C.Andrews Vickers Aircraft since 1908 (Putnam)

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   Experimental work was carried out with the Gunbus concept, and the E.F.B.6 was a variant flown in 1914 with extended top wing, presumably to obtain more lift for load carrying, but was not proceeded with.

P.Lewis British Aircraft 1809-1914 (Putnam)

Vickers Gunbus E.F.B.1 to F.B.6

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   A single experimental F.B.6 appeared in July, 1914, and was fitted with unequal-span wings, the considerable overhang of which was supported by king-posts and wires. The machine utilized the curved tailplane and the rudder had a straight trailing-edge.
   The Gunbuses were pleasant and easy machines to fly after the early unreliability of their 100 h.p. Monosoupape Gnomes had been attended to, and the type was notable as a pioneer among gun-carrying aeroplanes.

P.Lewis The British Fighter since 1912 (Putnam)

Also in July, Vickers produced another single experimental version of the Gunbus series, the F.B.6. This used, too, the 100 h.p. Monosoupape Gnome and was basically a modified F.B.5 with extended upper wingtips braced by kingposts and wire. At the same time the shape of the rudder was revised.

F.Mason The British Fighter since 1912 (Putnam)

Vickers E.F.B.6 and F.B.9

   The efforts to extend the successful F.B.5 Gunbus formula, as has been shown, brought forth the twin-engine F.B.7 and F.B.8, which appeared too late to warrant further work on them. Another design, the Vickers E.F.B.6, was less radical in that it retained the basic F.B.5 single pusher engine format. It did however adopt the upper wing’s greatly increased span with large overhang that characterised Flanders’ F.B.7, in an effort to increase the F.B.5’s load-carrying ability. Like the F.B.7, however, this aeroplane was blighted by the plethora of struts and bracing wires necessary for this wing configuration, and its poor performance on only a single engine resulted in the aircraft’s further development being abandoned.
   Instead efforts focussed on generally cleaning up the F.B.5 itself, and in December 1915 the prototype F.B.9 was first flown.
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Журнал Flight

Flight, July 10, 1914.

THE NEW VICKERS GUN-CARRYING BIPLANE.

   A NEW Vickers biplane of the gun-carrying type made its initial appearance at Brooklands last week under weather conditions which were anything but favourable. When Mr. Barnwell took the machine out there was a strong wind blowing, and matters were not improved by the heat eddies set up by the glaring sun. In spite of these disadvantages, however, the machine behaved excellently, and appeared to be well balanced both longitudinally and laterally, Mr. Barnwell commencing to do right- and left-hand turns after once having got the "feel" of the machine. On subsequent flights the engine was switched off in order to test the gliding angle, which appeared to be exceptionally good.
   A good idea of the general arrangement of the machine may be gained from the accompanying photographs. The nacelle, it will be seen, is comparatively shallow at the nose, thus greatly reducing the side area in front, whilst the rear vertical surface, formed by the rudder and fixed fin, is of ample proportions, so that there is little doubt that the machine will prove to be spirally stable. The main planes - of which the upper one has a considerable overhang with the weight taken by cables running over king posts - are separated by six pairs of struts. With the exception of the four inner struts, made of steel tubes, which pass through the nacelle, all the inter-plane struts as well as the struts in the tail outrigger are of wood.
   Four steel tubes, forming a V, as seen in plan, carry the tail planes, and practically all the cross bracing is effected by stranded cable in preference to piano wire. The engine fitted is a 100 h.p. Gnome monosoupape driving a Vickers propeller. In its constructional details such as clips and sockets the machine incorporates a number of highly ingenious ideas, and the workmanship throughout the machine is of very high quality.


Flight, July 31, 1914.

EDDIES.

   A new Vickers gun-carrying biplane made its first appearance at Brooklands last week. Mr. Barnwell had flown the older machine, which was described in FLIGHT a short time ago, over to the works at Joyce Green, and later returned on the new biplane, which had just left the stocks. In its general appearance the latest gun-carrier is a replica of the previous one, but several details have been altered. Head resistance has been reduced, wherever possible, as for instance in the arrangement of the control cables. The rudder and elevator cables pass along the tail booms in the usual way, but are then taken round pulleys and run parallel with the bracing cables of the inner bay of the main planes, whilst the aileron cables are taken through fair leads on the leading edge of the lower plane. Instead of the rotatable hand-wheel with which the previous machine was fitted, a single central lever actuates the ailerons. The bracing wires in the tail outrigger have been replaced by stranded cables, probably with a view to eliminate, as far as possible, any danger of breakage and consequent possibility of them getting entangled in the propeller. Constructionally, the machine is a beautiful piece of work, both as regards workmanship and finish, and aerodynamically it appears to be very efficient. Under the clever piloting of Mr. Barnwell, the new gun-carrier flies exceedingly well, and although it is comparatively new it has already been put through all manner of tests. The first day this machine was in the air Mr. Barnwell, on his arrival at Brooklands, did some fancy flying before coming down, including spirals and most alarming banks, that is to say, banks which would have been alarming had the pilot been less experienced.