The de Havilland DH98 Mosquito was a British multi-role combat aircraft with a two-man crew that served during the Second World War and the post war 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 Mosquito’s also played an important role operating in tactical support of the British Army during the 1944 Normandy Campaign. From 1943 Mosquito’s 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.
A total of 10 Mosquito PR Mk Is were built, four of them “long range” versions equipped with a 151 imperial gallons (690 L) overload fuel tank in the fuselage. The contract called for 10 of the PR Mk I airframes to be converted to B Mk IV Series 1s. All of the PR Mk Is, and the B Mk IV Series 1s, had the original short engine nacelles and short span (19 ft 5.5 in) tail-planes. Their engine cowling’s incorporated the original pattern of integrated exhaust manifolds which, after a relatively brief flight time, had a troublesome habit of burning and blistering the cowling panels. The first operational sortie by a Mosquito was made by a PR Mk I, W4055, on 17 September 1941; during this sortie the unarmed Mosquito PR.I evaded three Messerschmitt Bf 109s at 23,000 feet (7,000 m). Powered by two Merlin 21s, the PR Mk I had a maximum speed of 382 miles per hour (615 km/h), a cruise speed of 255 miles per hour (410 km/h), a ceiling of 35,000 feet (11,000 m), a range of 2,180 nautical miles (4,040 km), and a climb rate of 2,850 feet (870 m) per minute.
Over 30 Mosquito B Mk IV bombers were converted into the PR Mk IV photo-reconnaissance aircraft. The first operational flight by a PR Mk IV was made by DK284 in April 1942.
The Mosquito PR Mk VIII, built as a stopgap pending the introduction of the refined PR Mk IX, was the next photo-reconnaissance version. The five VIIIs were converted from B Mk IVs and became the first operational Mosquito version to be powered by two-stage, two-speed supercharged engines, using 1,565 hp (1,167 kW) Rolls-Royce Merlin 61 engines in place of Merlin 21/22s. The first PR Mk VIII, DK324 first flew on 20 October 1942. The PR Mk VIII had a maximum speed of 436 mph (702 km/h), an economical cruise speed of 295 mph (475 km/h) at 20,000ft, and 350 mph (560 km/h) at 30,000ft, a ceiling of 38,000 ft (12,000 m), a range of 2,550 nmi (4,720 km), and a climb rate of 2,500 ft per minute (760 m).
The Mosquito PR Mk IX, 90 of which were built, was the first Mosquito variant with two-stage, two-speed engines to be produced in quantity; the first of these, LR405, first flew in April 1943. The PR Mk IX was based on the Mosquito B Mk IX bomber and was powered by two 1,680 hp (1,250 kW) Merlin 72/73 or 76/77 engines. It could carry either two 50 imperial gallons (230 L), two 100 imperial gallons (450 L) or two 200 imperial gallons (910 L) drop-able fuel tanks.
The Mosquito PR Mk XVI had a pressurised cockpit and, like the Mk IX, was powered by two Rolls-Royce Merlin 72/73 or 76/77 piston engines. This version was equipped with three overload fuel tanks, totalling 760 imperial gallons (3,500 L) in the bomb bay, and could also carry two 50 imperial gallons (230 L) or 100 imperial gallons (450 L) drop tanks. A total of 435 of the PR Mk XVI were built. The PR Mk XVI had a maximum speed of 415 mph (668 km/h), a cruise speed of 250 mph (400 km/h), ceiling of 38,500 ft (11,700 m), a range of 2,450 nmi (4,540 km), and a climb rate of 2,900 feet per minute (884 m).
The Mosquito PR Mk 32 was a long-range, high-altitude, pressurised photo-reconnaissance version. It was powered by a pair of two-stage supercharged 1,960 hp (1,460 kW) Rolls-Royce Merlin 113 and Merlin 114 piston engines, the Merlin 113 on the starboard side and the Merlin 114 on the port. First flown in August 1944, only five were built and all were conversions from PR.XVIs.
The Mosquito PR Mk 34 and PR Mk 34A was a very long-range unarmed high altitude photo-reconnaissance version. The fuel tank and cockpit protection armour were removed. Additional fuel was carried in a bulged bomb bay: 1,192 gallons which was the equivalent of 5,419 miles (8,721 km). A further two 200-gallon (910-litre) drop tanks under the outer wings gave a range of 3,600 miles (5,800 km) cruising at 300 mph (480 km/h). Powered by two 1,690 hp (1,260 kW) Merlin 114s first used in the PR.32. The port Merlin 114 drove a Marshal cabin supercharger. A total of 181 were built, including 50 built by Percival Aircraft Company at Luton. The PR.34’s maximum speed (TAS) was 335 mph (539 km/h) at sea level, 405 mph (652 km/h) at 17,000 ft (5,200 m) and 425 mph (684 km/h) at 30,000 ft (9,100 m). All PR.34s were installed with four split F52 vertical cameras, two forward, two aft of the fuselage tank and one F24 oblique camera. Sometimes a K-17 camera was used for air surveys. In August 1945, the PR.34A was the final photo-reconnaissance variant with one Merlin 113A and 114A each delivering 1,710 hp (1,280 kW).
Colonel Roy M. Stanley II, USAF (RET) wrote: “I consider the Mosquito the best photo-reconnaissance aircraft of the war”.