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de Havilland D.H.98 Mosquito B Mk.35 Technical Description

The de Havilland Mosquito is a two-seat twin engined multi purpose monoplane constructed primarily of wood. The first example, built by hand at Salisbury Hall, London Colney, Hertfordshire, England first flew on November 25th 1940 and still survives, in a museum located at the site of its construction.

The type was initially designed as a high speed unarmed bomber, but because of the qualities inherent in the design it saw use in a multitude of tasks as follows. Advanced trainer, anti-shipping strike, bomber escort, electronic reconnaissance, ground attack fighter, high altitude interceptor, high speed personnel transport/airliner, high speed research, low/medium/high altitude photographic reconnaissance, mine layer, medium bomber, night fighter, target marker ('Pathfinder'), target tug, weather reconnaissance. A total of 7,781 Mosquitoes were built in Australia, Canada and England between 1940 and 1950.


Subsequently developed from the B.XVI bomber version, the B.35 was the penultimate Mosquito bomber variant, its warload was 4,000 lbs. The first example of the B.35 first flew on March 12th 1945 with the last being delivered in August 1946. 274 Mosquito B.35s were constructed, of which 105 were converted into TT.35 target tugs.


A single piece twin box spar mid-wing of Piercy Modified RAF 34 aerofoil section, with unswept leading edges and pronounced taper on the trailing edges to the wing tips. The wing spars are comprised of laminated spruce flanges with plywood webs and spruce and ply compression ribs between each spar. The leading edge is comprised of rib formers and a 'D' section skin attached directly to the forward wing spar. Spanwise spruce stringers provide support for the double layered plywood outer skin, which is entirely covered in 'Mandapolam' fabric. No. 8 rib in each wing is sufficiently strengthened to enable the fitting of an external load.

The center section of the wing has attachment strong points for welded steel tube engine mounts and undercarriage legs, and radiators in board of these. The leading edge is increased in chord by 22 inches to house the radiators, with cooling flaps located ahead of the forward spar on the underside of the wing. Each radiator is divided into three sections, an oil cooler outboard, the coolant radiator, and a cabin heater inboard.

The flaps are slotted and constructed of plywood, the ailerons are comprised of a light alloy frame and outer cover. The elevators are comprised of an alloy frame and skin and, whilst the rudder has an alloy frame with fabric covering. All control surfaces are fitted with an alloy trim tab flush with their trailing edges.


Constructed in two halves along the vertical plane, the fuselage is of tapering circular section built from two layers of laminated cedar ply separated by a single layer of balsa wood. The entire fuselage outer covering is covered in Mandapolam fabric. Seven internal bulkheads, constructed from two plywood skins supported by spruce blocks between each layer, provide support for the fuselage outer skin. At the points where the bulkheads are attached to each fuselage half, a spruce ring replaces the balsa core between each plywood skin.

The fuselage center section is cut out to enable the fitting of the single wing unit, which is attached by four attachment strong points at each corner of the fuselage cut out. A lower section of fuselage containing the fittings for the payload bay fits directly under the wing center section. The bomb bay doors are made of ply/balsa/ply and are bulged to enable a single 4,000-lb 'cookie' bomb to be carried internally.


The crew of two is housed directly ahead of the forward spar of the wing center section, the pilot on the left and navigator/bomb aimer, or 'observer' to the right and slightly further back than the pilot. The navigator/bomb aimer has a compartment ahead of the cockpit section fronted by a glazed bubble, with a flat oval pane on its lower hemisphere. A glazed rectangular quarterlight is provided in each fuselage half to the rear of the nose glazing for the navigator/bomb aimer. A framed transparent 'teardrop' canopy with a divided windscreen covers the cockpit. The navigator/bomb aimer

is provided with a blown Perspex bubble directly above his seat. Entrance to the cockpit is via a square cutout in the lower right side of the fuselage ahead of the navigator/bomb aimer's seat. This is covered over by a square ply/balsa/ply door with a circular transparency in its center


The Mosquito B.35 is powered by two Rolls Royce Merlin upright vee-twelve liquid cooled piston engines equipped with two speed, two stage superchargers. One 1,690 hp Merlin 113 to starboard and one Merlin 114 to port, which provides power via a blower drive for the Marshall cabin supercharger. Two 1,710 hp Merlin 114As can also be fitted to the B.35. The engines drive a three bladed D.H. Hydromatic variable pitch, fully feathering airscrew each.


Within the fuselage center section between the wing box spars are two 68 (imperial) gal. Tanks, and two 79 and two 65 gal. Tanks are located in each wing inboard of the engine nacelles. There are two each of 32 and 24 gal. Tanks in the outer wings. When carrying a 4,000-lb 'cookie' bomb internally, a 50 gal. Drop tank is carried under each wing, if the internal load is four 500-lb bombs, either a100 or 200 gal. Drop tank can be carried under each wing.


The de Havilland Mosquito is a 'tail dragger', its main legs are comprised of two struts sprung by compressed rubber blocks with a single Dunlop main wheel between each leg. Each undercarriage unit is interchangeable and retracts fully into the rear of the engine nacelles. The fully castoring tail wheel is semi-retractable.

The B.35 can carry a single 4,000-lb cylindrical 'cookie' bomb of General Purpose, Medium Case or High Explosive type or four 500-lb bombs internally, with an additional 500-lb bomb under each wing. No defensive armament is fitted to this variant.

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