(first posted 5/8/2016) We all know the significance of the Hurricane, Spitfire and Lancaster. All these great aircraft were powered by the immortal Rolls-Royce Merlin engine; brilliantly engineered and superbly built, diligently maintained and bravely flown, they were crucial to the victory of freedom in 1945. But there is another Merlin powered plane we must remember. Conceived as a bomber, it became a fighter, a fighter-bomber, a photo-reconnaissance plane, a night fighter, a tank buster, a U boat destroyer and a bombing target marker. It carried spies and secret documents at low level, and tracked weather systems at great heights. It carried a bombload to rival a B17 at a higher speed than a Spitfire. And, apart from the fighter versions, it had no defensive armament – it was designed to be light and fast, with speed its only defence. The de Havilland Mosquito was designed to be the fastest and most aerodynamic plane in the world. And it was built of wood.
Geoffrey de Havilland (1882-1965) was the son of a Church of England vicar who built his first aircraft in 1909. In 1912, his BE2 was the first plane to reach 10,000 feet. As Chief Draughtsman of the Aircraft Manufacturing Company (known as Airco), he designed some of the most successful British of WW1, including the DH6 and DH9.
His Airco DH4 of 1916 was produced in great numbers – eventually, over 6,000 across Britain and the USA. It was a two seat light bomber, liked for its reliability, speed and high altitude performance – such that it could undertake bombing missions across France without fighter escort.
De Havilland left Airco after the war, and in 1920 founded the de Havilland Aircraft Company, based at Edgware in north London and then further out at Hatfield, 40 miles north. It remained independent until it joined the Hawker Siddeley Group in 1960; ultimately, the business is part of BAE Systems.
Initially, de Havilland depended on maintenance and repair work on his wartime planes, rather than on new production. From 1925, the DH60 Moth family of small and light biplanes for training and civilian use began to appear; the DH 82 Tiger Moth became the RAF’s standard trainer throughout WW2, and it and the smaller Gypsy Moth were built in India, Australia, Canada and New Zealand.
The 1930s saw a fashion for air races; while the Supermarine company competed in seaplane races that ultimately led to the Spitfire, de Havilland chose long distance races, using the DH88 Comet. One flew from London to Melbourne in a record 71 hours in 1934, but the true significance was the construction – a stressed wooden monocoque.
This led to a range of small (even by 1930s standards) airliners, such as the DH84 Dragon and DH86 Dragon Rapide.
The DH90 Dragonfly moved forward to a stressed skin semi-monocoque, while the larger 22 passenger four engine DH91 Albatross featured a monocoque of inner and outer layers of birch plywood around balsa wood, all covered in traditional aircraft fabric. It could cruise at 210mph – 100mph faster than competing British airliners of the period.
De Havilland was in a dilemma in 1939; the onset of war ended development of the Albatross, after just 7 had been built, but his company had no major RAF contracts and didn’t have the facilities to compete with the likes of Hawker, Supermarine, Avro and the rest of the UK aircraft industry for the business. He needed something different to offer the RAF.
De Havilland had been convinced from 1938 onwards that, with a suitably aerodynamic shape, a light wooden fuselage and wings, and powerful enough engines, he could design a plane that could outrun German fighters – a virtuous circle where making the plane lighter made it faster and safer, removing the need for the weight of guns and gunners. So, in the same way the Supermarine racing seaplanes were developed in to the Spitfire, the techniques and materials behind the Albatross were reused to form the basis of a 2 engine, 2 crew light bomber. And no more gentle names like Moth and Dragonfly – de Havilland kept to the insect theme, but chose an altogether different type for his new bomber – Mosquito!
De Havilland first proposed what became the Mosquito to the RAF in 1938, as an alternative to a specification issued for a traditional metal bomber – a specification which ultimately produced the Avro Lancaster and Handley Page Halifax. He got a lukewarm response, and the RAF would have preferred de Havilland to build wings for the conventional metal skinned planes. De Havilland persisted with his design, arguing that while metal would be in short supply once war started, wood would be plentiful. He eventually won the support of Air Chief Marshal Wilfrid Freeman, the driving force in the rearmament of the RAF in the late 1930s. Freeman had to push the Mosquito project against the opposition of Lord Beaverbrook, Churchill’s Minster of Aircraft Production in 1939-40, who wanted de Havilland to concentrate on the Tiger Moth trainers, but eventually de Havilland were given a specification for a light bomber capable of 400mph and flying at 18,000ft.
The Mosquito’s fuselage is made of wood – but special and complex wood – in fact, it is more akin to modern composite materials. A core of Ecuadorean balsa wood, sandwiched between sheets of Canadian birch, formed a fuselage that was only 11mm thick, but needed no internal reinforcement between the wing and tail. It was constructed in 2 halves, over a mahogany mould, glued together, and strengthened with 7 bulkheads, of spruce. De Havilland made particular efforts to design a smooth and aerodynamic shape, for maximum speed.
The wings were also of wood, built as one structure, of spruce spars and plywood skins, which were then covered in traditional aircraft fabric. The wing passed through the fuselage and was secured by 4 large bolts. There was some metal in the flaps and engine mountings – but the weight of the metal parts of the structure was just 130kg.
The prototype was the first of a batch of 50, ordered in March 1940, and despite Beaverbrook ordering its cancellation (again), W4050 was ready to fly by November 1940. By now, the RAF could see its potential versatility, with the 50 originally ordered as bomber-reconnaissance craft changed to 20 bombers and 30 fighters. The fighters had four 0.303 machine guns in the nose. Prototype W4050 is now preserved by the De Havilland Aircraft Museum.
Incredibly, just 11 months after the start of detailed design work, the first Mosquito was flown by de Havilland’s son, also Geoffrey, who was the company’s chief test pilot. As early as January 1941, it was flying 10% faster than the latest Spitfire, and reaching 22,000ft. By June 1941, it was clearly the fastest aircraft in the world, and mass production was authorised – by January 1942, almost 1,400 had been ordered in Britain, and another 400 from de Havilland Canada.
The engines were, of course, the incomparable Rolls-Royce Merlin, seen here being assembled at Rolls-Royce’s factory at Hillingdon, near Glasgow. Early planes had mark 21 supercharged Merlins, offering 1,480hp each; the bomber versions had mark 76 Merlins, of 1,710hp.
One attraction of the wooden construction for both De Havilland and the RAF was the ability to build Mosquito wing and fuselage sections in small dispersed factories – de Havilland couldn’t compete with the likes of Avro and Hawker’s modern factories for capacity, and the dispersal of Mosquito production unlocked significant extra capacity. So the Mosquito ended up being built in the most unlikely of places – many of England’s famous furniture companies built fuselages and wing components for assembly at de Havilland’s factories. There was also production in Canada where de Havilland had a long established business.
In July 1941, the first photo reconnaissance Mosquito was in service, with no 1 Photographic Reconnaissance Unit, and the first operational flights were in September 1941. The first bombers, designated B mark IV, joined 105 Squadron in November 1941, and focused on daylight low level and shallow dive attacks. From mid-1942, they were fitted with Merlin 61 engines, with two stage two speed superchargers, and were capable of 440mph at 29,000ft – way beyond any German fighter and well above the range of anti-aircraft fire
The most common Mosquito variant was the FB mark VI fighter-bomber. It carried four 0.303 machine guns and four 20mm Hispano cannons, plus 2,000lbs of bombs – even so, it remained a light, agile and manoeuvrable plane. Bombload started at four 500lb bombs, but in August 1943, a B Mk IV bomber version was modified to carry a 4,000lb ‘cookie’ – the only alteration being new bomb bay doors with a bulge to accommodate the larger bomb. Carrying a cookie, the bomber could still reach 380mph, and comfortably fly to Berlin and back. Mosquitos also formed the Light Night Striking Force, which was tasked to drop 4,000lb bombs precisely on key targets and In early 1945 the force raided Berlin on 35 successive nights.
By way of comparison, the early versions of the B17 ‘Flying Fortress’ could carry 4,500lb of bombs to Berlin at under 300mph, which doesn’t seem much of a bonus for the extra eight crewmen. It isn’t quite a fair comparison, as the B17’s bombload was a more suitable one for area bombing. However, it does make you realise the versatility and capacity of the little wooden plane.
The fighter bomber version was soon fitted with strengthened wings to carry a 500lb bomb, or a package of eight rockets on each side, plus additional drop tanks for extended range and the usual 500lb bombs in the main bomb bay. Even with all this kit, the speed was still over 360mph. Almost 2,300 of these were built. A further variant was equipped with additional armour to protect the engines and cockpit, to allow the Mosquito to engage German U-boats and surface ships – something they did with much success.
The Mosquito was a superb night-fighter – fast, agile, and able to reach high altitudes quickly to allow it to chase and destroy intruding aircraft. They were fitted with progressively more advanced radar, and Hispano cannons and Browning machine guns.
Mosquitos weren’t confined to operations over western Europe. They also served as U-boat destroyers with RAF Coastal Command, and the Royal Navy developed a carrier based version with folding wings and an arrester hook, known as the Sea Mosquito, although it didn’t fly until after the end of the war.
Are you spotting a theme here? The Mosquito was the precursor of the modern multi-purpose warplane
Perhaps the most famous use of the Mosquito was by the RAF’s Pathfinder force, which from 1942 onwards was the RAF’s elite target marking unit, with specially qualified pilots. Pathfinders, flying Mosquitos and Lancasters and using the most advanced radar navigation the RAF had, would accurately locate by radar and then ‘mark’ a target with coloured flares in a pre-set sequence of colours to allow the main bombing force to bomb accurately. It was dangerous work – the Germans would focus their night-fighters and anti-aircraft effort on the Pathfinders, seeking to disrupt the raid – and absolute precision navigation was required. Pathfinders . In July 1943, 600 heavy bombers guided by nine Mosquitos pounded the Krupps works at Essen to a standstill – it was said the industrial smog over the Ruhr valley was dispersed for the first time ever.
Just as dangerous as being a Pathfinder was being Master Bomber, a tactic that evolved in the last years of the war. A Master Bomber would command his aircraft not from the lead Lancaster, flying to the target, bombing and immediately turning to return, but from a Mosquito, which would remain over the target as the bomber stream arrived , in order to ensure the maximum accuracy of the raid.
Overall, almost 7,800 Mosquitos were built before production ended in 1950. It served with all the Air forces of the British Empire – the RAF, RCAF, RAAF and RNZAF – and many others, including the USAAF, who had 40 for photo-reconnaissance duties. Its successor in the RAF was the English Electric Canberra, a twin engine fast light jet bomber, which set height and speed records of its own.
Regardless of role, the Mosquito carried a crew of 2, with the co-pilot, responsible for bomb aiming, navigation and wireless equipment, sitting alongside and slightly behind the pilot. Some were adapted to carry a ‘passenger’ lying in the bomb bay, for covert insertions into or escape from occupied Europe
It was September 1942 before the RAF told the world anything official about the Mosquito, following the first of the daring raids for which it became famous – the attack on Victoria Terrasse, the Gestapo headquarters in Oslo, in occupied Norway. Intended as a morale booster for the Norwegian people, four Mosquitos flew a return flight of 1,100 miles from Leuchars in eastern Scotland, flying at low level; three reached the target, but the bombs passed through the building before exploding, killing 80 civilians. The picture above was taken by one of the Mosquitos, and shows just how low the unarmed bombers were prepared to fly over an occupied city. The next day’s ‘Times’, the establishment paper in London, led with ‘Nazis stung by Mosquitos’
The RAF repeated this format of a small group of Mosquitos making a pinpoint attack on strategic targets at regular intervals. In January 1943, the RAF sent a group of Mosquitos to bomb the radio station in Berlin – timed to arrive at 11am, just as Herman Goering was beginning a typically bombastic speech to celebrate 10 years of Nazi rule. And, at 4pm, as propaganda minister Josef Goebbels was about to broadcast, they returned.
In February 1944, 18 Mosquitos FB Mark VI (the definitive fighter bomber version) attacked the prison at Amiens, northern France, which was being used by the Germans to hold members of the French Resistance. Mystery surrounds the raid to this day, as it does not appear to have been requested by the Resistance or have any particular military value, but the flying skill of the Mosquito pilots is beyond debate – crossing the Channel at 50ft in some of the worst winter weather ever recorded, and successfully blowing open the prison walls and cell blocks without civilian casualties.
But perhaps the greatest of these raids was the attack on the Gestapo’s Danish headquarters, in the city of Aarhus, on October 31 1944. Again, 18 Mosquitos, plus two photo reconnaissance planes, were involved, and with pinpoint accuracy the Gestapo building was hit and the adjacent hospitals were untouched. Such was the surprise the Mosquitos achieved, the city’s anti-aircraft batteries didn’t fire until 30 minutes after they had left. About 50 Gestapo personnel were killed, and significant damage was done to its records of the Danish Resistance, with 36 500lb bombs and 80 100lb incendiaries dropped.
Today, there are only two flying Mosquitos, one in Virginia and one in Vancouver. The last British example crashed in 1996. Now, a group of enthusiasts known as the People’s Mosquito has developed plans to rebuild a night fighter example that crashed in 1949. The main spar has been saved, and a new fuselage is being constructed in New Zealand, where a fuselage mould has survived. The plane will be assembled and tested in NZ, and then shipped to Britain, where it will fly as an educational tool and memorial. Ambitious, perhaps, but then we’ve already built a new steam express engine! This podcast gives a good history of the Mosquito, and of the project – we wish them well!
And this is what we’re waiting to see again in the skies of Britain.
The ‘Mossie’ – seen here helping the people of Copenhagen celebrate liberation of Denmark and the advent of peace in 1945 – was the prototype for 21st century warplanes, and was built of wood in the furniture workshops of England. The Mosquito was as important to the defeat of Nazism as the RAF’s other Merlin engine planes, was produced in great numbers and set the template for modern warplanes. Quite an achievement for something the RAF didn’t think would work and didn’t want!