Editing Boeing B-17 Flying Fortress (section)

== Development ==

=== Origins ===
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| image1    =Boeing XB-17 (Model 299).jpg
| image_caption1  = Model 299 ''NX13372''
| image3    =Boeing Model 299 crash.jpg
| image_caption3  = Crashed Model 299
| image4    =Boeing Y1B-17 in flight.jpg
| image_caption4  = Boeing Y1B-17 in flight
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On 8 August 1934, the USAAC tendered a proposal for a multiengine 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.<ref name="Tate.p164" /> Requirements were for it to carry a "useful bombload" at an altitude of {{convert|10000|ft|m|abbr=on}} for 10 hours with a top speed of at least {{convert|200|mph|km/h|abbr=on}}.<ref name="Swan Mil p74" />

They also desired, but did not require, a bomber with a range of {{convert|2000|mi|km|-2|abbr=on}} and a speed of {{cvt|250|mph|kn km/h}}. The competition for the air corps contract was to be decided by a "fly-off" between Boeing's design, the [[Douglas B-18 Bolo|Douglas DB-1]], and the [[Martin Model 146]] at [[Wilbur Wright Field]] in [[Dayton, Ohio]].

The prototype B-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.<ref name="WoF p41" /> It combined features of the company's experimental [[Boeing XB-15|XB-15]] bomber and [[Boeing 247|247]] transport.<ref name="Swan Mil p74" /> The B-17's armament consisted of five .30 caliber (7.62&nbsp;mm) [[machine gun]]s, with a payload up to {{convert|4800|lb|kg|abbr=on}} of bombs on two racks in the bomb bay behind the cockpit. The aircraft was powered by four [[Pratt & Whitney R-1690 Hornet]] [[radial engine]]s, each producing {{convert|750|hp|kW|-2|abbr=on}} at {{convert|7000|ft|m|-2|abbr=on}}.<ref name="Bowers Boeing p291-2" />

The first flight of the Model 299 was on {{Nowrap|28 July}} 1935 with Boeing chief test pilot Leslie Tower at the controls.<ref name="first flight" /><ref name="Sal.p46" /> 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.<ref>Freeman 1993, p. 8.</ref> The most distinctive mount was in the nose, which allowed the single machine gun to be fired toward nearly all frontal angles.<ref>[https://books.google.com/books?id=WSgDAAAAMBAJ&pg=PA24 "Army's Biggest Bomber Has Rotating Nose"]. ''Popular Science Monthly'', August 1937.</ref>

Boeing was quick to see the value of the name and had it trademarked for use.{{NoteTag |1 = The 1 January 1938 ''Air Corps News Letter'' noted the Langley Field correspondent used the appellation "Jeep" to the B-17, which it objected to as "not befitting" the aircraft and adding, "Why not let the term 'Flying Fortress' suffice?"<ref>{{citation |url=http://newpreview.afnews.af.mil/shared/media/document/AFD-110421-039.pdf |title= Performances of B-17's invokes enthusiasm |work=Air Corps News Letter |volume= XXI |number= 1 |date=1 January 1938 |page=7 |archive-url=https://web.archive.org/web/20150903213218/http://newpreview.afnews.af.mil/shared/media/document/AFD-110421-039.pdf |archive-date=3 September 2015 }}</ref> }} 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.<ref>[https://books.google.com/books?id=wN8DAAAAMBAJ&pg=PA519 "Giant Bomber Flies Four Miles Per Minute"]. ''Popular Mechanics'', October 1935.</ref> On {{Nowrap|20 August 1935}}, the prototype flew from Seattle to Wright Field in nine hours and three minutes with an average ground speed of {{cvt|252|mph|kn km/h}}, much faster than the competition.<ref name="NYTimes.299Record" />

At the fly-off, the four-engined 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 [[United States Army Air Corps#GHQ Air Force|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.<ref name="Zamzow.33" /><ref>{{cite web|url=https://media.defense.gov/2016/Mar/14/2001480192/-1/-1/0/0908GHQ.PDF|title=GHQ Air Force: This strange arrangement in 1935 split the Air Corps into two camps—but it led the way to an independent Air Force Page 64-66|work=Air Force Magazine|date=September 2008|access-date=January 3, 2024}}</ref> Their opinions were shared by the air corps procurement officers, and even before the competition had finished, they suggested buying 65 B-17s.<ref name="Tate 165" /><ref name="Zamzow.34" />

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 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.<ref name="Museum">{{cite web |url=http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2478 |title=Model 299 Crash, 15 November 1935 |archive-url=https://web.archive.org/web/20070516004104/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2478 |archive-date=16 May 2007 |access-date=18 February 2024 |url-status=dead}}.</ref> 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."<ref>{{cite book |last1=Doyle |first1=David |title=B-17 Flying Fortress, Vol. 1: Boeing's Model 299 through B-17D in World War II |date=2020 |publisher=Schiffer Publishing, Ltd. |location=Atglen |isbn=9780764359552 |pages=6–7}}</ref><ref name="Checks"/>

The crashed Model 299 could not finish the evaluation, thus disqualifying it from the competition.<ref name="Zamzow.34" /> While the Air Corps was still enthusiastic about the aircraft's potential, Army officials were daunted by its cost;<ref name="Sal.p48" /> Douglas quoted a unit price of $58,200 ({{inflation|US-GDP|58200|1935|r=-3|fmt=eq}}{{Inflation/fn|US-GDP}}) based on a production order of 220 aircraft, compared with $99,620 ({{inflation|US-GDP|99620|1935|r=-3|fmt=eq}}{{Inflation/fn|US-GDP}} ) from Boeing.<ref name="Francillon Doug p201-2" /> 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.<ref name="Tate 165" /><ref name="Zamzow.34" /><ref>{{cite web|url= https://www.airandspaceforces.com/article/rise-of-the-air-corps|title=Rise of the Air Corps|work=Air & Space Forces Magazine|date=May 12, 2022|access-date=January 3, 2024}}</ref>
{{blockquote|The loss was not total... But Boeing's hopes for a substantial bomber contract were dashed.|Peter Bowers, 1976<ref name="Bowers1976.p37">Bowers 1976, p. 37.</ref>}}

=== Initial orders ===
[[File:B17F - Woman workers at the Douglas Aircraft Company plant, Long Beach, Calif.jpg|thumb|Installation of fixtures and assemblies on a tail fuselage section of a B-17 at the [[Douglas Aircraft Company|Douglas]] plant in [[Long Beach, California]], October 1942]]

Despite the crash, the USAAC had been impressed by the prototype's performance, and on {{Nowrap|17 January}} 1936, through a legal loophole,<ref name="Erickson"/><ref name="Meilinger" /> the Air Corps ordered 13 YB-17s (designated Y1B-17 after November 1936 to denote its special F-1 funding) for service testing.<ref name="Zamzow.34" /> The YB-17 incorporated a number of significant changes from the Model 299, including more powerful [[Wright R-1820]]-39 Cyclone engines. Although the prototype was company-owned and never received a military serial (the B-17 designation itself did not appear officially until January 1936, nearly three months after the prototype crashed),<ref name="Bowers1976.p12" /> the term "XB-17" was retroactively applied to the ''NX13372's'' airframe and has entered the lexicon to describe the first Flying Fortress.

Between 1 March and 4 August 1937, 12 of the 13 Y1B-17s were delivered to the 2nd Bombardment Group at Langley Field in Virginia for operational development and flight tests.<ref name="Swan Mil p75" /> One suggestion adopted was the use of a [[pre-flight checklist|preflight checklist]] to avoid accidents such as that which befell the Model 299.<ref name="Meilinger" /><ref name="Checks2" />{{NoteTag|The idea of a pilot's checklist spread to other crew members, other air corps aircraft types, and eventually throughout the aviation world. ''Life'' published the lengthy B-17 checklist in its 24 August 1942 issue.<ref>[https://books.google.com/books?id=fk4EAAAAMBAJ&pg=PA65 "B-17 checklist"]. ''Life'', 24 August 1942.</ref>}} In one of their first missions, three B-17s, directed by lead navigator [[Lieutenant]] [[Curtis LeMay]], were sent by General Andrews to [[Interception of the Rex|"intercept" and photograph the Italian ocean liner ''Rex'']] {{convert|610|mi|km}} off the Atlantic coast.<ref name="Zamzow.47" /> The mission was successful and widely publicized.<ref name="Maurer" /><ref name="USAF Rex" /> The 13th Y1B-17 was delivered to the Material Division at Wright Field, Ohio, to be used for flight testing.<ref name="Y1B-17" />

A 14th Y1B-17 (''37-369''), originally constructed for ground testing of the airframe's strength, was upgraded by Boeing with exhaust-driven General Electric [[turbo-supercharger]]s, and designated Y1B-17A. Designed by [[Sanford Alexander Moss|Sanford Moss]], engine exhaust gases turned the turbine's steel-alloy blades, forcing high-pressure air into the Wright Cyclone GR-1820-39 engine supercharger.<ref>{{cite web |url = https://aviationshoppe.com/manuals/wwii_aircraft_superchargers/wwii_aircraft_turbosupercharger.html |title = World War II – General Electric Turbosupercharges |website = aviationshoppe.com |access-date = 8 June 2017 |archive-date = 8 October 2019 |archive-url = https://web.archive.org/web/20191008054906/https://aviationshoppe.com/manuals/wwii_aircraft_superchargers/wwii_aircraft_turbosupercharger.html |url-status = usurped }}</ref> Scheduled to fly in 1937, it encountered problems with the turbochargers, and its first flight was delayed until {{Nowrap|29 April}} 1938.<ref name="Donald" /> The aircraft was delivered to the Army on {{Nowrap|31 January}} 1939.<ref name="Bowers Boeing p293-4" /> Once service testing was complete, the Y1B-17s and Y1B-17A were redesignated B-17 and B-17A, respectively, to signify the change to operational status.<ref name="Wixley p23" />  The Y1B-17A had a maximum speed of {{cvt|311|mph|kn kph}}, at its best operational altitude, compared to {{cvt|239|mph|kn kph}} for the Y1B-17. Also, the Y1B-17A's new service ceiling was more than {{convert|2|miles|m}} higher at {{convert|38000|ft|m}}, compared to the Y1B-17's {{convert|27800|ft|m}}. These turbo-superchargers were incorporated into the B-17B.<ref>{{cite book |last1=Caidin |first1=Martin |title=Flying Forts: The B-17 in World War II |date=1968 |publisher=Bantam Books |location=New York |isbn=9780553287806 |pages=80, 95–99}}</ref>

Opposition to the Air Corps' ambitions for the acquisition of more B-17s faded, and in late 1937, 10 more aircraft designated B-17B were ordered to equip two bombardment groups, one on each U.S. coast.<ref name="B-17B" /> Improved with larger flaps and rudder and a well-framed, 10 panel [[Acrylic glass|plexiglass]] nose, the B-17Bs were delivered in five small batches between July 1939 and March 1940. In July 1940, an order for 512 B-17s was issued,<ref name="Pop1" /> but at the time of the [[attack on Pearl Harbor]], fewer than 200 were in service with the army.<ref name="Meilinger" />

A total of 155 B-17s of all variants were delivered between {{nowrap|11 January}} 1937 and {{nowrap|30 November}} 1941, but production quickly accelerated, with the B-17 once holding the record for the highest production rate for any large aircraft.<ref name="Serling.p55" />{{NoteTag|Quote: "At the peak of production, Boeing was rolling out as many as 363 B-17s a month, averaging between 14 and 16 Forts a day, the most incredible production rate for large aircraft in aviation history."<ref>Serling, p. 55</ref> This production rate was, however, surpassed by that of the [[Consolidated B-24 Liberator]]: at its peak in 1944, the [[Willow Run]] plant alone produced one B-24 per hour and 650 B-24s per month.<ref name="Willowrun">Nolan, Jenny. [http://info.detnews.com/redesign/history/story/historytemplate.cfm?id=73&category=locations "Michigan History: Willow Run and the Arsenal of Democracy."] {{webarchive |url=https://archive.today/20121204140927/http://info.detnews.com/redesign/history/story/historytemplate.cfm?id=73&category=locations |date=4 December 2012 }} ''The Detroit News'', 28 January 1997. Retrieved: 7 August 2010.</ref><!--end NoteTag-->}} The aircraft went on to serve in every World War&nbsp;II combat zone, and by the time production ended in May 1945, 12,731 B-17s had been built by Boeing, [[Douglas Aircraft Company|Douglas]], and [[Vega Aircraft Corporation|Vega]] (a subsidiary of [[Lockheed Corporation|Lockheed]]).<ref name="Yenne.p6" /><ref>Herman, Arthur. ''Freedom's Forge: How American Business Produced Victory in World War II'', pp. 292–99, 305, Random House, New York, 2012. {{ISBN|978-1-4000-6964-4}}.</ref><ref>Parker 2013, pp. 35, 40–48, 59, 74.</ref><ref>Borth 1945, pp. 70–71, 83, 92, 256, 268–69.</ref>
{{blockquote|Though the crash of the prototype 299 in 1935 had almost wiped out Boeing, now it was seen as a boon. Instead of building models based on experimental engineering, Boeing had been hard at work developing their bomber and now had versions ready for production far better than would have been possible otherwise. One of the most significant weapons of World War II would be ready, but only by a hair.|Jeff Ethell, 1985<ref name="Pop1" />}}