World War II: De Havilland Mosquito

The design for the de Havilland Mosquito originated in the late 1930s, when the de Havilland Aircraft Company began working on a bomber design for the Royal Air Force. Having had great success in designing high-speed civilian aircraft, such as the DH.88 Comet and DH.91 Albatross, both constructed largely of wood laminates, de Havilland sought to secure a contract from the Air Ministry. The use of wood laminates in its planes allowed de Havilland to reduce the overall weight of its aircraft while simplifying construction. 

A New Concept

In September 1936, the Air Ministry released Specification P.13/36 which called for a medium bomber capable of achieving 275 mph while carrying a payload of 3,000 lbs. a distance of 3,000 miles. Already an outsider due to their use of all-wood construction, de Havilland initially attempted to modify the Albatross to meet the Air Ministry's requirements. This effort fared poorly as the performance of the first design, possessing six to eight guns and a three-man crew, projected badly when studied. Powered by twin Rolls-Royce Merlin engines, the designers began seeking ways to improve the plane's performance.

While the P.13/36 specification resulted in the Avro Manchester and Vickers Warwick, it led to discussions that advanced the idea of the fast, unarmed bomber. Seized upon by Geoffrey de Havilland, he sought to develop this concept to create an aircraft would exceed the P.13/36 requirements. Returning to the Albatross project, the team at de Havilland, led by Ronald E. Bishop, began removing elements from the aircraft to decrease weight and increase speed.

This approach proved successful, and the designers quickly realized that by removing the bomber's entire defensive armament its speed would be on par with the fighters of the day allowing it to outrun danger rather than fighting. The end result was an aircraft, designated DH.98, that was radically different from the Albatross. A small bomber powered by two Rolls-Royce Merlin engines, it would be capable of speeds around 400 mph with a payload of 1,000 lbs. To enhance the aircraft's mission flexibility, the design team made allowance for the mounting of four 20 mm cannon in the bomb bay which would fire through blast tubes under the nose.

Development

Despite the new aircraft's projected high speed and superb performance, the Air Ministry rejected the new bomber in October 1938, over concerns regarding its wooden construction and lack of defensive armament. Unwilling to abandon the design, Bishop's team continued to refine it after the outbreak of World War II. Lobbying for the aircraft, de Havilland finally succeeded in obtaining an Air Ministry contract from Air Chief Marshal Sir Wilfrid Freeman for a prototype under Specification B.1/40 which had been tailor written for the DH.98. 

As the RAF expanded to meet wartime needs, the company was finally able to obtain a contract for fifty aircraft in March 1940. As work on the prototypes moved forward, the program was delayed as a result of the Dunkirk Evacuation. Restarting, the RAF also asked de Havilland to develop heavy fighter and reconnaissance variants of the aircraft. On November 19, 1940, the first prototype was completed and it took to the air six days later.

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Over the next few months, the newly dubbed Mosquito underwent flight testing at Boscombe Down and quickly impressed the RAF. Outpacing the Supermarine Spitfire Mk.II, the Mosquito also proved capable of carrying a bomb load four times larges (4,000 lbs.) than anticipated. Upon learning this, modifications were made to improve the Mosquito's performance with heavier loads.

Construction

The Mosquito's unique wood construction allowed parts to be made in furniture factories across Britain and Canada. To construct the fuselage, 3/8" sheets of Ecuadorean balsawood sandwiched between sheets of Canadian birch was formed inside large concrete molds. Each mold held half of the fuselage and once dry, the control lines and wires were installed and the two halves were glued and screwed together. To complete the process, the fuselage was covered in a doped Madapolam (woven cotton) finish. Construction of the wings followed a similar process, and a minimal amount of metal was used to reduce weight.

Specifications (DH.98 Mosquito B Mk XVI):

General

• Length: 44 ft. 6 in.
• Wingspan: 54 ft. 2 in.
• Height: 17 ft. 5 in.
• Wing Area: 454 sq. ft.
• Empty Weight: 14,300 lbs.
• Loaded Weight: 18,000 lbs.
• Crew: 2 (pilot, bombardier)

Performance

• Power Plant: 2 × Rolls-Royce Merlin 76/77 liquid-cooled V12 engine, 1,710 hp
• Range: 1,300 miles
• Max Speed: 415 mph
• Ceiling: 37,000 ft.

Armament

• Bombs: 4,000 lbs.

Operational History

Entering service in 1941, the Mosquito's versatility was utilized immediately. The first sortie was conducted by a photo reconnaissance variant on September 20, 1941. A year later, Mosquito bombers conducted a famed raid on the Gestapo headquarters in Oslo, Norway which demonstrated the aircraft's great range and speed. Serving as part of Bomber Command, the Mosquito quickly developed a reputation for being able to successfully carry out dangerous missions with minimal losses.

On January 30, 1943, Mosquitos carried out a daring daylight raid on Berlin, making a liar of Reichmarschall Hermann Göring who claimed such an attack impossible. Also serving in the Light Night Strike Force, Mosquitos flew high speed night missions designed to distract German air defenses from British heavy bomber raids. The night fighter variant of the Mosquito entered service in mid-1942, and was armed with four 20mm cannon in its belly and four .30 cal. machine guns in the nose. Scoring its first kill on May 30, 1942, night fighter Mosquitos downed over 600 enemy aircraft during the war.

Equipped with a variety of radars, Mosquito night fighters were used throughout the European Theater. In 1943, the lessons learned on the battlefield were incorporated into a fighter-bomber variant. Featuring the Mosquito's standard fighter armament, the FB variants were capable of carrying 1,000 lbs. of bombs or rockets. Utilized across the front, Mosquito FBs became renowned for being able to carry out pinpoint attacks such as striking the Gestapo headquarters in downtown Copenhagen and breeching the wall of the Amiens prison to facilitate the escape of French resistance fighters.

In addition to its combat roles, Mosquitos were also used as high-speed transports. Remaining in service after the war, the Mosquito was used by the RAF in various roles until 1956. During its ten-year production run (1940-1950), 7,781 Mosquitos were built of which 6,710 were constructed during the war. While production was centered in Britain, additional parts and aircraft were built in Canada and Australia. The Mosquito's final combat missions were flown as part of the Israeli Air Force's operations during the 1956 Suez Crisis. The Mosquito was also operated by the United States (in small numbers) during World War II and by Sweden (1948-1953).