 miles per hour (245 kilometers per hour) at 6,000 feet (1,829 meters), and a maximum speed of 200 miles per hour ( kilometers per hour) at 5,000 feet (1,524 meters). The service ceiling was 18,900 feet (5,761 meters) and maximum range was 5,130 miles (8,256 kilometers).

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 re-designated XC-105. In 1945 35-277 was stripped and abandoned at Albrook Field, Territory of the Canal Zone, Panama.

The Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit. (U.S. Air Force)

¹ FAI Record File Number 10865

1 August 1939

August 1, 2024Aviation37-369, Boeing Airplane Company, Boeing B-17 Flying Fortress, Boeing B-17A, Boeing Model 299F, Boeing Y1B-17A, Boeing YB-17A, Bomber, Carl J. Crane, Clarence S. Irvine, FAI, Fédération Aéronautique Internationale, Flight Test, P.G. Miller, Pearl H. Robey, R-1820-39, R-1820-51, R. Swofford, World Record for Altitude with a 5000 Kilogram Payload, World Record for Speed Over 1000 Kilometers With a 5000 Kilogram Payload, Wright Aeronautical Division, Wright Cyclone G59Bryan Swopes

The flight crew of the FAI World Altitude Record-setting Boeing Y1B-17A. Left to right: Captain Pearl H. Robey, Captain Clarence S. Irvine and R. Swofford. (FAI)

1 August 1939: Captains Clarence S. Irvine and Pearl H. Robey, United States Army Air Corps, used the Boeing Y1B-17A Flying Fortress (Model 299F), serial number 37-369, to set a Fédération Aéronautique Internationale (FAI) World Record for Altitude with a 5,000 Kilogram Payload. The bomber climbed to 10,371 meters (34,026 feet) with a payload of 11,023 pounds.¹ ²

On the same day, Irvine and Robey flew the Y1B-17 from Dayton, Ohio to St. Jacob, Illinois, setting an FAI World Record for Speed Over 1,000 Kilometers with a 5,000 Kilogram Payload, averaging 417.46 kilometers per hour (259.40 miles per hour).³

The flight crew of the FAI World Speed Record-setting Boeing Y1B-17A. Left to Right: Capatain C.J. Crane, P.G. Miller, Captain Clarence S. Irvine and Captain pearl H. Robey. (FAI) — The flight crew of the FAI World Speed Record-setting Boeing Y1B-17A. Left to Right: Captain Carl J. Crane, P.G. Miller, Captain Clarence S. Irvine and Captain Pearl H. Robey. (FAI)

The single Y1B-17A (Boeing Model 299F) was originally ordered as a static test article, but when that was determined to be unnecessary, it was used as an engine test aircraft. It was equipped with four 1,823.129-cubic-inch-displacement (29.875 liter) air-cooled, supercharged, Wright R-1820-51 (Cyclone G59) single-row nine-cylinder radial engines. Moss/General Electric turbo-superchargers were installed, initially on top of the wings, but were moved to the bottom of the engine nacelles.

The supercharged Wright R-1820-39 (Cyclone R-1820-G5) engines of the YB-17s were rated at 805 horsepower at 2,100 r.p.m., at Sea Level, 775 horsepower at 14,000 feet (4,267 meters), and 930 horsepower at 2,200 r.p.m., for take off. By contrast, the YB-17A’s R-1820-51 engines were rated at 800 horsepower at 2,100 r.p.m. at Sea Level, and 1,000 horsepower at 2,200 r.p.m. for take off. But the turbochargers allowed the engines to maintain their Sea Level power rating all the way to 25,000 feet (7,620 meters). Both the -39 and -51 engine had a 16:11 propeller gear reduction ratio. The R-1820-51 was 3 feet, 9.06 inches (1.145 meters) long, 4 feet, 6.12 inches (1.375 meters) in diameter, and weighed 1,200.50 pounds (544.54 kilograms). 259 were produced by Wright between September 1937 and February 1940.

The turbo-superchargers installed on the YB-17A greatly improved the performance of the bomber, giving it a 55 mile per hour (89 kilometer per hour) increase in speed over the supercharged YB-17s, and increasing the bomber’s service ceiling by 7,000 feet (2,132 meters). The turbo-superchargers worked so well that they were standard on all following B-17 production models.

Boeing Y1B-17A 37-369. (U.S. Air Force photo)

The Boeing Y1B-17A was 68 feet, 9 inches (20.955 meters) long with a wingspan of 103 feet, 9–3/8 inches (31.633 meters) and height of 14 feet, 11–5/16 inches (4.363 meters). Its empty weight was 26,520 pounds (12,029 kilograms). The maximum gross weight was 45,650 pounds (20,707 kilograms)

The Model 299F had a cruise speed of 230 miles per hour (370 kilometers per hour), a maximum speed of 271 miles per hour (436 kilometers per hour) at Sea Level and 295 miles per hour (475 kilometers per hour) at 25,000 feet (7,620 meters). The service ceiling was 38,000 feet (11,582 meters). The maximum range was 3,600 miles (5,794 kilometers). Carrying a 4,000 pound (1,814 kilogram) load of bombs, the range was 2,400 miles (3,862 kilometers).

The Y1B-17A could carry eight 600 pound (272 kilogram) bombs in an internal bomb bay. Defensive armament consisted of five .30-caliber machine guns.

Following the engine tests, 37-369 was re-designated B-17A.

The Boeing Y1B-17A in flight near Mt. Rainier on 28 February 1938. (U.S. Air Force)

¹ FAI Record File Number 8318

² This record-setting flight was dramatized in the motion picture “Test Pilot,” (1938, Metro-Goldwyn-Mayer) with Clark Gable, Spencer Tracy and Myrna Loy. This movie is now 80 years old and has a melodramatic plot, but is well worth seeing for aviation history enthusiasts.

³ FAI Record File Number 10443

28 July 1935

July 28, 2024AviationBoeing Airplane Company, Boeing B-17 Flying Fortress, Boeing Field, Boeing Model 299, Boeing XB-17, Bomber, Browning Aircraft Machine Gun Caliber .30 M2, First Flight, Heavy Bomber, Hornet, Les Tower, Leslie Ralph Tower, Louis Waite, Pratt & Whitney Hornet S1E-G, Prototype, Test Pilot, X13372Bryan Swopes

Boeing test pilot Les Tower. (Boeing) — Boeing’s Chief Test Pilot Leslie R. Tower.

28 July 1935, At Boeing Field, Seattle, Chief Test Pilot Leslie Ralph (“Les”) Tower and Louis Waite took off on the maiden flight of the Boeing Model 299, X13372,¹ a prototype four-engine long range heavy bomber. For approximately one-and-a-half hours, Tower flew back and forth between Tacoma and Fort Lewis. When he landed, he said, “It handles just like a little ship—a little bigger, of course.”

The Boeing Model 299 was a four-engine bomber operated by a crew of eight. It was designed to meet a U.S. Army Air Corps proposal for a multi-engine bomber that could carry a 2,000 pound (907 kilogram) bomb load a distance of 2,000 miles (3,219 kilometers) at a speed greater than 200 miles per hour (322 kilometers per hour). Design of the prototype began in June 1934 and construction was started 16 August 1934. The Air Corps designated it B-299, and later, XB-17. It did not carry a military serial number, being marked with civil experimental registration X13372.

The Boeing Model 299 with Mount Rainier. (U.S. Air Force)

The Model 299 was 68 feet, 9 inches (20.955 meters) long with a wingspan of 103 feet, 9–3/8 inches (31.633 meters) and height of 14 feet, 11–5/16 inches (4.554 meters). Its empty weight was 21,657 pounds (9,823 kilograms). The maximum gross weight was 38,053 pounds (17,261 kilograms).

The prototype was powered by four air-cooled, supercharged, 1,690.537-cubic-inch-displacement (27.703 liter) Pratt & Whitney Hornet S1E-G nine-cylinder radial engines with a compression ratio of 6.5:1. The S1E-G was rated at 750 horsepower at 2,250 r.p.m., and 875 horsepower at 2,300 r.p.m. for takeoff, using 87-octane gasoline. They turned 11 foot, 6 inch (3.505 meters) diameter, three-bladed, Hamilton Standard Hydromatic constant-speed propellers through a 3:2 gear reduction. The S1E-G was 4 feet, 1.38 inches (1.254 meters) long, 4 feet, 6.44 inches (1.383 meters) in diameter and weighed 1,064 pounds (483 kilograms)

In flight testing, the Model 299 had a cruise speed of 204 miles per hour (328 kilometers per hour) and a maximum speed of 236 miles per hour (380 kilometers per hour) at 10,000 feet (3,048 meters). The service ceiling was 24,620 feet (7,504.2 meters). Its maximum range was 3,101 miles (4,991 kilometers). Carrying a 2,573 pounds (1,167 kilograms) load of bombs, the range was 2,040 miles (3,283 kilometers).

Boeing 299 NX13372, all engines running. — Boeing 299 X13372, all engines running.

The XB-17 could carry eight 500 pound (226.8 kilogram) bombs in an internal bomb bay. Defensive armament consisted of five air-cooled Browning .30-caliber machine guns.

Nose turret of the Boeing Model 299, photographed 24 July 1935. (U.S. Air Force) — Nose turret of the Boeing Model 299, photographed 24 July 1935. (The Boeing Company)

X13372 was destroyed when it crashed on takeoff at Wright Field, Dayton, Ohio, 30 October 1935. An Army Air Corps pilot making his first familiarization flight neglected to remove the control locks. This incident led directly to the creation of the ”check list” which is used by all aircraft crew members.

Waist gun position of the Boeing 299. (U.S. Air force) — Waist gun position of the Boeing 299. (The Boeing Company)

Designated XB-17 by the Army Air Corps, this airplane and the YB-17 pre-production models that followed would undergo several years of testing and improvement before entering production as the B-17 Flying Fortress, a legendary airplane of World War II. By the end of the war 12,731 B-17s had been built by Boeing, Douglas and Lockheed Vega.

Boeing Model 299 X13372, designated XB-17, at Wright Field, Ohio, 1935. (U.S. Air Force)

Leslie Ralph Tower was born at Sisseton, South Dakota, 21 January 1903. He was the first of three children of Ralph R. Tower, a farmer who would later serve as a state senator for Montana, and Mayme Amanda Johnson Tower, a Swedish immigrant.

Les Tower attended high school at Polson, Montana, graduating in 1922. He then attended the University of Washington, where he studied engineering. He was a member of the Radio Club.

Tower enlisted in the United States Army as an aviation cadet, training at Brooks and Kelly airfields in Texas. He then served with the 2nd Bombardment Squadron at Langley Field, Virginia.

In 1925 Tower started working for Boeing as a draftsman, but soon began test flying new airplanes, which included the B-9 bomber and the Model 247 commercial airliner. He also demonstrated and delivered Boeing airplanes around the world.

On 20 August 1935, Tower and Louis Wait flew the Model 299 from Seattle to Dayton, approximately 2,100 miles, in 9 hours, 3 minutes, averaging 233 miles per hour (375 kilometers per hour).

Les Tower was aboard the XB-17 as an observer during the 30 October flight. He saw that the control locks had not been released and tried to reach them, but was unable. In the fire that followed the crash, Tower suffered severe burns to his face, right arm and both legs.

Leslie Ralph Tower died of his injuries 19 November 1935 at Miami Valley Hospital in Dayton. His remains were transported by train, escorted by Army airplanes, and were buried at Lakeview Cemetery, Polson, Montana.

¹ At that time, experimental and restricted category aircraft were prohibited from displaying the letter “N” at the beginning of their registration mark.

23 July 1956

July 23, 2024Aviation46-674, 48-096, Bell Aircraft Corporation, Bell X-2, Boeing Airplane Company, Boeing EB-50D Superfortress, Curtiss-Wright XLR25-CW-1, Edwards Air Force Base, Flight Test, Frank Kendall Everest, Pete Everest, Rocketplane, Test Pilot, The Fastest Man AliveBryan Swopes

Bell X-2 46-674 airdropped from Boeing EB-50D Superfortress 48-096 near Edwards Air Force Base, California. (U.S. Air Force)

Brigadier General Frank Kendall Everest, United States Air Force

23 July 1956: Lieutenant Colonel Frank Kendall “Pete” Everest, United States Air Force, became “The Fastest Man Alive” when he flew the USAF/NACA/Bell X-2 rocket plane, serial number 46-674, to Mach 2.87 (1,957 miles per hour, 3,150 kilometers per hour) at 87,808 feet (26,764 meters). The X-2 was air-dropped from Boeing EB-50D Superfortress 48-096, near Edwards Air Force Base, California.

The X-2 was a joint project of the U.S. Air Force and NACA (the National Advisory Committee for Aeronautics, the predecessor of NASA). The rocketplane was designed and built by Bell Aircraft Corporation of Buffalo, New York, to explore supersonic flight at speeds beyond the capabilities of the earlier Bell X-1 and Douglas D-558-2 Skyrocket. In addition to the aerodynamic effects of speeds in the Mach 2.0–Mach 3.0 range, engineers knew that the high temperatures created by aerodynamic friction would be a problem, so the aircraft was built from Stainless Steel and K-Monel, a copper-nickel alloy.

The Bell Aircraft Corporation X-2 was 37 feet, 10 inches (11.532 meters) long with a wingspan of 32 feet, 3 inches (9.830 meters) and height of 11 feet, 10 inches (3.607 meters). Its empty weight was 12,375 pounds (5,613 kilograms) and loaded weight was 24,910 pounds (11,299 kilograms).

The X-2 was powered by a throttleable Curtiss-Wright XLR25-CW-1 rocket engine that produced 2,500–15,000 pounds of thrust (11.12–66.72 kilonewtons) burning alcohol and liquid oxygen. The engine used two rocket chambers and had pneumatic, electrical and mechanical controls. The smaller chamber could produce a maximum 5,000 pounds of thrust, and the larger, 10,000 pounds (22.24 and 44.48 likonewtons, respectively). Professor Robert H. Goddard, “The Father of Modern Rocketry,” authorized Curtiss-Wright to use his patents, and his rocketry team went to work for the Curtiss-Wright Rocket Department. Royalties for use of the patents were paid to the Guggenheim Foundation and Clark university. Professor Goddard died before he could also make the move

Rather than use its limited fuel capacity to take off and climb to altitude, the X-2 was dropped from a modified heavy bomber as had been the earlier rocketplanes. The launch altitude was 30,000 feet (9,144 meters). After the fuel was exhausted, the X-2 glided to a touchdown on Rogers Dry Lake at Edwards Air Force Base.

A four-engine Boeing B-50A Superfortress bomber, serial number 46-011, was modified as the ”mothership.” A second Superfortress, B-50D-95-BO 48-096, was also modified to carry the X-2, and was redesignated EB-50D. During the flight test program, the X-2 reached a maximum speed of Mach 3.196 (2,094 miles per hour, 3,370 kilometers per hour) and a maximum altitude of 126,200 feet (38,466 meters).

Frank Kendall Everest was a fighter pilot and flight instructor during World War II. He flew combat missions in both the Mediterranean and China-Burma-India Theaters of Operation. In May 1945 he was shot down. Everest was captured by the Japanese, held as a prisoner and tortured until the end of the war. After the war, Everest flew as a test pilot at Wright-Patterson Air Force Base, Ohio, and then at Edwards Air Force Base. On 23 July 1956, he was The Fastest Man Alive. Pete Everest retired as a brigadier general in 1970, and died in 2004.

Lieutenant Colonel Frank Kendall Everest, U.S. Air Force, wearing a David Clark Co. T-1 capstan-type partial-pressure suit for protection at high altitude, with a Bell X-2 rocketplane at Edwards AFB, circa 1956. (U.S. Air Force)

16 July 1935

July 16, 2024AviationBoeing Airplane Company, Boeing B-17 Flying Fortress, Boeing Field, Boeing Model 299, Boeing XB-17, Bomber, Browning Machine Gun Caliber .30 M2, Browning Machine Gun Caliber .50 AN-M2, c/n 1963, Model 299, Pratt & Whitney Hornet S1E-G, Prototype, Rollout, World War II, X13372Bryan Swopes

16 July 1935: Just over a year after design began, the Boeing Model 299, X13372,¹ a prototype four engine long range heavy bomber, was rolled out of its hangar at Boeing Field, Seattle, Washington for the first time. The largest land airplane built up to that time, it seemed to have defensive machine guns aimed in every direction. A Seattle Times reporter, Roland Smith, wrote that it was a “flying fortress.” Boeing quickly copyrighted the name.

After several years of testing, the Model 299 went into production as the B-17 Flying Fortress. By the end of World War II, 12,731 B-17 Flying Fortresses had been built by Boeing, Douglas and Lockheed Vega.

Rollout of teh Boeing Model 299, NX13372, prototype XB-17. (Museum of Science and Industry) — Rollout of the Boeing Model 299, X13372, prototype XB-17. (Museum of Science and Industry via *Seattle Post-Intelligencer*)

The prototype was powered by four air-cooled, supercharged, 1,690.537-cubic-inch-displacement (27.703 liter) Pratt & Whitney Hornet S1E-G nine-cylinder radial engines with a compression ratio of 6.5:1. The S1E-G was rated at 750 horsepower at 2,250 r.p.m., and 875 horsepower at 2,300 r.p.m. for takeoff, using 87-octane gasoline. They turned 11 foot, 6 inch (3.505 meters) diameter, three-bladed Hamilton Standard Hydromatic constant-speed propellers through a 3:2 gear reduction. The S1E-G was 4 feet, 1.38 inches (1.254 meters) long, 4 feet, 6.44 inches (1.383 meters) in diameter and weighed 1,064 pounds (483 kilograms)

Cockpit of the Boeing Model 299. (U.S. Air Force) — Cockpit of the Boeing Model 299. (Boeing)

In flight testing, the Model 299 had a cruise speed of 204 miles per hour (328 kilometers per hour) and a maximum speed of 236 miles per hour (380 kilometers per hour) at 10,000 feet (3,048 meters). The service ceiling was 24,620 feet (7,504.2 meters). The maximum range was 3,101 miles (4,991 kilometers). Carrying a 2,573 pounds (1,167 kilograms) load of bombs, the range was 2,040 miles (3,283 kilometers).

Boeing XB-17 (Model 299) bombers and front gunners compartment. (U.S. Air Force photo) 060706-F-1234S-007

Nose turret of the Boeing Model 299, with .50-caliber machine gun, photographed 24 July 1935. (Boeing 8195)

Bomb sight position., 9 August 1935. (Boeing 8227-B)

The XB-17 could carry eight 500 pound (227 kilogram) bombs in an internal bomb bay. Defensive armament consisted of five air-cooled .30-caliber or .50-caliber Browning machine guns.

Starboard waist gunnner’s position of the Boeing 299. (Boeing)

Starboard waist gunners position, with Browning M2 .50-caliber machine gun and ammunition canisters. (Boeing)

NX13372 was destroyed when it crashed on takeoff at Wright Field, Dayton, Ohio, 30 October 1935. An Army Air Corps pilot making his first familiarization flight neglected to remove the control locks. This incident led directly to the creation of the “check list” which today is used by all aircraft crew members.

Boeing Model 299, left quarter, at Boeing Field, south of Seattle, Washington,August 1935. (Boeing)

Boeing Model 299, NXxxx72, the prototype XB-17. (U.S. Air Force) — Boeing Model 299, X13372, the prototype XB-17, at Wright Field, Ohio. (U.S. Air Force)

Boeing Model 299, left profile, at Boeing Field, 13 August 1935. (Boeing 8234-B)