Vickers F.B.5 ‘Gunbus’, Royal Air Force Museum – the first ‘fighting squadron’
Tags: Air Show, Aviation, biplane, Europe, First World War, France, French, German, Gnome Monosoupape rotary engine, Gunbus, Lewis machinegun, London, machinegun, museum, No 11 Squadron, pusher propeller, RAF, RFC, Royal Air Force, Vickers FB5, warbird, Wiltshire
The British armaments company Vickers Ltd had been thinking of building a ‘fighting aeroplane’, designed to carry a machinegun, from before the First World War broke out. Indeed, the company had exhibited the prototype of a two-seat pusher aircraft of this type at the 1913 Olympia Air Show in London. The aircraft was named ‘The Destroyer’, and caused a sensation, but unfortunately crashed on its maiden flight. Undeterred, Vickers began building a series of ‘Experimental Fighting Biplanes’, the first successful one being designated F.B.5. Because of the unusual nature of the aircraft – being armed from the outset – as well as being issued piecemeal to various units of the new Royal Flying Corps, a brand-new squadron, No. 11, was formed on the type on the 14th February, 1915 at Netheravon, Wiltshire, ‘for fighting duties’, that is specifically to destroy other aircraft. This makes No.11 Squadron the very first such unit in the history of flying. No.11’s motto, Ociores acrioresque aquilis (“Swifter and keener than eagles”) was rather ironic, because it is a fair bet that there are some eagles than can fly faster (in a dive) than the F.B.5’s top speed of 70mph, and certainly fly higher than its ceiling of 9,000 feet!
The slow top speed was due to a number of inter-related factors. Firstly, its 100hp Gnome Monosoupape engine was inefficient, as its single (exhaust) valve in the crown of each cylinder, and the inlet ports for the fuel/air mixture at the base of the cylinder (uncovered as the piston reached the end of its power stroke) made for poor fuel economy, and this was compounded by the fact early ‘pusher’ machines of WW1 had to place the tail behind the engine and propeller, giving rise to a wide, heavy structure forming the rear of the aircraft. In turn, this structure required a great deal of wire bracing, increasing drag, and reducing speed still further. Why a pusher configuration? Well, no-one had yet invented a reliable method of shooting a machinegun through a spinning propeller, so to give a clear field of fire the gun had to be mounted in an unobstructed position at the front of the aircraft. At this time, it was deemed necessary to employ a crew of two, one as the pilot, and a gunner to handle the machinegun and engage the enemy.
Archibald Lowe, the Vickers designer, had produced a substantial two-bay, equal span biplane, to carry this deadly weapon, the machinegun. At first, a belt-fed Maxim or Vickers .303″ weapon was used, on a pintle mount. Unfortunately, the cloth cartridge belt kept snagging on objects, and was difficult to manage, so a handy, drum-fed Lewis machine was substituted. As with many early warplanes, their shape and function evolved rapidly, and some F.B.5s had wing-warping (like the Wright Biplanes) and others had differing sizes and shapes of rudder. On the outbreak of war, various RFC units were sent to the Western Front, some of which had a few F.B.5 aircraft on strength; unfortunately, one of these early machines, crewed by Second Lieutenants D. C. W. Sanders and M. R. Chidson, landed behind enemy lines and made a present of the type to the German forces. No.11 Squadron arrived at an aerodrome next to the race-course at St. Omer in France in July, 1915. It was here that it likely acquired its nickname of ‘Gunbus’, as the type was used to perform escort duties (to unarmed machines), artillery observation, photography and long-range reconnaissance. The F.B.5 quickly established itself in the early air fighting, equipping Nos 2, 5, 7, 11, 16, 18, 24, 25, 32 and 35 Squadrons, RFC. A total of 125 aircraft were built in England, and it was also adopted by the Aeronautique Militaire, using 75 machines built by the French company, Darracq and also by the Tøjhusvoerkstedt, the Danish Arsenal Workshops, which built 12 for use by the Royal Danish Air Force.
One early action, on 7 November 1915, by the crew of a ‘Gunbus’ led to the award of a Victoria Cross to 2nd Lieutenant Gilbert Stuart Martin Insall who, along with his gunner, First Class Air Mechanic T. H. Donald, forced down and destroyed an German Aviatik machine, and after being shot down by ground fire, repaired their machine and returned to base. The Gunbus was soon outclassed by newer German machines, such as the Fokker Eindecker, with its synchronized 7.9mm lMG 08 ‘Spandau’ firing through the propeller. Its slow speed and low operational ceiling meant it could neither initiate combat, nor run away from opponents. An improved version, the F.B.9, with a neater, aluminium, forward fuselage and streamlined ‘RAF wires’ rather than drag-inducing steel cables, tried to improve matters but was not a great success. Although 119 F.B.9s were built (as opposed to just over 200 F.B.5s) the type soon faded from the RFC inventory.
As you would expect, no original F.B.5 aircraft survive. What you see here is an excellent flying replica, built by British Aircraft Corporation apprentices and volunteers, from original drawings held by the Science Museum in 1965/6. This was done to mark the centenary of the Royal Aeronautical Society. A working Gnome Monosoupape engine was constructed from parts of two others held by the RAF, and the machine (registerd as G-ATVP) was finished as ‘2345’, ‘Bombay’, one of 125 F.B.5 built at the Vickers plant at Crayford on the outskirts of London. The original ‘2345’ served in France with No 18 Squadron, RFC at Treizennes, being flown at times by no less a person than Captain Hereward de Havilland.
G-ATVP was first flown on the 14th June, 1966, the test pilot being the renowned D.G. ‘Dizzy’ Addicott, and in the next three years appeared at everything from the Biggin Hill Air Fair to the SBAC Farnborough Air Display. The highlight of its flying career was taking part in the RAF Golden Jubilee Display at RAF Abingdon in 1968, where it was formerly handed over to Sir Dermot Boyle, Chairman of the RAF Museum Trustees. After a period in store, the aircraft was delivered to the RAF Museum, Hendon for display; however, after some years the fabric was found to have seriously degraded and the replica was sent to RAF Cardington to be stripped and recovered with new fabric; the opportunity was taken to give the steel framework proper anti-corrosion treatment at this time. Finally, in May, 2003, the Gunbus joined many other superb WW1-era machines in the refurbished Grahame-White Factory on the Hendon site.
One interesting note. The replica Lewis gun is shown here complete with its outer cooling shroud in place. In practice, this was soon removed at unit level, as it was found to be unnecessary in air-to-air fighting.
The Vickers F.B.5 ‘Gunbus’, hardly a star performer, but a most significant fighting machine.