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The de Havilland Mosquito was a British combat aircraft that excelled in a number of roles during the Second World War. It served with the RAF and many other air forces both in the Second World War and postwar. The Mosquito was known affectionately as the "Mossie" to its crews and was also known as "The Wooden Wonder" or "The Timber Terror."
The Mosquito was a twin-engine aircraft, powered by a pair of Rolls-Royce Merlin engines with the pilot and navigator sitting side by side. Unorthodox in design, it used a plywood structure of spruce and balsa in a time when wooden construction was considered outmoded. In the conceptual design stage, de Havilland designers found that adding any defensive armament would significantly reduce the aircraft's maximum speed. Realising that the loss in performance was not worth the benefit, the initial bomber version was designed without any guns. The Mosquito was a very versatile aircraft; originally conceived as a fast day bomber, the various roles of the Mosquito included: tactical bomber, pathfinder, day or night fighter, fighter-bomber, intruder, maritime strike and photo reconnaissance aircraft.
The de Havilland company conceived the idea of a wooden aircraft to take advantage of the underused resources and skills of the furniture industry at a time of great pressure on the conventional aircraft industry combined with wartime shortages of steel and aluminium. The Air Ministry was initially not interested in the innovative approach; de Havilland, under chief designer Ronald Bishop, developed the Mosquito on a speculative basis. The ministry became interested when they saw the Mosquito prototype's performance.
Throughout the 1930s, de Havilland had established a reputation in developing innovative high-speed aircraft such as the DH.88 Comet mail-plane and DH.91 Albatross airliner that had already successfully employed the composite wood construction that the Mosquito would use.
The Mosquito was an all-wood mid-wing cantilever monoplane, with one-piece wing and an oval section jig-built fuselage and conventional tail unit. It was powered by two wing-mounted Rolls-Royce Merlin piston engines with three-bladed aircrews. The Mosquito had a retractable landing gear and tail wheel, the hydraulically operated main landing gear retracted into the rear of the engine nacelles. It had side-by-side accommodation for two in the nose with the entrance to the cockpit from a door in the starboard side. The unarmed bomber and photo-reconnaissance versions had a transparent nose for a bomb-aimer and the entrance door through hatch in the floor.
The genius of the aircraft's construction lay in the innovative and somewhat unorthodox use of seemingly commonplace materials and techniques. The bulk of the Mosquito was made of plywood. Stronger and lighter than most grades of plywood, this special plywood was produced by a combination of 3/8" sheets of Ecuadorean balsa wood sandwiched between sheets of Canadian birch plywood. Sheets of wood alternated with sheets of a special casein-based (later formaldehyde) wood glue.
The fuselage was formed in concrete moulds. Left and right sides of the fuselage were fitted with bulkheads and structural members separately while the glue cured. Reinforcing was achieved with hundreds of small brass wood screws. This arrangement greatly simplified the installation of hydraulic lines and other fittings, as the two halves of the fuselage were open for easy access by workers. The halves were then glued and bolted together, and covered with doped Madapolam fabric.
The wings were also made of wood. To increase strength, the wings were made as one single assembly, onto which the fuselage, once both halves had been mated, was lowered and attached.
Metal was used sparingly in the construction of structural elements. It was mostly used in engine mounts and fairings, control surfaces, and, of course, brass screws.
The glue used was initially casein-based. It was changed to a formaldehyde-based preparation when the Mosquito was introduced to fighting in semi-tropical and tropical climates, after some unexplained crashes led to the suspicion that the glue was unable to withstand the climate. De Havilland also developed a technique to accelerate the glue drying by heating it using microwaves.
In England fuselage shells were mainly made by E. Gomme, Parker-Knoll and Styles and Mealing. Wing spars were made by J. B. Heath and Dancer and Hearne. Many of the other parts, including flaps, flap shrouds, fins, leading edge assemblies and bomb doors were also produced in High Wycombe, which was well suited to these tasks due to a well established furniture making industry. Dancer and Hearne processed much of the wood from start to finish, receiving timber and transforming it into finished wing spars at their High Wycombe factory. Around 5,000 of the total 7,781 Mosquitos ever made contained parts made in High Wycombe.
In Canada, fuselages were built in the Oshawa, Ontario plant of General Motors of Canada Limited. These were shipped to De Havilland of Canada.
The specialized wood veneer used in the construction of the Mosquito was made by Roddis Manufacturing in Marshfield, Wisconsin, United States. Hamilton Roddis had teams of dexterous young women ironing the (unusually thin) strong wood veneer product before shipping to the UK.
The Mosquito is often described as having been faster than enemy fighters. On its introduction to service, the aircraft was about as fast as the front-line German fighters that opposed it, the BF 109F and Fw 190A. Advancements in those aircraft would eventually outpace performance improvements in the Mosquito. Nonetheless their speed margin was slim enough that, by the time those aircraft could reach interception altitude, the Mosquito would have completed its bombing run and would be racing for home. Furthermore, the Mosquito could sustain its dash over a greater distance than the opposing fighter aircraft.
With the introduction of the nitrous oxide boosted Bf 109s and the jet-powered Me 262 late in the war, the Luftwaffe had interceptors with a clear speed advantage over the Mosquito. The PR Mk 32 photo reconnaissance version of the Mosquito attempted to counter this with long-span wings, special high-altitude superchargers and the elimination of as much weight as possible, raising its cruising altitude to 42,000 feet (12,800 metres). Even with these changes, the Mosquito was not totally immune – in December 1944, one was intercepted at maximum altitude.
The first bomber squadrons to receive the Mosquito B IV used it for several low-level daylight raids. One was carried out in the morning of 30 January 1943, against a Nazi rally in Berlin, giving the lie to the speaker's (Reichmarschall Hermann Göring's) claim that such a mission was impossible. Not content with this, Mosquitos from RAF No 139 Squadron went to Berlin in the afternoon and tried to interrupt an important speech by Joseph Goebbels, Germany's Propaganda Minister.
Mosquito bomber versions were used as part of Bomber Command; the Pathfinders in No. 8 Group and the Light Night Striking Force (LNSF). The LNSF carried out high speed night raids with precision aiming and navigation. Their mission was twofold: first, they would target small but vital installations; and second, they would act as a diversion from the raids of the heavy bombers, simulating large formations through the use of chaff. On nights when no heavy bomber raid was planned, the LNSF would often strike so the German air defences would not get a rest.
As part of No. 8 Group Mosquitos took part in many bombing operations as pathfinders, marking targets accurately with flares for later attack by massive formations of heavy bombers. Bomber Command Mosquitos flew over 28,000 operations, dropping 35,000 tons of bombs, and losing just 193 aircraft in the process (a loss rate of 0.7%, compared to a 2.2% loss rate for the four engined heavies). It has been calculated that a Mosquito could be loaded with a 4,000 lb. "cookie" bomb, fly to Germany, drop the bomb, return, bomb up and refuel, fly to Germany again and drop a second 4,000 lb bomb and return, and still land before a Stirling (the slowest of Bomber Command's four-engined bombers) which left at the same time armed with a full bomb load, could strike Germany.
A Mosquito IX also holds the record for the most missions flown by an Allied bomber in the Second World War. LR503, "F for Freddie," first serving with 109 and subsequently 105 Squadron, flew 213 sorties during the war, only to crash on 10 May 1945, two days after VE Day at Calgary airport during a victory tour, an accident attributed to pilot error.
The use of the Mosquito as a night fighter came about when the Air Ministry project for a night fighter (based on the Gloster F.9/37) was terminated to concentrate production on other types.
The first fighter Mosquito introduced into service was the NF Mk II in mid 1942, with four 20 mm Hispano cannon in the fuselage belly and four 0.303 in. Browning machine-guns mounted in the nose. It carried Aircraft Interception radar (AI) Mk IV / Mk V when operating as a defensive night fighter over the UK, although at the time this was omitted from Mk IIs operating as night "Intruders," roaming over Europe at night to cause maximum disruption to lines of communications and flying operations.
In May 1942, the NF Mk II scored its first kill and until the end of the war, Mosquito night fighters claimed approximately 600 enemy aircraft, along with 600 V-1 flying bombs. This variant also operated over Malta, Italy, Sicily and North Africa from late 1942 on. The Mosquito NF XII became the first aircraft to carry the highly effective centimetric radar.
From early 1944 the Mosquito also operated in the bomber support role with Bomber Command's 100 Group, their task being to harass the Luftwaffe NachtJagd (night fighters) attacking the bomber streams over Germany. Some 258 Luftwaffe night fighters were claimed destroyed by the Group, for the loss of some 70 Mosquitoes. The omniprescence of the potent night fighter threat led to what the Luftwaffe crews dubbed "Mosquitoschreck" (Mosquito scare), as the German aircrews were never sure when or where they may come under attack from the marauding 100 Group fighters and indirectly led to a high proportion of both aircraft wastage from crashes as night fighters hurried in to land to avoid the Mosquito threat (real or imagined).
The Mosquito night fighters would meet their nemesis only in February, 1945, when Messerschmitt 262 jet fighters were being flown at night by pilots from 10./NJG 11. The commander of this unit, Oberleutnant Kurt Welter, claimed perhaps 25 Mosquitos shot down by night and two further Mosquitos by day while flying the Me 262, adding to his previous seven Mosquito kills in "hot-rodded" Bf 109G-6/AS fighters. This effort was too little and too late to have any effect of the outcome of the war.
Operational experience in its varied roles quickly led to the development of a versatile fighter-bomber version; the FB VI, which first saw service in early 1943. The Mark VI had a strengthened wing for external loads and along with its standard fighter armament could carry two 250 lb bombs in the rear of the bomb bay and two 250 lb bombs under the wings, or eight wing-mounted rockets. Later up-engined versions could carry 500 lb bombs. The FB VI became the most numerous version of the Mosquito, (2,292 built) equipping the day bomber 2 Group, the intruder squadrons of Fighter Command and 2nd TAF, and the strike wings of Coastal Command, who used the variant as a potent anti-shipping aircraft armed with eight "60 lb" rockets.
The USAAF ordered 120 Mosquitos for photographic reconnaissance, but only 40 were delivered and given the US designation F-8 (6 Canadian-built B Mk VII and 34 B Mk XX). Only 16 reached Europe, where 11 were turned over to the RAF and five were sent to Italy. The RAF provided 145 PR Mk XVI aircraft to the Eighth Air Force between 22 April 1944 and the end of the war. These were used for a variety of weather, photographic, and night reconnaissance missions; as chaff dispensers; as scouts for the heavy bomber force; on "Red Stocking" OSS missions; and as H2X Mickey platforms by the 802d Reconnaissance Group (Provisional), later re-named the 25th Bomb Group (Reconnaissance). The 25th BG flew 3,246 sorties and lost 29 PR Mk XVIs on operations.
Between 1943 and the end of the war, Mosquitos were used as transport aircraft on a regular route over the North Sea between Leuchars in Scotland and Stockholm. Lockheed Hudsons and Lodestars were also used but these slower aircraft could only fly this route at night or in bad weather to avoid the risk of being shot down. During the long daylight hours of summer, the Mosquito was the only safe alternative.
Because Sweden was neutral, the aircraft carried civilian markings and were operated by Norwegian officers, who were nominally "civilian employees" of BOAC. They carried small, high value cargos such as precision ball bearings and machine-tool steel. Occasionally, important passengers were carried in an improvised cabin in the bomb bay, one notable passenger being the physicist Niels Bohr, who was evacuated from Stockholm in 1943 in an unarmed Mosquito sent by the RAF. The flight almost ended in tragedy as Bohr did not don his oxygen equipment as instructed, and passed out. He would have died had not the pilot, surmising from Bohr's lack of response to intercom communication that he had lost consciousness, descended to a lower altitude for the remainder of the flight. Bohr's comment was that he had slept like a baby for the entire flight.
Mosquitos flying with the Israeli Air Force saw action during the 1956 Suez Crisis. Although, at the time, the Mosquito was being taken out of service, 13 aircraft of various marks were taken out of storage. An additional 13 TR 33 Mosquitos were purchased from a British scrap dealer in 1954.
Sweden purchased 60 ex-RAF Mk XIX Mosquitos in 1948 to be used as a night fighter under the J 30 designation. The planes were assigned to the F1 Wing at Västerås, thereby becoming the first (and only) dedicated night fighter unit of the Swedish Air Force. Its Mosquitos were replaced by jet fighters (de Havilland Venom Mk 51, designated J 33) in 1953. One third of the J 30s crashed or broke down during service, mainly due to rudder problems. However, Swedish air force general Björn Bjuggren writes in his memoirs that mechanical problems in the swivelling nose-mounted radar antenna caused destructive vibrations that broke apart one or two J 30s in the air.
Mosquito Mk I : First prototype aircraft.
Mosquito Mk II : Second prototype aircraft.
The photo-reconnaissance model became the basis for the Mosquito PR Mk I, while the bomber model became the Mosquito B Mk IV, of which 273 were built. The first operational sortie by a Mosquito was made by a PR Mk I on 20 September 1941, and the Mk IV entered service in May 1942 with No. 105 Squadron. The B Mk IV could accommodate 4 × 500 lb (227 kg) bombs in the bomb bay, and either two drop tanks or two additional 500 lb bombs on wing hardpoints.
Mosquito PR.Mk IV : This designation was given to 32 Mosquito B.Mk IV bombers, converted into two-seat photo-reconnaissance aircraft.
Mosquito PR.Mk VIII : Photo-reconniassance version. Powered by two Rolls-Royce Merlin 31 piston engines. 25 built.
Mosquito PR.Mk IX : Photo-reconnaissance version based on the Mosquito B.Mk IX bomber aircraft. Powered by two 1,680-hp (1253-kW) Rolls-Royce Merlin 72 piston engines.
Mosquito PR.Mk 32 : Long-range photo-reconnaissance version. Powered by two 1,960-hp (1260-kW) Rolls-Royce Merlin 32 piston engines. Five conversions.
Mosquito PR.Mk 34 : Very long-range photo-reconnaissance version. Addition fuel was carried in a bulged bomb-bay. 50 built.
Mosquito B.Mk V : One prototype bomber aircraft fitted with underwing pylons. One built.
Mosquito B.Mk 35 : Long-range high-altitude bomber version. Fitted with a pressurised cockpit. 122 built.
Developed during 1940, the Mosquito F Mk II was developed and the first prototype was completed on 15 May 1941. These aircraft were fitted with four 20 mm Hispano cannon in the fuselage belly and four 0.303 in. Browning machine guns mounted in the nose. This fit required the movement of the crew ingress/egress door from the bottom to the right side of the nose. The aircraft also featured a revised windscreen, with flat bullet proof panels in front, as opposed to the original design.
The first production night fighter Mosquitos were designated the Mosquito NF Mk II. 466 were built with the first entering service with No. 157 Squadron in January 1942, replacing the Douglas Havoc. These aircraft were similar to the F Mk II, but were fitted with the AI Mk IV metric wavelengthradar. The herring-bone transmit antenna was mounted on the nose and the dipole receive antennae were carried under the outer wings. A number of NF IIs had their radar equipment removed and additional fuel tanks installed for use as night intruders. These aircraft, designated NF II (Special) were deployed to Malta on 20 December 1942, and operated against targets in Italy.
Ninety-seven NF Mk IIs were upgraded with centrimetric AI Mk VIII radar and these were designated the Mosquito NF.Mk XII. The Mosquito NF Mk XIII, of which 270 were built, was the production equivalent of the Mk XII conversions. The centimetric radar sets were mounted in a solid "thimble" (Mk XII / XIII) or "bull nose" (Mk XVII / XIX) radome, which required the machine guns to be dispensed with. The other night-fighter variants were the Mk XV, Mk XVIII (converted Mk IIs), Mk XIX and Mk 30. The last three marks mounted the US-built AI Mk X radar.
Mosquito NF Mk X: Unbuilt night-fighter version.
Mosquito NF Mk XI: Unbuilt night-fighter version.
Mosquito NF Mk XIV: Unbuilt night-fighter version.
Mosquito NF Mk XV: This designation was given to five Mosquito B.Mk IV bombers, which were converted into two-seat high-altitude night-fighters.
Mosquito NF Mk XVII: Designation for 99 NF.II conversions, with single-stage Merlin 21, 22, or 23 engines, but British AI.X (US SCR-720) radar.
Mosquito NF Mk XVIII: This designation was given to 100 Mosquitos NF.Mk IIs, which were fitted with the American AI.Mk X radar.
Mosquito NF Mk XIX: Improved version of the Mosquito NF XIII night-fighter aircraft. It could be fitted with American or British AI radars. 220 built.
Mosquito NF Mk 30: High-alititude night-fighter version. Powered by two 1,710-hp (1275-kW) Roll-Royce Merlin 76 piston engines. It also carried early ECM equipment. 526 built.
Mosquito NF Mk 31: Unbuilt night-fighter version. After the war, two more night fighter versions were developed, the NF Mk 36 and the NF Mk 38.
Mosquito NF Mk 36: Similar to the mosquito NF.Mk 30 night-fighter, but fitted with the American-built AI.Mk X radar. Powered by two 1,690-hp (1260-kW) Roll-Royce Merlin 113/114 piston engines. 266 built.
Mosquito NF Mk 38: Similar to the Mosquito NF.Mk 30 night-fighter, but fitted with the British-built AI Mk IX radar. 50 built. To warn German night fighters that they were being tracked by these radars, the Germans introduced Naxos ZR radar detectors.
Mosquito night intruders of No. 100 Group RAF, Bomber Command, were also fitted with a device called "Serrate" to allow them to track down German night fighters from their Lichtenstein B/C and SN-2 radar emissions, as well as a device named "Perfectos" that tracked German IFF.
The most numerous Mosquito variant was the FB Mk VI fighter-bomber of which 2,718 were built. Originally converted from a Mk II, the Mk VI first flew in February 1943. Designed for a fighter-bomber role, the Mk VI could carry two 250 lb (110 kg) or two "short-fin" 500 lb (230 kg) bombs in the internal bomb bay as well as two more bombs under the wings. From early 1944, Coastal Command operated Mk VIs armed with eight 60 lb (27 kg) rockets to carry out anti-shipping strikes.
Other fighter-bomber variants were the Mosquito FB Mk XVIII (sometimes known as the Tsetse) of which 27 were made by converting Mk VIs. These were fitted with a Molins 57 mm cannon, a 6 pounder anti-tank gun modified with an auto-loader to allow both semi- or fully-automatic fire, in the nose, along with two .303 in (7.7 mm) sighting machine guns. The Air Ministry initially suspected that this variant would not work, but mock tests proved otherwise. Although the gun provided the Mosquito with yet more anti-shipping firepower to pit against U-boats, it required a steady and vulnerable approach-run to aim and fire the gun, thus making rockets more effective, especially because Mosquitos without the 6 pounder didn't suffer the weight penalty of the gun. The FB Mk 26 and FB Mk 40, based on the Mk VI, were built in Canada and Australia and were powered by Packard-built Merlin engines.
All the fighter variants shared a number of common features. They had a flat, single-piece armoured windscreen and the pilot was provided with a fighter-style control stick rather than a wheel. The guns in the nose also meant that the bomber variants' entry hatch in the nose had to be relocated to a door on the starboard side, forward of the leading edge.
The Mosquito was also built as a trainer.
Mosquito T.Mk III : Two-seat training version. Powered by two Rolls-Royce Merlin 21 piston engines. 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.
Mosquito B.Mk VII : Canadian version based on the Mosquito B.Mk V bomber aircraft. Powered by two 1,418-hp (1057-kW) 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 1,460-hp (1089-kW) 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 : Unbuilt bomber version.
Mosquito FB.Mk 24 : Canadian fighter-bomber version. Powere by two 1,620-hp (1208-kW) 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 1,620-hp (1208-kW) 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 1,620-hp (1208-kW) 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.
To meet specification N.15/44 for Royal Navy use, de Havilland produced a carrier-borne variant. This resulted in 50 Sea Mosquito TR Mk 33s which featured folding wings, a thimble nose radome and fuselage hardpoints for mounting torpedoes. These were followed by 14 Sea Mosquito TR Mk 37s, which differed in having ASV Mk. XIII radar instead of the TR.33's AN/APS-6.
The Royal Navy also operated the Mosquito TT Mk 39 for target towing. A number of B.Mk XVIs bombers were converted into TT.Mk 39 target tug aircraft. The RAF's target tug version was the Mosquito TT Mk 35 which were the last aircraft to remain in operational service, finally being retired in 1956.
Mosquito FB.Mk 40 : Two-seat fighter-bomber version for the RAAF. Powered by two 1,460-hp (1089-kW) Roll-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 built in Australia.
Mosquito PR.Mk 41 : Two-seat photo-survey version for the RAAF. A total of 17 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.
Total Mosquito production was 7,781 of which 6,710 were built during the war. De Havilland accounted for 5,007 aircraft built in three factories in the United Kingdom. Mosquitos were also built by Airspeed, Percival Aircraft Co and Standard Motor Co.
The Canadian and Australian arms of de Havilland produced 1,134 and 212 aircraft respectively. The ferry operation of the Mosquito from Canada to the war front was problematic, as a small fraction of the aircraft would mysteriously disappear over the mid-Atlantic. The theory of "auto-explosion" was offered, and, although a concentrated effort at de Havilland Canada to address production problems with engine and oil systems reduced the number of aircraft lost, it was unclear as to the actual cause of the losses. The company introduced an additional five hours flight testing to "clear" production aircraft before the ferry flight. By the end of the war, nearly 500 Mosquito bombers and fighter-bombers were delivered successfully by the Canadian operation.
The last Mosquito was completed in November 1950; an NF Mk 38 built at Broughton near Chester.
There were 7,781 produced