Boeing B-17 Flying Fortress
Illustrative image; it may differ from the actual aircraft.The Boeing B-17 Flying Fortress is an American four-engined heavy bomber aircraft that was developed in the mid-1930s for the United States Army Air Corps (USAAC). A fast and high-flying bomber used primarily in the European Theater of Operations, the B-17 dropped more bombs than any other aircraft during World War II. It is the third-most produced bomber in history, behind the American four-engined Consolidated B-24 Liberator and the German multirole, twin-engined Junkers Ju 88. The B-17 was also employed in transport, anti-submarine warfare, and search and rescue roles. In a USAAC competition, Boeing's prototype Model 299/XB-17 outperformed two other entries but crashed, losing the initial 200-bomber contract to the Douglas B-18 Bolo. Still, the Air Corps ordered 13 more B-17s for further evaluation, which were introduced into service in 1938.
Specifications
Figures for the B-17G (en sus conversiones civiles) variant, the most representative of the family
The type first flew in 1935 (91 years ago) · About 12,731 units built · Production ended in 1945
Figures for the type, not for this particular aircraft: each variant and each configuration changes something. They are shown in both systems used in aviation.
The story of the type
Development
Origins
On 8 August 1934, the USAAC tendered a proposal for a multi-engine bomber to replace the Martin B-10. The Air Corps was looking for a bomber capable of reinforcing the air forces in Hawaii, Panama, and Alaska. Requirements were for it to carry a "useful bomb-load" at an altitude of 10,000 ft (3,000 m) for 10 hours with a top speed of at least 200 mph (320 km/h).
They also desired, but did not require a bomber with a range of 2,000 mi (3,200 km) and a speed of 250 mph (220 kn; 400 km/h). The competition for the air corps contract was to be decided by a "fly-off" between Boeing's design, the Douglas DB-1, and the Martin Model 146 at Wilbur Wright Field in Dayton, Ohio.
The prototype XB-17, with the Boeing factory designation of Model 299, was designed by a team of engineers led by E. Gifford Emery and Edward Curtis Wells, and was built at Boeing's own expense. It combined features of the company's experimental XB-15 bomber and 247 transport. The B-17's armament consisted of five .30 caliber (7.62 mm) machine guns, with a payload up to 4,800 lb (2,200 kg) of bombs on two racks in the bomb bay behind the cockpit. The aircraft was powered by four Pratt & Whitney R-1690 Hornet radial engines, each producing 750 hp (600 kW) at 7,000 ft (2,100 m).
The first flight of the Model 299 was on 28 July 1935 with Boeing chief test pilot Leslie Tower at the controls. The day before, Richard Williams, a reporter for The Seattle Times, coined the name "Flying Fortress" when – observing the large number of machine guns sticking out from the new aircraft – he described it as a "15-ton flying fortress" in a picture caption. The most distinctive mount was in the nose, which allowed the single machine gun to be fired toward nearly all frontal angles.
Boeing was quick to see the value of the name and had it trademarked for use. Boeing also claimed in some of the early press releases that Model 299 was the first combat aircraft that could continue its mission if one of its four engines failed. On 20 August 1935, the prototype flew from Seattle to Wright Field in nine hours and three minutes with an average ground speed of 252 mph (219 kn; 406 km/h), much faster than the competition.
At the fly-off, the four-propped Boeing's performance was superior to those of the twin-engine DB-1 and Model 146. In March 1935 Army Chief of Staff General Douglas MacArthur created GHQ Air Force and promoted lieutenant colonel Frank Maxwell Andrews to brigadier general to become the head of GHQ Air Force. MacArthur and Andrews both believed that the capabilities of large four-engined aircraft exceeded those of shorter-ranged, twin-engine aircraft, and that the B-17 was better suited to new, emerging USAAC doctrine. Their opinions were shared by the air corps procurement officers, and even before the competition had finished, they suggested buying 65 B-17s.
On 30 October 1935, a test flight determining the rate of climb and service ceiling was planned. The command pilot was Major Ployer Peter Hill, Wright Field Material Division Chief of the Flying Branch, his first flight in the Model 299. Copilot was Lieutenant Donald L. Putt, while Boeing chief test pilot Leslie R. Tower was behind the pilots in an advisory role. Also on board were Wright Field test observer John Cutting and mechanic Mark Koegler. The plane stalled and spun into the ground soon after takeoff, bursting into flames. Though initially surviving the impact, Hill died within a few hours, and Tower on 19 November. Post-accident interviews with Tower and Putt determined the control surface gust lock had not been released. Doyle notes, "The loss of Hill and Tower, and the Model 299, was directly responsible for the creation of the modern written checklist used by pilots to this day."
The crashed Model 299 could not finish the evaluation, thus disqualifying it from the competition. While the Air Corps was still enthusiastic about the aircraft's potential, Army officials were daunted by its cost; Douglas quoted a unit price of $58,200 (equivalent to $1,045,000 in 2024) based on a production order of 220 aircraft, compared with $99,620 (equivalent to $1,788,000 in 2024 ) from Boeing. MacArthur's successor, Army Chief of Staff Malin Craig, canceled the order for 65 YB-17s and ordered 133 of the twin-engined Douglas B-18 Bolo, instead. Secretary of War Harry Hines Woodring in October 1938 decided that no four-engine bombers, including B-17s, would be purchased by the War Department in 1939.
The loss was not total... But Boeing's hopes for a substantial bomber contract were dashed.
Initial orders
Despite the crash, the USAAC had been impressed by the prototype's performance, and on 17 January 1936, through a legal loophole, the Air Corps ordered 13 YB-17s (designated Y1B-17 after November 1936 to denote its special F-1 funding) for service testing. The YB-17 incorporated a number of significant changes from the Model 299, including more powerful Wright R-1820-39 Cyclone engines.
Variants
The aircraft went through several alterations in each of its design stages and variants. Of the 13 YB-17s ordered for service testing, 12 were used by the 2nd Bomb Group at Langley Field, Virginia, to develop heavy bombing techniques, and the 13th was used for flight testing at the Material Division at Wright Field, Ohio. Experiments on this aircraft led to the use of 4 General Electric turbo-superchargers, which later became standard on the B-17 line. A 14th aircraft, the YB-17A, originally destined for ground testing only and upgraded with the turbochargers, was redesignated B-17A after testing had finished.
As the production line developed, Boeing engineers continued to improve upon the basic design. To enhance performance at slower speeds, the B-17B was altered to include larger rudders and flaps. The B-17C changed from three bulged, oval-shaped gun blisters to two flush, oval-shaped gun window openings, and on the lower fuselage, a single "bathtub" gun gondola housing, which resembled the similarly configured and located Bodenlafette/"Bola" ventral defensive emplacement on the German Heinkel He 111P-series medium bomber.
While models A through D of the B-17 were designed defensively, the large-tailed B-17E was the first model primarily focused on offensive warfare. The B-17E was an extensive revision of the Model 299 design: The fuselage was extended by 10 ft (3.0 m); a much larger rear fuselage, vertical tailfin, rudder, and horizontal stabilizer were added; a gunner's position was added in the new tail; the nose (especially the bombardier's framed, 10-panel nose glazing) remained relatively the same as the earlier B through D versions had; a Sperry electrically powered manned dorsal gun turret just behind the cockpit was added; a similarly powered (also built by Sperry) manned ventral ball turret just aft of the bomb bay – replaced the relatively hard-to-use, Sperry model 645705-D remotely operated ventral turret on the earliest examples of the E variant. These modifications resulted in a 20% increase in aircraft weight. The B-17's turbocharged Wright R-1820 Cyclone 9 engines were upgraded to increasingly more powerful versions of the same powerplants throughout its production, and similarly, the number of machine gun emplacement locations was increased.
The B-17F variant was the primary version used by the Eighth Air Force to face the Germans in 1943, and standardized the manned Sperry ball turret for ventral defense, also replacing the earlier, 10-panel framed bombardier's nose glazing from the B subtype with an enlarged, nearly frameless Plexiglas bombardier's nose enclosure for improved forward vision.
Two experimental versions of the B-17 were flown under different designations, the XB-38 'Flying Fortress' and the YB-40 'Flying Fortress.' The XB-38 was an engine testbed for Allison V-1710 liquid-cooled engines, should the Wright engines normally used on the B-17 become unavailable. The only prototype XB-38 to fly crashed on its ninth flight, and the concept was abandoned. The Allison V-1710 was reallocated to fighter aircraft.
The YB-40 was a heavily armed modification of the standard B-17 used before the North American P-51 Mustang, an effective long-range fighter, became available to act as escort. Additional armament included an additional dorsal turret in the radio room, a remotely operated and fired Bendix-built "chin turret" directly below the bombardier's accommodation, and twin 50 caliber (12.7 mm) guns in each of the waist positions. The ammunition load was over 11,000 rounds. All of these modifications made the YB-40 well over 10,000 lb (4,500 kg) heavier than a fully loaded B-17F. The YB-40s with their greater weight, had trouble keeping up with the lighter bombers once they had dropped their bombs, so the project was abandoned and finally phased out in July 1943.
Overview and history adapted from Wikipedia (CC BY-SA) · technical figures from the manufacturer’s published specifications and standard aviation references
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This page was last updated on October 11, 2026
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BibTeX
@misc{vuelopedia_en_model_b17,
author = {{Vuelopedia}},
title = {{Boeing B-17 Flying Fortress}},
publisher = {Fundación Poderia},
year = {2026},
date = {2026-10-11},
url = {https://vuelopedia.org/en/model/b17},
howpublished = {\url{https://vuelopedia.org/en/model/b17}},
urldate = {2026-10-16},
note = {Accessed 2026-10-16}
}Wikipedia
{{cite web |url=https://vuelopedia.org/en/model/b17 |title=Boeing B-17 Flying Fortress |website=Vuelopedia |publisher=Fundación Poderia |date=2026-10-11 |access-date=2026-10-16 |language=en}}