Editing De Havilland Mosquito (section)

===Inception of the de Havilland fast bomber===
[[File:Albatross 1938 prototype.jpg|thumb|One of de Havilland's proposals was to adapt the [[de Havilland Albatross]] design to create a fast bomber.]]
Based on his experience with the Albatross, Geoffrey de Havilland believed that a bomber with a good aerodynamic design and smooth, minimal skin area, would exceed the P.13/36 specification.<ref name="Birtles 2017, ch. 2">{{Harvnb | Birtles | 2017 | at = ch. 2}}.</ref> Furthermore, adapting the Albatross principles could save time. In April 1938, performance estimates were produced for a twin [[Rolls-Royce Merlin]]-powered DH.91, with the [[Bristol Hercules]] ([[radial engine]]) and [[Napier Sabre]] ([[H-engine]]) as alternatives.<ref name= "Sharb30" />  On 7 July 1938, de Havilland wrote to [[Air Marshal]] [[Wilfrid Freeman]], the Air Council's member for Research and Development, discussing the specification and arguing that in war, shortages of aluminium and steel would occur, but supplies of wood-based products were "adequate."{{Efn|The situation had changed by October 1941, Connor cites a message<ref name="Connor-Madison, pp. 2-3."/> that Britain was desperately short: – "One of four airscrew factories has run out of imported veneers… veneers for air frame plywood would enable… construction to continue till December only… direct contact between Ministry of Supply experts and U.S.A. suppliers of aircraft veneers will be necessary for next three months. Otherwise essential war production… will be further curtailed." Wood construction used a different sector of workforce, and at the time, dH's experience was almost exclusively in the use of timber.<ref>Cypher dated 2 October 1941: – To – British Supply Council in North America. From – Supply Committee.  LONUS 13, National Archives. London.</ref>}} Although inferior in [[Tension (physics)|tension]], the [[Specific strength|strength-to-weight ratio]] of wood is equal to or better than light alloys or steel, hence this approach was feasible.<ref name="Sharb30"/><ref name= "Birtles 2017, ch. 2" /> [[Max Aitken, 1st Baron Beaverbrook|Lord Beaverbrook]], Minister of Aircraft Production, nicknamed it "Freeman's Folly", alluding to Air Chief Marshal Sir [[Wilfrid Freeman]], who defended [[Geoffrey de Havilland]] and his design concept against orders to scrap the project.{{Sfn | Birtles | 2017 | at = ch. 3}}

A follow-up letter to Freeman on 27 July said that the P.13/36 specification could not be met by a twin Merlin-powered aircraft and either the top speed or load capacity would be compromised, depending on which was paramount. For example, a larger, slower, turret-armed aircraft would have a range of {{cvt|1500|mi|km}} carrying a 4,000&nbsp;lb bomb load, with a maximum of {{cvt|260|mph|km/h}} at {{cvt |19000|ft|m}}, and a cruising speed of {{cvt|230|mph|km/h}} at {{cvt|18000|ft|m}}. De Havilland believed that a compromise, including eliminating surplus equipment, would improve matters.<ref name="Sharb30"/> On 4 October 1938, de Havilland projected the performance of another design based on the Albatross, powered by two Merlin&nbsp;Xs, with a three-man crew and six or eight forward-firing guns, plus one or two manually operated guns and a tail turret. Based on a total loaded weight of {{cvt|19000|lb|kg|abbr=on}}, it would have a top speed of {{cvt|300|mph|km/h|abbr=on}} and cruising speed of {{cvt |268|mph|km/h|abbr=on}} at {{cvt|22500|ft|m|abbr=on}}.<ref name="Sharb31" />

Still believing this could be improved, and after examining more concepts based on the Albatross and the new all-metal [[de Havilland Flamingo|DH.95 Flamingo]], de Havilland settled on designing a new aircraft that would be aerodynamically clean, wooden, and powered by the Merlin, which offered substantial future development.<ref name="Sharb31"/> The new design would be faster than foreseeable enemy [[fighter aircraft]], and could dispense with defensive armament which would slow it and make interception or losses to antiaircraft guns more likely. Instead, high speed and good manoeuvrability would make evading fighters and ground fire easier.<ref name="Sharb31" /> The lack of turrets simplified production, reduced drag, and reduced production time, with a delivery rate far in advance of competing designs. Without armament, the crew could be reduced to a pilot and navigator. Whereas contemporary RAF design philosophy favoured well-armed heavy bombers, this mode of design was more akin to the German philosophy of the ''[[Schnellbomber]]''.<ref name= "Batchelor and Lowe 2008, p. 5.">Batchelor and Lowe 2008, p. 5.</ref>  At a meeting in early October 1938 with Geoffrey de Havilland and Charles Walker (de Havilland's chief engineer), the Air Ministry showed little interest, and instead asked de Havilland to build wings for other bombers as a subcontractor.<ref name="Batchelor and Lowe 2008, p. 6.">Batchelor and Lowe 2008, p. 6.</ref>

By September 1939, de Havilland had produced preliminary estimates for single- and twin-engined variations of light-bomber designs using different engines, speculating on the effects of defensive armament on their designs.<ref name="Buttler, p. 78">Buttler 2004, p. 78.</ref> One design, completed on 6 September, was for an aircraft powered by a single {{cvt|2000|hp|kW|abbr=on}}  Napier Sabre, with a wingspan of {{cvt|47|ft|m}} and capable of carrying a {{cvt|1000|lb|kg|adj=on}} bomb load {{cvt|1500|mi|km}}. On 20 September, in another letter to Wilfrid Freeman, de Havilland wrote "…we believe that we could produce a twin-engine bomber which would have a performance so outstanding that little defensive equipment would be needed."<ref name= "Buttler, p. 78"/> By 4 October, work had progressed to a twin-engined light bomber with a wingspan of {{cvt |51|ft|m|abbr=on}} and powered by Merlin or Griffon engines, the Merlin favoured because of availability.<ref name="Buttler, p. 78"/> On 7 October 1939, a month into the war, the nucleus of a design team under [[Ronald Eric Bishop|Eric Bishop]] moved to the security and secrecy of [[De Havilland Aircraft Heritage Centre#Salisbury Hall|Salisbury Hall]] to work on what was later known as the DH.98.<ref name="Sharb34">Sharp and Bowyer 1971, p. 34.</ref>{{Efn|Bishop had worked on the DH.88 Comet and the Albatross under de Havilland's then-chief designer A. E. Hagg.<ref>Bishop 1995,{{page needed|date= January 2012}}</ref>}} For more versatility, Bishop made provision for four 20&nbsp;mm cannon in the forward half of the [[bomb bay]], under the cockpit, firing via blast tubes and troughs under the fuselage.<ref name="Bowman 2005, p. 11.">Bowman 2005, p. 11.</ref>

The DH.98 was too radical for the ministry, which wanted a heavily armed, multirole aircraft, combining medium bomber, reconnaissance, and general-purpose roles, that was also capable of carrying torpedoes.{{Sfn | Batchelor | Lowe | 2008 | p = 6}}  With the outbreak of war, the ministry became more receptive, but was still sceptical about an unarmed bomber. They thought the Germans would produce fighters that were faster than had been expected.<ref>Sharp and Bowyer 1971, pp. 31–32,</ref> and suggested the incorporation of two forward- and two rear-firing machine guns for defence.<ref name="Bow0510">Bowman 2005, p. 10.</ref> The ministry also opposed a two-man bomber, wanting at least a third crewman to reduce the work of the others on long flights.<ref name="Bowman 2005, p. 11."/> The Air Council added further requirements such as remotely controlled guns, a top speed of {{cvt|275|mph|km/h|abbr=on|round=5}} at 15,000&nbsp;ft on two-thirds engine power, and a range of {{cvt|3000|mi|km|abbr=on}} with a 4,000-lb bomb load.<ref name="Bow0510"/> To appease the ministry, de Havilland built mock-ups with a gun turret just aft of the cockpit, but apart from this compromise, de Havilland made no changes.<ref name="Bowman 2005, p. 11."/>

On 12 November, at a meeting considering fast-bomber ideas put forward by de Havilland, [[Blackburn Aircraft|Blackburn]], and [[Bristol Aeroplane Company|Bristol]], Air Marshal Freeman directed de Havilland to produce a fast aircraft, powered initially by Merlin engines, with options of using progressively more powerful engines, including the [[Rolls-Royce Griffon]] and the [[Napier Sabre]].  Although estimates were presented for a slightly larger Griffon-powered aircraft, armed with a four-gun tail turret, Freeman got the requirement for defensive weapons dropped, and a draft requirement was raised calling for a high-speed, light-reconnaissance bomber capable of {{cvt|400|mph|km/h|abbr=on|round=5}} at 18,000&nbsp;ft.<ref>Buttler 2004, p. 79.</ref>

On 12 December, the [[Vice-Chief of the Air Staff (United Kingdom)|Vice-Chief of the Air Staff]], Director General of Research and Development, and the [[Air Officer Commanding |Air Officer Commanding-in-Chief]] (AOC-in-C) of [[RAF Bomber Command]] met to finalise the design and decide how to fit it into the RAF's aims.  The AOC-in-C would not accept an unarmed bomber, but insisted on its suitability for reconnaissance missions with F8 or [[F24 camera]]s.<ref name="Bowman 2005, p. 12.">Bowman 2005, p. 12.</ref> After company representatives, the ministry, and the RAF's operational commands examined a full-scale mock-up at Hatfield on 29 December 1939, the project received backing.<ref name= "Bu80">Buttler 2004, p. 80.</ref> This was confirmed on 1 January 1940, when Freeman chaired a meeting with Geoffrey de Havilland, John Buchanan (Deputy of Aircraft Production), and John Connolly (Buchanan's chief of staff). De Havilland claimed the DH.98 was the "fastest bomber in the world… it must be useful".  Freeman supported it for RAF service, ordering a single prototype for an unarmed bomber to specification B.1/40/dh, which called for a light bomber/reconnaissance aircraft powered by two {{cvt |1280|hp|kW|abbr= on}} Rolls-Royce RM3SM (an early designation for the Merlin 21) with [[Meredith effect|ducted radiators]], capable of carrying a {{cvt|1000|lb|kg|adj=on}} bomb load.<ref name="Sharb34"/><ref name="Bowman 2005, p. 12." /> The aircraft was to have a speed of {{cvt|400|mph|km/h}} at {{cvt|24000|ft|m}} and a cruising speed of {{cvt|325|mph|km/h|round=5}} at {{cvt|26500|ft|m}} with a range of {{cvt|1500|mi|km}} at {{cvt|25000|ft|m}} on full tanks. Maximum service ceiling was to be {{cvt|32000|ft|m}}.<ref name= "Bowman 2005, p. 12." />

On 1 March 1940, [[Air Marshal]] [[Roderic Hill]] issued a contract under Specification B.1/40, for 50 bomber-reconnaissance variants of the DH.98; this contract included the prototype, which was given the [[United Kingdom aircraft test serials|factory serial]] ''E-0234''.<ref>Sharp and Bowyer 1971, p. 35.</ref><ref>Price 2009, p. 51.</ref> In May 1940, specification F.21/40 was issued, calling for a long-range fighter armed with four 20&nbsp;mm cannon and four .303 machine guns in the nose, after which de Havilland was authorised to build a prototype of a fighter version of the DH.98. After debate, it was decided that this prototype, given the [[United Kingdom military aircraft serials|military serial number]] ''W4052'', was to carry [[aircraft interception radar|aircraft interception (AI)]] Mk&nbsp;IV radar equipment as both a day fighter and night fighter.{{Efn |The term [[radar]], which originated in the USA, was not used by the British until later.}} By June 1940, the DH.98 had been named "Mosquito".<ref name= "Bu80" /> Having the fighter variant kept the Mosquito project alive, as doubts remained within the government and Air Ministry regarding the usefulness of an unarmed bomber, even after the prototype had shown its capabilities.<ref name="Bu80"/>