The de Havilland DH.98 Mosquito was a British multi-role combat aircraft with a two-man crew that served during the Second World War and the postwar era. The Mosquito was one of the few operational front-line aircraft of the World War II era to be constructed almost entirely of wood and, as such, was nicknamed "The Wooden Wonder". The Mosquito was also known affectionately as the "Mossie" to its crews. 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 aircraft, and fast photo-reconnaissance aircraft. It was also used by the British Overseas Airways Corporation (BOAC) as a transport.
When the Mosquito entered production in 1941, it was one of the fastest operational aircraft in the world. Entering widespread service in 1942, the Mosquito first operated as a high-speed, high-altitude photo-reconnaissance aircraft, and continued to operate in this role throughout the war. From mid-1942 to mid-1943 Mosquito bombers were used in high-speed, medium- or low-altitude missions, attacking factories, railways and other pinpoint targets within Germany and German-occupied Europe. From late 1943, Mosquito bomber units were formed into the Light Night Strike Force and used as pathfinders for RAF Bomber Command's heavy-bomber raids. They were also used as "nuisance" bombers, often dropping 4,000 lb (1,812 kg) "cookies", in high-altitude, high-speed raids that German night fighters were almost powerless to intercept.
As a night fighter, from mid-1942, the Mosquito was used to intercept Luftwaffe raids on the United Kingdom, most notably defeating the German aerial offensive, Operation Steinbock, in 1944. Offensively, starting in July 1942, some Mosquito night-fighter units conducted intruder raids over Luftwaffe airfields and, as part of 100 Group, the Mosquito was used as a night fighter and intruder in support of RAF Bomber Command's heavy bombers, and played an important role in reducing bomber losses during 1944 and 1945. As a fighter-bomber in the Second Tactical Air Force, the Mosquito took part in "special raids", such as the attack on Amiens Prison in early 1944, and in other precision attacks against Gestapo or German intelligence and security forces. Second Tactical Air Force Mosquitos also played an important role operating in tactical support of the British Army during the 1944 Normandy Campaign. From 1943 Mosquitos were used by RAF Coastal Command strike squadrons, attacking Kriegsmarine U-boats (particularly in the 1943 Bay of Biscay offensive, where significant numbers of U-boats were sunk or damaged) and intercepting transport ship concentrations.
The Mosquito saw service with the Royal Air Force (RAF) and many other air forces in the European theatre, and the Mediterranean and Italian theatres. The Mosquito was also used by the RAF in the South East Asian theatre, and by the Royal Australian Air Force (RAAF) based in the Halmaheras and Borneo during the Pacific War.
On 21 June 1941 the Air Ministry ordered that the last 10 Mosquitoes, ordered as photo-reconnaissance aircraft, should be converted to bombers. These 10 aircraft were part of the original 1 March 1940 production order and became the B Mk IV Series 1. W4052 was to be the prototype and flew for the first time on 8 September 1941.
The bomber prototype led to the B Mk IV, of which 273 were built: apart from the 10 Series 1s, all of the rest were built as Series 2s with extended nacelles, revised exhaust manifolds, with integrated flame dampers, and larger tailplanes. Series 2 bombers also differed from the Series 1 in having a larger bomb bay to increase the payload to four 500 lb (230 kg) bombs, instead of the four 250 pounds (110 kg) bombs of Series 1. This was made possible by shortening the tail of the 500 pounds (230 kg) bomb so that these four larger weapons could be carried (or a 2,000 lb (920;kg) total load). The B Mk IV entered service in May 1942 with 105 Squadron.
In April 1943 it was decided to convert a B Mk IV to carry a 4,000 lb (1,812 kg), thin-cased high explosive bomb (nicknamed "Cookie"). The conversion, including modified bomb bay suspension arrangements, bulged bomb bay doors and fairings, was relatively straightforward, and 54 B.IVs were subsequently modified and distributed to squadrons of RAF Bomber Command's Light Night Striking Force. 27 B Mk IVs were later converted for special operations with the Highball anti-shipping weapon, and were used by 618 Squadron, formed in April 1943 specifically to use this weapon. A B Mk IV, DK290 was initially used as a trials aircraft for the bomb, followed by DZ471,530 and 533. The B Mk IV had a maximum speed of 380 mph (610 km/h), a cruising speed of 265 mph (426 km/h), ceiling of 34,000 ft (10,000 m), a range of 2,040 nmi (3,780 km), and a climb rate of 2,500 ft per minute (762 m).
Other bomber variants of the Mosquito included the Merlin 21 powered B Mk V high-altitude version. Trials with this configuration were made with W4057 which had the wings strengthened and an addition of two fuel tanks, or alternatively two 500 pounds (230 kg) bombs. This design was not produced in Britain, but formed the basic design of the Canadian-built B.VII. Only W4057 was built in prototype form. The Merlin 31 powered B Mk VII was built by de Havilland Canada. It was based on the B.V. and first flown on 24 September 1942. It only saw service in Canada and only 25 were built. Six were handed over to the United States Army Air Forces.
B Mk IX (54 built) was powered by the Merlin 72,73, 76 or 77. The two-stage Merlin variant was based on the PR.IX. The prototype DK 324 was converted from a PR.VIII and first flew on 24 March 1943. In October 1943 it was decided that all B Mk IVs and all B Mk IXs then in service would be converted to carry the 4,000 pounds (1,800 kg) "Cookie", and all B Mk IXs built after that date were designed to allow them to be converted to carry the weapon. The B Mk IX had a maximum speed of 408 mph (657 km/h), an economical cruise speed of 295 mph (475 km/h) at 20,000 ft, and 350 mph (560 km/h) at 30,000 ft, ceiling of 36,000 ft (11,000 m), a range of 2,450 nmi (4,540 km), and a climb rate of 2,850 feet per minute (869 m). The IX could carry a maximum load of 2,000–4,000 lb (910–1,800 kg) of bombs. A Mosquito B Mk IX holds the record for the most combat operations flown by an Allied bomber in the Second World War. LR503, known as "F for Freddie" (from its squadron code letters, GB*F), first served with No. 109 and subsequently, No. 105 RAF squadrons. It flew 213 sorties during the war, only to crash at Calgary airport during the Eighth Victory Loan Bond Drive on 10 May 1945, two days after Victory in Europe Day, killing both the pilot, Flt. Lt. Maurice Briggs, DSO, DFC, DFM and navigator Fl. Off. John Baker, DFC and Bar.
The B Mk XVI was powered by the same variations as the B.IX. All B Mk XVIs were capable of being converted to carry the 4,000 pounds (1,800 kg) "Cookie". The two-stage powerplants were added along with a pressurised cabin. DZ540 first flew on 1 January 1944. The prototype was converted from a IV (402 built). The next variant, the B Mk XX, was powered by Packard Merlins 31 and 33s. It was the Canadian version of the IV. Altogether, 245 were built. The B Mk XVI had a maximum speed of 408 mph (657 km/h), an economical cruise speed of 295 mph (475 km/h) at 20,000 ft, and 350 mph (560 km/h) at 30,000 ft, ceiling of 37,000 ft (11,000 m), a range of 1,485 nmi (2,750 km), and a climb rate of 2,800 ft per minute (853 m). The type could carry 4,000 pounds (1,800 kg) of bombs.
The B.35 was powered by Merlin 113 and 114As. Some were converted to TT.35s (Target Tugs) and others were used as PR.35s (photo-reconnaissance). The B.35 had a maximum speed of 422 mph (679 km/h), a cruising speed of 276 mph (444 km/h), ceiling of 42,000 ft (13,000 m), a range of 1,750 nmi (3,240 km), and a climb rate of 2,700 ft per minute (823 m). A total of 174 B.35s were delivered up to the end of 1945. A further 100 were delivered from 1946 for a grand total of 274, 65 of which were built by Airspeed Ltd.