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The de Havilland DH.98 Mosquito is a British twin-engined, shoulder-winged,
multirole combat aircraft A multirole combat aircraft (MRCA) is a combat aircraft intended to perform different roles in combat. A multirole fighter is a multirole combat aircraft which is, at the same time, also a fighter aircraft; in other words, an aircraft whose vario ...
, introduced during the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
. Unusual in that its frame was constructed mostly of wood, it was nicknamed the "Wooden Wonder", or "Mossie".
Lord Beaverbrook William Maxwell Aitken, 1st Baron Beaverbrook, Privy Council of the United Kingdom, PC, Order of New Brunswick, ONB (25 May 1879 – 9 June 1964), generally known as Lord Beaverbrook, was a Canadian-British newspaper publisher and backstage poli ...
, Minister of Aircraft Production, nicknamed it "Freeman's Folly", alluding to Air Chief Marshal Sir
Wilfrid Freeman Air Chief Marshal Sir Wilfrid Rhodes Freeman, 1st Baronet, (18 July 1888 – 15 May 1953) was one of the most important influences on the rearmament of the Royal Air Force (RAF) in the years up to and including the Second World War. RAF career H ...
, who defended
Geoffrey de Havilland
Geoffrey de Havilland
and his design concept against orders to scrap the project. In 1941, it was one of the fastest operational aircraft in the world.Bowman 2005, p. 21. Originally conceived as an unarmed fast bomber, the Mosquito's use evolved during the war into many roles, including low- to medium-altitude daytime
tactical bomber 250px, Bombing exercises conducted by South Korean McDonnell Douglas F-4 Phantom II, F-4s Tactical bombing is aerial bombing aimed at targets of immediate military value, such as combatants, Military base, military installations, or Military tec ...
, high-altitude
night bomber Image:Firebombing of Tokyo.jpg, 250px, Bombing of Tokyo by Boeing B-29 Superfortresses with firebombing, firebombs on the night of May 26, 1945. A night bomber is a bomber Fixed-wing aircraft, aircraft intended specifically for carrying out bombin ...
,
pathfinder Pathfinder may refer to: Computing * Path Finder, a Macintosh file browser * ''Pathfinder'' (website) * Pathfinder networks, a psychometric scaling method * Java Pathfinder, a software testing tool * Pathfinder (library science), a subject bib ...
,
day The word day has a number of meanings, depending on the context it is used such as of astronomy, physics, and various calendar systems. As a term in physics and astronomy it is approximately the period during which the Earth completes one ro ...
or
night fighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to ...
,
fighter-bomber A fighter-bomber is a fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that ...
, intruder, maritime strike, and
photo-reconnaissance Aerial reconnaissance is reconnaissance for a military or Strategy, strategic purpose that is conducted using reconnaissance aircraft. The role of reconnaissance can fulfil a variety of requirements including Artillery observer, artillery spottin ...
aircraft. It was also used by the
British Overseas Airways Corporation British may refer to: Peoples, culture, and language * British people The British people, or Britons, are the citizens of the United Kingdom of Great Britain and Northern Ireland The United Kingdom of Great Britain and Northern Ir ...
as a fast transport to carry small, high-value cargo to and from neutral countries through
enemy-controlled airspace
enemy-controlled airspace
. The crew of two, pilot and navigator, sat side by side. A single passenger could ride in the aircraft's bomb bay when necessary. The Mosquito FBVI was often flown in special raids, such as
Operation Jericho Operation Jericho (Ramrod 564) on 18 February 1944 during the Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a global war that lasted from 1939 to 1945. It involved the vast majority of ...
(an attack on Amiens Prison in early 1944), and precision attacks against military intelligence, security, and police facilities (such as
Gestapo The (), abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full version of the word or phrase; for ...

Gestapo
headquarters). On 30 January 1943, the 10th anniversary of the
Nazis Nazism (), officially National Socialism (german: Nationalsozialismus; ), is the ideology and practices associated with Adolf Hitler and the Nazi Party (german: link=no, Nationalsozialistische Deutsche Arbeiterpartei, NSDAP, or National Socia ...
' seizure of power, a morning Mosquito attack knocked out the main Berlin broadcasting station while
Hermann Göring Hermann Wilhelm Göring (or Goering; ; 12 January 1893 – 15 October 1946) was a German politician, military leader and convicted war criminal. He was one of the most powerful figures in the Nazi Party The Nazi Party, officially ...

Hermann Göring
was speaking, taking his speech off the air. The Mosquito flew with the
Royal Air Force The Royal Air Force (RAF) is the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a synonym for th ...
(RAF) and other air forces in the
European European, or Europeans, may refer to: In general * ''European'', an adjective referring to something of, from, or related to Europe ** Ethnic groups in Europe ** Demographics of Europe ** European cuisine, the cuisines of Europe and other Western ...
,
Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...
, and
Italian Italian may refer to: * Anything of, from, or related to the country and nation of Italy ** Italians, an ethnic group or simply a citizen of the Italian Republic ** Italian language, a Romance language *** Regional Italian, regional variants of the ...
theatres. The Mosquito was also operated by the RAF in the Southeast Asian theatre and by the
Royal Australian Air Force "Through Adversity to the Stars" , colours = , colours_label = , march = Royal Australian Air Force March Past (Eagles of Australia) , mascot = , anni ...
based in and
Borneo Borneo (; id, Kalimantan) is the third-List of islands by area, largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Is ...

Borneo
during the
Pacific War The Pacific War, sometimes called the Asia–Pacific War, was the theater Theatre or theater is a collaborative form of performing art that uses live performers, usually actors or actresses, to present the experience of a real or i ...
. During the 1950s, the RAF replaced the Mosquito with the jet-powered
English Electric Canberra The English Electric Canberra is a British first-generation, jet-powered medium bomber A medium bomber is a military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily inte ...

English Electric Canberra
.


Development

By the early to mid-1930s,
de Havilland The de Havilland Aircraft Company Limited () was a British aviation manufacturer established in late 1920 by Geoffrey de Havilland at Stag Lane Aerodrome Stag Lane Aerodrome was a private aerodrome between 1915 and 1933 in Edgware Edgwa ...
had built a reputation for innovative high-speed aircraft with the DH.88 Comet racer. Later, the DH.91 Albatross airliner pioneered the composite wood construction used for the Mosquito. The 22-passenger Albatross could cruise at at , faster than the
Handley Page H.P.42 The Handley Page H.P.42 and H.P.45 were four-engine biplane A biplane is a fixed-wing aircraft with two main wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have stre ...
and other biplanes it was replacing. The wooden
monocoque Monocoque (), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, a ...
construction not only saved weight and compensated for the low power of the
de Havilland Gipsy Twelve The de Havilland Gipsy Twelve was a British aero engine developed by the de Havilland Engine Company in 1937. Approximately 95 were manufactured. It was known as the Gipsy King in Royal Air Force service. Applications * de Havilland Albatross ...
engines used by this aircraft, but also simplified production and reduced construction time.Bowman 2005, p. 9.


Air Ministry bomber requirements and concepts

On 8 September 1936, the British Air Ministry issued
Specification A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard A technical standard is an established norm (social), norm or require ...
P.13/36, which called for a twin-engined, medium bomber capable of carrying a bomb load of for with a maximum speed of at ; a maximum bomb load of that could be carried over shorter ranges was also specified.Sharp and Bowyer 1971, p. 30. Aviation firms entered heavy designs with new high-powered engines and multiple defensive turrets, leading to the production of the
Avro Manchester The Avro 679 Manchester was a British twin-engine heavy bomber Heavy bombers are bomber Fixed-wing aircraft, aircraft capable of delivering the largest payload of air-to-ground weaponry (usually Aerial bomb, bombs) and longest range (aeronauti ...

Avro Manchester
and
Handley Page Halifax The Handley Page Halifax is a British Royal Air Force The Royal Air Force (RAF) is the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. T ...

Handley Page Halifax
.Sharp and Bowyer 1971, p. 31. In May 1937, as a comparison to P.13/36,
George Volkert George Rudolph Volkert CBE FRAeS (4 July 1891 – 16 May 1978) was a British aircraft designer. Early life He was born in Fulham Fulham () is an area of the London Borough of Hammersmith and Fulham The London Borough of Hammersmith and ...
, the chief designer of
Handley Page Handley Page Limited was a United Kingdom, British aerospace manufacturer. Founded by Frederick Handley Page (later Sir Frederick) in 1909, it was the United Kingdom's first publicly traded aircraft manufacturing company. It went into voluntar ...

Handley Page
, put forward the concept of a fast, unarmed bomber. In 20 pages, Volkert planned an aerodynamically clean, medium bomber to carry of bombs at a cruising speed of . Support existed in the RAF and Air Ministry; Captain R. N. Liptrot, Research Director Aircraft 3, appraised Volkert's design, calculating that its top speed would exceed that of the new
Supermarine Spitfire The Supermarine Spitfire is a British single-seat fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) ...

Supermarine Spitfire
, but counter-arguments held that although such a design had merit, it would not necessarily be faster than enemy fighters for long. The ministry was also considering using non
strategic Strategy (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...
materials for aircraft production, which, in 1938, had led to specification B.9/38 and the
Armstrong Whitworth Albemarle The Armstrong Whitworth A.W.41 Albemarle was a twin-engine transport aircraft developed by the British aircraft manufacturer Armstrong Whitworth and primarily produced by A.W. Hawksley Ltd, a subsidiary of the Gloster Aircraft Company. It w ...
medium bomber, largely constructed from spruce and plywood attached to a steel-tube frame. The idea of a small, fast bomber gained support at a much earlier stage than is sometimes acknowledged, though the Air Ministry likely envisaged it using light alloy components.


Inception of the de Havilland 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.Birtles 2017, ch. 2. Furthermore, adapting the Albatross principles could save time. In April 1938, performance estimates were produced for a twin
Rolls-Royce Merlin The Rolls-Royce Merlin is a British liquid-cooled Liquid cooling refers to cooling by means of the convection or circulation (fluid dynamics), circulation of a liquid. Examples of liquid cooling technologies include: * Water cooling * Coo ...

Rolls-Royce Merlin
-powered DH.91, with the
Bristol Hercules The Bristol Hercules was a 14-cylinder two-row radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance, a directional coordinate ...
(
radial engine The radial engine is a reciprocating engine, reciprocating type internal combustion engine, internal combustion engine configuration in which the cylinder (engine), cylinders "radiate" outward from a central crankcase like the spokes of a wheel. ...

radial engine
) and
Napier Sabre The Napier Sabre is a British H-24-cylinder, liquid-cooled Liquid cooling refers to cooling by means of the convection or circulation (fluid dynamics), circulation of a liquid. Examples of liquid cooling technologies include: * Water cooli ...

Napier Sabre
(
H-engine An H engine is a piston engine A reciprocating engine, also often known as a piston engine, is typically a heat engine In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temp ...

H-engine
) as alternatives. On 7 July 1938, de Havilland wrote to Air Marshal
Wilfrid Freeman Air Chief Marshal Sir Wilfrid Rhodes Freeman, 1st Baronet, (18 July 1888 – 15 May 1953) was one of the most important influences on the rearmament of the Royal Air Force (RAF) in the years up to and including the Second World War. RAF career H ...
, 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." Although inferior in
tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opposite of compression) * Tension (geology), a stress which stretches rocks in two opposite directions * Voltage or elect ...
, the
strength-to-weight ratio The specific strength is a material's strength (force per unit area at failure) divided by its density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The sym ...
of wood is equal to or better than light alloys or steel, hence this approach was feasible. 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 carrying a 4,000 lb bomb load, with a maximum of at , and a cruising speed of at . De Havilland believed that a compromise, including eliminating surplus equipment, would improve matters. On 4 October 1938, de Havilland projected the performance of another design based on the Albatross, powered by two Merlin 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 , it would have a top speed of and cruising speed of at . Still believing this could be improved, and after examining more concepts based on the Albatross and the new all-metal 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. The new design would be faster than foreseeable enemy
fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet e ...

fighter aircraft
, and could dispense with a defensive armament, which would slow it and make interception or losses to antiaircraft guns more likely. Instead, high speed and good manoeuverability would make evading fighters and ground fire easier. 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 A ''Schnellbomber'' (German; literally "fast bomber") is a bomber A bomber is a combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying ...
''.Batchelor and Lowe 2008, p. 5. 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.Batchelor and Lowe 2008, p. 6. 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.Buttler 2004, p. 78. One design, completed on 6 September, was for an aircraft powered by a single Napier Sabre, with a wingspan of and capable of carrying a bomb load . 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." By 4 October, work had progressed to a twin-engined light bomber with a wingspan of and powered by Merlin or Griffon engines, the Merlin favoured because of availability. On 7 October 1939, a month into the war, the nucleus of a design team under Eric Bishop moved to the security and secrecy of
Salisbury Hall The de Havilland Aircraft Museum, formerly the de Havilland Aircraft Heritage Centre, is a volunteer-run aviation museum in London Colney, Hertfordshire Hertfordshire (; often abbreviated Herts) is one of the home counties in southern En ...

Salisbury Hall
to work on what was later known as the DH.98.Sharp and Bowyer 1971, p. 34. For more versatility, Bishop made provision for four 20 mm cannon in the forward half of the
bomb bay An Avro Vulcan showing its bomb bay open The bomb bay or weapons bay on some military aircraft A military aircraft is any fixed-wing or rotary-wing aircraft An aircraft is a vehicle that is able to flight, fly by gaining support fr ...
, under the cockpit, firing via blast tubes and troughs under the fuselage.Bowman 2005, p. 11. 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. With the outbreak of war, the ministry became more receptive, but was still skeptical about an unarmed bomber. They thought the Germans would produce fighters that were faster than had been expected. and suggested the incorporation of two forward- and two rear-firing machine guns for defence.Bowman 2005, p. 10. The ministry also opposed a two-man bomber, wanting at least a third crewman to reduce the work of the others on long flights. The Air Council added further requirements such as remotely controlled guns, a top speed of at 15,000 ft on two-thirds engine power, and a range of with a 4,000-lb bomb load. 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. On 12 November, at a meeting considering fast-bomber ideas put forward by de Havilland,
Blackburn Blackburn is a large industrial town located in Lancashire, England, north of the West Pennine Moors on the southern edge of the River Ribble, Ribble Valley, east of Preston, Lancashire, Preston and boxing the compass, NNW of Manchester. Bla ...
, and
Bristol Bristol () is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routle ...
, 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 The Rolls-Royce Griffon is a British 37-litre (2,240 cubic inch, cu in) Engine displacement, capacity, 60-degree V12 engine, V-12, liquid-cooled Aircraft engine, aero engine designed and built by Rolls-Royce Limited. In keeping with company ...
and the
Napier Sabre The Napier Sabre is a British H-24-cylinder, liquid-cooled Liquid cooling refers to cooling by means of the convection or circulation (fluid dynamics), circulation of a liquid. Examples of liquid cooling technologies include: * Water cooli ...

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 at 18,000 ft. On 12 December, the Vice-Chief of the Air Staff, Director General of Research and Development, and the
Air Officer Commanding-in-Chief File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together compose about 0.043391% of the atmosphere (0.04402961% at April 2019 concentration ). Number ...
(AOC-in-C) of
RAF Bomber Command RAF Bomber Command controlled the Royal Air Force The Royal Air Force (RAF) is the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The G ...
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 The F24 camera is a 1920s British camera used for aerial reconnaissance Aerial reconnaissance is reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information abou ...
s.Bowman 2005, p. 12. 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.Buttler 2004, p. 80. 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 Rolls-Royce RM3SM (an early designation for the Merlin 21) with ducted radiators, capable of carrying a bomb load. The aircraft was to have a speed of at and a cruising speed of at with a range of at on full tanks. Maximum service ceiling was to be . On 1 March 1940, Air Marshal
Roderic Hill Air Chief Marshal Sir Roderic Maxwell Hill, (1 March 1894 – 6 October 1954) was a senior Royal Air Force commander during the Second World War. He was a former Rector of Imperial College and Vice-Chancellor of London University. The Department ...
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 factory serial ''E-0234''. In May 1940, specification F.21/40 was issued, calling for a long-range fighter armed with four 20 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, that this prototype, given the military serial number ''W4052'', was decided to carry airborne interception (AI) Mk IV equipment as a day and night fighter. By June 1940, the DH.98 had been named "Mosquito". 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.


Project Mosquito

With design of the DH.98 started, mock-ups were built, the most detailed at Salisbury Hall, where ''E-0234'' was later constructed. Initially, the concept was for the crew to be enclosed in the fuselage behind a transparent nose (similar to the Bristol Blenheim or
Heinkel He 111 The Heinkel He 111 was a German bomber aircraft designed by Siegfried and Walter Günter at Heinkel Flugzeugwerke in 1934. Through development it was described as a "wolf in sheep's clothing A wolf in sheep's clothing is an idiom of Biblical ...

Heinkel He 111
H), but this was quickly altered to a more solid nose with a conventional canopy. Work was cancelled again after the
Battle of Dunkirk The Battle of Dunkirk (french: Bataille de Dunkerque, link=no) was fought in Dunkirk (Dunkerque), France France (), officially the French Republic (french: link=no, République française), is a transcontinental country Thi ...
, when
Lord Beaverbrook William Maxwell Aitken, 1st Baron Beaverbrook, Privy Council of the United Kingdom, PC, Order of New Brunswick, ONB (25 May 1879 – 9 June 1964), generally known as Lord Beaverbrook, was a Canadian-British newspaper publisher and backstage poli ...
, as
Minister of Aircraft Production The Minister of Aircraft Production was, from 1940 to 1945, the British government minister at the Ministry of Aircraft Production, one of the specialised supply ministries set up by the British Government The Government of the United King ...
, decided no production capacity remained for aircraft like the DH.98, which was not expected to be in service until early 1942. Beaverbrook told Air Vice-Marshal Freeman that work on the project should stop, but he did not issue a specific instruction, and Freeman ignored the request. In June 1940, however, Lord Beaverbrook and the Air Staff ordered that production should concentrate on five existing types, namely the
Supermarine Spitfire The Supermarine Spitfire is a British single-seat fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) ...

Supermarine Spitfire
,
Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) is a ...

Hawker Hurricane
fighter,
Vickers Wellington The Vickers Wellington was a British twin-engined, long-range medium bomber. It was designed during the mid-1930s at Brooklands in Weybridge, Surrey. Led by Vickers-Armstrongs' chief designer Rex Pierson; a key feature of the aircraft is its ge ...

Vickers Wellington
,
Armstrong-Whitworth Whitley The Armstrong Whitworth A.W.38 Whitley was one of three United Kingdom, British twin-engined, front line bomber types that were in service with the Royal Air Force (RAF) at the outbreak of the World War II, Second World War. Alongside the Vicker ...
, and
Bristol Blenheim The Bristol Blenheim is a British light bomber 1943. A twin-engine Lockheed Hudson of No. 2 Squadron RAAF. Its crew and ground staff pose for the photographer, prior to loading the Hudson with its bomb load in the foreground. A light bombe ...

Bristol Blenheim
bombers. Work on the DH.98 prototype stopped. Apparently, the project shut down when the design team were denied materials for the prototype.Jackson 2003, p. 7. The Mosquito was only reinstated as a priority in July 1940, after de Havilland's general manager, L.C.L. Murray, promised Lord Beaverbrook 50 Mosquitos by December 1941. This was only after Beaverbrook was satisfied that Mosquito production would not hinder de Havilland's primary work of producing
Tiger Moth The de Havilland DH.82 Tiger Moth is a 1930s British biplane designed by Geoffrey de Havilland and built by the de Havilland, de Havilland Aircraft Company. It was operated by the Royal Air Force (RAF) and other operators as a primary traine ...

Tiger Moth
and
Airspeed Oxford The Airspeed AS.10 Oxford was a twin-engine monoplane aircraft developed and manufactured by Airspeed. It saw widespread use for training British Commonwealth British may refer to: Peoples, culture, and language * British people The ...
trainers, repairing
Hurricanes A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation Atmospheric circulation is the large-scale movement of air File:Atmosphere gas proportions.svg ...
, and manufacturing Merlin engines under licence. In promising Beaverbrook such a number by the end of 1941, de Havilland was taking a gamble, because they were unlikely to be built in such a limited time. As it transpired, only 20 aircraft were built in 1941, but the other 30 were delivered by mid-March 1942. During the
Battle of Britain The Battle of Britain (german: die Luftschlacht um England, "the Air Battle for England") was a military campaign A military campaign is large-scale long-duration significant military strategy Military strategy is a set of ideas implemented ...

Battle of Britain
, interruptions to production due to air raid warnings caused nearly a third of de Havilland's factory time to be lost. Nevertheless, work on the prototype went ahead quickly at Salisbury Hall since ''E-0234'' was completed by November 1940. In the aftermath of the Battle of Britain, the original order was changed to 20 bomber variants and 30 fighters. Whether the fighter version should have dual or single controls, or should carry a turret, was still uncertain, so three prototypes were built: ''W4052'', ''W4053'', and ''W4073''. The second and third, both turret armed, were later disarmed, to become the prototypes for the T.III trainer. This caused some delays, since half-built wing components had to be strengthened for the required higher combat loading. The nose sections also had to be changed from a design with a clear
perspex Poly(methyl methacrylate) (PMMA), also known as acrylic, acrylic glass, or plexiglass, as well as by the trade names Crylux, Plexiglas, Acrylite, Astariglas, Lucite, Perclax, and Perspex, among several others ( see below), is a transparent th ...
bomb-aimer's position, to one with a solid nose housing four .303 machine guns and their ammunition.


Prototypes and test flights

On 3 November 1940, the prototype aircraft, painted in "prototype yellow" and still coded ''E-0234'', was dismantled, transported by road to Hatfield and placed in a small, blast-proof assembly building. Two Merlin 21 two-speed, single-stage supercharged engines were installed, driving three-bladed de Havilland Hydromatic constant-speed controllable-pitch propellers. Engine runs were made on 19 November. On 24 November, taxiing trials were carried out by Geoffrey de Havilland Jr., the de Havilland
test pilot A test pilot is an aircraft pilot An aircraft pilot or aviator is a person who controls the flight of an aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Lat ...
. On 25 November, the aircraft made its first flight, piloted by de Havilland Jr., accompanied by John E. Walker, the chief engine installation designer. For this maiden flight, ''E-0234'', weighing , took off from the grass airstrip at the Hatfield site. The takeoff was reported as "straightforward and easy" and the undercarriage was not retracted until a considerable altitude was attained.Thirsk 2006, p. 25. The aircraft reached , with the only problem being the undercarriage doors – which were operated by
bungee cord Bungee cords equipped with metal hooks A bungee cord (sometimes spelled bungie; also known as a shock cord) is an elastic cord composed of one or more elastic strands forming a core, usually covered in a woven cotton or polypropylene Polypropyl ...
s attached to the main undercarriage legs – that remained open by some at that speed. This problem persisted for some time. The left wing of ''E-0234'' also had a tendency to drag to port slightly, so a
rigging Rigging comprises the system of ropes, cables and chains, which support a sailing ship A sailing ship is a sea-going vessel that uses sails mounted on Mast (sailing), masts to harness the power of wind and propel the vessel. There is a v ...
adjustment, i.e., a slight change in the angle of the wing, was carried out before further flights.Bowman 2005, p. 18. On 5 December 1940, the prototype, with the military serial number '' W4050'', experienced tail buffeting at speeds between . The pilot noticed this most in the control column, with handling becoming more difficult. During testing on 10 December, wool tufts were attached to suspect areas to investigate the direction of airflow. The conclusion was that the airflow separating from the rear section of the inner engine
nacelle A nacelle ( ) is a "streamlined body sized according to what it contains", such as an engine An engine or motor is a machine A machine is any physical system with ordered structural and functional properties. It may represent human-m ...

nacelle
s was disturbed, leading to a localised
stall Stall may refer to: Enclosures * Animal stall, a small enclosure, as for market goods, or for an animal * Restroom stall, an enclosure providing privacy to the user of a single toilet in a public restroom * Market stall, a makeshift or mobile struc ...
and the disturbed airflow was striking the tailplane, causing buffeting. To smooth the air flow and deflect it from forcefully striking the tailplane, nonretractable fitted to the inner engine nacelles and to the leading edge of the tailplane were tested. These slots and wing-root fairings fitted to the forward fuselage and leading edge of the radiator intakes, stopped some of the vibration experienced, but did not cure the tailplane buffeting. In February 1941, buffeting was eliminated by incorporating triangular fillets on the trailing edge of the wings and lengthening the nacelles, the trailing edge of which curved up to fair into the fillet some behind the wing's trailing edge; this meant the flaps had to be divided into inboard and outboard sections.Bowman 2005, p. 19. With the buffeting problems largely resolved, John Cunningham flew ''W4050'' on 9 February 1941. He was greatly impressed by the "lightness of the controls and generally pleasant handling characteristics". Cunningham concluded that when the type was fitted with AI equipment, it might replace the
Bristol Beaufighter Bristol () is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routle ...

Bristol Beaufighter
night fighter. During its trials on 16 January 1941, ''W4050'' outpaced a Spitfire at . The original estimates were that as the Mosquito prototype had twice the surface area and over twice the weight of the Spitfire Mk II, but also with twice its power, the Mosquito would end up being faster. Over the next few months, ''W4050'' surpassed this estimate, easily beating the Spitfire Mk II in testing at
RAF Boscombe Down MoD Boscombe Down ' is the home of a military aircraft testing site, located near the town of Amesbury in Wiltshire, England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders ...
in February 1941, reaching a top speed of at altitude, compared to a top speed of at for the Spitfire. On 19 February, official trials began at the
Aeroplane and Armament Experimental Establishment The Aeroplane and Armament Experimental Establishment (A&AEE) was a research facility for British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, ...
(AAEE) based at
Boscombe Down MoD Boscombe Down ' is the home of a military aircraft A military aircraft is any fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) is a fixed- ...
, although the de Havilland representative was surprised by a delay in starting the tests.Sharp and Bowyer 1971, pp. 44–45. On 24 February, as ''W4050'' taxied across the rough airfield, the tailwheel jammed leading to the fuselage fracturing. Repairs were made by early March, using part of the fuselage of the photo-reconnaissance prototype ''W4051''. In spite of this setback, the ''Initial Handling Report 767'' issued by the AAEE stated, "The aeroplane is pleasant to fly ... aileron control light and effective..." The maximum speed reached was at , with an estimated maximum ceiling of and a maximum rate of climb of at . ''W4050'' continued to be used for various test programmes, as the experimental "workhorse" for the Mosquito family. In late October 1941, it returned to the factory to be fitted with , the first production Merlins fitted with a two-speed, two-stage supercharger. The first flight with the new engines was on 20 June 1942. ''W4050'' recorded a maximum speed of at (fitted with straight-through air intakes with snow guards, engines in full supercharger gear) and at without snow guards.Thirsk 2006, p. 34. In October 1942, in connection with development work on the NF Mk XV, ''W4050'' was fitted with extended wingtips, increasing the span to , first flying in this configuration on 8 December. Fitted with high-altitude-rated, two-stage, two-speed Merlin 77s, it reached in December 1943. Soon after these flights, ''W4050'' was grounded and scheduled to be scrapped, but instead served as an instructional airframe at Hatfield. In September 1958, ''W4050'' was returned to the Salisbury Hall hangar where it was built, restored to its original configuration, and became one of the primary exhibits of the
de Havilland Aircraft Heritage Centre The de Havilland Aircraft Museum, formerly the de Havilland Aircraft Heritage Centre, is a volunteer-run aviation museum in London Colney, Hertfordshire, England. The collection is built around the definitive prototype and restoration shops f ...
. ''W4051'', which was designed from the outset to be the prototype for the photo-reconnaissance versions of the Mosquito, was slated to make its first flight in early 1941. However, the fuselage fracture in ''W4050'' meant that ''W4051's'' fuselage was used as a replacement; ''W4051'' was then rebuilt using a production standard fuselage and first flew on 10 June 1941. This prototype continued to use the short engine nacelles, single-piece trailing-edge flaps, and the "No. 1" tailplane used by ''W4050'', but had production-standard wings and became the only Mosquito prototype to fly operationally.Thirsk 2006, p. 269. Construction of the fighter prototype, ''W4052'', was also carried out at the secret Salisbury Hall facility. It was powered by Merlin 21s, and had an altered canopy structure with a flat, bullet-proof windscreen; the solid nose had mounted four .303 British Browning machine guns and their ammunition boxes, accessible by a large, sideways hinged panel. Four 20-mm Hispano Mk II cannon were housed in a compartment under the cockpit floor with the breeches projecting into the bomb bay and the automatic bomb bay doors were replaced by manually operated bay doors, which incorporated cartridge ejector chutes.Thirsk 2006, pp. 125, 134. As a day and night fighter, prototype ''W4052'' was equipped with AI Mk IV equipment, complete with an "arrowhead" transmission aerial mounted between the central Brownings and receiving aerials through the outer wing tips, and it was painted in black RDM2a "Special Night" finish. It was also the first prototype constructed with the extended engine nacelles. ''W4052'' was later tested with other modifications, including bomb racks, drop tanks,
barrage balloon A barrage balloon is a large uncrewed tethered kite balloon . This sparless, ram-air inflated kite, has a complex bridle formed of many strings attached to the face of the wing. A kite is a tethered heavier than air flight, heavier-than-air o ...
cable cutters in the leading edge of the wings, Hamilton airscrews and braking propellers, and drooping aileron systems that enabled steep approaches and a larger rudder tab. The prototype continued to serve as a test machine until it was scrapped on 28 January 1946. ''4055'' flew the first operational Mosquito flight on 17 September 1941. During flight testing, the Mosquito prototypes were modified to test a number of configurations. ''W4050'' was fitted with a turret behind the cockpit for drag tests, after which the idea was abandoned in July 1941. ''W4052'' had the first version of the Youngman Frill airbrake fitted to the fighter prototype. The frill was mounted around the fuselage behind the wing and was opened by bellows and
venturi effect The Venturi effect is the reduction in fluid pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''ph ...
to provide rapid deceleration during interceptions and was tested between January and August 1942, but was also abandoned when lowering the undercarriage was found to have the same effect with less buffeting.


Production plans and American interest

The Air Ministry authorised mass production plans on 21 June 1941, by which time the Mosquito had become one of the world's fastest operational aircraft. It ordered 19 photo-reconnaissance (PR) models and 176 fighters. A further 50 were unspecified; in July 1941, these were confirmed to be unarmed fast bombers. By the end of January 1942, contracts had been awarded for 1,378 Mosquitos of all variants, including 20 T.III trainers and 334 FB.VI bombers. Another 400 were to be built by
de Havilland Canada De Havilland Aircraft of Canada Ltd. is an aircraft manufacturer with facilities based in the Downsview, Toronto, Downsview area of Toronto, Ontario, Canada. The original home of de Havilland Canada was the home of the Canadian Air and Space Mus ...
.Bowman 2005, p. 24. On 20 April 1941, ''W4050'' was demonstrated to Lord Beaverbrook, the
Minister of Aircraft Production The Minister of Aircraft Production was, from 1940 to 1945, the British government minister at the Ministry of Aircraft Production, one of the specialised supply ministries set up by the British Government The Government of the United King ...
. The Mosquito made a series of flights, including one rolling climb on one engine. Also present were US General
Henry H. Arnold Henry Harley Arnold (June 25, 1886 – January 15, 1950) was an American general officer A general officer is an Officer (armed forces), officer of highest military ranks, high rank in the army, armies, and in some nations' air force ...

Henry H. Arnold
and his aide
Major Major is a military rank Military ranks are a system of hierarchical A hierarchy (from the Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) in which the items are repre ...

Major
Elwood Quesada, who wrote "I ... recall the first time I saw the Mosquito as being impressed by its performance, which we were aware of. We were impressed by the appearance of the airplane that looks fast usually is fast, and the Mosquito was, by the standards of the time, an extremely well-streamlined airplane, and it was highly regarded, highly respected." The trials set up future production plans between Britain,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
, and
Canada Canada is a country in the northern part of North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, ...

Canada
. Six days later, Arnold returned to America with a full set of manufacturer's drawings. As a result of his report, five companies (Beech,
Curtiss-Wright The Curtiss-Wright Corporation is an American, global diversified product manufacturer and service provider, incorporated in Delaware Delaware ( ) is a state in the Mid-AtlanticMid-Atlantic or Mid Atlantic can refer to: *The middle of ...
,
FairchildFairchild may refer to: Organizations * Fairchild Aerial Surveys, operated in cooperation with a subsidiary of Fairey Aviation Company * Fairchild Camera and Instrument * List of Sherman Fairchild companies, "Fairchild" companies * Fairchild Fashi ...
, Fleetwings, and Hughes) were asked to evaluate the de Havilland data. The report by Beech Aircraft summed up the general view: "It appears as though this airplane has sacrificed serviceability, structural strength, ease of construction and flying characteristics in an attempt to use construction material which is not suitable for the manufacture of efficient airplanes." The Americans did not pursue the proposal for licensed production, the consensus arguing that the
Lockheed P-38 Lightning The Lockheed P-38 Lightning is an American single-seated, twin piston-engined fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or a ...

Lockheed P-38 Lightning
could fulfill the same duties. However, Arnold urged the
United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare Aerial warfare is the use of military aircraft A military aircraft is any fixed-wing A fixed-wing aircraft is a heavier-than-air flying machi ...
(USAAF) to evaluate the design even if they would not adopt it. On 12 December 1941, after the
attack on Pearl Harbor The Attack on Pearl HarborAlso known as the Battle of Pearl Harbor was a surprise military strike In the United States Armed Forces, military of the United States, strikes and raids are a group of military operations that, alongside quite ...

attack on Pearl Harbor
, the USAAF requested one airframe for this purpose.Bowman 2005, p. 20.


Design and manufacture


Overview

While timber construction was considered outmoded by some, de Havilland claimed that their successes with techniques used for the DH 91 Albatross could lead to a fast, light bomber using monocoque-sandwich shell construction. Arguments in favour of this included speed of prototyping, rapid development, minimisation of jig-building time, and employment of a separate category of workforce. The ply-balsa-ply monocoque fuselage and one-piece wings with doped fabric covering would give excellent aerodynamic performance and low weight, combined with strength and stiffness. At the same time, the design team had to fight conservative Air Ministry views on defensive armament. Guns and gun turrets, favoured by the ministry, would impair the aircraft's aerodynamic properties and reduce speed and manoeuvrability, in the opinion of the designers. Whilst submitting these arguments, Geoffrey de Havilland funded his private venture until a very late stage. The project was a success beyond all expectations. The initial bomber and photo-reconnaissance versions were extremely fast, whilst the armament of subsequent variants might be regarded as primarily offensive. The most-produced variant,
designated Designation (from Latin ''designatio'') is the process of determining an incumbent's successor. A candidate that won an election for example, is the ''designated'' holder of the office the candidate has been elected to, up until the candidate's ina ...
the FB Mk VI (Fighter-bomber Mark 6), was powered by two Merlin Mk 23 or Mk 25 engines driving three-bladed de Havilland hydromatic propellers. The typical fixed armament for an FB Mk VI was four Browning .303 machine guns and four 20-mm Hispano cannons, while the offensive load consisted of up to of bombs, or eight RP-3 unguided rockets.


Performance

The design was noted for light and effective control surfaces that provided good manoeuvrability, but required that the rudder not be used aggressively at high speeds. Poor aileron control at low speeds when landing and taking off was also a problem for inexperienced crews. For flying at low speeds, the flaps had to be set at 15°, speed reduced to , and
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is the number of turns in one minute The minute is a unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the ...
set to 2,650. The speed could be reduced to an acceptable for low-speed flying. For cruising, the optimum speed for obtaining maximum range was at weight. The Mosquito had a low stalling speed of with undercarriage and flaps raised. When both were lowered, the stalling speed decreased from . Stall speed at normal approach angle and conditions was . Warning of the stall was given by buffeting and would occur before stall was reached. The conditions and impact of the stall were not severe. The wing did not drop unless the control column was pulled back. The nose drooped gently and recovery was easy.Air Ministry 1945, p. 29. (FB 6 notes). Early on in the Mosquito's operational life, the intake shrouds that were to cool the exhausts on production aircraft overheated. Flame dampers prevented exhaust glow on night operations, but they had an effect on performance. Multiple ejector and open-ended exhaust stubs helped solve the problem and were used in the PR.VIII, B.IX, and B.XVI variants. This increased speed performance in the B.IX alone by .


Fuselage

The oval-section fuselage was a frameless monocoque shell built in two vertically separate halves formed over a
mahogany Mahogany is a straight-grained, reddish-brown timber Lumber, also known as timber, is wood Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant wit ...
or
concrete Concrete is a composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material Material is a substance Substance may refer to: * Substance (Jainism), a ter ...

concrete
mould. Pressure was applied with
band clamp A band clamp is a generic term for a holding device usually consisting of a strap of metal or cloth formed into a loop, with a mechanism to forcibly adjust the diameter, thereby exerting a squeezing force on an object within the loop. One type of ...

band clamp
s. The shell sandwich skins comprised birch three-ply outers, with cores of Ecuadorean
balsa ''Ochroma pyramidale'', commonly known as the balsa tree, is a large, fast-growing tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. ...

balsa
. In many generally smaller but vital areas, such as around apertures and attachment zones, stronger timbers, including aircraft-quality spruce, replaced the balsa core. The main areas of the sandwich skin were only thick.Aviation, May and June 1944, Vol. 43, Nos. 5 & 6, McGraw Hill, New York; Design Analysis No 6, DeHavilland Mosquito, Online PDF courtesy of J.L. McClellan, 2005
accessed 23 August 2017
/ref> Together with various forms of wood reinforcement, often of laminated construction, the sandwich skin gave great stiffness and torsional resistance. The separate fuselage halves speeded construction, permitting access by personnel working in parallel with others, as the work progressed.Bowman 2005, p. 15. Work on the separate half-fuselages included installation of control mechanisms and cabling. Screwed inserts into the inner skins that would be under stress in service were reinforced using round shear plates made from a fabric-Bakelite composite. Transverse bulkheads were also compositely built-up with several species of timber, plywood, and balsa. Seven vertically halved bulkheads were installed within each moulded fuselage shell before the main "boxing up" operation. Bulkhead number seven was especially strongly built, since it carried the fitments and transmitted the aerodynamic loadings for the tailplane and rudder. The fuselage had a large ventral section cut-out, strongly reinforced, that allowed the fuselage to be lowered onto the wing centre-section at a later stage of assembly.Aviation, 1944 p. 6. For early production aircraft, the structural assembly adhesive was
casein Casein ( , from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in rel ...

casein
-based. At a later stage, this was replaced by " Aerolite", a synthetic
urea-formaldehyde Urea-formaldehyde (UF), also known as urea-methanal, so named for its common synthesis pathway and overall structure, is a nontransparent thermosetting resin In polymer chemistry and materials science The interdisciplinary field of materi ...
type, which was more durable. To provide for the edge joints for the fuselage halves, zones near the outer edges of the shells had their balsa sandwich cores replaced by much stronger inner laminations of birch plywood. For the bonding together of the two halves ("boxing up"), a longitudinal cut was machined into these edges. The profile of this cut was a form of V-groove. Part of the edge bonding process also included adding further longitudinal plywood lap strips on the outside of the shells. The half bulkheads of each shell were bonded to their corresponding pair in a similar way. Two laminated wooden clamps were used in the after portion of the fuselage to provide supports during this complex gluing work. The resulting large structural components had to be kept completely still and held in the correct environment until the glue cured.Jackson 2003, p. 8. For finishing, a covering of doped madapollam (a fine, plain-woven cotton) fabric was stretched tightly over the shell and several coats of red, followed by silver dope, were added, followed by the final camouflage paint.


Wing

The all-wood wing pairs comprised a single structural unit throughout the wingspan, with no central longitudinal joint. Instead, the spars ran from wingtip to wingtip. There was a single continuous main spar and another continuous rear spar. Because of the combination of dihedral with the forward sweep of the trailing edges of the wings, this rear spar was one of the most complex units to laminate and to finish machining after the bonding and curing. It had to produce the correct 3D tilt in each of two planes. Also, it was designed and made to taper from the wing roots towards the wingtips. Both principal spars were of ply box construction, using in general 0.25-in plywood webs with laminated spruce flanges, plus a number of additional reinforcements and special details. Spruce and plywood ribs were connected with gusset joints. Some heavy-duty ribs contained pieces of ash and walnut, as well as the special five ply that included veneers laid up at 45°. The upper skin construction was in two layers of 0.25-in five-ply birch, separated by Douglas fir stringers running in the span-wise direction. The wings were covered with madapollam fabric and doped in a similar manner to the fuselage. The wing was installed into the roots by means of four large attachment points.Batchelor and Lowe 2008, p. 7. The engine radiators were fitted in the inner wing, just outboard of the fuselage on either side. These gave less drag. The radiators themselves were split into three sections: an oil cooler section outboard, the middle section forming the coolant radiator and the inboard section serving the cabin heater.Jackson 2003, p. 87. The wing contained metal-framed and -skinned
ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude Attitude may refer to: Phil ...
, but the flaps were made of wood and were hydraulically controlled. The nacelles were mostly wood, although for strength, the engine mounts were all metal, as were the undercarriage parts.Jackson 2003, p. 9. Engine mounts of welded steel tube were added, along with simple landing gear oleos filled with rubber blocks. Wood was used to carry only in-plane loads, with metal fittings used for all triaxially loaded components such as landing gear, engine mounts, control-surface mounting brackets, and the wing-to-fuselage junction. The outer leading wing edge had to be brought further forward to accommodate this design. The main tail unit was all wood built. The control surfaces, the
rudder A rudder is a primary control surface used to steer a ship A ship is a large watercraft Watercraft, also known as water vessels or waterborne vessels, are vehicles A vehicle (from la, vehiculum) is a machine A machine is any ...

rudder
, and
elevator An elevator (North American English North American English (NAmE, NAE) is the most generalized variety (linguistics), variety of the English language as spoken in the United States and Canada. Because of their related histories and ...
were
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
-framed and fabric-covered. The total weight of metal castings and forgings used in the aircraft was only ."History of the de Havilland Mosquito."
Archived fro

''RAAF Museum Point Cook'', 2007. Retrieved: 13 August 2009.
In November 1944, several crashes occurred in the
Far East The Far East is a term to refer to the geographical regions that includes East and Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is the geographical United Nati ...

Far East
. At first, these were thought to be a result of wing-structure failures. The casein glue, it was said, cracked when exposed to extreme heat and/or monsoon conditions. This caused the upper surfaces to "lift" from the main spar. An investigating team led by Major
Hereward de Havilland Hereward de Havilland (2 December 1894 in Nuneaton, Warwickshire – 12 September 1976 in Australia) was a pioneer British aviator, test pilot and member of the de Havilland company. One of the three sons of Rev. Charles de Havilland, he was the ...
travelled to India and produced a report in early December 1944 stating, "the accidents were not caused by the deterioration of the glue, but by shrinkage of the airframe during the wet monsoon season". However, a later inquiry by Cabot & Myers firmly attributed the accidents to faulty manufacture and this was confirmed by a further investigation team by the Ministry of Aircraft Production at
Defford Defford is a small village in the county of Worcestershire Worcestershire ( , ; written abbreviation: Worcs) is a non-metropolitan administrative, ceremonial and historic county A county is a geographical region of a country used f ...
, which found faults in six Mosquito marks (all built at de Havilland's Hatfield and Leavesden plants). The defects were similar, and none of the aircraft had been exposed to monsoon conditions or termite attack. The investigators concluded that construction defects occurred at the two plants. They found that the "...standard of glueing...left much to be desired."Bowman 2005, pp. 15–16. Records at the time showed that accidents caused by "loss of control" were three times more frequent on Mosquitos than on any other type of aircraft. The Air Ministry forestalled any loss of confidence in the Mosquito by holding to Major de Havilland's initial investigation in India that the accidents were caused "largely by climate" To solve the problem of seepage into the interior, a strip of plywood was set along the span of the wing to seal the entire length of the skin joint.


Systems

The fuel systems gave the Mosquito good range and endurance, using up to nine fuel tanks. Two outer wing tanks each contained of fuel.Air Ministry 1945, p. 11. (FB 6 notes). These were complemented by two inner wing fuel tanks, each containing , located between the wing root and engine nacelle. In the central fuselage were twin fuel tanks mounted between bulkhead number two and three aft of the cockpit.Bowman 2005, p. 22. In the FB.VI, these tanks contained each, while in the B.IV and other unarmed Mosquitos each of the two centre tanks contained .Air Ministry 1943, p. 6. (B IV notes).Air Ministry 1944, p. 6. (PR VIII, PR IX, B IX, PR XVI, B XVI notes). Both the inner wing, and fuselage tanks are listed as the "main tanks" and the total internal fuel load of was initially deemed appropriate for the type. In addition, the FB Mk VI could have larger fuselage tanks, increasing the capacity to . Drop tanks of or could be mounted under each wing, increasing the total fuel load to . The design of the Mark VI allowed for a provisional long-range fuel tank to increase range for action over enemy territory, for the installation of bomb release equipment specific to
depth charge A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive Shock factor, hydraulic shock. Most depth ...
s for strikes against enemy shipping, or for the simultaneous use of rocket projectiles along with a drop tank under each wing supplementing the main fuel cells. The FB.VI had a wingspan of , a length (over guns) of . It had a maximum speed of at . Maximum take-off weight was and the range of the aircraft was with a service ceiling of . To reduce fuel vaporisation at the high altitudes of photographic reconnaissance variants, the central and inner wing tanks were pressurised. The pressure venting cock located behind the pilot's seat controlled the pressure valve. As the altitude increased, the valve increased the volume applied by a pump. This system was extended to include field modifications of the fuel tank system. The engine oil tanks were in the engine nacelles. Each nacelle contained a oil tank, including a air space. The oil tanks themselves had no separate coolant controlling systems. The coolant header tank was in the forward nacelle, behind the propeller. The remaining coolant systems were controlled by the coolant radiators shutters in the forward inner wing compartment, between the nacelle and the fuselage and behind the main engine cooling radiators, which were fitted in the leading edge. Electric-pneumatic operated radiator shutters directed and controlled airflow through the ducts and into the coolant valves, to predetermined temperatures.Air Ministry 1945, p. 14. (FB 6 notes). Electrical power came from a 24 volt DC generator on the starboard (No. 2) engine and an alternator on the port engine, which also supplied AC power for radios. The radiator shutters, supercharger gear change, gun camera, bomb bay, bomb/rocket release and all the other crew controlled instruments were powered by a 24 V battery. The radio communication devices included
VHF Very high frequency (VHF) is the ITU 260px, ITU Monument, Bern The International Telecommunication Union is a specialized agency of the United Nations responsible for all matters related to information and communication technologies ...
and HF communications, GEE navigation, and
IFF IFF, Iff or iff may refer to: Arts and entertainment * Simon Iff, a fictional character by Aleister Crowley * Iff of the Unpronounceable Name, a fictional character in the Riddle-Master trilogy by Patricia A. McKillip * "IFF", an List of The ...
and G.P. devices. The electric generators also powered the fire extinguishers. Located on the starboard side of the cockpit, the switches would operate automatically in the event of a crash. In flight, a warning light would flash to indicate a fire, should the pilot not already be aware of it. In later models, to save liquids and engine clean up time in case of belly landing, the fire extinguisher was changed to semi-automatic triggers.Air Ministry 1945, p. 44. (FB 6 notes). The main landing gear, housed in the nacelles behind the engines, were raised and lowered hydraulically. The main landing gear shock absorbers were de Havilland manufactured and used a system of rubber in compression, rather than hydraulic oleos, with twin pneumatic brakes for each wheel.Bishop 1995, Appendix 1 The Dunlop-Marstrand anti-shimmy tailwheel was also retractable.


Operational history

The de Havilland Mosquito operated in many roles, performing
medium bomber A medium bomber is a military bomber Fixed-wing aircraft, aircraft designed to operate with medium-sized Aerial bomb, bombloads over medium Range (aeronautics), range distances; the name serves to distinguish this type from larger heavy bombe ...
,
reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain Relief map of Sierra Nevada, Spain Terrain or relief (also topographical Topogr ...
, tactical strike,
anti-submarine warfare Anti-submarine warfare (ASW, or in older form A/S) is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, and/or destroy enemy submarines. Such operations are ...
, shipping attacks and
night fighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to ...
duties, until the end of the war. In July 1941, the first production Mosquito ''W4051'' (a production fuselage combined with some prototype flying surfaces – see Prototypes and test flights) was sent to No. 1 Photographic Reconnaissance Unit (PRU), at
RAF Benson Royal Air Force Benson or RAF Benson is a Royal Air Force The Royal Air Force (RAF) is the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mi ...

RAF Benson
. The secret reconnaissance flights of this aircraft were the first operational missions of the Mosquito. In 1944, the journal ''
Flight Flight or flying is the process by which an object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Entity, something that is tangible and within the grasp of the senses ** Object (abstract), an o ...
'' gave 19 September 1941 as date of the first PR mission, at an altitude "of some 20,000 ft". On 15 November 1941, 105 Squadron, RAF, took delivery at RAF Swanton Morley, Norfolk, of the first operational Mosquito Mk. B.IV bomber, serial no. ''W4064''. Throughout 1942, 105 Squadron, based next at RAF Horsham St. Faith, then from 29 September, RAF Marham, undertook daylight low-level and shallow dive attacks.Wooldridge 1993, Frontispiece. Apart from the Oslo and Berlin raids, the strikes were mainly on industrial and infrastructure targets in occupied Netherlands and Norway, France and northern and western Germany. The crews faced deadly flak and fighters, particularly
Focke-Wulf Fw 190 The Focke-Wulf Fw 190 (nicknamed ''Würger''; en, Shrike Shrikes () are carnivore, carnivorous passerine birds of the family Laniidae. The family is composed of 34 species in four genus, genera. The family name, and that of the largest genu ...

Focke-Wulf Fw 190
s, which they called ''snappers''. Germany still controlled continental airspace and the Fw 190s were often already airborne and at an advantageous altitude. Collisions within the formations also caused casualties. It was the Mosquito's excellent handling capabilities, rather than pure speed, that facilitated successful evasions. The Mosquito was first announced publicly on 26 September 1942 after the
Oslo Mosquito raid The Oslo Mosquito raid (25 September 1942) was a United Kingdom, British air raid on Oslo, Norway, during the World War II, Second World War. The target of the raid was the ''Victoria Terrasse'' building, the headquarters of the Gestapo. It was i ...
of 25 September. It was featured in ''
The Times ''The Times'' is a British Newspaper#Daily, daily Newspaper#National, national newspaper based in London. It began in 1785 under the title ''The Daily Universal Register'', adopting its current name on 1 January 1788. ''The Times'' and its s ...
'' on 28 September and the next day the newspaper published two captioned photographs illustrating the bomb strikes and damage. On 6 December 1942, Mosquitos from Nos. 105 and 139 Squadrons made up part of the bomber force used in Operation Oyster, the large No. 2 Group raid against the
Philips Koninklijke Philips N.V. (in Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () *Dutch language , spoken in Belgium (also referred as ''flemish'') Dutch may also refer t ...

Philips
works at
Eindhoven Eindhoven ( , ) is the List of cities in the Netherlands by province, fifth-largest city and a List of municipalities of the Netherlands, municipality of the Netherlands, located in the south of the country. It had a population of 235,923 in 202 ...

Eindhoven
. From mid-1942 to mid-1943, Mosquito bombers flew high-speed, medium and low-altitude daylight missions against factories, railways and other pinpoint targets in Germany and German-occupied Europe. From June 1943, Mosquito bombers were formed into the
Light Night Striking Force The Pathfinders were target-marking Squadron (aviation), squadrons in RAF Bomber Command during World War II. They located and marked targets with flares, which a main bomber force could aim at, increasing the accuracy of their bombing. The Path ...
to guide
RAF Bomber Command RAF Bomber Command controlled the Royal Air Force The Royal Air Force (RAF) is the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The G ...
heavy bomber raids and as "nuisance" bombers, dropping Blockbuster bombs – "cookies" – in high-altitude, high-speed raids that German night fighters were almost powerless to intercept. As a night fighter from mid-1942, the Mosquito intercepted ''
Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht The ''Wehrmacht'' (, ) was the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the German Army (1935–1945), ''Heer'' (army), th ...
'' raids on Britain, notably those of
Operation Steinbock Operation Steinbock (german: Unternehmen Steinbock), sometimes called the Baby Blitz, was a strategic bombing campaign by the German Air Force (the Luftwaffe) during the Second World War. It targeted southern England and lasted from January to May ...
in 1944. Starting in July 1942, Mosquito night-fighter units raided ''Luftwaffe'' airfields. As part of 100 Group, it was flown as a night fighter and as an intruder supporting Bomber Command heavy bombers that reduced losses during 1944 and 1945.Hastings 1979, p. 240. The Mosquito
fighter-bomber A fighter-bomber is a fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that ...
served as a
strike aircraft An attack aircraft, strike aircraft, or attack bomber is a tactical military aircraft that has a primary role of carrying out airstrikes with greater precision than bomber A bomber is a combat aircraft designed to attack ground and naval targ ...
in the
Second Tactical Air Force The RAF Second Tactical Air Force (2TAF) was one of three tactical air forces within the Royal Air Force "Through Adversity to the Stars" , colours = , colours_label = , march ...
(2TAF) from its inception on 1 June 1943. The main objective was to prepare for the invasion of occupied Europe a year later. In
Operation Overlord Operation Overlord was the codename for the Battle of Normandy, the Allies of World War II, Allied operation that launched the successful invasion of German-occupied Western Front (World War II), Western Europe during World War II. The operat ...
three Mosquito FB VI wings flew close air support for the Allied armies in co-operation with other RAF units equipped with the
North American B-25 Mitchell The North American B-25 Mitchell is an American medium bomber A medium bomber is a military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare ...

North American B-25 Mitchell
medium bomber. In the months between the foundation of 2TAF and its duties from
D day The Normandy landings were the landing operation Allied invasion of Sicily, 1943 A landing operation is a military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended fo ...
onwards, vital training was interspersed with attacks on
V-1 flying bomb The V-1 flying bomb (german: Vergeltungswaffe V-weapons, known in original German as (, German: "retaliatory weapons", "reprisal weapons"), were a particular set of long-range artillery weapons designed for strategic bombing during Wor ...

V-1 flying bomb
launch sites. In another example of the daylight precision raids carried out by the Mosquitos of Nos. 105 and 139 Squadrons, on 30 January 1943, the 10th anniversary of the
Nazis Nazism (), officially National Socialism (german: Nationalsozialismus; ), is the ideology and practices associated with Adolf Hitler and the Nazi Party (german: link=no, Nationalsozialistische Deutsche Arbeiterpartei, NSDAP, or National Socia ...

Nazis
' seizure of power, a morning Mosquito attack knocked out the main Berlin broadcasting station while ''Luftwaffe'' Chief
Reichsmarschall (german: Reichsmarschall des Großdeutschen Reiches; ) was the highest military rank in the ''Wehrmacht The ''Wehrmacht'' (, ) was the unified armed forces A military, also known collectively as armed forces, is a heavily armed ...
Hermann Göring Hermann Wilhelm Göring (or Goering; ; 12 January 1893 – 15 October 1946) was a German politician, military leader and convicted war criminal. He was one of the most powerful figures in the Nazi Party The Nazi Party, officially ...

Hermann Göring
was speaking, putting his speech off the air. A second sortie in the afternoon inconvenienced another speech, by Propaganda Minister
Joseph Goebbels Paul Joseph Goebbels (; 29 October 1897 – 1 May 1945) was a German Nazi Nazism (), officially National Socialism (german: Nationalsozialismus; ), is the ideology An ideology () is a set of beliefs or philosophies attributed ...
. Lecturing a group of German aircraft manufacturers, Göring said: During this daylight-raiding phase, Nos. 105 and 139 Squadrons flew 139 combat operations and aircrew losses were high. Even the losses incurred in the squadrons' dangerous era were exceeded in percentage terms. The Roll of Honour shows 51 aircrew deaths from the end of May 1942 to April 1943. In the corresponding period, crews gained three Mentions in Despatches, two DFMs and three DFCs. The low-level daylight attacks finished on 27 May 1943 with strikes on the Schott glass and Zeiss instrument works, both in
Jena Jena (; ) is a German city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Rou ...

Jena
. Subsequently, when low-level precision attacks required Mosquitos, they were allotted to squadrons operating the FB.IV version. Examples include the Aarhus air raid and
Operation Jericho Operation Jericho (Ramrod 564) on 18 February 1944 during the Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a global war that lasted from 1939 to 1945. It involved the vast majority of ...
. Since the beginning of the year, the German fighter force had become seriously overstretched.Boog et al. 2006, pp 160–166. In April 1943, in response to "political humiliation" caused by the Mosquito, Göring ordered the formation of special ''
Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht The ''Wehrmacht'' (, ) was the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the German Army (1935–1945), ''Heer'' (army), th ...
'' units (''Jagdgeschwader 25'', commanded by ''Oberstleutnant'' Herbert Ihlefeld and ''Jagdgeschwader 50'', under ''
Major Major is a military rank Military ranks are a system of hierarchical A hierarchy (from the Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) in which the items are repre ...

Major
'' Hermann Graf) to combat the Mosquito attacks, though these units, which were "little more than glorified squadrons", were unsuccessful against the elusive RAF aircraft. Post-war German histories also indicate that there was a belief within the Luftwaffe that Mosquito aircraft "gave only a weak radar signal.". The first Mosquito Squadron to be equipped with Oboe (navigation) was No. 109, based at RAF Wyton, after working as an experimental unit at
RAF Boscombe Down MoD Boscombe Down ' is the home of a military aircraft testing site, located near the town of Amesbury in Wiltshire, England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders ...
. They used Oboe in anger for the first time on 31 December 1942 and 1 January 1943, target marking for a force of heavy bombers attacking Düsseldorf.. On 1 June, the two pioneering Squadrons joined No. 109 Squadron in the re-formed No. 8 Group RAF (Bomber Command). Initially they were engaged in moderately high altitude (about ) night bombing, with 67 trips during that summer, mainly to Berlin. Soon after, Nos. 105 and 139 Squadron bombers were widely used by the Pathfinder (RAF), RAF Pathfinder Force, marking targets for the main night-time strategic bombing force. In what were, initially, diversionary "nuisance raids," Mosquito bombers dropped 4,000 lb Blockbuster bombs or "Cookies." Particularly after the introduction of H2S (radar) in some Mosquitos, these raids carrying larger bombs succeeded to the extent that they provided a significant additional form of attack to the large formations of "heavies." Latterly in the war, there were a significant number of all-Mosquito raids on big German cities involving up to 100 or more aircraft. On the night of 20/21 February 1945, for example, Mosquitos of No. 8 Group mounted the first of 36 consecutive night raids on Berlin.Harris 1993, p. 43. From 1943, Mosquitos with RAF Coastal Command attacked ''Kriegsmarine'' U-boats and intercepted transport ship concentrations. After
Operation Overlord Operation Overlord was the codename for the Battle of Normandy, the Allies of World War II, Allied operation that launched the successful invasion of German-occupied Western Front (World War II), Western Europe during World War II. The operat ...
, the U-boat threat in the Western Approaches decreased fairly quickly, but correspondingly the Norwegian and Danish waters posed greater dangers. Hence the RAF Coastal Command Mosquitos were moved to Scotland to counter this threat. The Strike Wing at Banff stood up in September 1944 and comprised Mosquito aircraft of No's 143, 144, 235 and 248 Squadrons Royal Air Force and No.333 Squadron Royal Norwegian Air Force. Despite an initially high loss rate, the Mosquito bomber variants ended the war with the lowest losses of any aircraft in
RAF Bomber Command RAF Bomber Command controlled the Royal Air Force The Royal Air Force (RAF) is the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The G ...
service. The Mosquito also proved a very capable
night fighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to ...
. Some of the most successful RAF pilots flew these variants. For example, Wing Commander (rank), Wing Commander Branse Burbridge claimed 21 kills, and Wing Commander John Cunningham claimed 19 of his 20 victories at night on Mosquitos. Mosquitos of No. 100 Group RAF acted as night intruders operating at high level in support of the Bomber Command "heavies", to counter the enemy tactic of merging into the bomber stream, which, towards the end of 1943, was causing serious allied losses.Harris 1993, p. 126. These RCM (radio countermeasures) aircraft were fitted with a device called "Serrate radar detector, Serrate" to allow them to track down German night fighters from their Lichtenstein radar#FuG 202 Lichtenstein B/C, ''Lichtenstein B/C'' (low-UHF-band) and Lichtenstein radar#FuG 220 Lichtenstein SN-2, ''Lichtenstein SN-2'' (lower end of the VHF FM broadcast band) radar emissions, as well as a device named "Perfectos" that tracked German
IFF IFF, Iff or iff may refer to: Arts and entertainment * Simon Iff, a fictional character by Aleister Crowley * Iff of the Unpronounceable Name, a fictional character in the Riddle-Master trilogy by Patricia A. McKillip * "IFF", an List of The ...
signals. These methods were responsible for the destruction of 257 German aircraft from December 1943 to April 1945. Mosquito fighters from all units accounted for 487 German aircraft during the war, the vast majority of which were night fighters. One Mosquito is listed as belonging to German secret operations unit ''Kampfgeschwader 200'', which tested, evaluated and sometimes clandestinely operated captured enemy aircraft during the war. The aircraft was listed on the order of battle of ''Versuchsverband OKL''s, ''2 Staffel'', ''Stab Gruppe'' on 10 November and 31 December 1944. However, on both lists, the Mosquito is listed as unserviceable. The Mosquito flew its last official European war mission on 21 May 1945, when Mosquitos of 143 Squadron and 248 Squadron RAF were ordered to continue to hunt German submarines that might be tempted to continue the fight; instead of submarines all the Mosquitos encountered were passive E-boats. The last operational RAF Mosquitos were the Mosquito TT.35's, which were finally retired from No. 3 Civilian Anti-Aircraft Co-Operation Unit (CAACU) in May 1963. In 1947–49, up to 180 Canadian surplus Mosquitoes flew many operations for the Nationalist Chinese under Chiang Kai-shek in the civil war against Communist forces. Pilots from three squadrons of Mosquitoes claimed to have sunk or damaged 500 ships during one invasion attempt. As the Communists assumed control, the remaining aircraft were evacuated to Formosa, where they flew missions against shipping.


Variants

Until the end of 1942 the RAF always used Roman numerals (I, II, ...) for British military aircraft designation systems, mark numbers; 1943–1948 was a transition period during which new aircraft entering service were given Arabic numerals (1, 2, ...) for mark numbers, but older aircraft retained their Roman numerals. From 1948 onwards, Arabic numerals were used exclusively.


Prototypes

Three prototypes were built, each with a different configuration. The first to fly was ''W4050'' on 25 November 1940, followed by the fighter ''W4052'' on 15 May 1941 and the photo-reconnaissance prototype ''W4051'' on 10 June 1941. ''W4051'' later flew operationally with 1 Photographic Reconnaissance Unit (1 PRU).


Photo-reconnaissance


A total of 10 Mosquito PR Mk Is were built, four of them "long range" versions equipped with a overload fuel tank in the fuselage. The contract called for 10 of the PR Mk I airframes to be converted to B Mk IV Series 1s. All of the PR Mk Is, and the B Mk IV Series 1s, had the original short engine nacelles and short span (19 ft 5.5 in) tailplanes. Their engine cowlings incorporated the original pattern of integrated exhaust manifolds, which, after relatively brief flight time, had a troublesome habit of burning and blistering the cowling panels. The first operational sortie by a Mosquito was made by a PR Mk I, W4055, on 17 September 1941; during this sortie the unarmed Mosquito PR.I evaded three Messerschmitt Bf 109s at .Bowman 2005, p. 27. Powered by two Merlin 21s, the PR Mk I had a maximum speed of , a cruise speed of , a ceiling of , a range of , and a climb rate of per minute. Over 30 Mosquito B Mk IV bombers were converted into the PR Mk IV photo-reconnaissance aircraft. The first operational flight by a PR Mk IV was made by ''DK284'' in April 1942.Bowman 2005, p. 164. The Mosquito PR Mk VIII, built as a stopgap pending the introduction of the refined PR Mk IX, was the next photo-reconnaissance version. The five VIIIs were converted from B Mk IVs and became the first operational Mosquito version to be powered by two-stage, two-speed supercharged engines, using Rolls-Royce Merlin 61 engines in place of Merlin 21/22s. The first PR Mk VIII, ''DK324'' first flew on 20 October 1942.Thirsk 2006, p. 272. The PR Mk VIII had a maximum speed of , an economical cruise speed of at 20,000 ft, and at 30,000 ft, a ceiling of , a range of , and a climb rate of 2,500 ft per minute (760 m).Bowman 2005, p. 25. The Mosquito PR Mk IX, 90 of which were built, was the first Mosquito variant with two-stage, two-speed engines to be produced in quantity; the first of these, ''LR405'', first flew in April 1943. The PR Mk IX was based on the Mosquito B Mk IX bomber and was powered by two Merlin 72/73 or 76/77 engines. It could carry either two , two or two droppable fuel tanks. The Mosquito PR Mk XVI had a pressurised cockpit and, like the Mk IX, was powered by two Rolls-Royce Merlin 72/73 or 76/77 piston engines. This version was equipped with three overload fuel tanks, totalling in the bomb bay, and could also carry two or drop tanks. A total of 435 of the PR Mk XVI were built. The PR Mk XVI had a maximum speed of , a cruise speed of , ceiling of , a range of , and a climb rate of 2,900 feet per minute (884 m). The Mosquito PR Mk 32 was a long-range, high-altitude, pressurised photo-reconnaissance version. It was powered by a pair of two-stage supercharged Rolls-Royce Merlin 113 and Merlin 114 piston engines, the Merlin 113 on the starboard side and the Merlin 114 on the port. First flown in August 1944, only five were built and all were conversions from PR.XVIs.Bowman 2005, p. 165. The Mosquito PR Mk 34 and PR Mk 34A was a very long-range unarmed high altitude photo-reconnaissance version. The fuel tank and cockpit protection armour were removed. Additional fuel was carried in a bulged bomb bay: 1,192 gallons—the equivalent of . A further two 200-gallon (910-litre) drop tanks under the outer wings gave a range of cruising at . Powered by two Merlin 114s first used in the PR.32. The port Merlin 114 drove a Marshal cabin supercharger. A total of 181 were built, including 50 built by Percival Aircraft Company at Luton. The PR.34's maximum speed (TAS) was at sea level, at and at ."The Latest Mosquitoes."
''Flight,'' 28 February 1946 via ''flightglobal.com''. Retrieved: 17 August 2010.
All PR.34s were installed with four split F52 vertical cameras, two forward, two aft of the fuselage tank and one F24 oblique camera. Sometimes a K-17 camera was used for air surveys. In August 1945, the PR.34A was the final photo-reconnaissance variant with one Merlin 113A and 114A each delivering .Bowman 2005, p. 166. Colonel Roy M. Stanley II, USAF (RET) wrote: "I consider the Mosquito the best photo-reconnaissance aircraft of the war".Stanley 2010, p. 35. After the end of World War II Spartan Air Services used 10 ex-RAF Mosquitoes, mostly B.35's plus one of only six PR.35's built, for high-altitude photographic survey work in Canada.


Bombers


On 21 June 1941 the Air Ministry ordered that the last 10 Mosquitos, ordered as photo-reconnaissance aircraft, should be converted to bombers. These 10 aircraft were part of the original 1 March 1940 production order and became the B Mk IV Series 1. ''W4052'' was to be the prototype and flew for the first time on 8 September 1941.Bowman 2005, pp. 22–23. The bomber prototype led to the B Mk IV, of which 273 were built: apart from the 10 Series 1s, all of the rest were built as Series 2s with extended nacelles, revised exhaust manifolds, with integrated flame dampers, and larger tailplanes.Jackson 2003, p. 15. Series 2 bombers also differed from the Series 1 in having an increased payload of four bombs, instead of the four bombs of Series 1. This was made possible by ''cropping'', or shortening the tail of the bomb so that these four heavier weapons could be carried (or a 2,000 lb (920;kg) total load). The B Mk IV entered service in May 1942 with 105 Squadron. In April 1943 it was decided to convert a B Mk IV to carry a Blockbuster bomb (nicknamed a Cookie). The conversion, including modified bomb bay suspension arrangements, bulged bomb bay doors and fairings, was relatively straightforward and 54 B.IVs were modified and distributed to squadrons of the Light Night Striking Force. 27 B Mk IVs were later converted for special operations with the Bouncing bomb, Highball anti-shipping weapon, and were used by No. 618 Squadron RAF, 618 Squadron, formed in April 1943 specifically to use this weapon. A B Mk IV, ''DK290'' was initially used as a trials aircraft for the bomb, followed by ''DZ471,530 and 533''. The B Mk IV had a maximum speed of , a cruising speed of , ceiling of , a range of , and a climb rate of 2,500 ft per minute (762 m). Other bomber variants of the Mosquito included the Merlin 21 powered B Mk V high-altitude version. Trials with this configuration were made with ''W4057'', which had strengthened wings and two additional fuel tanks, or alternatively, two bombs. This design was not produced in Britain, but formed the basic design of the Canadian-built B.VII. Only ''W4057'' was built in prototype form.Jackson 2003, p. 16. The Merlin 31 powered B Mk VII was built by de Havilland Canada and first flown on 24 September 1942. It only saw service in Canada, 25 were built. Six were handed over to the
United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare Aerial warfare is the use of military aircraft A military aircraft is any fixed-wing A fixed-wing aircraft is a heavier-than-air flying machi ...
. B Mk IX (54 built) was powered by the Merlin 72,73, 76 or 77. The two-stage Merlin variant was based on the PR.IX. The prototype ''DK 324'' was converted from a PR.VIII and first flew on 24 March 1943.Jackson 2003, p. 17. In October 1943 it was decided that all B Mk IVs and all B Mk IXs then in service would be converted to carry the "Cookie", and all B Mk IXs built after that date were designed to allow them to be converted to carry the weapon.Sharp and Bowyer 1971, p. 306 The B Mk IX had a maximum speed of , an economical cruise speed of at 20,000 ft, and at 30,000 ft, ceiling of , a range of , and a climb rate of 2,850 feet per minute (869 m). The IX could carry a maximum load of of bombs. A Mosquito B Mk IX holds the record for the most combat operations flown by an Allied bomber in the Second World War. ''LR503'', known as "F for Freddie" (from its squadron code letters, GB*F), first served with No. 109 Squadron RAF, No. 109 and subsequently, No. 105 Squadron RAF, No. 105 RAF squadrons. It flew 213 sorties during the war, only to crash at Calgary airport during the Eighth Victory Loan Bond Drive on 10 May 1945, two days after Victory in Europe Day, killing both the pilot, Flt. Lt. Maurice Briggs, DSO, DFC, DFM and navigator Fl. Off. John Baker, DFC and Bar. The B Mk XVI was powered by the same variations as the B.IX. All B Mk XVIs were capable of being converted to carry the "Cookie". The two-stage powerplants were added along with a pressurised cabin. ''DZ540'' first flew on 1 January 1944. The prototype was converted from a IV (402 built). The next variant, the B Mk XX, was powered by Packard Merlins 31 and 33s. It was the Canadian version of the IV. Altogether, 245 were built. The B Mk XVI had a maximum speed of , an economical cruise speed of at 20,000 ft, and at 30,000 ft, ceiling of , a range of , and a climb rate of 2,800 ft per minute (853 m). The type could carry of bombs. The B.35 was powered by Merlin 113 and 114As. Some were converted to TT.35s (Target Tugs) and others were used as PR.35s (photo-reconnaissance). The B.35 had a maximum speed of , a cruising speed of , ceiling of , a range of , and a climb rate of 2,700 ft per minute (823 m). A total of 174 B.35s were delivered up to the end of 1945. A further 100 were delivered from 1946 for a grand total of 274, 65 of which were built by Airspeed Ltd.


Fighters

Developed during 1940, the first prototype of the Mosquito F Mk II was completed on 15 May 1941. These Mosquitos were fitted with four Hispano-Suiza HS.404, Hispano cannon in the fuselage belly and four .303 British, .303 (7.7 mm) M1919 Browning machine gun, Browning machine guns mounted in the nose. On production Mk IIs the machine guns and ammunition tanks were accessed via two centrally hinged, sideways opening doors in the upper nose section. To arm and service the cannon the bomb bay doors were replaced by manually operated bay doors: the F and NF Mk IIs could not carry bombs. The type was also fitted with a gun camera in a compartment above the machine guns in the nose and was fitted with exhaust flame dampers to reduce the glare from the Merlin XXs. In the summer of 1942, Britain experienced day-time incursions of the high-altitude reconnaissance bomber, the Junkers Ju 86, Junkers Ju 86P.Birtles 2017, ch. 6. Although the Ju 86P only carried a light bomb load, it overflew sensitive areas, including Bristol, Bedfordshire and Hertfordshire. Bombs were dropped on Luton and elsewhere, and this particular aircraft was seen from the main de Havilland offices and factory at Hatfield. An attempt to intercept it with a Spitfire from RAF Manston was unsuccessful. As a result of the potential threat, a decision was quickly taken to develop a high-altitude Mosquito interceptor, using the ''MP469'' prototype. ''MP469'' entered the experimental shop on 7 September and made its initial flight on 14 September, piloted by John de Havilland. The bomber nose was altered using a normal fighter nose, armed with four standard .303 British, .303 (7.7 mm) M1919 Browning machine gun, Browning machine guns. The low pressure cabin retained a bomber canopy structure and a two-piece windscreen. The control wheel was replaced with a fighter control stick. The wingspan was increased to . The airframe was lightened by removing armour plating, some fuel tanks and other fitments. Smaller-diameter main wheels were fitted after the first few flights. At a loaded weight of this HA Mk XV was lighter than a standard Mk II. For this first conversion, the engines were a pair of Merlin 61s. On 15 September, John de Havilland reached an altitude of in this version. The aircraft was delivered to a High Altitude Flight which had been formed at RAF Northolt. However, the high-level German daylight intruders were no longer to be seen. It was subsequently revealed that only five Ju 86P aircraft had been built and they had only flown 12 sorties. Nevertheless, the general need for high altitude interceptors was recognised – but now the emphasis was to be upon night fighters. The A&AEE tested the climb and speed of night fighter conversion of MP469 in January 1943 for the Ministry of Aircraft Production. Wingspan had been increased to , the Brownings had been moved to a fairing below the fuselage. According to Birtles, an AI radar was mounted in the nose and the Merlins were upgraded to Mk76 type, although Boscombe Down reported Merlin 61s. In addition to MP469, four more B Mk IVs were converted into NF MK XVs. The Fighter Interception Unit at RAF Ford carried out service trials, March 1943, and then these five aircraft went to 85 Squadron, Hunsdon, where they were flown from April until August of that year. The greatest height reached in service was . Apart from the F Mk XV, all Mosquito fighters and fighter bombers featured a modified canopy structure incorporating a flat, single piece Bulletproof glass, armoured windscreen, and the crew entry/exit door was moved from the bottom of the forward fuselage to the right side of the nose, just forward of the wing leading edge.


Night fighters


At the end of 1940, the Air Staff's preferred turret-equipped night fighter design to List of Air Ministry specifications, Operational Requirement O.R. 95 was the Gloster F.18/40 (derived from Gloster F.9/37, their F.9/37). However, although in agreement as to the quality of the Gloster company's design, the Ministry of Aircraft Production was concerned that Gloster would not be able to work on the F.18/40 and also the jet fighter design, considered the greater priority. Consequently, in mid-1941 the Air Staff and MAP agreed that the Gloster aircraft would be dropped and the Mosquito, when fitted with a turret would be considered for the night fighter requirement. The first production
night fighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a that lasted from 1939 to ...
Mosquitos – minus turrets – were designated NF Mk II. A total of 466 were built with the first entering service with No. 157 Squadron RAF, No. 157 Squadron in January 1942, replacing the A-20 Havoc, Douglas Havoc. These aircraft were similar to the F Mk II, but were fitted with the AI Mk. IV radar, AI Mk IV metric wavelength radar. The herring-bone transmitter, transmitting Antenna (radio), antenna was mounted on the nose and the dipole receiver (radio), receiving antennae were carried under the outer wings. A number of NF IIs had their radar equipment removed and additional fuel tanks installed in the bay behind the cannon for use as night intruders. These aircraft, designated NF II (Special) were first used by No. 23 Squadron RAF, 23 Squadron in operations over Europe in 1942. 23 Squadron was then deployed to Malta on 20 December 1942, and operated against targets in Italy. Ninety-seven NF Mk IIs were upgraded with 3.3 GHz frequency, low-Super high frequency, SHF-band AI Mk. VIII radar, AI Mk VIII radar and these were designated NF Mk XII. The NF Mk XIII, of which 270 were built, was the production equivalent of the Mk XII conversions. These "centimetric" radar sets were mounted in a solid "thimble" (Mk XII / XIII) or universal "bull nose" (Mk XVII / XIX) radome, which required the machine guns to be dispensed with. Four F Mk XVs were converted to the NF Mk XV. These were fitted with AI Mk VIII in a "thimble" radome, and the .303 Brownings were moved into a gun pack fitted under the forward fuselage. NF Mk XVII was the designation for 99 NF Mk II conversions, with single-stage Merlin 21, 22, or 23 engines, but British AI.X (US SCR-720) radar. The NF Mk XIX was an improved version of the NF XIII. It could be fitted with American or British AI radars; 220 were built. The NF Mk 30 was the final wartime variant and was a high-altitude version, powered by two Rolls-Royce Merlin 76s. The NF Mk 30 had a maximum speed of at . It also carried early electronic countermeasures equipment. 526 were built. Other Mosquito night fighter variants planned but never built included the NF Mk X and NF Mk XIV (the latter based on the NF Mk XIII), both of which were to have two-stage Merlins. The NF Mk 31 was a variant of the NF Mk 30, but powered by Packard Merlins. After the war, two more night fighter versions were developed: The NF Mk 36 was similar to the Mosquito NF Mk 30, but fitted with the American-built AI.Mk X radar. Powered by two Rolls-Royce Merlin 113/114 piston engines; 266 built. Max level speeds (TAS) with flame dampers fitted were at sea level, at , and at . The NF Mk 38, 101 of which were built, was also similar to the Mosquito NF Mk 30, but fitted with the British-built AI Mk IX radar. This variant suffered from stability problems and did not enter RAF service: 60 were eventually sold to Yugoslavia. According to the Pilot's Notes and Air Ministry 'Special Flying Instruction TF/487', which posted limits on the Mosquito's maximum speeds, the NF Mk 38 had a VNE of 370 knots (425 mph), without under-wing stores, and within the altitude range of sea level to . However, from 10,000 to the maximum speed was 348 knots (400 mph). As the height increased other recorded speeds were; 15,000 to 320 knots (368 mph); 20,000 to , 295 knots (339 mph); 25,000 to , 260 knots (299 mph); 30,000 to , 235 knots (270 mph). With two added 100-gallon fuel tanks this performance fell; between sea level and 15,000 feet 330 knots (379 mph); between 15,000 and 320 knots (368 mph); 20,000 to , 295 knots (339 mph); 25,000 to , 260 knots (299 mph); 30,000 to , 235 knots (270 mph). Little difference was noted above .


Strike ("fighter-bomber") variants

The FB Mk VI, which first flew on 1 June 1942, was powered by two, single-stage two-speed, Merlin 21s or Merlin 25s, and introduced a re-stressed and reinforced "basic" wing structure capable of carrying single bombs on racks housed in streamlined fairings under each wing, or up to eight RP-3, RP-3 25lb or 60 lb rockets. In addition fuel lines were added to the wings to enable single or drop tanks to be carried under each wing.Streetly 1981, p. 177. The usual fixed armament was four 20 mm Hispano-Suiza HS.404, Hispano Mk.II cannon and four .303 (7.7 mm) M1919 Browning machine gun, Browning machine guns, while two bombs could be carried in the bomb bay. Unlike the F Mk II, the ventral bay doors were split into two pairs, with the forward pair being used to access the cannon, while the rear pair acted as bomb bay doors. The maximum fuel load was distributed between internal fuel tanks, plus two overload tanks, each of capacity, which could be fitted in the bomb bay, and two drop tanks. All-out level speed is often given as , although this speed applies to aircraft fitted with saxophone exhausts. The test aircraft (''HJ679'') fitted with stub exhausts was found to be performing below expectations. It was returned to de Havilland at Hatfield where it was serviced. Its top speed was then tested and found to be , in line with expectations. 2,298 FB Mk VIs were built, nearly one-third of Mosquito production. Two were converted to TR.33 aircraft carrier, carrier-borne, maritime strike prototypes. The FB Mk VI proved capable of holding its own against
fighter aircraft Fighter aircraft are fixed-wing A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet e ...

fighter aircraft
, in addition to strike/bombing roles. For example, on 15 January 1945 Mosquito FB Mk VIs of No. 143 Squadron RAF, 143 Squadron were engaged by 30
Focke-Wulf Fw 190 The Focke-Wulf Fw 190 (nicknamed ''Würger''; en, Shrike Shrikes () are carnivore, carnivorous passerine birds of the family Laniidae. The family is composed of 34 species in four genus, genera. The family name, and that of the largest genu ...

Focke-Wulf Fw 190
s from ''Jagdgeschwader 5'': the Mosquitos sank an armed trawler and two merchant ships, but five Mosquitos were lost (two reportedly to flak), while shooting down five Fw 190s. Another fighter-bomber variant was the Mosquito FB Mk XVIII (sometimes known as the ''Tsetse fly, Tsetse'') of which one was converted from a FB Mk VI to serve as prototype and 17 were purpose-built. The Mk XVIII was armed with a Molins "6-pounder Class M" cannon: this was a modified Ordnance QF 6 pounder, QF 6-pounder (57 mm) anti-tank gun fitted with an auto-loader to allow both semi- or fully automatic fire. 25 rounds were carried, with the entire installation weighing . In addition, of armour was added within the engine cowlings, around the nose and under the cockpit floor to protect the engines and crew from heavily armed U-boats, the intended primary target of the Mk XVIII. Two or four .303 (7.7 mm) Browning machine guns were retained in the nose and were used to "sight" the main weapon onto the target. The Air Ministry initially suspected that this variant would not work, but tests proved otherwise. Although the gun provided the Mosquito with yet more anti-shipping firepower for use against U-boats, it required a steady approach run to aim and fire the gun, making its wooden construction an even greater liability, in the face of intense anti-aircraft fire. The gun had a muzzle velocity of and an excellent range of some . It was sensitive to sidewards movement; an attack required a dive from at a 30° angle with the turn and bank indicator on centre. A move during the dive could jam the gun. The prototype ''HJ732'' was converted from a FB.VI and was first flown on 8 June 1943. The effect of the new weapon was demonstrated on 10 March 1944 when Mk XVIIIs from No. 248 Squadron RAF, 248 Squadron (escorted by four Mk VIs) engaged a German convoy of one U-boat and four destroyers, protected by 10 Junkers Ju 88, Ju 88s. Three of the Ju 88s were shot down. Pilot Tony Phillips destroyed one Ju 88 with four shells, one of which tore an engine off the Ju 88. The U-boat was damaged. On 25 March, was sunk by Molins-equipped Mosquitos. On 10 June, was abandoned in the face of intense air attack from No. 248 Squadron, and was later sunk by a Consolidated B-24 Liberator, Liberator of No. 206 Squadron. On 5 April 1945 Mosquitos with Molins attacked five German surface ships in the Kattegat and again demonstrated their value by setting them all on fire and sinking them.Bowman 2005, p. 115. A German ''Sperrbrecher'' ("minefield breaker") was lost with all hands, with some 200 bodies being recovered by Sweden, Swedish vessels. Some 900 German soldiers died in total. On 9 April, German U-boats , and were spotted in formation heading for Norway. All were sunk with rockets. and followed on 19 April and 2 May 1945, also sunk by rockets. Despite the preference for rockets, a further development of the large gun idea was carried out using the even larger, 96 mm calibre Ordnance QF 32 pounder, QF 32-pounder, a gun based on the QF 3.7-inch AA gun designed for tank use, the airborne version using a novel form of muzzle brake. Developed to prove the feasibility of using such a large weapon in the Mosquito, this installation was not completed until after the war, when it was flown and fired in a single aircraft without problems, then scrapped. Designs based on the Mk VI were the FB Mk 26, built in Canada, and the FB Mk 40, built in Australia, powered by Packard V-1650, Packard Merlins. The FB.26 improved from the FB.21 using single stage Packard Merlin 225s. Some 300 were built and another 37 converted to T.29 standard. 212 FB.40s were built by de Havilland Australia. Six were converted to PR.40; 28 to PR.41s, one to FB.42 and 22 to T.43 trainers. Most were powered by Packard-built Merlin 31 or 33s.


Trainers

The Mosquito was also built as the Mosquito T Mk III two-seat Trainer (aircraft), trainer. This version, powered by two Rolls-Royce Merlin 21s, was unarmed and had a modified cockpit fitted with dual control arrangements. A total of 348 of the T Mk III were built for the RAF and Fleet Air Arm. de Havilland Australia built 11 T Mk 43 trainers, similar to the Mk III.


Torpedo-bombers

To meet specification N.15/44 for a navalised Mosquito for Royal Navy use as a torpedo bomber, de Havilland produced a aircraft carrier, carrier-borne variant. A Mosquito FB.VI was modified as a prototype designated Sea Mosquito TR Mk 33 with folding wings, arrester hook, thimble nose radome, Merlin 25 engines with four-bladed propellers and a new oleo-pneumatic landing gear rather than the standard rubber-in-compression gear. Initial carrier tests of the Sea Mosquito were carried out by Eric Brown (pilot), Eric "Winkle" Brown aboard HMS Indefatigable (R10), HMS ''Indefatigable'', the first landing-on taking place on 25 March 1944. An order for 100 TR.33s was placed although only 50 were built at Leavesden. Armament was four 20 mm cannon, two 500 lb bombs in the bomb bay (another two could be fitted under the wings), eight 60 lb rockets (four under each wing) and a standard torpedo under the fuselage. The first production TR.33 flew on 10 November 1945. This series was followed by six Sea Mosquito TR Mk 37s, which differed in having ASV Mk XIII radar instead of the TR.33's AN/APS-6.


Target tugs

The RAF's target tug version was the Mosquito TT Mk 35, which were the last aircraft to remain in operational service with No 3 CAACU at Exeter, being finally retired in 1963. These aircraft were then featured in the film 633 Squadron. A number of B Mk XVIs bombers were converted into TT Mk 39 target tug aircraft. The Royal Navy also operated the Mosquito TT Mk 39 for target towing. Two ex-RAF FB.6s were converted to TT.6 standard at Manchester Airport, Manchester (Ringway) Airport by Fairey Aviation in 1953–1954, and delivered to the Belgian Air Force for use as towing aircraft from the Sylt firing ranges.


Canadian-built

A total of 1,032 (wartime + 2 afterwards) Mosquitos were built by De Havilland Canada at CFB Downsview, Downsview Airfield in Downsview Ontario (now Downsview Park in Toronto Ontario). * Mosquito B Mk VII : Canadian version based on the Mosquito B Mk V bomber aircraft. Powered by two Packard Merlin 31 piston engines; 25 built. * Mosquito B Mk XX : Canadian version of the Mosquito B Mk IV bomber aircraft; 145 built, of which 40 were converted into F-8 photo-reconnaissance aircraft for the USAAF. * Mosquito FB Mk 21 : Canadian version of the Mosquito FB Mk VI fighter-bomber aircraft. Powered by two Rolls-Royce Merlin 31 piston engines, three built. * Mosquito T Mk 22 : Canadian version of the Mosquito T Mk III training aircraft. * Mosquito B Mk 23 : Unused designation for a bomber variant. * Mosquito FB Mk 24 : Canadian fighter-bomber version. Powered by two Rolls-Royce Merlin 301 piston engines; two built. * Mosquito B Mk 25 : Improved version of the Mosquito B Mk XX Bomber aircraft. Powered by two Packard Merlin 225 piston engines; 400 built. * Mosquito FB Mk 26 : Improved version of the Mosquito FB Mk 21 fighter-bomber aircraft. Powered by two Packard Merlin 225 piston engines; 338 built. * Mosquito T Mk 27 : Canadian-built training aircraft. * Mosquito T Mk 29 : A number of FB Mk 26 fighters were converted into T Mk 29 trainers.


Australian-built

* Mosquito FB Mk 40 : Two-seat fighter-bomber version for the RAAF. Powered by two Rolls-Royce Merlin 31 piston engines. A total of 178 built in Australia. * Mosquito PR Mk 40 : This designation was given to six FB Mk 40s, which were converted into photo-reconnaissance aircraft. * Mosquito FB Mk 41 : Two-seat fighter-bomber version for the RAAF. A total of 11 were built in Australia. * Mosquito PR Mk 41 : Two-seat photo-survey version for the RAAF. A total of 17 were built in Australia. * Mosquito FB Mk 42 : Two-seat fighter-bomber version. Powered by two Rolls-Royce Merlin 69 piston engines. One FB Mk 40 aircraft was converted into a Mosquito FB Mk 42. * Mosquito T Mk 43 : Two-seat training version for the RAAF. A total of 11 FB Mk 40s were converted into Mosquito T Mk 43s.


Highball

A number of Mosquito IVs were modified by Vickers-Armstrongs to carry Highball "bouncing bombs" and were allocated Vickers Type numbers: * Type 463 – Prototype Highball conversion of Mosquito IV ''DZ741''. * Type 465 – Conversion of 33 Mosquito IVs to carry Highball.


Production

About 5,000 of the total of 7,781 Mosquitos built had major structural components fabricated from wood in High Wycombe, Buckinghamshire, England. Fuselages, wings and tailplanes were made at furniture companies such as Ronson, G-Plan, E. Gomme, Parker Knoll, Austinsuite and Styles & Mealing. Wing spars were made by J. B. Heath and Dancer & Hearne. Many of the other parts, including flaps, flap shrouds, fins, leading edge assemblies and bomb doors were also produced in the Buckinghamshire town. Dancer & Hearne processed much of the wood from start to finish, receiving timber and transforming it into finished wing spars at their factory in Penn Street on the outskirts of High Wycombe. Initially much of the specialised yellow birch wood veneer and finished plywood used for the prototypes and early production aircraft was shipped from firms in Wisconsin, US.Connor-Madison 2007, pp. 2–3. Prominent in this role were Roddis Plywood and Veneer Manufacturing in Marshfield, Wisconsin, Marshfield. In conjunction with the USDA Forest Products Laboratory, Hamilton Roddis had developed new plywood adhesives and hot pressing technology. Later on, paper birch was logged in large quantities from the interior of British Columbia along the Fraser and Quesnel Rivers and processed in Quesnel and New Westminster by the Pacific Veneer Company. According to the Quesnel archives, BC paper birch supplied ½ of the wartime British Empire birch used for Mosquitos and other aircraft.


Canada

In July 1941, it was decided that DH Canada would build Mosquitos at Downsview, Ontario. This was to continue even if Germany invaded Great Britain. Packard Merlin engines produced under licence were bench-tested by August and the first two aircraft were built in September. Production was to increase to fifty per month by early 1942. Initially, the Canadian production was for bomber variants; later, fighters, fighter-bombers and training aircraft were also made. DH Chief Production Engineer, Harry Povey, was sent first, then W. D. Hunter followed on an extended stay, to liaise with materials and parts suppliers. As was the case with initial UK production, Tego-bonded plywood and birch veneer was obtained from firms in Wisconsin, principally Roddis Plywood and Veneer Manufacturing, Marshfield. Enemy action delayed the shipping of jigs and moulds and it was decided to build these locally. During 1942, production improved to over 80 machines per month, as sub-contractors and suppliers became established. A mechanised production line based in part on car building methods started in 1944. As the war progressed, Canadian mosquitos may have utilized paper birch supplied by the Pacific Veneer Company of New Westminster using birch logs from the Cariboo, although records only say this birch was shipped to England for production there. When flight testing could no longer keep up, this was moved to the Central Aircraft Company airfield, London, Ontario, where the approved Mosquitos left for commissioning and subsequent ferry transfer to Europe. Ferrying Mosquitos and many other types of WWII aircraft from Canada to Europe was dangerous, resulting in losses of lives and machines, but in the exigencies of war it was regarded as the best option for twin-engine and multi-engine aircraft. In the parlance of the day, among RAF personnel, "it was no piece of cake." Considerable efforts were made by de Havilland Canada to resolve problems with engine and oil systems and an additional five hours of flight testing were introduced before the ferry flight, but the actual cause of some of the losses was unknown. Nevertheless, by the end of the war, nearly 500 Mosquito bombers and fighter-bombers had been ferried successfully by the Canadian operation. After DH Canada had been established for the Mosquito, further manufacturing was set up at DH Australia, in Sydney. One of the DH staff who travelled there was the distinguished test pilot, Pat Fillingham. These production lines added totals of 1,133 aircraft of varying types from Canada plus 212 aircraft from Australia.


Exports

In total, both during the war and after, de Havilland exported 46 FB.VIs and 29 PR. XVIs to Australia; two FB.VI and 18 NF.30s to Belgium; approximately 250 FB.26, T.29 and T.27s from Canada to Republic of China (1912–1949), Nationalist China. A significant number never went into service due to deterioration on the voyage and to crashes during Chinese pilot training; however, five were captured by the People's Liberation Army during the Chinese Civil War; 19 FB.VIs to Czechoslovakia in 1948; 6 FB.VIs to Dominica; a few B.IVs, 57 FB.VIs, 29 PR.XVIs and 23 NF.30s to France. Some T.IIIs were exported to Israel along with 60 FB.VIs, and at least five PR.XVIs and 14 naval versions. Four T.IIIs, 76 FB.VIs, one FB.40 and four T.43s were exported to New Zealand. Three T.IIIs were exported to Norway, and 18 FB.VIs, which were later converted to night fighter standard. South Africa received two F.II and 14 PR.XVI/XIs and Sweden received 60 NF.XIXs. Turkey received 96 FB.VIs and several T.IIIs, and Socialist Federal Republic of Yugoslavia, Yugoslavia had 60 NF.38s, 80 FB.VIs and three T.IIIs delivered. At least a single de Havilland Mosquito was delivered to the Soviet Union marked 'DK 296'.


Sites

Total Mosquito production was 7,781, of which 6,710 were built during the war.


Civilian accidents and incidents

A number of Mosquitos were lost in civilian airline service, mostly with
British Overseas Airways Corporation British may refer to: Peoples, culture, and language * British people The British people, or Britons, are the citizens of the United Kingdom of Great Britain and Northern Ireland The United Kingdom of Great Britain and Northern Ir ...
during World War II. * On 17 August 1943, G-AGGF crashed near Glenshee, Perthshire. * On 25 October 1943, G-AGGG crashed near RAF Leuchars. * On 3 January 1944, de Havilland Mosquito G-AGGD stalled on landing at Lidköping-Hovby Airport, Såtenäs, Sweden, and was written off. * On 19 August 1944, de Havilland Mosquito G-AGKP crashed into the North Sea off Leuchars, Fife. All three people on board were killed. * On 29 August 1944, de Havilland Mosquito G-AGKR disappeared on a flight from Gothenburg, Sweden, to RAF Leuchars with the loss of both crew members. What was probably the crash that affected the Mosquito the most in recent times was on 21 July 1996, when de Havilland Mosquito G-ASKH, wearing the markings of RR299, crashed 1 mile west of Manchester Barton Airport. Pilot Kevin Moorhouse and Engineer Steve Watson were both killed in the crash. At the time, this was the last airworthy Mosquito T.III.


Operators


Surviving aircraft

There are approximately 30 non-flying Mosquitos around the world with four airworthy examples, three in the United States and one in Canada. The largest collection of Mosquitos is at the
de Havilland Aircraft Heritage Centre The de Havilland Aircraft Museum, formerly the de Havilland Aircraft Heritage Centre, is a volunteer-run aviation museum in London Colney, Hertfordshire, England. The collection is built around the definitive prototype and restoration shops f ...
in the United Kingdom, which owns three aircraft, including the first prototype, ''W4050'', the only initial prototype of a Second World War British aircraft design still in existence in the 21st century.


Specifications (B Mk.XVI)


Notable appearances in media


See also


Notes


References


Citations


Sources

* Air Ministry. Pilot's Notes For Mosquito B IV. London: 1943. A.P.2019D-PN. * Air Ministry. Pilot's Notes For Mosquito, Marks VIII and IX, Mark XVI. London: 1944. A.P.2653A, B, F, H & J-PN. * Air Ministry. ''Pilot's Notes For Mosquito FB 6''. London: 1945. . * Air Ministry. ''Pilot's Notes For Mosquito NF 38''. London: 1945. . * Batchelor, John and Malcolm Low. ''de Havilland Mosquito Manual'' (Plane Essentials). Victoria, Australia: Publishing Solutions, 2008. . * Bird, Andrew. ''A Separate Little War''. London, UK: Grub Street, 2003. . * Birtles, Philip. ''De Havilland Mosquito: The Original Multirole Combat Aircraft''. Stroud, England: Fonthill Media, 2017. . * Bishop, Edward. ''The Wooden Wonder''. Shrewsbury, UK: Airlife Publishing Ltd., 3rd edition 1995. . * Boiten, Theo. Nachtjagd: the night fighter versus bomber war over the Third Reich, 1939–45. Crowood Press Ltd, 1997 London. * Boog, Horst, Gerhard Krebs and Detlef Vogel. ''Germany and the Second World War: Volume VII: The Strategic Air War in Europe and the War in the West and East Asia, 1943-1944/5.'' Oxford, UK: Clarendon Press, 2006. . * Bowman, Martin. ''de Havilland Mosquito'' (Crowood Aviation series). Ramsbury, Marlborough, Wiltshire, UK: The Crowood Press, 2005. . * Bowman, Martin. ''Mosquito Bomber/Fighter-bomber Units 1942–45''. Oxford, UK: Osprey Publishing, 1997. . * Bowman, Martin. ''Mosquito Fighter/Fighter-bomber Units of World War 2''. Oxford, UK: Osprey Publishing, 1998. . * Bowman, Martin. ''Mosquito Photo-Reconnaissance Units of World War 2''. Oxford, UK: Osprey Publishing, 1999. . * Bowyer, Chaz. ''Mosquito at War''. Shepperton, Surrey, UK: Ian Allan Ltd., 4th impression 1979. . * Bowyer, Michael J.F., Bryan Philpott and Stuart Howe. ''Mosquito (Classic Aircraft No. 7: Their History and How to Model Them)''. Cambridge, UK: Patrick Stephens Ltd., 1980. . * Bridgman, Leonard, ed. "The D.H.98 Mosquito." ''Jane's Fighting Aircraft of World War II''. London: Studio, 1946. . * Buttler, Tony. ''British Secret Projects: Fighters & Bombers 1935–1950''. Hinckley, UK: Midland Publishing, 2004. . * Caldwell, Donald L. and Richard Muller. ''The Luftwaffe Over Germany: Defense of the Reich'' . London: Greenhill MBI Publishing Company, 2007. * Cole, Roger. ''High Wycombe – Local History Series''. Stroud, Gloucestershire, UK: Tempus Publishing Ltd., 2001. . * Connor, Sara Witter, Hamilton Roddis Memorial Lecture Series No. 11. ''Wisconsin Flying Trees: Wisconsin Plywood Industry's Contribution to WWII''. Department of Forest & Wildlife Ecology, Kemp Natural Resources Station, College of Agricultural and Life Sciences, University of Wisconsin – Madison 31 January 2007
Wayback Machine
* Christie, Carl A. ''Ocean Bridge – The history of RAF Ferry Command'' Midland Publishing, Leicester, England, 1995. . * Harris, Sir Arthur T. et al. ''Despatch on War Operations – 23rd. February 1942 to 8th. May 1945''. Frank Cass, England, 1993. . * Hotson, Fred. ''The De Havilland Canada Story''. Toronto: CANAV Books, 1983. . * Malayney, Norman, The 25th Bomb Group (Rcn) History in WWII, Schiffer Publishers Ltd. 2011.. * Miracle, Daniel B. and Steven L. Donaldson. ''ASM Handbook: Composites''. Cleveland, Ohio: ASM International, 2001. . * Mujumdar, A. S. ''Drying '92: Proceedings of the 8th International Drying Symposium''. Toronto: Elsevier, 1992. . * Rhodes, Tom. ''Stress Without Tears''. Jacobs Publishing, 1st edition 1 December 2008. . * Scott, Stuart R. "Mosquito Thunder: No. 105 Squadron RAF at war 1942-5." Sutton Publishing, Stroud, Gloucestershire, UK, 1999. . * Scutts, Jerry. ''Mosquito in Action, Part 2''. Carrollton, Texas: Squadron/Signal Publications Inc., 1993. . * Sharp, C. Martin and Michael J.F. Bowyer. ''Mosquito''. London: Faber & Faber, 1971. . * Sharp, C. Martin and Michael J.F. Bowyer. ''Mosquito (2nd ed.)''. Manchester, UK: Crécy Books Ltd, 1995. . * Simons, Graham M. ''Mosquito: The Original Multi-Role Combat Aircraft''. Barnsley, Yorkshire, UK: Pen & Sword, 2011. * Streetly, Martin. "The Aircraft of 100 Group: Part 14. DH Mosquito, Internal Detail". ''Scale Models'', Volume 12, Issue 139, April 1981. * Stroud, John. "Wings of Peace:- de Havilland Albatross.
''Aeroplane Monthly,''
Volume 18, Issue 206, June 1990. * Thirsk, Ian.''de Havilland Mosquito: An Illustrated History Volume 2''. Manchester, UK: Crécy Publishing Limited, 2006. . * Thomas, Geoffrey J. and Barry Ketely. ''KG 200: The Luftwaffe's Most Secret Unit''. Tokyo: Hikoki Publications, 2003. . * Wooldridge, John de L. ''Low Attack – The story of two Mosquito squadrons, 1940–1943''. Crecy Books, England, 1993. .


Further reading

* Anoni, Shlomo. "The Last of the Wooden Wonders: The DH Mosquito in Israeli Service". ''Air Enthusiast'', No. 83, September–October 1999, pp. 30–51. * Birtles, Philip. ''Mosquito: A Pictorial History of the DH98''. London: Jane's Publishing Company Ltd., 1980. . * Birtles, Philip. ''De Havilland Mosquito: The Original Multirole Combat Aircraft''. Stroud, England: Fonthill Media, 2017. . * * Gilman J.D. and J. Clive. ''KG 200''. London: Pan Books, 1978. . * Hardy, M.J. ''The de Havilland Mosquito''. Devon, UK/New York: David & Charles (Publishers) Ltd./Arco Publishing, 1977. , (David & Charles) (Arco). * Hinchcliffe, Peter. ''The Other Battle: Luftwaffe Night Aces vs Bomber Command''. London: Zenith Press, 1996. . * Holliday, Joe. ''Mosquito! The Wooden Wonder Aircraft of World War II''. Toronto: Doubleday, 1970. . * Howe, Stuart. ''Mosquito Portfolio''. London: Ian Allan Ltd., 1984. . * Jackson, Robert. ''de Havilland Mosquito'' (Combat Legend). Shrewsbury, UK: Airlife Publishing Ltd., 2003. . * Jones, R.C. ''de Havilland Mosquito: RAF Northern Europe 1936–45''. London: Ducimus Books Ltd., 1970. * Mason, Francis K. and Richard Ward. ''De Havilland Mosquito in RAF-FAA-RAAF-SAAF-RNZAF-RCAF-USAAF-French & Foreign Service''. Canterbury, Kent, UK: Osprey Publishing Ltd., 1972. . * McKee, Alexander. ''The Mosquito Log''. London: Souvenir Press Ltd., 1988. . * Morgan, Hugh and John Weal. ''German Jet Aces of World War 2''. London: Osprey Publishing Ltd, 1998. . * Price, Nigel (ed.). "Mosquito: A Celebration of de Havilland's 'Wooden Wonder'.
FlyPast Special
Stamford, Lincolnshire, UK: Key Publishing Ltd., 2009. * Radinger, Will and Walter Schick. ''Me262'' (German lang. ed.), Berlin: Avantic Verlag GmbH, 1996. . * Sasbye, Kjeld Mahler. ''Operation Carthage''. Copenhagen: Den Danske Luftfartsskole, 1994. . * Scholefield, R.A. ''Manchester Airport''. Stroud, UK: Sutton Publishing, 1998. . * Scutts, Jerry. ''Mosquito in Action, Part 1''. Carrollton, Texas: Squadron/Signal Publications Inc., 1993. . * Shacklady, Edward. ''De Havilland Mosquito (Classic WWII Aviation, Volume 6)''. Bristol, UK: Cerberus Publishing Ltd., 2003. . * Stanley, Colonel Roy M. II, USAF (Ret). ''V-Weapons Hunt: Defeating German Secret Weapons.'' Barnsley, South Yorkshire, UK: Pen & Sword, 2010. . * Sweetman, Bill and Rikyu Watanabe. ''Mosquito''. London: Jane's Publishing Company Ltd., 1981. .


External links


The Mosquito Page at Mossie.org

de Havilland Aircraft Heritage Centre a.k.a. Mosquito Aircraft Museum

Calgary Mosquito Aircraft Preservation Association
*
Victoria Air Maintenance Ltd. Restoring a Mosquito to flying condition

The People's Mosquito Ltd. UK charity restoring Mosquito RL249 to flight. Website features WW2 colour film of the Mosquito

de Havilland Mosquito magazine articles and publications



Mosquito restoration project New Zealand (633 Squadron theme)
Retrieved: 3 January 2012.
Wartime film of the construction of the Mosquito in Australia
Retrieved: 3 January 2012.
"Flying Plywood With A Sting": ''Popular Science'' article, December 1943

A close-up picture of the nose of a Tsetse Mosquito FB Mk XVIII showing the Molins 57 mm gun muzzle



"Mosquito Wars on U-Boats With 6-pound Shells.": ''Popular Mechanics'' article, February 1945, p. 39.

Wartime footage of Coastal Command 57mm cannon and 60lb rocket-armed Mosquitos

Mosquito Pathfinders, Pathfinder Museum

627 Squadron RAF Mosquito Pathfinders Based at RAF Woodall Spa

Air Accidents Investigation Branch (AAIB) report on the crash of T.III G-ASKH, 1996

IWM Image of Mosquito PR34 ''RG241'', which holds the twin piston-engine Atlantic crossing record.

"America Reports On Aid To Allies etc. (1942)."
''Universal Newsreel''
"Mosquito Makes Base"
a 1943 ''Flight'' article on a Mosquito Intruder's battle damage

a 1944 ''Flight'' advertisement

a 1969 ''Flight'' article by Air Commodore Allen Wheeler
Mosquito
from the IBCC Digital Archive at the University of Lincoln. {{Authority control De Havilland Mosquito, 1940s British bomber aircraft De Havilland aircraft, Mosquito De Havilland Canada aircraft, Mosquito Mid-wing aircraft Reconnaissance aircraft Twin piston-engined tractor aircraft World War II British bombers World War II British fighter aircraft World War II British night fighter aircraft Aircraft first flown in 1940