THE WOODEN WONDER
During the mid 1930's, the Royal Air Force became interested in the concept of a fast bomber, one which would carry a minimum of armament with a speed greater than enemy fighters of the day. During this blog we'll trace the development of this vision into a truly great combat aircraft-the De Havilland Mosquito.
In September 1936, the British Air Ministry issued a requirement for a twin-engine, medium bomber capable of carrying a bomb load of 3,000 lbs. for a range of 3,000 miles with a top speed of 275 mph. The aircraft was to accommodate a bomb load of 8,000 lbs. for short range missions. De Havilland had an established reputation for innovative high-speed aircraft with the DH.88 Comet racer and followed up with another aircraft, the DH.91 Albatross. The Albatross, a 22 passenger airliner, was perhaps the first airliner to be built of composite wood materials-a concept which would serve the Mosquito well throughout its service. Due to its wood construction, the Albatross could cruise at least 20 mph. faster than the latest biplanes. Other advantages of wood construction were simplified construction techniques, as well as reducing production time.
The following year, George Volkert, the chief designer of Handley Page Aircraft, put forth a similar proposal, using non-strategic materials for aircraft production with the Armstrong Whitworth Albemarle medium bomber to be constructed of spruce and plywood attached to a steel-tube frame. Geoffrey De Havilland offered a counterproposal to the Air Ministry in early 1938, based upon the Albatross design to create a fast bomber. De Havilland believed the Albatross production techniques could save time, emphasizing shortages of aluminum and steel could occur in wartime, while supplies of wood products were at least adequate to projected needs. A series of material tests determined wood strength-to-weight is equal to or better than light alloys or steel, although having reduced tension qualities. Powerplants for the proposed aircraft included twin Rolls-Royce Merlin DH.91 inline engines, twin Bristol Hercules radial engines, and Napier Sabre H-engines. In a letter to Air Marshal Wilfrid Freeman, Air Council Member for Research and Development, De Havilland expressed a belief that the Air Ministry specifications for the proposed aircraft could not be met with the twin Merlin engines without sacrifices in speed, payload or range. In October 1938, De Havilland proposed a new design based on the Albatross, having a three man crew, armed with six or eight forward firing machine guns, or two manually operated guns and a tail turret. Powered by two Merlin X engines, the new design would have a top speed of 300 mph. with a cruising speed of 268 mph. and a gross weight of 19,000 lbs. Due to the prevailing RAF philosophy of well armed bomber aircraft, the De Havilland design was rejected by the Air Ministry with the aircraft company designated to act as a subcontractor building wings for RAF bombers.
However, when World War II began in September 1939, there was a renewed interest by the Air Ministry in the De Havilland project. They were asked in October 1939 to submit new proposals for the fast bomber project. Though the Air Ministry still had reservations about an aerodynamically clean fast bomber, they began to envision a multi-role aircraft, which could perform a number of missions. In another letter to Air Council Member Freeman, Goeffrey De Havilland suggested development of a twin engine bomber with enough speed to outrun any current or potential enemy fighters. With the war now in full swing, Freeman authorized De Havilland to proceed with the project, now designated as the DH.98. As 1940 drew on, the Air Ministry began interest in a fighter role for the plane. In March 1940, Air Marshal Roderic Hill issued a contract for 50 bomber-reconnaissance variants of the DH.98. In May 1940, a new specification was issued, which called for a long-range fighter variant, armed with four 20mm cannon and four .303 machine guns mounted in the nose. In June 1940, the DH.98 was officially designated as the Mosquito, with a night fighter version under development. After production delays to produce Spitfires and Hurricanes during the Battle of Britain, production and development resumed on the Mosquito in November 1940. After several modifications in early 1941, the aircraft became operational in September of that year.
Powered by two MK23 or MK25 Merlin engines with a crew of two (pilot, navigator/bombardier), the Mosquito began low level missions in France in early 1942. Though these raids were of short duration, they proved the value of the Mosquito in low level bombing. Concurrently with the low level daylight missions, the Mosquito began to serve in the night fighter role. The first dedicated night fighter version entered service in May 1942. Gloster was to have produced a night fighter aircraft, the F.9/37, but this project was abandoned due to the demands of the Meteor jet program. These Mosquitos carried the latest radar and operated in the interception role over the British Isles while operating as intruders over the Continent at night, disrupting communications and flight operations. These aircraft were fitted with the Serrate radar detector which allowed the Mosquitos to track Luftwaffe night fighters by their radar transmissions. Mosquito units continued to operate over both Europe and the Mediterranean till the end of the war with a relatively low casualty rate. As an addition to the night fighter role, Mosquitos operated in a defensive role for the bomber streams, as well as bombing Luftwaffe bases to delay interception by night fighters. Mosquito squadrons of 100 Group which bombed the Luftwaffe fields in advance were called Malmounds, which operated independently of Bomber Command, also attacked assembly points for German fighters. A number of Group 100 Mosquitos were used for Electronic Intelligence (ELINT) operations, using special receiver units to detect German radar and radio transmissions. Mosquitos also conducted pathfinder missions, dropping tin foil and marking targets ahead of the bomber stream. These missions were highly successful, with some 258 Luftwaffe night fighters destroyed during the course of the war, with the loss of 70 Mosquitos.
In early 1943 a number of Mosquitos were developed for the fighter-bomber role. This variant, the FB VI was built with a strengthened wing for external loads along with the standard armament of 4 20mm cannon in the nose with 4 nose mounted .303 machine guns. The fighter-bomber units could carry two 250 lb. bombs in the rear of the bomb bay and two 250 lb. bombs under the wings, or eight wing-mounted rockets. The fighter-bomber aircraft were involved in several notable precision bombing missions. In February 1944, RAF Mosquitos conducted Operation Jericho, a mission to destroy the walls and guards' quarters of Amiens prison to allow members of the French Resistance to escape. Though Group Captain Percy Pickard was shot down returning from the mission, it was deemed a success with both walls and guards quarters destroyed, which aided the escape of the Resistance fighters. Two months later, following a request by Dutch Resistance workers, six Mosquito FB VIs made a pinpoint daylight attack at rooftop level on the Kunstzaal Kleykamp Art Gallery in the Hague, Netherlands. The top floor of the gallery was used to store the Dutch Central Population Registry. The first two planes dropped high explosive bombs in order to provide openings in which to drop incendiaries from the following aircraft. The strike was extremely accurate, with all records destroyed and only people working in the building killed as a result of the bombing. Almost a year later, at the request of the Danish Resistance, Mosquitos bombed Gestapo headquarters in the Shellhus, near the town square of Copenhagen, Denmark. Operation Carthage was flown on March 21, 1945 with twenty Mosquitos attacking the headquarters building in three waves, escorted to the target by thirty RAF P-51 Mustangs. The attack was successful with the main attack killing 55 German soldiers, as well as 47 Danes working for the Gestapo. Eight prisoners were killed inside the headquarters, while eighteen escaped. However, a Mosquito flying in the first wave of the attack, struck a tall lamp pole, crashing into a Catholic school nearby. Mosquitos of the third wave attacked the school, believing it to be the headquarters, due to the crashed aircraft. The tragedy of this was 86 children were killed along with 39 school staff. Four Mosquitos were shot down during the raid, resulting in the deaths of nine crew. While the loss of civilian lives was appalling, the lives of many Danish Resistance were saved due to the destruction of Gestapo records and personnel. Such missions wouldn't have been possible without detailed photo reconnaissance-another mission of the Mosquito. These missions were conducted using modified day bomber, photo-reconnaissance, long range, high altitude units such as the PR Mk 32 and the PR Mk 34. These aircraft set a number of speed, altitude and distance records for twin-engine, piston-powered aircraft with an Mk 34 achieving a record 425 mph. in level flight at an altitude of 37,000 ft. for a total flight of 1,950 miles.
The Mosquito was a versatile aircraft, made in thirty different variants before production ended in 1950. It was used in all theaters during World War II and served for a number of years after-used by Israel during the 1956 war. Though difficult to fly at times, the aircraft had a better safety record than many of its steel and aluminum contemporaries, along with a simple design, which was easy to produce. For the many roles the aircraft played at a critical time, it was truly a wooden wonder.