M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)

P.Hare Royal Aircraft Factory (Putnam)

Another project carried out early in 1907, in parallel with Cody's work, was the construction of a full-sized aeroplane in accordance with the ideas developed by Lt Dunne as a result of his extensive experiments. This craft, designated simply D l , was initially to be tested as a glider before fitting the propulsion system which had been designed for it by Capt Carden.
   By arrangement with the Marquis of Tullibardine, eldest son of the Duke of Atholl, the flight tests took place, in secret, at a remote location near Blair Atholl, on his family estate in the Grampian highlands, during the summer of 1907. This desire for secrecy, especially when compared with the Factory's normal habit of operating from a public common, clearly illustrates the significance attached to Dunne's 'discovery'. Since Cody's work was an extension of his already well-known kite experiments, any attempt at secrecy would have been futile, and none was made. It was also entirely possible that Capper hoped to focus all attention on Cody, thereby allowing Dunne to work without distraction.
   A number of successful glides were made, the craft being piloted by various officers from the Balloon School, as Dunne's frail health was not considered up to the task. A minor crash occurred while Capper was at the controls, during a brief visit to judge what progress was being made. The glider made contact with a wall, and flight trials were stopped pending repairs. During the course of this work the glider was converted into a powered aeroplane, the D1-B (the glider thus becoming, retrospectively, the D1-A). The propulsion system comprised twin propellers mounted on outriggers and driven, via belts or chains, by two 12hp Buchet engines, one of which had previously powered Cody's power kite. The two engines were coupled to a single shaft, and some initial difficulties were resolved when it was discovered that they had been installed so as to run in opposite directions.
   It was intended that the powered aeroplane would be launched from a wheeled trolley running along a raised pathway of planks, laid to provide a reasonably level surface. Unfortunately the trolley ran off the planks during the first take-off attempt, and the machine was damaged to an extent which almost certainly would have required its return to Farnborough. It was felt that this would make it impossible to resume flight trials before the onset of winter, so the experiments were abandoned until the following year. The team's enthusiasm does not appear to have been diminished by this setback, and Capper seems to have had little trouble in convincing the War Office that they should be allowed to continue with the project.
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   By early September Lt Dunne had returned to Blair Atholl. He was accompanied by a team of helpers which included Lt Westlake, who had been a member of the previous year's party, and a young militia lieutenant, Lancelot Gibbs, who was to act as pilot. They took with them a new glider, the D3, trials of which were intended to provide information required to complete the powered machine, D4, which was under construction at Farnborough.
   The glider proved quite promising at first, with a good number of short flights being made by Lt Gibbs on the very first day of the trials. However, later efforts were less successful, being hampered by the roughness of the terrain and the turbulence of the wind. As a consequence, the party appears to have spent a considerable amount of time roaming over a wide area, seeking a location which offered more favourable operating conditions, but without success.
   At the end of the month Dunne left Gibbs in charge of the group testing the glider in the hills while he, together with a few assistants, returned to Blair Atholl itself to begin erecting the powered D4, which had by then arrived from Farnborough. This operation appears to have been extremely difficult, especially at a distance of some 500 miles from the Balloon Factory's workshops. Problems with warped timber and inadequate tools delayed completion of the aeroplane until the middle of November 1908, by which time Capt Carden had come up to supervise the installation of the engine and to take charge of the testing.
   Flight trials started on 15 November, with Gibbs at the controls, but difficulties with the undercarriage caused an immediate halt. Ground runs, interspersed with engine malfunctions, occupied the remainder of the month, and the first take-off, covering a distance of about thirty feet, did not occur until 4 December. Two days later Carden had to return to Farnborough, and the tests continued in his absence, more short hops being achieved despite the lack of his skills with the engine. On 10 December Gibbs managed a flight of 120 feet, and on this note of minor triumph the trials were ended.
   In common with many of its contemporaries, the Dunne D4 appears to have been rather underpowered, especially in view of its very heavy undercarriage, and the final acceptance of this shortcoming may well have been the reason for the seemingly premature ending of the tests. Alternatively, it is equally possible that the Dunne party was defeated by the weather, for winters in the Scottish highlands can be very severe. In any event, the test flights of the D3 and D4 seemed to uphold Dunne's theories regarding stability, even if his designs of aeroplanes and their control systems needed further development.

P.Lewis British Aircraft 1809-1914 (Putnam)

Dunne D.1 and D.4

   An interest in the problems of successful flight was aroused in Lt. John William Dunne, son of Lt.-General Sir John Dunne, during 1900 after he was invalided home from the Boer War, in which he had served as an officer of the Wiltshire Regiment. His friendship with Sir Hiram Maxim and H. G. Wells brought the encouragement of both of these scientific visionaries.
   Dunne's first thoughts on the subject turned towards the helicopter as a means of leaving the ground, but in 1904 he concentrated his studies on achieving a fixed-wing aeroplane of inherently stable lay-out. Practical experiments were conducted for nearly two years with paper models until, in 1905, he felt that the time had come to enlist official support to enable his ideas to be put into full-size form. At that time, Dunne's official position was that of a designer of man-lifting kites at H.M. Balloon Factory, South Farnborough, Hants., a task which he shared with S. F. Cody, the kiting instructor. Sufficient interest was aroused in the War Office by Col. J. E. Capper for Dunne to start construction of his first aircraft in the Balloon Factory. Security measures were stringent from the outset. The work was carried out in complete secrecy behind locked doors, and Dunne himself was not allowed to wear his uniform, being shown in the Army List as an invalided officer on half-pay. A condition of War Office assistance was that he should be paid half a guinea a day "when actually at work".
   Dunne's automatically-stable lay-out was centred around vee-shaped swept-back wings of parallel chord, a pair of which were superimposed and connected by interplane struts to form a biplane in which the tips were washed-out at negative incidence to ensure maximum stability. The D.I, as it was named, was constructed first as a glider, the intention being to fit engine power once the general design had demonstrated its feasibility.
   The project had the support of R. B. Haldane, the Secretary of War, who to ensure that the flying tests also were conducted in secret requested the Marquis of Tullibardine, the heir to the Duke of Atholl, to allow the use of his estate among the mountains at Blair Atholl in Perthshire, Scotland, for the purpose. The Marquis agreed, and a wooden shed was built on a lonely grouse moor at Glen Tilt to house the aircraft, which was taken there and assembled by a small party of men in plain clothes, consisting of Lt. Dunne, Lt. Westland, three other officers, two N.C.O.s of the Royal Engineers and a few servants. In addition to the aircraft's deal shed, eight tents were set up 4 mile away to house the men in a self-contained camp. In spite of the measures taken to prevent news of the work becoming public, something of what was being done leaked out, and Glen Tilt was besieged by newspaper reporters and German spies, the Duke of Atholl's private army of gillies being kept busy warding off the intruders. In order to conceal the details of the machine as much as possible from prying eyes, the subterfuge of camouflage was resorted to. This was applied by painting chordwise thin white stripes and irregular outlines across the dark upper surfaces of the wings.
   Tests of the glider were conducted in 1907 by Col. J. E. Capper, the Superintendent of the Balloon Factory, as Dunne's health made it unwise for him to attempt to fly it. Repairs were necessary following a crash into a wall during a brief flight, and the machine was next fitted with a pair of Buchet engines whose total combined output was 15 h.p., but although the War Office contended that 15 h.p. was sufficient for the use of the Army, the D.1 was under-powered and failed completely to take-off. The undercarriage consisted of skids on both the glider and the powered D.1, and a four-wheeled platform was employed finally to get the D.1 to fly by launching it down an inclined plankway built a few feet above the ground level. When the carriage was started down the track the rubber-tyred wheels climbed the curb fitted to the edge of the plankway, and it fell over the side, carrying the aeroplane with it. The D.1 was damaged too badly for it to be repaired in time for any further experiments before the winter snows were expected.
   By mid-1908, the D.1 had been rebuilt and at the same time modified in an attempt to make a success of it. Redesignated D.4 it was now a more practical machine fitted with a 25 h.p. R.E.P. engine driving a pair of propellers by crossed flat belts over drums, and an enclosed nacelle for the pilot which was embodied on the underside of the lower wings' centre-section. Below this there was attached to the tubing chassis a sprung, four-wheeled undercarriage in place of the original skids. Vertical fins were added to the extremities of the wings. Once again, the upper surfaces were disguised with the thin white lines and designs. Lt. Lancelot D. L. Gibbs, of the Royal Field Artillery, undertook the testing of the D.4 for the War Office in the Lower Park at Blair Atholl during the autumn of 1908. The R.E.P. engine could not be persuaded to develop enough power to take the machine fully into the air, but it did manage to leave the ground on the level for short hops without an accidents occurring. Eight of these brief flights were accomplished between 16th November and 10th December, a distance of 40 yds. being covered on the last date.
   Finally, in 1909, the War Office decided that, after spending ?2,500 on the experiments without any significant results being achieved, it would have to discontinue its sponsorship of the project. Lt. Dunne severed his connection with the Balloon Factory and the D.4 was presented to him when he left.


Dunne D.2

   The D.2 designation was given to a small glider version of the Dunne-Huntington Triplane, which was proposed but not built.


Dunne D.3

   The D.3 was a smaller glider version of the D.4 and was built at H.M. Balloon Factory. It was fitted with a twin-skid undercarriage, launching being carried out from a four-wheeled trolley. As with the D.1 and the D.4, camouflage was applied in white stripes and linear patterns to break up the continuity of the dark upper surfaces.
   The D.3 was tested during September and October, 1908, at Glen Tilt, Blair Atholl, Perthshire, by Col. J. E. Capper, who rose to about 15 ft. height sitting in it, and also by Lt. L. D. L. Gibbs, who flew the machine for a distance of 44 yds. on 9th October, 1908, before crashing it a little later.

Журнал Flight

Flight, September 3, 1910

THE BLAIR ATHOLL EXPERIMENTS.

   THE accompanying photographs of early Dunne aeroplanes have a particular interest on account of their association with the secret War Office experiments that were carried out during 1906, 1907, and 1908 on the Duke of Atholl's estate at Glen Tilt. Our readers doubtless recollect the mysterious accounts of these experiments that appeared in the daily Press. It is safe to say that no reporter ever saw the machine - the Scotch gillies who acted as outposts saw to that; indeed we believe that it is rumoured thereabouts to this day that a broken walking-stick is all that remains in existence of a concealed telescope camera and of the foreign spy who carried it. Be that as it may - and we have no doubt that the individual in question will enjoy the story as much as another - the fact remains that very important experiments were, at that time, conducted under Government supervision, and that the machines employed were the direct forerunners of the Dunne aeroplane that is now attracting so much attention at Eastchurch.
   The accompanying photographs were, as we have mentioned, actually taken on the spot. Fig. 1 shows the machine being brought out of its shed, and incidentally it gives a very good idea of the bleakness of the surrounding country, which is quite characteristic of the Highlands in this respect. We can quite easily imagine that an interested, but unauthorised, spectator would be seen from afar long before he could see anything worth noting, and it is not difficult to suppose that he might have a wry arduous time of it before he could make himself scarce on such a desolate waste. Like the ostrich, he would doubtless be willing to bury his head in a hole if he could persuade himself that this would by any means protect his body from an onslaught of the aforesaid Scotch gillies.
   Fig. 2 shows the machine being lifted on to its trolley. The initial experiments were carried out with the aeroplane as a glider. It will be observed that the machine is mounted on a skid for landing; circular springs, which look like wheels, can be seen between the skids and the lower plane. In Fig. 3 the glider is undergoing inspection by the authorities, among whom were General Hadden, General Ruck and the Duke of Atholl.
   Fig. 4 shows the start of a glide with Colonel Capper as pilot. In this attempt he attained a height of about 15 ft. above the ground, and finally charged the wall that is visible in the foreground of the picture. Subsequent to these experiments another machine was commenced in 1907, and was tried in the lower park at Blair Castle during 1908. The fifth photograph shows this machine, which is a power-driven aeroplane, ready for flight. Lieutenant Lancelot D. Gibbs, whose name is now well known as an aviator, was at the helm. Mr. Gibbs made most of the glides on the Dunne aeroplane at the hill camp earlier in 1908, when he used a small scale replica of this machine.
   A peculiarity in the appearance of "D4," which might perhaps escape notice, is that it has been disguised by painting so as to obliterate as far as possible evidence of its essential characteristics, so far as they might be ascertained by an observer at a distance. The special curvature of the planes and other peculiarities which were fully described in our article on the Dunne aeroplane that appeared in FLIGHT of June 18th and June 25th, 1910, were thus rendered so far as possible invisible to the ubiquitous gentleman of the camera and the telescope.