Dedicated to all those who served with or supported the 456th Fighter Squadron or 456th Fighter Interceptor Squadron or the UNITED STATES AIR FORCE
The Stratocruiser had the same By late 1942 the Mosquito was becoming operational in ever increasing numbers, and its unique qualities of very high speed and long range were clearly ideal for many missions. (Graphic courtesy of www.skywear.com)
The origins of the Mosquito can be traced to Air Ministry Specification P.13/36 issued on 24th August 1936 by Air Commodore R.H.Verney on behalf of the RAF Directorate of Technical Development (DTD). Specification P.13/36 called for a 'twin-engined medium bomber for world-wide use' and continued: 'It should be an aircraft that can exploit the alternatives between long range and very heavy bomb load which are made possible by catapult launching in heavily loaded condition. During all operations it is necessary to reduce time spent over enemy territory to a minimum. Therefore the highest possible cruising speed is necessary.'
The Specification also called for defensive armament consisting of nose and tail gun turrets, horizontal bomb stowage in tiers if needed and suitability for outdoor maintenance at home or abroad. 'It appears', it said, 'there is a possibility of combining medium-bomber, general reconnaissance and general purpose classes in one basic design,' and went on to suggest that two 18-inch torpedoes might be carried. A top speed of 275 mph was required at 15,000 feet, and a range of 3,000 miles with a 4,000-lb. Bomb load. Consideration would be given to remotely controlled guns.
De Havilland was one of the companies invited to tender for military specifications, but generally at the time preferred to build civil aircraft for the open market following experiences in the 1920's, and a wariness of government specifications. When the threat from Hitler began to appear grave however, consideration was given to Specification P.13/36 by de Havilland. The DH.91 Albatross airliner, manufactured from wood with stressed skin construction, and DH.94 Moth Minor light aircraft were the company's newest projects at the time, having flown for the first time on 20th May and 22nd June 1937 respectively.
Following experiences with the Albatross, de Havilland noted that the concepts of aerodynamic cleanliness and minimum skin area to keep drag to a minimum were equally valid for the design of a bomber as a fighter, and initially a military version of the Albatross was one time saving possibility considered to meet the specification. A twin Merlin Albatross estimate appeared in April 1938, with Hercules HE 1M and Sabre engine comparisons.
On 7th July a letter was sent to Sir Wilfred Freeman, an old friend of de Havilland's from WW1, now Air Council Member for Research and Development, discussing the specification and arguing for wood construction. De Havilland noted that except in torsion, wood's strength for weight was as great as that of duralumin or steel. The letter further suggested that should war break out without warning, the adequate supplies of suitable timber and a capable workforce in the form of labour from the furniture, coach building and other woodworking trades would aid in having the new aircraft in service rapidly. De Havilland felt however that Specification P.13/36 would produce a mediocre aircraft and suggested a different approach.
In a second letter dated 27th July, de Havilland distanced themselves still further when they concluded that the specification could not be met by two Merlins - if speed was paramount, then only half the required bomb load could be carried, if load was paramount, a larger, slower aircraft would result. A two Merlin compromise design was arrived at on 11 August, with a bomb load of 4,000 lb., a top speed of 260 mph and a range of 1,500 miles. However it was felt that to continue would have been an admission of defeat in design principles and the company soon rejected the idea.
The Munich crisis of September 1938 brought greater urgency to the preparations for hostilities. De Havilland began to consider a new, smaller aircraft with a crew of two, powered by two Merlin engines and completely sacrificing armament for speed. De Havilland and C.C Walker went to the Air Ministry early in October to make this proposal. Again they advocated wood construction, estimating a saving of a year in the prototype stage and also timesaving in aircraft production and development of subsequent variants.
The Blenheim, Whitley, Wellington and Hapden, heavily (for the time) armed bombers of metal construction, were by now in production, with the trend being towards larger four-engined machines. Not surprisingly perhaps, de Havilland's proposal was unceremoniously rejected; the Air Ministry was simply not interested in the unarmed bomber concept. Perhaps de Havilland could take on building wings for one of the other bombers instead?
De Havilland "Mosquito" Fighter Bomber
The prototype made its first flight on November 25,1940. This was only ten months and twenty-six days after detailed design work had commenced.
It is one of the paradoxes of aircraft development that some of the world's greatest aeroplanes have achieved their fame doing jobs other than the one for which they were originally designed. No better example of this could be found than the Mosquito, which, conceived as a bomber, became one of the war's most potent fighters. More than this, indeed, it was probably the most successfully versatile of any twin-engined type built between 1939 and 1945. It excelled in all the widely varied roles. Its duties included the duties of low-level and high-attack day and night bomber, long-range photo-reconnaissance, mine layer, pathfinder, high-speed military transport, long-range day and night fighter, and fighter-bomber. It served in Europe, the Middle and Far east and on the Russian front. In fact, the ubiquitous Mosquito reigned supreme among General Purpose types. Of the grand total of 7,781 Mosquitos built, 6,710 were delivered during the war years.
On March 1, 1940, the first contract was placed, for fifty D.H.98 bombers (including prototypes) to be built to specification B.1/40 which had been written around De Havilland's proposals, and the name Mosquito was approved. The period was an inauspicious one for the initiation of so radical a design. With the war going against Britain, the tendency was to concentrate on existing designs. With the fall of France and the Dunkirk evacuation, the Mosquito was actually dropped from Ministry of Aircraft Production programs at one stage, setting back the ordering of materials. But permission to proceed was later given again, although De Havillands were told that their Tiger Moth and Oxford production were to take priority. Had it not been that the Mosquito used "non-strategic" molded plywood for its construction, it might well never have been reinstated.
The prototype night fighter with a circular segmented air brake installation.
Construction of the prototype was pressed ahead through the difficult months of 1940. While the "Battle of Britain" was fought out overhead, bombs fell within a mile of the Hatfield factory, on one day in every five. Nearly 25 per cent of the working hours, day and night, were spent in air-raid shelters. Despite all these vicissitudes, the prototype (W4050) made its first flight on November 25, 1940, only ten months and twenty-six days after detailed design work had commenced. The pilot was Geoffrey De Havilland, Jr. Meanwhile, inevitably, requirements had been changing. There was some loss of confidence in the high-speed bomber, while the heavily armed long range fighter grew in favor. The contract was therefore changed to twenty bombers and thirty fighters, necessitating the modification of a number of parts already manufactured. Construction of a fighter prototype proceeded at Salisbury Hall, London Colney, which served as a dispersal for the Hatfield design office and experimental shop. Two days before this prototype (W4052) was ready to fly, a German agent was dropped by parachute close to Salisbury Hall, in plain clothes and with a portable radio. He was captured next day, and the day after, May 15, 1941, Geoffrey De Havilland flew the fighter prototype from a 450-yard field beside the shed in which it had been built.
The first Mosquito sortie was made on September 20,1941, when a single aircraft made a reconnaissance flight over France. At home, the Mosquito night fighter, carrying A.I Mk IV airborne radar, began to take over from the Bristol Blenheim. By late 1942, the Mosquito was becoming operational in ever increasing numbers, and its unique qualities of very high speed and long range were clearly ideal for a particular mission then being planned.
It had been decided that an attack should be made on the German Gestapo headquarters in Oslo, Norway, which contained records of members of underground resistance organizations. Such a mission would, if successful, help protect those who were supplying Britain with secret information. Therefore, on September 25,1942, Mosquitos carried out a long range attack on the HQ, accurately bombing the building and then returning home at high speed.
A De Havilland Mosquito Mk. B-4 .
The basic fighter Mosquito introduced into squadron service in 1942 was the N.F.Mk.II, equipped primarily as a night-fighter and used for home defense alongside the Bristol Beaufighter. Its armament comprised four 20 mm cannon in the front fuselage belly and four 0.303 in. Browning machine-guns in the extreme nose. It carried Aircraft Interception (AI) Mk.IV or AI Mk.V "arrowhead" radar and a G-45 machine gun. Its matt-black overall finish, incidentally, reduced its maximum speed by 16 mph. Power was provided either by two Merlin 21 engines giving 1,280 hp for takeoff and 1,480 hp at 12,250 feet, or two Merlin 23 engines giving 1,390 hp for takeoff and the same maximum power at 12,250 feet.
On the night of May 28-29,1942, Mosquito N.F.IIs scored their first "probable," and in the following three years, Mosquito night-fighters racked up a score of approximately 600 enemy aircraft over the British Isles, and also destroyed 600 flying bombs in a two month period. They later operated in the bomber support role, their task being to defend the main heavy bomber streams over enemy territory. Of the 466 Mark II Mosquito fighters produced, some of the later aircraft had day-fighter finish and, with the AI radar removed, operated over Malta, Italy, Sicily and North Africa from the end of 1942 onwards.
Operational experience with the Mosquito II in its day-fighter and intruder roles led to the development of the F.B.VI, a potent fighter-bomber which came into service during the early months of 1943. It had been discovered that the Mosquito was able to accommodate a much greater warload than that for which it had been designed, and thus the Mark VI, with a strengthened wing for external loads which later became known as the "basic" wing, carried a full complement of cannon and machine-guns, two 500 lb. bombs in the rear half of the bomb bay (the front half containing the cannon breeches) and two 500 lb. bombs under the wings. Actually, the full 2,000 lb. bomb load was only carried by the Mark VI Series 2 which took advantage of the 1,620 hp available from the Merlin 25 for takeoff, the first 300 machines being F.B.VI Series 1 Mosquitos with Merlin 21s or 23s and carrying two 250 lb. bombs internally.
Specifications: De Havilland D.H.98 Mosquito N.F.XIX Dimensions: Wing span: 54 ft. 2 in. (16.5 m) Length: 41 ft. 2 in. (12.54 m) Height: 15 ft. 3 in. (4.64 m) Weights: Empty: 15,970 lb (7,243 kg) Normal: 20,600 lb. (9,344 kg) Max Gross: 21,750 lb. (9,865 kg) Performance: Maximum Speed: 378 mph (608 km/h) @ 13,200 ft. (4,023 m) Cruise Speed: 295 mph (474 km/h) @ 20,000 ft. (6,096 m) Service Ceiling: 28,000 ft. (8,534 m) Range: 1,400 miles (2,253 km) (with 453 Imp. gal.)
1,905 miles (3,065 km) (with 616 Imp. gal.,
including two 50-gal. droptanks)
Powerplant: Two Rolls-Royce Merlin 25 twelve-cylinder 60ř Vee liquid-cooled engines each providing 1,620 hp (1,208 kw) @ takeoff and
1,500 hp (1,118 kw) @ 9,500 ft. (2,895 m).
Armament: Four 20-mm. British Hispano cannon
Later, in mid-1943, the Mosquito FB Mk VI was becoming operational. As well as the usual RAF duties, it was used by Coastal Command as an anti-shipping aircraft, armed with eight 60 lb. rocket projectiles. More unusual weapons carried by some Mosquitos included a 57 mm cannon for ground attack (this devastating gun was capable of destroying any armored vehicle), and the 4,000 lb. 'block-buster' bomb. Even with this bomb on board, the Mosquito could out fly most German night fighters, and on numerous occasions it attacked far-off Berlin and German V1 flying-bomb sites.
An entirely separate line of development from the Mosquito Night Fighter (NF) II produced a series of night-fighting variants which were primarily used for home-defense purposes. The first of these was the NF XII, plans to produce the NF VI with Merlin 21s and the "basic" wing, and the NF X with Merlin 61s and the "basic" wing, having been abandoned. The Mosquito NF XII became the first British aircraft to carry centimetric AI radar. This form of radar introduced the spinning-dish scanner with greatly improved performance compared with the earlier "arrow-head" type, but it resulted in some singularly unattractive nose contours on the aircraft in which it was carried. The centimetric radar supplanted the four machine guns in the fuselage nose, reducing the armament to four 20 mm Hispano cannon. To expedite its service debut, the Mosquito XII was based directly on the Mark II and ninety-seven machines were converted by the installation of the new radar.
Of the Mosquitos built in Canada, the F.B.26 was one of the chief variants, the design of which was based upon that of the F.B.VI. With the same armament as its British counterpart, it had Packard Merlin 225 engines and weighed 21,473 lbs. The sole F.B.24 was similar but had Packard Merlin 69s, while the F.B.21, of which only three were built, had Packard Merlin 31 or 33 engines. Australian production was also based initially on the fighter-bomber, the F.B.40 being similar to the F.B.VI but having Packard Merlin 31 (first hundred production machines) or 33 (last seventy-eight) engines. One F.B.40 was re-engined with Packard Merlin 69s and redesignated Mosquito F.B.42, but no production of this version was undertaken.
No fewer than twenty-seven different versions of the Mosquito went into service during the war years, and some of the most spectacular operations of the air war stood to its credit. The Mosquito carried phenomenal loads over extremely long distances, performing feats out of all proportion to the specification originally envisaged by its designers. In short, the Mosquito was an outstanding warplane on every count.
Mosquitos were active on D-Day, and right up to the end of the war. Others were license built in Canada and Australia. Production did not end in Britain until late 1950.
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The de Havilland DH.98 Mosquito was a British combat aircraft that excelled in versatility during the Second World War. It was known affectionately as the "Mossie" to its crews and was also nicknamed "The Wooden Wonder" or "The Timber Terror" as the bulk of the aircraft was made of laminated plywood. It saw service with the Royal Air Force (RAF) and many other air forces in the European theatre, the Pacific theatre of Operations and the Mediterranean Theatre, as well as postwar.
Originally conceived as an unarmed fast bomber, the Mosquito was adapted to many other roles during the air war, including: low to medium altitude daytime tactical bomber, high altitude night bomber, pathfinder, day or night fighter, fighter-bomber, intruder, maritime strike and fast photo reconnaissance aircraft carrying out aerial reconnaissance. It was even used by the British Overseas Airways Corporation (BOAC) as a transport. It was also the basis for a single-seat heavy fighter, the de Havilland Hornet.
Upon the Air Ministry's decision to enter the Mosquito into production in 1941, it was the fastest operational aircraft in the world. Entering widespread service in 1942, the Mosquito supported RAF strategic night fighter defence forces in the United Kingdom from Luftwaffe raids, most notably defeating the German aerial offensive Operation Steinbock in 1944. Offensively, the Mosquito units also conducted night time fighter sweeps in indirect and direct protection of RAF Bomber Command's bomber fleets to reduce RAF bomber losses in 1944 and 1945. The Mosquito increased German night fighter losses to such an extent the Germans were said to have awarded two victories for shooting one down. As a bomber it took part in "special raids", such as pinpoint attacks on prisoner-of-war camp, Gestapo or German intelligence and security force bases as well as tactical strikes in support of the British Army in the Normandy Campaign. Some Mosquitos also saw action in RAF Coastal Command during the Battle of the Atlantic, attacking Kriegsmarine U-Boat and transport ship concentrations, particularly in the Bay of Biscay offensive in 1943 in which significant numbers of U-Boats were sunk or damaged.
It was famously praised by Hermann Göring, whose remarks are usually translated as:
"In 1940 I could at least fly as far as Glasgow in most of my aircraft, but not now! It makes me furious when I see the Mosquito. I turn green and yellow with envy. The British, who can afford aluminium better than we can, knock together a beautiful wooden aircraft that every piano factory over there is building, and they give it a speed which they have now increased yet again. What do you make of that? There is nothing the British do not have. They have the geniuses and we have the nincompoops. After the war is over I'm going to buy a British radio set - then at least I'll own something that has always worked."
– Hermann Göring, 1943
The De Havilland "Mosquito"
Greg Goebel / Public Domain
The Mosquito was an unusual machine, reflecting unconventional thinking in both operational concept and manufacture. It had to overcome stiff official resistance before it was finally accepted for service. Once it was, it was built in the thousands, with dozens of marks.
This chapter describes the origin and technical evolution of the Mosquito. The number of different variants makes description difficult and confusing, and the cleanest approach is to to break down the variant descriptions by category. Details of operational service are described in the next chapter. To further simplify the discussion, a few postwar Mosquito conversions and foreign-built Mosquito variants are also discussed in the next chapter, as they are something of a footnote.
The Birth Of The Mosquito
A 1943 advertisement for de Havilland taken from Flight & Aircraft Engineer magazine trumpets the speed of the bomber version
As Britain was under pressure to rearm as fast as possible in 1938, DH was under pressure to get to work building combat aircraft, or the company might well end up in the second-string role of building subassemblies for the aircraft companies that did.
The P.13/36 proposal had specified nose and tail turrets. The fact that the DH submission had proven underpowered using just two Merlin engines might have provoked the company's engineers into building just another bomber with four Merlins, but in a brilliant stroke of Zen thinking they came up with an idea: Why not stay with the twin engines, get rid of the defensive armament, and obtain protection through simple speed?
The idea fed on itself. With no defensive armament, the crew could be reduced, making the aircraft still lighter. A smaller aircraft with a smaller crew would be in principle cheaper and easier to build, support, and fly than a larger aircraft, and would put fewer aircrew at risk. The latest types of Merlin engines, the "Merlin XX" series with a two-speed single-stage supercharger, were offering increased horsepower that could provide outstanding performance.
A design team under chief engineer Ronald E. Bishop came up with a concept designated the "DH.98", which could carry two crew and a bombload of 450 kilograms (1,000 pounds) over a range of 2,400 kilometers (1,500 miles) at a maximum speed of almost 655 KPH (400 MPH). It would be even faster than a Spitfire fighter.
A fast unarmed bomber was very contrary to British Air Ministry thinking at the time. There were concerns that the Germans would simply field faster fighters; that two crew weren't enough; that a bomber needed to have some defensive armament. DH engineers knew that if they compromised the design to any great extent by adding crew or gun turrets, it would then become just another medium bomber of no particular merit, so the company insistently stayed with the configuration.
Despite the fact that the Air Ministry felt that wooden aircraft were obsolete, the wood construction actually turned out to be something of a plus. With the mad scramble to get weapons production ramped up for war, Britain was facing shortages of raw materials, and the DH.98's wooden construction would relieve the pressure on metal supplies.
That might have not been enough to turn the Air Ministry around, but DH found an ally in Air Marshall Sir Wilfrid Freeman, a friend of Geoffrey de Havilland back to World War I, and a member of the "Air Council" that provided the government with advice on matters aeronautical. Freeman was a common-sensible person who understood and appreciated the fast-bomber concept, and more importantly was willing and able to challenge organizational conventional wisdom.
When DH pitched the DH.98 concept to the Air Ministry again in September 1939, a few days after the outbreak of war with Germany, construction of prototypes was authorized. The aircraft was partly pushed through by emphasizing its potential as a photographic reconnaissance machine, since Britain lacked a long-range reconnaissance aircraft at the time.
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DH was formally told to go ahead with full development on 29 December 1939, while the Air Ministry drew up Specification "B.1/40" around the design, awarding a contract for construction of a single prototype on 1 January 1940. In early October 1939, the company had already set up the design team for the new machine in their own facility, a rented manor named Salisbury Hall, not far from the DH Hatfield plant.
It was an ancient place with a moat, and King Charles II's famous mistress Nell Gwynne had lived there in the 17th century. Residents claimed she haunted the place, the evidence being the occasional sound of the rythymic squeaking of her four-poster bed late at night. Winston Churchill's American mother Jennie Jerome Churchill, another mistress of the great and powerful, also lived there before World War I.
Salisbury Hall was selected not for its historical interest, but for its relative seclusion and its spacious facilities. Geoffrey de Havilland felt that the engineers would work faster if they were left in peace, and it also provided secrecy. The mock-up was built in the enormous kitchen, suspended from the ceiling. A hangar disguised as a barn was built on the manor estate for construction of the prototype.
Good progress with prototype development led a contract on 1 March 1940 that confirmed construction of the prototype and added an order 49 more DH.98s, to be built as reconnaissance-bombers. The DH.98 was not out of the woods quite yet, however. After the fall of France and the evacuation of the British Army at Dunkirk that spring, Britain seemed to be facing imminent invasion. Lord Beaverbrook, the new Minister of Aircraft Production, was not unreasonably focused on producing existing types instead of development of new machines, and there was no available production capacity for new aircraft at the time. In fact, DH was busy fitting Tiger Moth trainers with bomb racks in expectation of German landings.
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Beaverbrook told Freeman several times to halt the project, which was known in some circles as "Freeman's Folly", but Freeman stalled for time and pushed the effort. Britons were being armed for home defense in the summer of 1940, and Freeman kept a Tommy gun in his office. He was so determined to drive ahead with the DH.98 that there were those who thought he might shoot "the Beaver" if the Mosquito was cancelled. Whether from persuasion or threats, Beaverbrook came around in July 1940 and decided that the project should continue, as long as it did not interfere with DH's priority war work.
The threat of invasion faded in the fall of 1940, and DH engineers working on the DH.98 breathed easier and went on with their efforts. There was a tragic interruption in the work on 3 October 1940, when a German Junkers Ju-88 bomber came in low before the Hatfield plant and bounced four bombs over the wet grass into the buildings. 21 people were killed, 70 injured, and considerable amount of materials needed for DH.98 development were destroyed. The Ju-88 didn't make it back home. It was shot down over Britain and the pilot captured. As it turned out, he was thoroughly familiar with the target, having attended the de Havilland Technical School at the site before the war.
Despite the delay, prototype development moved ahead quickly. The prototype was dismantled and trucked from the "barn" at Salisbury Hall to Hatfield on 3 November, where it was reassembled, if with some difficulty as the assemblies were reluctant to mate up again. Its initial flight was on 25 November 1940, with Geoffrey de Havilland JR, the company's chief test pilot, at the controls. The prototype originally had the serial "E-0234", but this was quickly changed to "W4050".
The machine was painted bright yellow in hopes of discouraging anti-aircraft gunners from taking potshots at the unfamiliar aircraft. W4050 was fitted out as a bomber, but it demonstrated the speed and agility of a leading-edge fighter, justifying the faith of the aircraft's backers. Wilfrid Freeman was no longer in the Ministry of Air Production, having left to become Vice Chief of the Air Staff at the beginning of November, but it still had to be gratifying to know that his "Folly" was flying.
A fighter DH.98 was now considered a high priority. British shipping losses from Focke-Wulf "FW-200 Kondor" long-range ocean patrol aircraft indicated a need for a long range fighter to shoot down the Kondors. As a result, in July 1940, the initial order for 50 DH.98s had been changed from one initial prototype and 49 reconnaissance machines -- to the prototype, 19 reconnaissance machines, and 29 fighters, with the fighter defined under Air Ministry specification "F.21/40".
With the switch of the Luftwaffe from daylight bombing raids on Britain to night attacks in the fall of 1940, the DH.98 was also seen as a potential night fighter. A specification for such a variant was issued in October with the designation "F.18/40", though apparently there was no commitment to production for the moment.
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On 29 December, W4050 went through its paces for Beaverbrook, Freeman, and other dignitaries. The next day, the Air Ministry issued an order for 150 more day fighter versions of the DH.98s. By this time, the aircraft had acquired the name that would prove famous: "Mosquito".
The prototype was delivered to the Aircraft & Armament Experimental Establishment at Boscombe Down in early 1941. Service trials showed the aircraft to be highly satisfactory and in no need of major design changes.
In July 1941, the initial order for 50 Mosquitos was further modified, with nine of the orders for reconnaissance machines switched to bomber variants, the Air Ministry having become more somewhat more comfortable with the fast bomber concept. Britain was unavoidably in the mode of responding to the hottest fire of the moment for the time being, which inevitably led to confusion and delays in the Mosquito development program.
Along with the shuffling between reconnaissance, fighter, and bomber variants of the Mosquito, the Royal Navy had muddied the waters further by lobbying to get their share of DH.98 production, to use it as a fast target tug. After substantial frustration on the part of all concerned, Lord Beaverbrook was able to put a stake through the idea by replying that using an aircraft with twin Merlins as a target tug was a gross waste of precious engine production. The Royal Navy gave in, but remained interested in the Mosquito.
Describing The Mosquito
Although the Mosquito was extensively modified and updated in production, its basic configuration would always remain very much like that of the initial prototypes. It made use of the wooden construction techniques of the Albatross, with a number of refinements. The two wing spars were made of spruce, with spruce stringers and two-layer birch plywood skinning, not spruce planking as with the Albatross. The spars were laminates, using modest-size pieces to ensure that large trees wouldn't be required, and formed under heat and pressure. The wing was built as a single assembly, covered with fabric, and painted.
The Mosquito's fuselage, like that of the Albatross, was made of a sandwich of balsa between exterior layers of plywood about two millimeters thick, wrapped around seven bulkheads built as a sandwich of spruce blocks between plywood layers. Spruce was used in the fuselage where greater strength was needed, for example around doors or in the wing roots. The fuselage was built in halves, split lengthwise vertically, with the halves formed around male moulds and the assembly held together by steel straps while the glue dried.
The split fuselage scheme allowed many critical systems to be installed before the two halves were bonded together. This reduced the need for workers to crawl around in the fuselage and sped up assembly, though getting the halves to fit was something of a chore for early prototypes. However, work crews claimed that modifying the airframe was not difficult, the only tool required being a saw. Once fitted together, the fuselage was covered with fabric and painted. The fuselage was sawed out to allow fit of the wing, with part of the sawed-out piece replaced after wing installation. Holes for doors were also sawed out of the fuselage.
The glue and wood construction not only led to light weight, elegant lines, and reduced demand for strategic materials, but also minimized demands on production tooling, meaning that subassemblies could be and were built by such firms as furniture and piano manufacturers. The modular design of the machine also helped support distributed production, with various subcontractors providing subassemblies that could be integrated in the factory.
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There were potential drawbacks. The casein glues were strong, but there were worries that they weren't up to high temperature, high humidity tropical conditions found in South Asia, and that Mosquitos sent there might come "unglued". There were in fact some structural failures of Mosquitos in the Far East, but it is possible they were blamed on the glues partially because nobody in charge wanted to suggest to aircrew that they were riding in badly-manufactured machines. In any case, the casein glues were completely replaced by synthetics, and the problem was declared solved.
Except for the flaps, which were made of fabric over wood frames, the framework for the flight control surfaces was made of light alloy, with metal skinning on the ailerons, fabric on the tail surface, and wood on the flaps.
The prototype had leading-edge slats but these were deleted in production aircraft, since the type had proven to have reasonable low-speed handling characteristics. Takeoff performance was improved by flaps, with an inboard and outboard flap on each wing, split by the engine nacelle. The prototype and early production aircraft had shorter nacelles and a single long flap, but buffeting problems led to the extension of the nacelles and the split flap scheme in all later production.
The twin Merlin engines, which drove three-bladed variable-pitch propellers, were mounted on welded steel-tube frames inside low-drag nacelles, with the radiators fitted into the wing between the fuselage and the nacelles. The presence of the radiator extended the wing section that contained it forward of the rest of the wing, resulting in a distinctive "step" in the wing outline when the aircraft was seen from above.
Incidentally, most or all Mosquito variants did not use "handed" engines, that is, both the left and right propellers turned the same direction, since the same models of engines were used on both sides. Surprisingly, this did not seem to cause much trouble in handling. Some late-mark Mosquitos did use different models of engines on each side, but it appears that the difference was that one had a pneumatic compressor and the other did not.
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The Mosquito was a "taildragger", with the main gear retracting backwards into the nacelles, and a retractable tailwheel without tailwheel doors. The main gear featured twin shock struts, filled with rubber blocks, which was simple, cheap, and reliable, if a bit stiff.
The pilot and crewman sat side-by-side, with the pilot's seat on the right and the crewman's seat slightly staggered back. In the reconnaissance and bomber versions, the crewman could crawl forward to a prone bombardier's position in the glass nose.
The greenhouse-style cockpit was set forward of the leading edge of the wing and provided excellent forward visibility, except for the obstruction of the engine nacelles. Rearward visibility wasn't so good. Some of the later reconnaissance variants had a transparent bubble on top of the greenhouse, allowing a navigator to stick his head up and take sightings, and also check the "6:00" position for troublemakers.
Fighter versions had a flat forward windscreen, which increased drag relative to bomber and reconnaissance variants but improved aiming. Bomber and reconnaissance versions had blisters on the side window panels to give a downward view, and these blisters were not fitted to fighter variants.
The Mosquito Photo-Reconnaissance Variance
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The first production examples of the Mosquito were photo-reconnaissance machines. The prototype for the "Mosquito Photo-Reconnaissance Mark I (PR.I)", with the tailcode "W4051", performed its first flight on 10 June 1941. Despite the fact that the original Mosquito prototype was W4050, the PR.I prototype was the third Mosquito prototype to fly, being preceded by the prototype "F.II" version, discussed in the next section.
W4051 was fitted with Merlin 21 engines with 1,090 kW (1,460 HP) each. The aircraft had longer wings than W4050, with the span extended by 50 centimeters (20 inches), though W4051 and the production PR.Is retained the short engine nacelles. The PR.I looked very much like a Mosquito bomber variant, as it retained the glass nose for camera targeting and the bombbay doors, but it included five camera ports.
There was a port for an F24 oblique camera behind and below the wing, and twin ports for an F52 stereo camera pair behind the bombbay doors. There was a port in the front of each bombbay doors, with the bombbay accommodating either an F24 stereo camera pair or a single K17 camera. The cameras were fitted on steel mounts, but this was later switched to wooden mounts as they reduced vibration.
A total of ten Mosquito PR.Is were completed, including the prototype, which was brought up to production standards. They were all painted blue-gray overall, a color scheme that had been evaluated on Spitfire reconnaissance machines and which was believed a good scheme for high-altitude reconnaissance.
The Mosquito was introduced into RAF service with the Number 1 Photo-Reconnaissance Unit (PRU) at RAF Benson, with a PR.I delivered by Geoffrey de Havilland JR on 13 July 1941. Four more were delivered over the next two months, and the type performed its first sorties in September 1941. By the middle of 1942, photo-reconnaissance Mosquitos were sweeping over Europe with little interference, ranging as far as Czechoslovakia and northern Norway.
The PR.I had proven so useful that 29 Mosquito B.IV bombers (discussed later) were modified to the PR.I reconnaissance fit, and designated "PR.IV". They had increased fuel capacity, with tanks filling up the bombbay, raising the total internal fuel load from 2,450 liters (540 imperial gallons / 646 US gallons) to 3,180 liters (700 imperial gallons / 839 US gallons). Some of the PR.Is were also fitted with additional fuel tanks.
Although Rolls-Royce was working on a new engine, the Griffon, in 1941 the RAF had issued an urgent request for a high-altitude engine. In response, Rolls-Royce began development of the new "Merlin 61" series engines, with two-stage supercharging and 1,255 kW (1,680 HP).
The two-stage Merlin 61 proved to be the right thing at the right time, since the RAF's Spitfire V was finding themselves outclassed by the Focke-Wulf FW-190, and the new engine variant was hastily fitted to the Spitfire V airframe to create the more potent Spitfire IX. It was also fitted to the US P-51 Mustang, replacing the P-51's original Allison V-1710 engine to create the much more capable P-51B.
DH was quick to evaluate the new version of the engine on the Mosquito. The first Mosquito prototype, W4050, was refitted with Merlin 61s and put through flight tests, which proved an outstanding success. In June 1942, on its second flight in this configuration, W4050 reached an altitude of 12,200 meters (40,000 feet). The Merlin 61s gave the machine a top speed of 695 KPH (432 MPH) at altitude, a good 80 KPH (50 MPH) faster than the B.IV.
W4050 was later refitted with two-stage Merlin 71 engines with 1,275 kW (1,710 HP) each and reached a top speed of 704 KPH (437 MPH), making it the fastest Mosquito ever. Incidentally, W4050 is now on display at Salisbury Hall, which now includes an air museum.
As the Merlin 61 became available in production quantity, new Mosquito variants were introduced to take advantage of it. Five B.IVs were refitted with the Merlin 61 and converted to a reconnaissance standard as "PR.VIIIs", with initial delivery in January 1943, but that was an interim solution.
The first production reconnaissance variant of the Mosquito with two-stage Merlin engines was the "PR.IX", which was introduced in parallel with a similar bomber variant, the B.IX, discussed later. The first two PR.IXs were delivered to Number 540 Squadron in April 1943, and a total of 90 PR.IXs were built.
The PR.IX was powered by the Merlin 72, with 1,255 kW (1,680 HP). The new engine fit required modified nacelles. While the prop spinners in earlier marks were flush to the nacelles, the PR.IX's nacelles featured a distinctive "chin" intake for the supercharger intercooler, as well as a larger carburetor intake under the nacelle, and six exhaust stacks instead of the five of earlier variants. Exhaust shrouds were not normally fitted.
The PR.IX was also fitted with a new "universal" wing that permitted carriage of the original 227 liter (50 Imperial gallon / 59 US gallon) tank; or new 454 liter (100 Imperial gallon / 118 US gallon) tanks; or a 225 kilogram (500 pound) bomb, with one store under each wing. The PR.IX rarely if ever carried bombs, but the big wing tanks helped significantly stretch range, to a maximum of 3,945 kilometers (2,450 miles).
In early 1943, the RAF began to evaluate US-made M46 photoflash bombs, which were much brighter than British photoflash bombs. The M46 went into operational service with the PR.IX in the spring of 1943, and did much to increase the effectiveness of Mosquito night reconnaissance.
Eight PR.IXs were refitted with uprated Merlin 76/77 engines and American-designed Hamilton Standard four-bladed paddle propellers. The four-bladed propellers provided improved high-altitude performance, at the expense of poorer low-altitude performance.
A B.IV was refitted with Merlin 72 engines and cabin pressurization, first flying in July 1943, to become the prototype for the "PR.XVI" and "B.XVI", which like the PR.IX and B.IX were built in parallel. The PR.XVI introduced the canopy top blister for the navigator. A total of 432 PR.XVIs were built.
The RAF decided to use the pressurized PR.XVI as the basis for a specialized high-altitude reconnaissance variant, and modified one to serve as the prototype "PR.32", the RAF having decided to give up on classy but slightly confusing Roman numerals and adopt Arabic numbers instead. The PR.32 featured the long-span wing developed for the NF.XV, discussed later, and two-stage "Merlin 113/114" engines optimized for high-altitude operation. Everything that could be removed to lighten the aircraft was taken out.
Five production PR.32s followed. They were used in the last months of the war in Europe, operating at altitudes of 12,800 meters (42,000 feet).
The last production Mosquito reconnaissance variant, the "PR.34", was essentially a PR.XVI with bulged bombbay doors to accommodate long-range fuel tanks.
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DE HAVILLAND MOSQUITO PR.34: _____________________ _________________ _______________________ spec metric english _____________________ _________________ _______________________ wingspan 16.51 meters 54 feet 2 inches wing area 33.54 sq_meters 361 sq_feet length 12.65 meters 41 feet 6 inches height 4.65 meters 15 feet 3 inches empty weight 7,545 kilograms 16,630 pounds max loaded weight 11,565 kilograms 25,500 pounds maximum speed 685 KPH 425 MPH / 370 KT service ceiling 13,100 meters 43,000 feet range 5,375 kilometers 3,340 MI / 2,905 NMI _____________________ _________________ _______________________
181 PR.34s were built, with 50 of these produced by Percival. The PR.34 was intended for service in the Far East, and a number were deployed to the theater before the end of the war in the Pacific in August 1945. The PR.34 was apparently something of a handful to get off the runway with fully loaded tanks. It was the heaviest of all the Mosquitos, with a maximum takeoff weight about 35% greater than had been ever expected when W4050 took to the air.
Ten "B.35s", described later, were converted to a reconnaissance configuration and redesignated "PR.35". These machines did not reach operational service until after World War II.
The Mosquito Day Fighters, Trainers, & Night Fighterd
When the Mosquito was being designed, the DH engineering team made sure they included provision for gun armament in the design on the assumption that people would come around to the idea of using the machine as a fighter. They were proven right.
The second Mosquito prototype to fly, "W4052", was originally fitted out as a long-range fighter, the "F.II". It was armed with with four 7.7 millimeter (0.303 caliber) Browning machine guns in the nose and four 20 millimeter Hispano Mark II cannon in a ventral tray. The guns were all belt-fed and actuated electro-pneumatically, driven by a compressor in the left engine nacelle. The compressor also drove the pneumatic wheel brakes. The clustering of the guns meant the pilot had to be a good shot, but in compensation they also had terrific focus, and once on target they usually made short work of it.
Although reconnaissance and bomber versions of the Mosquito had a hatch on the bottom of the left side of the nose for crew entry, the armament blocked entry by that route in the F.II, and so all fighter versions featured a door on the right side of the fuselage forward of the wing. The fighter's wing spars were also reinforced to permit more aggressive maneuvers; armor glass was fitted in the (flat) windscreen; and the pilot used a stick, instead of the yoke used in the reconnaissance and bomber variants.
W4052 performed its initial flight on 15 May 1941, with Geoffrey de Havilland JR at the controls. The machine was flown from a field next to Salisbury Hall, to save the time needed to break it down, transport it to Hatfield, and reassembled again. The field was a bit on the short side, but de Havilland negotiated with the farmer who owned the adjoining property to allow the removal of some hedges that blocked the way.
Just before dawn on 13 May, an SS officer named Karl Richter parachuted into England, landing not far from Salisbury Hall. It appears he did not know the significance of the manor and both his landing spot and timing were coincidental, as he was trying to make his way into London when he was arrested the next day. Although many of the German agents the British had captured ended up working (in some cases with surprising enthusiasm) for the Allied cause under the "Double Cross" system to feed back false information to German intelligence, Richter was uncooperative. He was hanged on 10 December 1941.
With the shift of the Luftwaffe to night raids in the fall of 1940, the priority of the moment switched to night fighters, and in the summer of 1941 W4052 was fitted with longwave "airborne intercept Mark IV (AI.IV)" radar.
The success of this fit led to the "Night Fighter Mark II (NF.II)". It featured the same armament as the F.II, but was painted black and had an arrow-shaped arrowhead-shaped transmit antenna in the nose for the AI.IV radar, and dipole receive antennas mounted through the wingtips.
The NF.II went into operational service with RAF Number 151 & 157 Squadrons in early 1942, replacing the sturdy but relatively slow Bristol Beaufighter. They scored their first kills that spring.
A total of 494 F.IIs and NF.IIs were built. It is unclear what the proportions of day fighters and night fighters were, but it appears that most were built as night fighters. The NF.II was rushed into service so fast that there were some surprises for service crews that should have been caught in test and evaluation, such as the the fact that firing the 7.7 millimeter guns wiped out the pilot's night vision. The guns were refitted with cone-shaped muzzle flash suppressors in the field, with this item rolled into production.
Apparently most NF.IIs were fitted with "AI.V" radar, which was generally similar to AI.IV but included a cockpit panel display for the pilot that helped the radar operator direct him to a target. The radar was regarded as a top secret and NF.IIs carrying it were not allowed to fly over Occupied Europe, but beginning in mid-1942, about 25 NF.IIs had their radar removed and were fitted with additional fuel tanks for night intruder operations. They would fly over the Channel to lurk around Luftwaffe airfields and pounce on German pilots who were flying with their landing lights on. These Mosquitos were redesignated "NF.II (Special)".
One NF.II was fitted with a "Turbinlite" searchlight in the nose for night fighting, but trials showed the scheme to be ineffective. A few F.IIs were built with dual controls, becoming the basis for the "Trainer Mark III (T.III)", most of which were unarmed, though some retained their guns for weapons training. The first T.IIIs were built in 1943, though most production would take place after the war, with a total of 358 built, including six conversions from F.IIs.
The AI.V radar was workable but had limited accuracy and range, as well as a long minimum range that meant the NF.II's crew would lose radar contact before the pilot could actually see the target. New "centimetric" (microwave) radars that were much more capable soon became available, and an NF.II was refitted by Marshalls at Cambridge with "AI.VIII" centimetric radar in the summer of 1942.
The AI.VIII had a modern radar dish accommodated in a "thimble" radome on the night fighter's nose, which meant deletion of the four 7.7 millimeter Brownings. The new radar fit worked very well, and so 97 more NF.IIs were converted to the same standard during the first half of 1943, and redesignated "NF.XII". The type scored its first kill in February 1943.
The NF.XII led in late 1943 to the "NF.XIII", which was essentially a production version of the NF.XII, modified from an "FB.VI" fighter-bomber version of the Mosquito, discussed later, by fitting AI.VIII radar. The NF.XIII inherited wing attachments for 227 liter (50 Imperial gallon / 57 US gallon) "slipper" tanks from the FB.VI, giving the night-fighter the range to to accompany RAF bomber streams over Occupied Europe to take on German night fighters. 260 NF.XIIIs were built.
In the meantime, the Americans were beginning production of their "SCR-720" radar, arguably the best AI sets of the war, and the British adopted it as the "AI.X". Marshalls modified 99 more NF.IIs to a night-fighter configuration, this time with the AI.X radar, resulting in the "NF.XVII".
This of course led to production of an enhanced version of the NF.XIII with the AI.X radar, designated the "NF.XIX". It actually had a "bullnose" radome that could accommodate either an AI.VIII or AI.X radar, as production deliveries permitted. The NF.XIX also had Merlin 25 engines with greater low altitude power. Initial flight was in April 1944, and 280 were built.
Following high-altitude incursions over Britain by pressurized Luftwaffe Junkers Ju-86 bombers, five Mosquito "NF.XVs" were built as high-altitude night fighters. DH workers were particularly keen on getting these aircraft to work, as the Ju-86s had been occasionally overflying the Hatfield plant.
They were based on the B.IV and retained the bomber-style canopy, but featured two-stage Merlin 73 engines, lengthened wingspans, and pressurized cabins. As much gear as possible was removed to reduce the weight of the aircraft. The Hispano cannon were removed and replaced with a lighter belly pack of four 7.7 millimeter guns. That armament was regarded as sufficient to deal with the Ju-86, which lacked armament and armor and used height as its only real defense.
The NF.XVs were fitted with AI.VIII radar in a thimble radome. The NF.XVs never saw any action, as the Germans had largely given up on high-altitude overflights by the time the NF.XV was ready for service.
The last Mosquito night-fighter version to see significant combat service was the "NF.30", which was similar to the NF.XIII, but had two-stage Merlin engines, either Merlin 72s or 76s, and AI.X radar in a bullnose radome. Initial flight of the NF.30 prototype was in March 1944, with the type entering operational service in June and performing its first kills in August. There were operational teething problems with the exhaust shrouds that led to a new louvered shroud design. 526 NF.30s were built.
The Mosquito night-fighter served on in the postwar period as an interim solution until the arrival of jet-powered night fighters. Two Mosquito night-fighter variants were produced after the war, including the "NF.36" and the "NF.38". The NF.36 was similar to the NF.30, but had Merlin 113 engines and a "bullnose" radome. Initial flight was in May 1945 and 163 were built into 1947, with some of them put into service for weather reconnaissance.
The NF.38 was basically an NF.36 with Merlin 114A engines and AI.IX radar, which the British had continued to work on after the war. Following conversion of a single NF.36 as a prototype, 101 NF.38s were built. The NF.38 was the last Mosquito variant to be produced, with the final example rolled out in 1950.
It was also one of the least successful variants. AI.IX was wasted effort, not the match of the AI.X and substantially heavier. The new engines and the heavier radar made the aircraft unpleasantly nose-heavy and troublesome to fly. Ironically, it never entered RAF service, with 54 supplied to Yugoslavia and the rest scrapped.
The Mosquito Bomber Variants
The initial Mosquito bomber variants were based on the PR.I The nine Mosquitos diverted from PR.I production to be completed as bombers became "Bomber Mark IV (B.IV) Series I" machines. They were much like the PR.I, with a glass nose, no gun armament, and short engine nacelles, but had no camera ports.
They were followed by the "B.IV Series II", with 263 built. They had the longer nacelles, as well as shrouded exhausts to hide the exhaust flames for night operations. They also had wing attachment points for the 50 Imperial gallon slipper tanks mentioned earlier, though it is unclear if this was included in production from the outset. Later B.IV Series II machines would have exhausts modified to provide a slight jet effect to improve the aircraft's performance by about 16 KPH (10 MPH), improving its speed advantage over the German Focke-Wulf FW-190.
The B.IV had a glass nose for a bombardier and no gun armament. The Mosquito had been designed to carry four 112 kilogram (250 pound) bombs, but the bomb load was limited simply by space and not lifting capacity. In the fall of 1941 consideration was given to carriage of four 225 kilogram (500 pound) bombs. The bomb tailfin span had to be cut down to allow a fit, but tests performed at Boscombe Down with the Mark V showed that the smaller tailfins did not affect stability, and the new tailfins were incorporated into bomb production.
The first B.IV Series I was delivered to RAF Bomber Command Squadron Number 105 on 15 November 1941, with Geoffrey de Havilland JR at the controls. The first B.IV Series II was delivered in May 1942, and the first strikes were performed at the end of the month.
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DE HAVILLAND MOSQUITO B.IV SERIES II: _____________________ _________________ _______________________ spec metric english _____________________ _________________ _______________________ wingspan 16.51 meters 54 feet 2 inches wing area 33.54 sq_meters 361 sq_feet length 12.43 meters 40 feet 10 inches height 4.65 meters 15 feet 3 inches empty weight 5,942 kilograms 13,100 pounds max loaded weight 10,150 kilograms 22.380 pounds maximum speed 612 KPH 380 MPH / 330 KT service ceiling 9,450 meters 31,000 feet range 1,965 kilometers 1,220 MI / 1,060 NMI _____________________ _________________ _______________________
Although initially being used for bombing attacks, Bomber Command decided that the best use of the Mosquito bomber was for "pathfinding", marking targets with huge flares that other bombers would use as an aim point. B.IVs were fitted with the latest electronic navigation aids, including "Oboe" and "H2S", which are discussed in the next chapter, to help them find their way to targets at night and in overcast weather.
With the B.IV in service as a pathfinder, Bomber Command then gradually began to use the machine for nuisance attacks, arriving at the conclusion that it would be an even greater nuisance if it could carry a much bigger bomb. Beginning in April 1943, a B.IV was modified with bulged bomb-bay doors to allow it to carry a single 1,815 kilogram (4,000 pound) "High Capacity (HC)" bomb, known as a "Cookie", little more than a very big thin-shelled can full of explosives and with no fins. The modified B.IV also featured nose ballast, reduced fuel tankage, and modified elevators. The scheme proved workable, and 22 more B.IVs were modified to this specification, beginning operations in early 1944. They were sometimes referred to as "B.IV (Specials)".
Surprisingly, apparently even to the people involved at the time, the heavily-loaded Mosquito had little problem getting off the runway, though unsurprisingly Mosquito bomber variants with two-stage engines were more comfortable wtih the load. In any case, if the aircraft lost an engine, the crew needed to get rid of the Cookie as fast as possible. Crews sometimes called it the "Dangerous Dustbin". It is unclear if they meant it was dangerous to the enemy or to themselves.
60 B.IVs were also modified to carry the "Highball" antiship bomb, an unusual weapon that is described in more detail in the next chapter.
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Although a single "B.V" was built, it didn't go into production. As mentioned earlier, availability of the new two-stage Merlin engines led to the next production bomber variant, the "B.IX", equivalent to the PR.IX with Merlin 72 engines and the universal wing. The first production machine performed its initial flight on 24 March 1943, with the first service delivery to Number 109 Squadron on 21 April 1943. 54 B.IXs were built in all.
With four 225 kilogram (500 pound) bombs in the bombbay and a 225 kilogram bomb under each wing, the B.IX normally had a maximum bombload of 1,350 kilograms (3,000 pounds). Some of the B.IXs were fitted with bulged bombbay doors to carry a Cookie bomb. The B.IX was generally used for Pathfinder duties.
The last Mosquito bomber variant to see wide service was the "B.XVI", which was generally similar to the B.IX but had a pressurized cabin. 402 were built, with all but the first 12 fitted with the bulged bombbay doors for Cookie carriage.
The final Mosquito bomber variant produced was the "B.35", which was very similar to the B.XVI with the bulged bombbay doors, but had uprated Merlin 114 engines with 1,275 kW (1,710 HP) each, and was fitted with a "Gee-H" radio navigation system. The Gee-H fit featured three distinctive dipole antennas fitted vertically through each wingtip. First flight of the B.35 prototype was on 12 March 1945, though they didn't reach RAF operational service until 1948. A total of 265 were built.
The Mosquito Fighter-Bomber Variants
The most versatile, and most heavily produced, of all Mosquito versions were the fighter-bomber variants. A total of 2,584 "FB.VIs" were built, featuring four 7.7 millimeter machine guns in the nose and four 20 millimeter cannon in the belly, with a small bombbay added behind the cannon tray to carry two 112 kilogram (250 pound) or, in practice, two 225 kilogram (500 pound) bombs.
Two external hardpoints, one under each wing, could be used to carry two slipper tanks or two more bombs. The wings were reinforced to help handle the loads. Not long after its operational introduction, the FB.VI was given another armament option, underwing racks for eight "60 pounder" (27 kilogram) rocket projectiles (RPs), which were solid-fuel rockets with bulbous high-explosive warheads. The RP proved very effective for ground attack.
Initial flight of a prototype FB.VI was in July 1942, but met with an accident. Other delays stretched rollout of the first production FB.VI to February 1943, with Number 418 Squadron of RAF Fighter Command accepting their first FB.VI in May of that year, and Number 605 Squadron following in July. These two squadrons performed intruder attacks over occupied Europe. The FB.VI was also used in the fighter-bomber role against the Japanese in Burma.
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DE HAVILLAND MOSQUITO FB.VI: _____________________ _________________ _______________________ spec metric english _____________________ _________________ _______________________ wingspan 16.51 meters 54 feet 2 inches wing area 33.54 sq_meters 361 sq_feet length 12.47 meters 40 feet 11 inches height 4.65 meters 15 feet 3 inches empty weight 6,485 kilograms 14,300 pounds max loaded weight 10,115 kilograms 22,300 pounds maximum speed 585 KPH 360 MPH / 315 KT service ceiling 10,000 meters 33,000 feet range 2,655 kilometers 1,650 MI / 1,435 NMI _____________________ _________________ _______________________
RAF Coastal Command obtained a specialized derivative of the FB.VI, the "FB.VIII", which had a 57 millimeter autoloading Molins gun, an airborne modification of the light 6-pounder antitank gun, installed in place of the four 20 millimeter cannon. Two of the 7.7 millimeter Brownings were often removed in the field, with the two remaining used for sighting the big gun.
The Molins gun was adopted to help Mosquitos hit German submarines from out of range of the vessel's antiaircraft guns and proved effective, but Coastal Command Mosquitos were then qualified to carry a variant of the RP with a solid warhead. Aircrews felt the RP was a much better weapon. 25 FB.VIIIs were built, all as conversions of FB.VIs, with the first flying in mid-1943.
Interestingly, all the Mosquito FB marks used single-stage Merlins. There were many demands on two-stage Merlin production, and the fighter-bombers almost always operated at low level and did not need improved high-altitude performance. An "FB.XI" with two-stage engines was considered but not built.
The Naval Mosquitos
The Royal Navy's Fleet Air Arm (FAA) operated both FB.VI and T.III Mosquitos from shore bases beginning in 1944, and it was a logical step to then operate the Mosquito off of aircraft carriers.
The first truly navalized Mosquito was an FB.VI modified by DH with an arresting hook, pneumatic landing gear struts, a strengthened fuselage, and four-blade paddle propellers. It began trials on board the HMS INDEFATIGUEABLE on 25 March 1944, and was the first British twin-engine aircraft to land on a carrier. The trials were successful, and another FB.VI was converted to an improved navalized configuration, adding folding wings and a nose radome.
These two prototypes led to the production Mosquito "Torpedo Reconnaissance 33 (TR.33)", with the initial TR.33 performing its first flight on 10 November 1945, after the end of the war. The FAA ordered 97, but with postwar cutbacks, the total buy was cut to 50. The first 23 TR.33s had nonfolding wings and conventional Mosquito landing gear, but the remainder had folding wings and reinforced landing gear. The TR.33 had the four 20 millimeter cannon but no machine guns, with the nose fitted with a small "thimble" radome containing US ASH (AN/APS-6) three-centimeter radar.
The TR.33 could carry two 225 kilogram (500 pound) bombs in its bombbay or a single 46 centimeter (18 inch) torpedo slung under the fuselage, while different configurations of external tanks, rockets, or bombs could be carried under the wing. With two 227 liter (60 US gallon) external tanks, the TR.33 had a range of 2,415 kilometers (1,500 miles). The aircraft could be fitted with "rocket assisted take-off gear (RATOG)", with a RATOG bottle on each side of the rear fuselage, for shorter takeoffs under heavily loaded conditions.
The TR.33 entered service with FAA Number 811 Squadron in August 1946, but the Sea Mosquito's service life was very short, with the squadron disbanded in July 1947 and the aircraft put to second-line duties. None of these machines ever served operationally on an aircraft carrier.
The FAA also obtained fourteen "TR.37 Sea Mosquitos", which were almost identical to the TR.33, except for a much bigger radome somewhat like that of the NF.30, to accommodate British "ASV Mark XIII" radar instead of ASH radar. The service life of the TR.37 was short as well.
Well over 7,000 Mosquitos were built from 1941 to 1950, with most British production from DH at Hatfield and also the company's plant at Leavesden. Standard Motors also built the Mosquito in quantity, and small numbers were built by Percival and Airspeed. Canadian and Australian production is detailed in the next chapter.
The Mosquito In Service & Its Foreign Users
De Havilland Mosquito B Mk. 35
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The Mosquito entered RAF service towards the end of 1941, but production remained limited through 1942, while the brass and the aircrews figured out what should be done with the fast new machine. By the beginning of 1943, the Mosquito was beginning to become available in large numbers and the Germans were learning to hate it thoroughly. It remained one of the Luftwaffe's major headaches for the rest of the war.
This chapter outlines the Mosquito's combat service with the RAF in World War II, its postwar service, and foreign production and operation.
The Mosquito Goes Into Combat
As mentioned earlier, the Mosquito performed its first sortie in September 1941. On 18 September, Squadron Leader Rupert Clerke and his observer, Sergeant Sowerbutts, of the RAF Number 1 PRU took off in a Mosquito PR.I on a mission to Southern France. Intelligence suggested that the Nazis were massing troops to occupy Spain, and the Mosquito was to check it out. However, the aircraft's electrical generator failed and the batteries ran down, rendering the cameras so much dead weight. The Mosquito had to return to base. In some compensation, the aircraft was jumped by three Messerschmitt Bf-109s but easily outran them, no doubt leaving behind very startled Luftwaffe pilots wondering what the hell they had been chasing.
The same Mosquito performed another reconnaissance mission over Southern France two days later, on 20 September, with Flight Lieutenant Alistair Taylor at the controls. The mission was successful, and from that time on Number 1 PRU's began to range widely over Western Europe. Unfortunately, Taylor and his Mosquito were lost ten weeks later, shot down by German flak during a mission against Trondheim and Bergen, Norway. It was the Mosquito's first combat loss.
A total of 20 Mosquitos was completed by the end of 1941. While reconnaissance machines were the immediate priority, some Mosquito bomber and night-fighter variants were delivered to RAF frontline squadrons during the winter of 1941:42, but foul weather kept them from seeing much combat during that time. The first Mosquito bomb raid was on 31 May 1942, as a follow-up to the first RAF "thousand bomber raid", performed on Cologne the night before. Five B.IVs were sent in singly to hit Cologne from altitude during the day to keep the Germans off-balance.
It wasn't a very good use of the machine, and one was shot down by flak, allowing the Germans to examine the wreckage. Ironically, the existence of the Mosquito remained an official secret for some time after that, with one British newspaper called to task by the authorities for mentioning it.
Bomber Command didn't really know what to do with the Mosquito and remained unenthusiastic about it, all the more so because subsequent bombing missions with the machine produced lower-than-average results and higher-than-average losses. The German Focke-Wulf FW-190 proved able to perform a dive from altitude and "creep up" on the Mosquito, with crews unable to do anything but pray since they had no way to shoot back. The Soviets had developed an "aerial mine", a small fragmentation bomb on a parachute, to deal with comparable situations and apparently with good effect, but if the RAF thought of it they decided against it. Gradually, various engineering refinements, such as the jet-boost exhausts and improved engines, increased the gap between the Mosquito and the FW-190. Pilots also learned they could shake the FW-190 by going into a shallow dive and performing a corkscrew maneuver, since the Focke-Wulf's controls tended "freeze up" at high speeds more quickly than those of the Mosquito.
There was another reason for the indifferent attitude towards the Mosquito bomber. At the time, under Air Marshall Sir Arthur "Bomber" Harris, Bomber Command was focused on indiscriminately plastering German cities, which required heavy bombers such as the Avro Lancaster and the Handley-Page Halifax. Geoffrey de Havilland JR's younger brother, Major Hereward de Havilland, wrote Hatfield in the fall of 1942: "Lunched at Bomber Command with Air Commodore Harrison. Harrison is the only person I have met at Bomber Command who has any enthusiasm for the Mosquito. The C-in-C certainly has none ... "
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Here we see two ground crew arming the 20mm cannon on a de Havilland Mosquito. This view inside the gun bays shows the hidden complexities of the guns.
Even as Hereward de Havilland was writing this, however, the situation was finally beginning to turn around. Pilots in Bomber Command Number 105 and Number 109 Squadrons decided that the Mosquito was best suited to low-level precision bombing and were operationally experimenting with the technique.
There were some bugs to be worked out of the concept. On one mission against a Dutch target, for example, a Mosquito ran into a flock of curlews, one of which smashed through the windscreen and knocked out the pilot. The navigator managed to grab the yoke and pull it back just in time to keep from plowing up the ground. The pilot came to, but he was blinded by blood and the wind was howling into the shattered windscreen. The navigator managed to get them back home by crawling forward into the nose and directing the pilot with soft kicks to the shins. Bomber Mosquitos quickly acquired strengthened windscreens to deal with birdstrikes.
Results were not immediately forthcoming, either. On 19 September, the Mosquito made its first attack on Berlin. Six B.IVs performed the attack, or at least tried to, since Berlin was so socked in by the weather that only one of the attackers managed to drop bombs on the target. The others either bombed Hamburg, the alternate target, or jettisoned their warloads. One Mosquito didn't come home.
The first break was on 25 September. Vidkun Quisling, the Nazi stooge ruler of occupied Norway, was to give a rally at the Gestapo headquarters in Oslo that day, and four B.IVs of Number 105 Squadron were assigned to break up the party. The building was hit by four bombs, three of which detonated. One Mosquito was shot down by FW-190s. The mission was successful, if expensive. The Mosquito was still suspect in Bomber Command, but it was now on the road up. The Mosquito was finally announced to the British public on 26 September 1942 along with the news about the successful raid on the Gestapo headquarters in Oslo. By this time, the Germans were thoroughly familiar with the machine and it was certainly no secret to them.
Although night fighter Mosquitos were a high priority and the RAF had NF.IIs in service by early 1942, they didn't score a "kill" for months. Heavy Luftwaffe night raids on Britain had dried up, since Hitler had shifted the weight of the Luftwaffe east for the invasion of the USSR in the spring of 1941.
Not only were targets hard to come by, but getting the Mosquitos up to full working condition proved difficult. The hasty introduction of muzzle flash suppressors was mentioned earlier; the engine exhaust shrouds cut down the machine's speed and wore out quickly. The initial velvet-black finish cut down the machine's speed as well, forcing a switch to matte-black paint. Crews definitely needed more training in night operations, with a number of aircraft lost in accidents.
Problems were worked out, the crews grew more confident, and they still had a few targets, since the Luftwaffe continued to perform small nuisance raids on Britain. These raids focused on targets of historic or cultural importance and were therefore called "Baedeker raids", in reference to popular travel books of the time. Number 151 Squadron may have scored the Mosquito's first "kill" in the dark hours of the morning on 30 May 1942, claiming a Heinkel He-111 on the night of 29 May, but the kill was not confirmed. Number 157 Squadron competitively claimed damage to a Dornier Do-217 the next night.
Number 151 Squadron scored the first confirmed kills on the night of 24 June, when an NF.II shot down an He-111 and a Do-217 within ten minutes of each other. More kills were claimed over the following months, though they came in at a slow rate.
Click on Picture to enlarge
This dramatic picture shows all eight guns on a de Havilland Mosquito FB VI firing at the same time, giving a good idea of the impressive firepower concentrated in the nose of the aircraft.
Initial successes revealed another problem with the Mosquito. Night fighters generally had to come to close quarters on their opponents, who often blew up under attack. The radiators in the wing leading edge tended to be vulnerable to damage under such circumstances, and it was not unusual for a night fighter to come back to base on a single engine. Although experiments were made with different radiator fits, they cut down the aircraft's performance too much to be worthwhile and the problem was never really fixed.
Night intruder sorties against Luftwaffe training fields in Northern France began in July 1942, as part of a general campaign of day and night "fighter sweeps" begun in late 1941, designed to give the RAF more combat experience and the Germans more headaches. The NF.II Specials were stripped of AI radar so that its secrets would not fall into German hands, but Mosquito pilots were able to jump Luftwaffe aircraft flying lit up with their landing and navigation lights on. The intruders made the Germans so jumpy that in at least one case a pilot simply flew into the ground while being pursued by a Mosquito. The intruders soon forced the Luftwaffe to move the training squadrons back to Germany.
By fall, the Mosquito was also performing meteorological reconnaissance flights over occupied Europe, plotting the weather to support bombing raids and other military activities. Bomber Command was still leery of the Mosquito, but the rest of the RAF was increasingly appreciating the machine's capabilities and was in fierce competition for the slowly rising trickle of production.
The Mosquito In Service
General view of the aircraft, standing in a dark and somewhat crowded corner of RAF Museum's Bomber Hall. Hard to find any good spot for photography!
Aircrews had liked the Mosquito from the start. There were initial teething problems, but these were to be expected with a new machine, and they didn't disguise the fact that the DH.98 was fast and agile. A lightly-loaded Mosquito performed so well even with an engine out that pilots said DH had designed it as a single-engine aircraft, and added a second engine for good luck. According to one story, later in the war an incautious Yank pilot at the controls of a Martin B-26 Marauder, itself regarded as a fairly hot twin-engine aircraft, once challenged a Mosquito pilot to a race. The Mosquito left the B-26 in the dust, flying past inverted with one prop feathered.
However, since it was a hot aircraft the Mosquito was not perfectly friendly. It was by no means a beast, it just provided a lot of performance and the pilot had to be aware of what he had his hands on. Its high wing loading gave it a relatively smooth low-level ride, at the expense of hot landings. Its agility allowed a hamfisted pilot to tear the wings off in aggressive maneuvers. It was touchy in pitch trim, with bomber variants tending to be tailheavy and fighter variants tending to be noseheavy. One of the worst problems was that getting into and, more significantly, out of a Mosquito was something of a chore. The bottom hatch in the bomber and reconnaissance versions and the side door in the fighter versions were a tight fit, particularly for aircrew in flight gear and parachute. Most aircrew liked an aircraft that was easy to get out of in a hurry should the thing decide to stop flying.
Ground crews were suspicious of it at first because of its unusual construction, but gradually came to appreciate that it was a sturdy and reliable machine. The Mosquito became known as the "Wooden Wonder", less respectfully the "Termite's Dream", or just generally the "Mozzie".
The Reconnaissance Mosquitoes At War
The starboard engine panels have been removed, exposing all internal structure from the spinner to the firewall. The engine, as stated before, is a Merlin 113, mounted on a welded steel frame.
If the Mosquito was having a hard time proving itself as a bomber, nobody had the slightest misgivings over it as a reconnaissance aircraft -- it could go wherever it liked and there wasn't much the Germans could do about it. Number 1 PRU was finding itself much needed and correspondingly heavily taxed, and was effectively upgraded from a squadron to a wing in October 1942 by being split into five squadrons.
One of the squadrons, Number 540, was equipped with the Mosquito, which was preferred for long-range missions into hostile airspace over reconnaissance Spitfires, which simply didn't have the reach. The PR Mosquitos ranged all over Europe and returned with spectacular images that provided useful military intelligence as well as some propaganda value. Crisp photographs of major targets, such as the German battle cruiser GNIESENAU, were released to the press to demonstrate that RAF aircraft could go where they chose with apparent impunity.
Since the PR Mosquitos operated mostly by day and by themselves, they had the greatest need for speed and height, and were given priority for the Mosquitos with two-stage Merlins, beginning with the PR.VIII. They were reequipped with the improved machines through 1943, and the PR.Is and PR.IVs were all retired by October 1943.
A PR.VIII became the first Mosquito to photograph Berlin, on 8 March 1943. On 2 June 1943 a PR.VIII overflew the German technical research center at Peenemunde on the Baltic coast. Previous missions there had turned up nothing, but this flight brought back images of the new German V-2 long-range ballistic missile. The installation was heavily bombed by the RAF in August under Operation HYDRA.
The PR.IX's more powerful engines and greater fuel load were put to good use. During 1943, one made a "grand tour" of central Europe, flying out of RAF Benson and overflying Regensburg, Germany; Vienna, Austria; Budapest, Hungary; and Foggia, Italy, before landing in Catania, Sicily. The trip covered 3,060 kilometers (1,900 miles), took 6 hours 30 minutes flying time, with an average speed of 407 KPH (292 MPH). The Mosquito ran out of gas before it could taxi to its parking spot.
In the winter of 1943:1944, PRU Mosquitos began to reach for higher altitude in order to evade improved defenses. This led to the eight PR.IXs modified with uprated Merlins and four-bladed propellers, but the height and cold were hell on both crews and aircraft. The pressurized PR.XVI was designed in response, but various teething problems kept it out of service until May 1944.
The handful of long-winged PR.32s were up to the task, but by the time they got into service there wasn't much of a task left, at least in Europe. This was fortunate for the PRU, since by late 1944 the Mosquito was beginning to encounter the Messerschmitt Me-262 jet fighter, which could easily outrun even the quick Mosquito. Fortunately for the Allies, the Me-262 was too little and too late, with most of those produced usually grounded for lack of fuel.
Mosquitos were first sent to the Far East in the spring of 1943, performing reconnaissance sorties from Calcutta over Southeast Asia. The ultimate reconnaissance Mosquito, the PR.34, began flying out of the Cocos Islands, in the Indian Ocean south of Sumatra, in July 1944 to overfly Japanese installations in Southeast Asia.
The Bomber Mosquitoes At War
These are the cowling panels laying on the ground. The middle panel shows the asymmetrical profile of the air intake fairing.
By early 1943, even Bomber Command was beginning to warm to the Mosquito. Attrition was still high, the rate being about 8% of sorties compared to about 5% for the "heavies", but the loss rate was slowly declining. In compensation, the Mosquito was proving extremely useful for precision bombing. Number 105 and Number 139 Squadrons had refined their low-level attack techniques. A first wave would zoom in, dropping bombs with 11-second delay fuzes, to be followed by a second wave performing a shallow dive attack with instantaneous fuzes.
105 Squadron paid their first visit to Berlin on 31 January 1943, with the attack timed to interrupt a parade being addressed by Reichsmarshal Hermann Goering. Later on the same day, Number 139 Squadron B.IVs similarly disrupted a rally being addressed by Reich Propaganda Minister Joseph Goebbels. These two nuisance raids made for good propaganda, and in the meantime the Mosquitos were also inflicting real damage on certain high priority targets.
Major Hereford de Havilland was able to write his brother: "Air Marshall Harris told me that he had, quite frankly, been surprised at the success Mosquitos had had on low-level attacks, and he said as much in a letter he addressed to the units concerned." However, Bomber Harris still had his priorities. The letter continued: "But he still considers that only a very small force should be diverted from the normal bombing routine for this type of work. For Pathfinding, which, he stated, will become the most important of all duties, the Mosquito is indispensable."
Harris reassigned his Mosquitos to the Pathfinder role, marking targets for heavy bomber strikes. Despite that, the RAF barely skipped a beat on low-level strikes with the Mosquito, the technique being quickly picked up by RAF tactical support squadrons, as discussed below.
The B.IV was absorbed into RAF 8 Group, the "Pathfinder Force (PFF)", which was set up in July 1942, and fitted with electronic navigation aids. The British had already put the "Gee" navigation system into service in the spring of 1942, which picked up signals from radio beacons in Britain and gave the aircraft's position by a scheme similar to triangulation. Gee was inaccurate for targeting purposes, and by the time the B.IV was being put into service as a pathfinder the Germans were jamming it anyway. Gee did stay in service as a navigation aid, and Gee receivers were fitted to some variants of Mosquitos.
Pathfinder Mosquitos were initially fitted with another navigation system, named "Oboe". This involved two radars set up in Britain, one named "Cat" that tracked the pathfinder along a constant-range path, the other named "Mouse" that determined when it was over the target. The system was called "Oboe" because the aircraft stayed on its constant range path using a tone fed into the pilot's headphones that varied in pitch if he strayed. Oboe was almost as accurate as clear-daylight bombing, though it was limited to line-of-sight operation. This at least put it in range of the Ruhr Valley, Germany's industrial heartland, and PFF Mosquitos fitted with Oboe kicked off the "Battle of the Ruhr" in March 1943, marking Essen for a raid by the heavies. The original Oboe was a longwave radar system and by the time the Germans got wise to it in the summer of 1943 and set out to jam it, the British had already moved to a centimetric system, though they continued to transmit the longwave signals as a deception.
For targets beyond the range of Oboe, PFF Mosquitos were fitted with a British centimetric targeting radar, known as "H2S"; the meaning of the acronym is now unclear. Pathfinder Mosquitos were modified to carry H2S using a radome under the rear fuselage, though some experimental fits had the radome under the forward fuselage. H2S gave a very rough and ambiguous radar map of a target and could only clearly recognize targets identified by distinctive bodies of water, but it was better than nothing. It went into service in July 1943.
Although the PFF used the Mosquito B.IV and the new B.IX to mark targets for heavies, the group also used it as the basis for what became the "Light Night Striking Force (LNSF)", sometimes called the "Fast Night Striking Force", which began by performing diversions for heavy-bomber raids, dropping markers and a few bombs on a "fake" target to distract the defense, then tossing out aluminum strips called "Window" (chaff) to jam German radars.
Gradually, as more bomber Mosquitos fitted with the oversized bombbay doors to carry Cookie bombs came into service, the LNSF's "diversionary" raids turned into effective attacks of their own. The B.IV didn't really have the horsepower to carry the Cookie well, but the B.IX and the B.XVI, with two-stage engines, were reasonably comfortable with the load. The B.XVI, built standard to carry the Cookie, entered service in early 1944, at about the same time that the LNSF started dropping Cookies on the Germans in earnest.
The B.XVIs became very energetic in the late stages of the war, in particular performing about 170 strikes on Berlin, reaching a peak on the night of 21 March 1945, when a total 142 Mosquitos hit the city in two attacks. The crews hit Berlin so often they called it the trip the "Berlin Express".
During the Battle of the Bulge in December 1944, Bomber Command B.XVIs performed an interesting variation on the low-level attack, attempting to toss Cookies into railroad tunnels. This was tricky and not completely successful, though at least one tunnel was caved in using the trick. The LNSF also laid mines in German ports and canals. The last Bomber Command raid of the war was performed by 16 Mosquito B.XVIs of Number 608 Squadron on Kiel on 2 May 1945.
Despite the fact the Mosquito began its career with Bomber Command with all the respect given a bastard child, by the end of the war it was a star player. Although the idea of an unarmed fast bomber had seemed like heresy, none of the British jet bombers introduced after the war would carry defensive armament.
One of the most unusual warloads carried by the B.IV was the "Highball" bomb, mentioned in the previous chapter, which was essentially a smaller version of the "Upkeep" bomb developed by British engineer Barnes Wallis and carried by Lancasters to attack the Moehne, Eder, and Sorpe dams on the night of 16 May 1943.
Upkeep was a drum-shaped bomb, carried crosswise under the belly of a Lancaster, and given a backspin before release. It was dropped at a precise height and distance in front of a dam, skipped over the water to the face of the dam, and then rolled downward into the water to detonate at a preset depth. The confining effect of the high-pressure water around the bomb helped crack the dam. The smaller 272 kilogram (600 pound) Highball was spherical, not drum-shaped, but was used in much the same way, being given a backspin and then released to skip over the water, roll down the face of the target, and explode at depth. However, its primary target was not a dam but the German battleship TIRPITZ.
Trials of the Highball began in March 1943, and a total of 60 B.IVs were adapted to carry the munition. The Highball was carried in a special fairing under an FB.VI, with a ram-air turbine used to drive the spin mechanism. A special squadron, RAF Number 618, was formed to use the weapon, but various problems kept the Highball out of service until May 1944, by which time it was not regarded as particularly needed in Europe.
There was still the Far East, however. 618 Squadron learned how to perform carrier-deck landings, and the squadron left for Australia at the end of October 1944. They languished there for the rest of the war, since the brass couldn't agree on what to do with them. The Royal Navy continued to tinker with Highball after the war, coming up with a "Mark 2" version, but finally abandoned the idea in 1947.
The Night-Fighter Mosquitoes At War
Click on Picture to enlarge
All bomber versions of the Mosquito featured a glazed nose, featuring a bomb sight behind an optically flat panel.
RAF night fighter squadrons were well up to strength by early 1943, with 159 NF.IIs in service. In the meantime, the centimetric radars were being beginning service with the Mosquito night fighter force, beginning with the NF.XII conversions of NF.IIs, to be quickly followed by the production NF.XIII.
They arrived just in time to help deal with new enemy tactics. The Baedeker raids, using small formations of twin-engine bombers, had proven too expensive, and so the Luftwaffe turned to performing "tip and run" strikes on British targets, using FW-190s and then fast Ju-88S bombers to come in low and fast in small numbers, hit a target, then run away in the dark. The older longwave AI.IV had a wide beam that led to ground reflection interference or "clutter" at low altitude. The new AI.VIII centimetric radar had a much narrower beam and could operate at lower altitudes without being blinded by clutter. On the night of 16 May 1943, Mosquito NF.XIIs of Number 82 Squadron shot down five FW-190s.
The NF.XVII and NF.XIX, with uprated Merlins and American AI.X radar, were a big step forward, and the new variant saw good service in the "Baby Blitz", the short-lived Luftwaffe bombing campaign against London in early 1944. Although the Germans used "Dueppel" (chaff) and jamming to try to confuse the radars of the night-fighters, the AI.X was able to cut through the countermeasures and helped inflict serious losses on the intruders.
By this time, all the NF.IIs had been converted into NF.XIIs and NF.XVIIs. NF.IIs had been performing night intruder sorties over Occupied Europe since mid-1943 to help Bomber Command deal with German night fighters. The British had decided that the Germans had little to learn from the old AI.V longwave radar, but worries that the Germans might learn the secrets of centimetric radar kept the NF.XII and later night-fighter marks out of enemy airspace until May 1944. In fact, the Germans had pulled an H2S centimetric bombing radar out of the wreck of a British bombers over a year earlier and the secret was pretty much out of the bag anyway. It did the Germans little good; they never managed to put a centimetric radar into large-scale service, though they did build a device named "Naxos" that could home in on centimetric emissions.
In the meantime, Mosquito night-fighters added to their bag of tricks to use against the Luftwaffe. They carried "Serrate", a box that could home in on German night fighter radars; "Perfectos", a box that could home in on German "identification friend or foe (IFF)" transmitters; and a tail-warning radar named "Monica". Mosquito tactics included the tried-and-true night intruder game, orbiting around Luftwaffe airfields to pounce on unwary enemy night fighters; and "Lure", which involved getting in the bomber stream, throttling down to simulate a heavy bomber, and then waiting for Monica to indicate the approach of a Luftwaffe night fighter. The German night fighter crew would then observe, to their terror, the "heavy" nimbly turning about and putting on speed for the kill. However, targets grew ever more scarce in the last year of the war, as the Germans ran out of fuel, pilots, and every other resource needed to hold off defeat.
Mosquito night fighters based in Britain helped in the defense against the last German air offensive against England, the "V-1 flying bomb" campaign that began after D-Day and continued into the fall. The V-1s were small robot jet aircraft that came in low and fast, with a guidance system adequate to allow them to hit a large city like London. British defenses were weak at first but gradually improved, and the Mosquito night fighters were put to work intercepting the flying bombs at night. As the missile tended to go up in a big bang when shot up, Mosquito pilots learned to fly across its bow to perform a "soft kill", disrupting its automatic guidance and causing it to crash.
The flying bomb launch sites in northern France were soon overrun, but then the Germans began to launch the flying bombs from Heinkel He-111s operating out of the Low Countries. Although service entry of the NF.30 had been delayed due to various teething problems, they were available to be put to use hunting down the He-111s. This turned out to be a tricky job, since the heavily-laden He-111s flew so slowly that the Mosquitos had to slow down themselves, making them vulnerable to defensive fire.
However, the Heinkels suffered high losses, and the Germans were forced to give up the effort. By the time the flying bomb campaign fizzled out in the winter, the Mosquitos had shot down 600 V-1s. Unfortunately, the Germans had switched to V-2 rockets by that time for which there was no defense. The missile attacks were finally ended by the surrender of Germany in May 1945.
The Fighter-Bomber Mosquitoes At War & The Ball-Bearing Run
The bomb bay of this variant was bulged, like on the Mk. XVI, allowing even a 4000lb bomb to be carried. Brown objects visible inside are fuselage fuel tanks.
The fighter-bomber versions of the Mosquito were inspired by the exploits of radar-stripped NF.II Specials over France in the last half of 1942. The success of these mission suggested that a new variant of the Mosquito should be built, carrying both guns and bombs, to perform similar missions.
As mentioned, the FB.VI went into service in the spring of 1943, and was the most heavily produced Mosquito variant. The key to its popularity was its flexibility. FB.VIs were put to use performing "Intruder" sorties against specific enemy target areas; "Ranger" fighter sweeps to hit rolling stock and fighters on the ground; and "Instep" fighter patrols over the Bay of Biscay to take on Luftwaffe Junkers Ju-88 and Messerschmitt Me-110 long-range fighters out to intercept RAF Coastal Command ocean patrol aircraft.
However, the FB.VI became most famous in service with the RAF "2nd Tactical Air Force (2TAF)", which was formed in June 1943, building up two "big wings" of FB.VIs, one at Sculthorpe and the other at Lasham. 2TAF was created after Bomber Command transferred their Mosquitos to the Pathfinder Force, and carried on the low-level precision strike missions devised by Bomber Command, beginning such attacks in October 1943.
2TAF Mosquitos focused on German targets sited in cities in Occupied Europe , where the RAF was understandably reluctant to perform imprecise high altitude attacks. Power stations were a favored target, but the FB.VIs took on other targets as well.
On 18 February 1944, 18 Mosquitos from Number 21, 464, and 481 Squadrons attacked the prison at Amiens, France, under Operation JERICHO. The objective was to "tumble down the walls" of the prison to allow condemned French Resistance fighters being held there to escape. The attack was successful, with about 250 prisoners managing to escape. However, about a hundred prisoners were killed in the raid, and a good number of those who escaped were quickly recaptured. The raid was led by RAF Group Captain Charles Pickard, whose Mosquito was shot down by FW-190s during the action. He and his navigator are now at rest under a memorial in Amiens.
Now the Mosquitos turned their attention back to the Gestapo, engaging in what almost became a private war. On 11 April 1944, six FB.VIs of Number 613 Squadron struck Gestapo headquarters in The Hague, the Netherlands, destroying German records on the Dutch Resistance. Two bombs were tossed into the front door of the building.
On 31 October 1944, 18 FB.VIs hit a Gestapo office building at Aarhus University in Denmark. They came in so low that one Mosquito went back home with a piece of masonry in the fuselage. On 21 March 1945, Mosquitos hit Gestapo headquarters in the middle of Copenhagen. The mission was successful except that the strike leader's Mosquito hit a bridge and slammed into an elementary school, with many civilian casualties.
In the meantime, Mosquito fighter-bombers were operating in support of the landings in France, striking German communications. The FB.VIs were also active in attacks on the launch sites for V-1 flying bombs in Northern France. The V-1s had been photographed at Peenemunde, and then on 28 November 1943 a PR Mosquito spotted the first French launch site. Both the RAF and the US Army Air Forces (USAAF) began to bomb the sites on 5 December 1943.
The campaign lasted into the fall of 1944, and statistics compiled later showed that the Mosquito destroyed one site for each 36.4 tonnes (40 tons) of bombs dropped, as opposed to 150 tonnes (165 tons) for USAAF Boeing B-17 Flying Fortresses, 158 tonnes (182 tons) for Martin B-26 Marauders, and 200 tonnes (219 tons) for North American B-25 Mitchells. However, the Germans were able to complete enough launch sites to fire off V-1s in quantity.
Apparently some FB.VIs were converted to a night fighter configuration, with a small radome fitted with American ASH radar and Serrate radar homing gear to help harass German night fighters. Details of these machines are otherwise unclear.
RAF Coastal Command did not get their hands on the Mosquito until June 1944, the beginning of the end of the Germans in France, and so their FB.VIs operated in the North Sea, with a Mosquito "Sea Strike Force" headquartered at Banff in Scotland to perform antishipping and antisubmarine strikes.
The "Banff Strike Wing" found the Mosquito even better at the job than the rugged and well-armed Bristol Beaufighters they had been using. The FB.XVIII and its Molins gun gave the Mosquito more punch, but was rendered obsolete when Coastal Command FB.VIs were qualified to fire rocket projectiles with solid metal warheads to punch holes in ships below the waterline. The Mosquitos also used depth charges with fuzes set to shallow depth to attack U-boats on the surface.
One of the more unusual applications of the Mosquito was as a transport. These Mosquito transports were operated by BOAC for flights to neutral Sweden, since any commercial airliner that attempted such a flight would have been easily intercepted. The service began in early 1943 and continued through the war.
A single B.IV and nine FB.VIs were assigned to this duty. They carried mail, including diplomatic documents; high-value cargoes such as Swedish precision ball-bearings; and the occasional passenger tucked away in the bombbay. The bombbay was fitted with oxygen, a reading light, an intercom, and a bunk, and passengers were packed in wearing double flight suits, a life preserver, and a parachute. They were given reading material and refreshments to allow them to pass the time on the "ball-bearing" route. One of the most famous passengers was Danish physicist Niels Bohr, who was spirited out of Denmark to Sweden when the Nazis took full control of the country in 1943.
Its Post War Service
The canopy had been equipped with an astrodome above bombardier/navigator's seat at the starboard side.
Although the Mosquito is identified with its wartime exploits, it remained in active RAF service for a decade after the end of the war. The T.III was extensively used for training, while combat machines remained in service with front-line units.
The FB.VI served with the British Air Forces of Occupation (BAFO) in Germany. The NF.30 and NF.36 remained first-line night fighters for British home defense until replacement by the de Havilland Vampire and Armstrong-Whitworth Meteor in that role in 1951.
The Mosquito PR.34 was the primary reconnaissance asset for the RAF until replaced by the English Electric Canberra in the early 1950s. In the early years of the Cold War, it was used for clandestine sorties over Eastern Europe and the USSR, and also saw combat during the insurgency in Malaya in the early 1950s.
The PR.34 set a number of records. A PR.34 of Number 540 Squadron set a record east-west transatlantic flight in September 1945, and one flew from London to Cape Town, South Africa, in 21 hours 31 minutes in May 1944. The PR.34 also served in the Middle and Far East in the postwar period, and a PR.34A of Number 81 Squadron flew the Mosquito's last combat sortie over Malaya on 15 December 1955.
Bomber Command and BAFO kept the Mosquito B.35 in service until 1953. Some B.35s were converted to night photo-reconnaissance platforms as the PR.35 and remained in service for some time longer. 105 were converted in 1952 and 1953 by Brooklands Aviation to "TT.35" target tugs, with a target carried in the bombbay and an air-driven winch attached below the fuselage. The TT.35s were operated by the Number 3 Civilian Anti-Aircraft Cooperation Unit at Exeter in the UK. The TT.35 was the last version of the Mosquito in formal RAF service, and was not phased completely out until 1961.
The Royal Navy also operated the Mosquito as a target tug, with 26 B.XVIs and PR.XVIs extensively modified by General Aircraft in 1950 to the "TT.39" configuration. The TT.39 was without argument the ugliest of all Mosquito variants; it was fitted with a glass cylindrical dome on the spine for the target winch operator, and had an extended "greenhouse" nose where a cameraman could film the action. The propellers had to be clipped to keep from striking the extended nose. The target winch was stowed in the bombbay along with the target. The winch was driven by a ram-air turbine that could be extended out of the bombbay. Apparently their operational life was short, with the type phased out by 1952, possibly because nobody could stand to look at it.
A number of different Mosquito variants were used for trials in the postwar period, for example evaluating rockets and other munitions. The Mosquito performed a "curtain call" in 1963, when five RAF TT.35s were dressed up as FB.VIs to perform in the movie 633 SQUADRON, starring Cliff Robertson and describing the adventures of a fictional squadron of the 2TAF. Three of these TT.35s were joined by a T.III in 1966 to participate in a sequel, MOSQUITO SQUADRON, starring David McCallum.
In a sad note to the Mosquito's postwar accomplishments, Geoffrey de Havilland JR, who had been so intimately involved with the machine, was killed on 27 September 1946 when the "DH.108" experimental jet he was piloting lost its wings.
The Mosquito In Foreign Service
Of course, the Mosquito saw extensive service with British Commonwealth forces, and Mosquitos were built in Canada and Australia.
The wheels began turning on Canadian production in July 1941, just as the first Mosquitos were being delivered to Number 1 PRU. The DH Canada plant at Downsview, in the Toronto area, was tooled up for the job.
The first Canadian-built variant was the "B.VII", which was essentially a B.IV but with Merlins built under license by Packard, a Detroit engine manufacturer. Only 25 B.VIIs were built, all of which remained in North America.
They were followed by the similar "B.XX", which went into full production. The first B.XXs arrived in the UK in August 1943, and were in operational service by December. Most or all Canadian Mosquitos delivered to the UK were flown across the Atlantic, a hazardous flight on which aircraft occasionally disappeared. Early production was fitted with Packard Merlin 31 engines, while later production featured Packard Merlin 33s, with both engines providing 1,080 kW (1,450 HP) each. 245 B.XXs were built.
With the introduction of the two-stage Merlins, Canadian production then went to the "B.25", fitted with two-stage Packard Merlin 225s providing 1,210 kW (1,620 HP) each. A total of 343 B.25s was built, with 38 going to the RCAF, 70 to the Royal Navy, and the rest to the RAF.
The Canadians also built fighter-bomber Mosquitos derived from the FB.VI. The first was the "FB.21", which was almost identical to the FB.VI, the only distinction being Packard Merlin 31 engines, with 1,090 kW (1,460 HP) each. Only six FB.21s were built, with production quickly moving to the "FB.26", with minor improvements. A total of 337 FB.26s was built.
The Canadians also built a series of unarmed dual-control trainers. The first was the "T.22" trainer, which was based on the FB.VI and had single-stage Packard Merlin 33 engines. Only six were built, with the Canadians quickly moving to an improved derivative, the "T.27", with 49 built. They also converted 37 FB.26 fighter-bombers to a trainer designated the "T.29". The Canadians built a total of 1,034 Mosquitos, the majority of them going into RAF service.
* Australian Mosquito production was much more limited than Canadian production and is an untidy subject. The Australians focused on production of a FB.VI clone, the "FB.40", with 203 built, six more being converted before rollout to the "PR.40" specification. They were powered by Packard Merlins. Initial deliveries were in 1944.
Many of the FB.40s that were built were converted into other marks. 28 were converted to "PR.41s"; 22 were converted to "T.43s", which were dual-control trainers similar to the T.III with full armament, but featuring some Australian and US instruments; and one was converted to an "FB.42" prototype that went no further, and then became one of the conversions to PR.41s.
The undercarriage unit was a simple affair, built around rubber rather than hydraulic shock absorbers. The curved mudguard plate behind the wheel can be seen in this view.
The New Zealanders did not operate the Mosquito during the war, but obtained four T.43s and an FB.40 from Australia for training in 1946. Later on in that same year, the British provided four T.IIIs and eight FB.VIs (including 30 new-build fighter-bombers), though two crashed in Australia on the last leg of the ferry flight. Only a single squadron was formed, however, with most of the aircraft stored until they were all disposed of in 1953.
Another Commonwealth country, South Africa, operated Mosquito reconnaissance variants in the Mediterranean theater. After the war, the South Africans used their Mosquitos for aerial survey work.
General Henry "Hap" Arnold, commander of the United States Army Air Forces, witnessed a demonstration of the Mosquito on 20 April 1941 as a guest of Lord Beaverbrook. Geoffrey de Havilland JR was in prime form that day, screaming the machine low over the ground and performing sharp maneuvers with one engine feathered. Arnold was extremely impressed, and returned to the US with engineering drawings of the machine.
There matters more or less stood with the Yanks until late 1942, when a B.IV Mosquito was handed over to Colonel Elliot Roosevelt, the American President's son and commander of a USAAF reconnaissance squadron in North Africa, equipped with Lockheed F-4 Lightning reconnaissance aircraft. The B.IV was faster and had much longer range than the Lockheeds, and Elliot Roosevelt began to press for adopting the British machine.
In the meantime, Mosquitos were finally beginning to roll off the production lines at de Havilland Canada in the Toronto area, and in December 1942 Geoffrey de Havilland JR brought one of the first Canadian Mosquitos down to Washington DC. Hap Arnold ordered that airport traffic be held off for a half hour to allow de Havilland to put on an aerial demonstration over the city. Geoffrey De Havilland then left for California to perform more demonstrations. He went by train in order to see the country, while the Mosquito went separately. In Los Angeles he met with his cousin, actress Olivia de Havilland.
Hap Arnold now became very determined to get his hands on the Mossie, beginning with a offer to swap P-51 Mustangs for Mosquitos. The British turned him down. The Mosquito was increasingly seen as difficult to replace. Had Canada been producing Mosquitos in volume at the time, the Americans might have been able to get their hands on part of the production, but the Canadians were slow to ramp up, with only 90 Mosquitos built there in 1943. At least Arnold's persistent lobbying to get Mosquitos helped convince Bomber Command that they had something of value.
The Americans did manage to get their hands on a relatively small batch of Canadian aircraft. The US signed an agreement with the British government in October 1943 for 120 Canadian-built Mosquito bombers, but limited production meant that the US only got 5 B.VIIs and 35 B.XXs. They were converted to a reconnaissance configuration with US-built cameras, redesignated "F.8", and sent to the UK for service with the USAAF Eighth Air Force.
The F.8's camera suite was minimal and the single-stage Merlins really didn't provide the performance the USAAF wanted, and so the F.8s were eventually replaced by PR.XVIs. The Americans obtained over a hundred PR.XVIs, along with a handful of T.IIIs for conversion or continuance training.
American pilots converting from their Lockheed F-4 and F-5 Lightnings, which had "handed" propellers, had to be trained to deal with the Mosquito's tendency to roll against the rotation of its propellers on takeoff. There was a worse problem in that over-anxious fighter pilots tended to mistake Mosquitos for Messerschmitt Me-410s, which in fact did have a similar configuration, and so the USAAF gave their PR.XVIs red-painted tails as a recognition aid.
Click on Picture to enlarge
The majority of the Yank PR.XVIs were used in their intended photoreconnaissance role, but a good number of them were used for weather reconnaissance, and they were also modified for special tasks. Some were fitted with US-built "H2X" targeting radar, the American three-centimeter counterpart to the British ten-centimeter H2S, mounted in the nose radome. Since American crews referred to H2X as "Mickey" for some forgotten reason, these were known as "Mickey Ships". Some USAAF Mosquitos were fitted out for dispensing chaff, and seven were fitted with communications gear to support Allied agents and resistance forces in Occupied Europe.
USAAF Mosquitos were also fitted to use the LORAN navigation system, the American answer to Gee, and since LORAN was something of an Allied standard later in the war it is plausible that some RAF Mosquitos had LORAN receivers as well. Some sources also mention that the USAAF operated a squadron of NF.30s in Italy late in the war, but details are unclear. The USAAF returned all their Mosquitos at the end of the war, as part of the reverse Lend-Lease agreement.
A number of nations obtained hand-me-down Mosquitos from various sources:
Another view of the main undercarriage unit reveals even more elements of the structure.
Threaded tyres as one shown were common for all marks of the Mosquito.
An interesting detail is that the undercarriage doors have bulged fairings on the inside, with quite a tick profile. Easy to model, if you use those crude injection-moulded doors - just file the edges down and would look like the real thing!
The Belgians obtained a set of Mosquitos from British stocks, including two T,IIIs, two FB.VIs, and 24 NF.30s. Some of the T.IIIs and FB.VIs were later converted to target tugs.
- A small number served with Burma after the nation won independence from Britain in 1948.
- About 200 Mosquitos of various types served with the Chinese Nationalists beginning in the fall of 1948, and saw some action against the Red Chinese until the expulsion of the Nationalists to Taiwan the next year. The survivors made their way to Taiwan and served into the 1950s.
- Czechoslovakia operated 19 FB.VIs for a short time after the end of World War II, with the machines then replaced by Soviet types. As the Czechoslovakians had plenty of German ammunition but not much Allied ammunition, in some cases the FB.VI's guns were swapped with German types.
- The Dominican Republic obtained five FB.VIs in 1948, with the machines refurbished by Fairey and fitted with four-bladed propellers, to be followed by three T.29s from RCAF service. All Dominican Mosquitos were withdrawn from service in 1954 due to the lack of spares.
- The Free French Air Force did not use the Mosquito during the war, but after the war the French bought 57 FB.VIs, 29 PR.XVIs and PR.34s, 23 NF.30s, and a few T.IIIs. The French FB.VIs saw some action against Viet Minh guerrillas in French Indochina, but they were quickly withdrawn from combat service. The French removed all their Mosquitos from service in 1950.
- The Israeli Air Force was an enthusiastic user of the Mosquito. Three PR.XVIs were smuggled into the country through arms embargo by various means in the late 1940s, and when the French decided to sell off their Mosquitos in 1950, the Israels bought 60 FB.VIs, a few T.IIIs, and five PR.XVIs. In 1954, the Israelis picked up 14 TR.33s from the Royal Navy, with all naval gear removed, and a few more PR.XVIs. They provided excellent service during Operation MUSKETEER, the 1956 Anglo-French-Israeli seizure of the Suez canal, with no combat losses.
Vertical tail, like all other wooden components of the airframe, shows no joints or panel lines whatsoever.
The emblem shown belongs to No. 98 Squadron, stationed at Celle, Germany during the late
The Swedes obtained sixty NF.XIXs in 1948. They were refurbished by Fairey, fitted with four-blade propellers, and given the designation "J 30" in Swedish service.
- Switzerland apparently interned a single Mosquito during the war, then purchased after the war and used it as a jet engine testbed.
- The Turks obtained 137 FB.VIs and F.IIIs in 1947, with the machines also refurbished by Fairey and given four-blade propellers. The Mosquito remained in Turkish service until 1954.
- Yugoslavia received 46 FB.VIs, 60 NF.38s, and a handful of T.IIIs in the postwar period.
A number of Mosquitos were operated by civilian organizations after the war. A company from Los Angeles, Jack Amman Photographic Engineers, bought a number of PR.34s. These machines were converted by DH at Hatfield for survey work in Libya. Spartan Air Services in Canada obtained a number of B.35s and also converted them for survey work, the last of the batch surviving in operation until 1963. The Spartan machines had a number of modifications, in particular a forward-hinging canopy.
Although a few Mosquitos were bought up for use as air racers, most of those available for sale had single-stage engines and flat fighter windscreens and didn't have the performance to meet the competition.
While many Mosquitos remain on static display, only a handful remain airworthy. One of the drawbacks of its wooden construction was that the Mosquito hasn't aged as gracefully as all-metal aircraft. This should not be interpreted as a criticism of the DH engineering team, since none of them would have expected any Mosquitos to be flying in the 21st century.
Greg Goebel / Public Domain