FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1911
1911 - 0230.PDF
I/LIGHT] PROBLEMS 16. How the Three Classes Glide. found in Class S that when the engine stops the machine automatically adopts its proper angle for a glide, and indeed cannot easily—with the engine stopped—be made to glide too steeply so long as the Vee is maintained. (See Fig. 16.) If, however, any plane which is in the full propeller blast be a loaded plane, that is, one given a slope for the purpose of lifting part of the weight (and usually of curved profile), such a plane loses part of its normal lifting power in pro portion to the falling off of air velocity past it, due to the stopping of the engine. Class F, Gliding. — As an instance, every Farman machine drops its tail the moment the engine stops—a movement which requires that the airman shall at once give a diving movement to his elevator planes lest he begin to glide backwards. Class B, Gliding.—In the case of Class B, the Bleriot machine, which usually has a lifting tail, both the main wings and tail ride over the propeller blast, therefore the stopping of the engine diminishes the lift of both—with the result that the speed of travel downwards with the engine stopped, tends to increase a little over the normal speed— a matter which may involve alighting somewhat more rapidly from a glide, but the tail does not drop. 17. CUss S, Gliding,—In the case of Class S, the gliding conditions appear to be very favourable with a good design of machine. The head resistance can be made low, and I rather think the small number in use is chiefly due to its not resembling a bird, a fact which need have no particular relation to its merits. For the moment it is fashionable to have a tail. MARCH 18, 1911. RELATING TO AIRCRAFT. By MERVYN O'GORMAN. Continuedfrom page 212.) For example, it is study in France up to that time had moved on somewhat different lines. 20. Dihedral Angle. The Vee between Wings.—The first to make any mark in actual flying there was Santos Dumont (1906). His biplane was in some respects the same as the Wrights', but the wings were set at a Vee to one another, that is, a dihedral angle as a help to lateral stability. More important than this was the fact that the front elevator was fairly large, and, unlike the Wright elevator, was set to bear a part of the weight (Fig. 6). This introduced an advance in that it provided a fore and aft Vee for longitudinal stability, an important departure from that of the Wright Bros., whose front plane was merely directional, and was at times set at a negative angle of incidence. 21. The Trying of Boxed Ends.—Dumont paid no heed to wing warping, and he apparently recovered his balance by a process the reverse of what one does on a bicycle, namely, by steering away from the side he was falling to. This will be explained later when turning is dealt with. The first machine that flew for any considerable distance in France was that made by Voisin and flown by Farman in 1907, and this was a biplane which was not boxed in, with a tail which was set to take a part of the lift (Fig. 7). This formed a shallow Vee with the main wings, and there fore helped towards fore and aft stability. It was also fitted with a front elevator placed so very close to the main plane as not to exert an important effect on stability. Voisin then very seriously tried the boxed-in ends ; he left them in 1910, learning the lesson from his own disciple Farman, but he returned to them in 1911. The Voisin plane was also, like a bicycle, kept from tilting sideways by the use Fig. 5.—Wright. Fig:. 6.—Santos-Dumont. Fig. 7.—Voisin. Fig. 8. —Farman. Fig. 9.—Wright, 1910. The original Wright machine appears to belong to this Class S, but is not truly in it, because the Wrights openly abandoned the attempt to secure fore and aft stability. Their elevator plane was not a lifting plane, and they trusted to their own skill for balance. I have, however, learnt from those who flew this machine that the fatigue of three or four hours' balancing was very great indeed, and the Wrights at present fit a tail.* 18. The History of Stability.—I am not in these notes concerned with the claims of inventors to priority, but wish to consider for the moment the doings of builders merely as experiments on stability, and not as attaching prime importance to the date when the experiments were made, and accordingly I have not attempted to verify exact dates. I neglect the early trials of Lilienthal (1886), Pilcher (1892- 93), Ader (1897), and others, and note that the first successful Wright aeroplane was tailless. It was evolved from a biplane glider fitted with a rudder (1901) and elevator. I do not know whether a tail, properly so called, had been seriously considered by them since they found so much trouble with the breaking of their rudder by slipping back on to it that they hinged it vertically. 19. Abandoning the Tail.—It was on the results of their gliding tests that they decided not to use a tail, and hence their first power machine was a biplane with no tail, but having a plane in front which acted as an elevator, and which did no weight bearing (Fig. 5). Such a machine has no automatic stability. It was solely the skill and activity of the man which prevented tipping forwards or backwards, and stability in these directions had to be attended to cease lessly. Lateral stability was secured by a system of warping one wing and simultaneously counter-warping the other ; this was only slightly automatic, due to the intentional looseness of the girder work. This was the state of progress when Wilbur Wright arrived in France (August, 1908), where the reports of his doings which had come from America had incited others to produce notable results, though the * I use the term tail for a plane which is horizontal and behind the main wings. The Wrights fitted a rudder behind their early machines, but not a tail of steering rudders, until 1910. The steering method has advantages, and is freely used by all aviators on all machines when they have acquired a little skill. The effect on France of Wilbur Wright's visit was the adoption there of either his system of wing warping or else the use of flaps or ailerons, which are inferior in efficiency and speed of response, but which answer the purpose of raising the wing of which the aileron is lowered. The draw backs of ailerons are touched upon in para. 32. 22. Ailerons for Lateral Stability and Banking.—Take the Voisin biplane, omit the side panels, give it ailerons, and we have the Farman machine (Fig. 8). This was done by Henry Farman in 1909. The elevator is farther in front than that of the Voisin, and not being set to form a Vee with the main planes, it tends, so far, to reduce longitudinal stability, an effect which is countered by increasing the size of the tail, which does form a Vee with the wings. 23. Tail Flap for Elevating.—Later, in addition to the front elevator, a flap was put on the tail (1910) to serve as an additional elevator (Fig. 3). It is a question whether the Wrights learnt in Europe the practicability and advantages of employing the Vee, but it was after their visit here that they used a Vee relationship between the wings and a tail which has been added. It is particularly interesting to note that their front elevator has been abandoned, thereby avoiding the necessity for increasing the size of the tail plane, while we find the French influence in that the rear of the tail is hinged to act as an elevator. 24. Blinkers for Turning.—It will be noticed that Mr. George, Mr. Curtiss, Mr. de Havilland, and the Valkyrie Company seem to have learnt from Wright to use their small vertical planes (or blinkers) in front of the machine as a point to thrust against when steering round a corner. Pischoff also uses a vertical plane, but it is so near the centre that it is evidently only used to damp oscillation due to a very low centre of gravity. It is to be observed that the latest Wright model retains the blinkers. It would seem to be a feature weighing so little that it is worth retaining on the F Class at least, even if the advantage gained be but small, which is by no means clear. 232
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
