Mosquito B. Mk IV, production number DZ464, from 139-th Squadron at 1942.

DE HAVILLAND DH.98 MOSQUITO - The De Havilland Mosquito was developed in the course of 1938-39 by a design team headed by R E Bishop in accordance with an original concept for a high-speed two-seat unarmed bomber of wooden construction proposed by Capt Geoffrey de Havilland. Development proceeded during 1940 to Specification B.l/40, written round the DH proposal and covering a bomber/reconnaissance aircraft with provision for development of a fighter variant also, powered by 1,280 hp Merlin RM35M engines. Initial contract placed March 1, 1940, for 50 bomber/reconnaissance aircraft, including one prototype; amended July 1940 to include one fighter prototype and in January 1941 to include a reconnaissance prototype, with many subsequent amendments and additions to contracts which eventually covered production of 6,411 De Havilland Mosquitoes in Britain, 1,134 in Canada and 212 in Australia, production continuing until 1950. In the UK, production shared between de Havilland at Hatfield, Leavesden and (post-war) Chester, Airspeed at Christchurch, Percival at Luton and Standard Motors at Coventry; Canadian and Australian production was by the de Havilland companies at Toronto and Sydney respectively.

De Havilland Mosquito prototype (W4050) with span of 52 ft 6 in (16.0 m), first flown at Hatfield November 25, 1940, with 1,460 hp Merlin 21 engines; gross weight, 16,000 lb (7,264 kg) and speed of 392 mph (631 km/h) recorded in FS gear at full-throttle height of 22,000 ft (6,705 m), establishing De Havilland Mosquito as world's fastest operational aircraft at that time, a distinction retained by subsequent De Havilland Mosquito marks for next 2'/2 years. Merlin 61s fitted in prototype and first flown June 20, 1942, when speed of 414 mph (666 km/h) recorded in MS gear at weight of 17,800 lb (8,081 kg). Merlin 77s fitted in October 1942 and span increased to 59 ft 2 in (18.03 m); speed of 437 mph (703 km/h) achieved at 29,000 ft (8,839 m) at 18,000 lb (8,172 kg) - the fastest of any De Havilland Mosquito. Flown with dummy four-gun dorsal turret aft of cabin, July 1941.

De Havilland Mosquito PR Mk I: Ten of initial production batch completed in photorecce configuration, including one prototype, first flown June 10, 1941. Span 54 ft 2 in (16,51 m), as for all production aircraft; short nacelles for 1,300 hp Merlin 21 engines; three vertical and one oblique camera; gross weight 18,050 lb (8,195 kg). Two had extra fuel and higher weight; two modified for tropical service. Issued to No 1 PRU, Benson and flew first operational sortie September 17, 1941.

De Havilland Mosquito F Mk II: Variant of basic DH.98 design evolved to Specification F.21/40 as two-seat twin-engined day and night long-range fighter and intruder, with Merlin 21 or 23 engines in long nacelles, and four 20-mm cannon in the lower front fuselage plus four 0.303-in (7.7-mm) Brownings in the nose. Prototype (from initial De Havilland Mosquito production batch) first flown May 15, 1941. Production aircraft carried AI Mk IV or Mk V (with arrow-head aerials), and used primarily as UK-based night fighters, in overall black finish, often referred to as NF Mk IIs. Total 589 built (including 199 converted to NF Mk XII & XVII), initial deliveries to No 157 Sqn, March 1942. Twenty-five modified as Special Intruders for No 23 Sqn, without AI and with extra fuel. Two flown with dorsal four-gun turrets, on September 14 and December 5, 1941, respectively, but not further developed. One fitted with Turbinlite airborne searchlight in nose for trials with Nos 151, 532 and 85 Sqns in 1943. One to RAAF in Australia as pattern for FB Mk 40.

Max speed, 370 mph (595 km/h) at 22,000 ft (6,706 m). Initial climb, 3,000 ftlmin (15.2 m/sec). Ceiling, 36,000 ft (10,973 m). Max range, 1,705 mis (2,743 km). Empty weight, 13,431 lb (6,098 kg). Gross weight, 18,547 lb (8,420 kg). Span, 54ft 2 in (16.51 m). Length, 40ft 6 in (12.34 m).

De Havilland Mosquito T Mk III: Dual control unarmed training version, initially with Merlin 21 and later with Merlin 23 and 25. Five of initial production batch completed as Mk Us with dual controls, the first of these being one of the two examples with dorsal turrets, flown on December 5, 1941. 200 built at Leavesden up to July 1945, 164 more post-war at Leavesden and Hatfield. Fourteen to RAAF and 24 to RCAF.

De Havilland Mosquito B Mk IV: Initial day and night bomber variant. Ten aircraft in initial production batch started as PR Mk I airframes but completed as bombers, known initially as PR/Bomber Conversion Type but redesignated B Mk IV Series 1 before service, including the bomber prototype first flown mid-September 1941, also considered as prototype for B Mk V. B Mk IV Srs Is had Merlin 21s, short nacelles and bomb load of 2,000 lb (908 kg) in two or four bombs. Deliveries to No 105 Sqn began November 1941 but large-scale operations awaited arrival of B Mk IV Srs 2, the first example of which flew March 1942, this having long-tail nacelles, Merlin 21 or 23 engines and provision for 50-Imp gal (227-1) wing drop tanks. First operation (four aircraft to Cologne) on May 31, 1942. Production of 300 B Mk IV Srs 2, less nine converted to other versions in production. Post-delivery modifications of 27 to PR Mk IV, with cameras as PR Mk I; 20 to carry one 4,000-lb (1,816-kg) bomb each in bulged bomb-bay, with gross weight of 21,500 lb (9,760 kg), commenced operations with Nos 627 and 692 Sqns February 23, 1944; 36 aircraft modified 1943 to carry Highball anti-ship-ping spinning bomb for operations with No 618 Sqn, 24 of these later having arrester gear, Merlin 25s and other mods for carrier-based operations in Pacific, but no operations undertaken. Data for standard B Mk IV Srs 2:

Max speed, 380 mph (611 km/h). Cruising speed, 265 mph (426 km/h). Rate of climb., 2,500 ft/win (12.71 m/sec). Ceiling, 34,000 ft (10,363 m). Max range, 2,040 mis (3,282 km). Empty weight, 13,400 lb (6,084 kg). Gross weight, 21,462 lb (9,744 kg).

De Havilland Mosquito PR Mk IV: Twenty-seven B Mk IV Srs 2 converted, April 1942 onwards, to have cameras as PR Mk I.

De Havilland Mosquito B Mk V: Proposed version of B Mk IV with provision for two 1,000-lb (454-kg) internal and two 500-lb (227-kg) underwing bombs. Tests on B Mk IV prototype; no production.

De Havilland Mosquito PR Mk V: Projected photorecce version with same wing as B Mk V and extra fuel capacity. Not built.

De Havilland Mosquito B Mk VII: Initial Canadian production version, based on B Mk V design and powered by 1,460 hp Packard-built Merlin 31s. Twenty-five built, first flight September 24, 1942. All retained in Canada; six transferred to USAAF as F-8 with cameras for PR duties.

De Havilland Mosquito PR Mk VIII: Similar to PR Mk IV but fitted with Merlin 61s with two-speed two-stage superchargers. One B Mk IV converted to prototype and flown October 20, 1942, and four others converted from B Mk IVs in production.

De Havilland Mosquito PR Mk IX: As PR Mk VIII but powered by 1,680 hp Merlin 72 engines. First of 90 production examples flown April 1943. Service introduction June 1943 by No 540 Sqn; also flown by No 60 Sqn, SAAF, 1944-45. At least eight modified to have 1,710 hp Merlin 76/77 engines with paddle blade propellers, and one with 1,705 hp Merlin 67s (RM10SM).

De Havilland Mosquito B Mk IX: As B Mk IV but powered by 1,680 hp Merlin 72 engines. First of 54 production examples flown March 24, 1943; provision for four 500-lb (227-kg) bombs internal and one under each wing. Normal gross weight 22,823 lb (10,360 kg), or 24,753 lb (11,238 kg) with 100-Imp gal (454-1) drop tanks. Some modified to carry 4,000-b (1,816-kg) bomb in bulged bomb-bay and Oboe in nose; a few fitted with H2S Mk VI.

De Havilland Mosquito PR Mk XVI: Similar to PR Mk IX, but with pressurised cockpit. Pressure cabin prototype flown August 8, 1942, and first pressurised PR De Havilland Mosquito (a converted B MK IV) in July 1943. Production deliveries began November 1943; first operational use by No 140 Sqn, February 1944. Total of 433 built of which 79 supplied to USAAF units in UK including six trials aircraft with H2X in nose. Twenty-three to RAAF and also used by No 60 Sqn, SAAF, in Italy, 1944-45.

De Havilland Mosquito B Mk XVI: Similar to B Mk IX with pressure cabin, based on prototype development (see PR Mk XVI). First production B Mk XVI flown October 1943; 80 built with Merlin 72/73 and 320 with Merlin 76/77; all but first 12 with bulged bomb-bay for 4,000-lb (1, 816-kg) bomb. Some fitted with Oboe H2S and other bombing navaids. Initial deliveries to Nos 109 and 139 Sqns, end-1943.

Max speed (with 4,000-lb/1,816-kg bomb), 408 mph (656 km/h) at 28,500 ft (8,687 m) and 329 mph (529 km/h) at sea level. Intitial operating ceiling, 28,500 ft (8,687 m). Operational range, 1,100 mis (1,770 km) with 597 Imp gal (2,714 I) including two 100-Imp gal (454-l) drop tanks. Empty weight, 14,901 lb (6,765 kg). Gross weight, 25,200 lb (11,440 kg). Span, 54 ft 2 in (15.51 m). Length, 40ft 6 in (12.34 m).

De Havilland Mosquito B Mk XX: Principal Canadian production version, similar to B Mk VII with 1,460 hp Packard-built Merlin 31 or 33 engines and North American equipment. Two-hundred-and forty-five built, 1943-June 1944, of which 98 to RCAF, 34 to USAAF as F-8 with cameras for PR duties and balance to RAF in UK, August 1943 onwards.

De Havilland Mosquito T Mk 22: Canadian production equivalent of T Mk III, with Merlin 33s. Six built in 1943.

De Havilland Mosquito B Mk 23: Projected Canadian production equivalent of B Mk IX with Packard Merlin 69s or 76s. Not built.

De Havilland Mosquito B Mk 25: Canadian production version to succeed B Mk XX, with 1,620 hp Packard Merlin 225 engines. Total 400 built, June 1944 onwards, of which 51 to RCAF and balance to RAF in UK. Few modified to carry 4,000-lb (1,816-kg) bomb in deep-ened bay. One converted to have two-stage modified Merlin 68s by Marshalls of Cambridge, January 1945.

De Havilland Mosquito T Mk 27: Similar to T Mk 22 with Packard Merlin 225 engines. Forty-nine built, 1945, of which 19 to RCAF.

De Havilland Mosquito 28: Unused mark number for Canadian production.

De Havilland Mosquito T Mk 29: Dual control conversions of FB Mk 26; 39 completed 1945.

Max speed, 338 mph (544 km/h) at sea level and 424 mph (682 km/h) at 26,500ft (8,077 m). Initial rate of climb, 2,250 ftlmin (11.4 m/sec). Operational ceiling, 35,000 ft (10,668 m). Cruising speed, 288 mph (463 km/h) at sea level and 380 mph (611 km/h) at 30,500 ft (9,296 m). Cruising range, 1,180 mis (1,900 km). Empty weight, 15,l70 lb (6,880 kg). Gross weight, 21,105 lb (33,958 kg). Span, 54ft 2 in (16.51 m). Length, 41 ft 4 in (12.59 m).

De Havilland Mosquito PR Mk 32: Lightened version of PR Mk 16 with extended wingtips for very high altitude operation. Five built, first flown August 1944, operational from December with No 540 Sqn.

De Havilland Sea Mosquito TR Mk 33: Variant of FB Mk VI evolved to Specification N.I5/44 for a carrier-borne torpedo-reconnaissance fighter/bomber. Converted Mk VI with arrester gear made first deck landings on HMS Indefatigable, March 25, 1944. Second converted Mk VI in August 1945 had folding wing and two Sea De Havilland Mosquito prototypes with fixed wings flown in 1945 followed by first production TR Mk 33 on November 10, 1945, with Merlin 25 engines, folding wings, four-bladed propellers, JATO provision, four 20-mm cannon, underwing bombs as FB Mk VI and provision for two 500-lb (227-kg) bombs in rear bomb-bay in lieu of a 2,000-lb (908-kg) torpedo, bomb or mine externally under fuselage. Length increased to 42 ft 3 in (12.88 m) by ASH radar in nose.

De Havilland Mosquito PR Mk 34: Very-long-range reconnaissance version with extra fuel in deepened fuselage and two 200-Imp gal (909-1) wing drop tanks. Total fuel capacity 1,269 Imp gal (5,769 l) giving cruising range of 3,600 mis (5,792 km) at 300 mph (483 km/h) at 25,000 ft (7,620 m), on Merlin 113/114 engines and gross weight of 25,500 lb (11,577 kg). Four F.52 vertical and one F.24 oblique cameras. First flown December 4, 1944, and 231 built. Service principally post-war.

De Havilland Mosquito B Mk 35: Final De Havilland Mosquito bomber variant. Similar to B Mk XVI with 1,690 hp Merlin 113/114 engines. First flown March 12, 1945, and 276 built, completed early 1948. Some post-war conversions to TT Mk 35.

Sea De Havilland Mosquito TR Mk 37, De Havilland Mosquito NF Mk 38 and TT Mk 39: Post-war production and conversion programmes.

De Havilland Mosquito PR Mk 40: Six FB Mk 40 converted for PR role, May-October 1944, with increased internal fuel, drop tanks and three vertical and two oblique cameras.

De Havilland Mosquito PR Mk 41: Twenty-eight FB Mk 40 converted for PR role, 1947-48, with Merlin 69s.

De Havilland Mosquito T Mk 43: Twenty-two converted FB Mk 40s as dual control trainers with Merlin 33s, June 1944 onwards.

Photo	Description
	Drawing Mosquito B Mk.IV srs II
	Mosquito IVs of 105 Squadron at Marhamn on 11 December 1942. DZ360 'A' failed to return from Termonde on 22 December 1942, and F/Sgt J. E. Cloutier and Sgt A. C. Foxley were both killed in action. DZ353 'E' later served with 139 Squadron, becoming AZ-B of 627 Squadron, but failed to return from Rennes on 8 June 1944 when F/L H. Steere DFM and F/O K. W. 'Windy' Gale DFC RAAF were killed in action. DZ367 'J', flown on the Eindhoven raid by F/О W. С.S. 'Bill' Blessing, failed to return from Berlin on 30 January 1943 and S/L D.F W. Darling DFC and F/O W. Wright were both killed in action. DK336 'P' lost its starboard engine returning from a raid on Copenhagen on 27 January 1943, struck a balloon cable and a tree, and crashed at Yaxham, Norfolk, killing Sgt R. Clare and F/O Е. Doyle. DZ378 'K' was damaged on 20 December 1942 after two sorties. DZ379 'H' later joined 139 Squadron at Wyton, and on 17 August 1943, the diversion for the Peenenmunde raid, failed to return from Berlin when it was shot down by a night-fighter and crashed at Berge, Germany. F/O Cook, the American pilot, from Wichita Falls, Texas, and his navigator, Sgt D.A.H. Dixon, were killed (via Phillip J. Birtles)

Bibliography

• "Encyclopedia of military engineering" /Aerospace Publising/
• "British warplanes of World War II" /under cor. Daniel March/
• THE REICH INTRUDERS. Dramatic RAF medium bomber raids over Europe in World War 2. /MARTIN W BOWMAN/