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Aviation History
1911
1911 - 0542.PDF
[pMI JUNE 24. 1911. Three-quarter view of the Dunne monoplane from in front. " Flight " Copyr point, however, we must refer our readers to our above mentioned article. Since the tips are set back behind the shoulder, owing to the V plan form of the wings, the change in angle between shoulder and tip introduces the principle of the longitudinal dihedral. In order to render this clear it is convenient to imagine that the middle section of each wing is removed. In this case the extremities form two tails at a negative angle in respect to the leading main plane. In practice the extremities act as tails, and being out of the influence of the draught of the propeller they do not tend to disturb the balance of the machine if the propeller stops in flight. As to where the tail portion begins and the main plane ends, it seems impossible to say, for it seems only reasonable to suppose that the dividing line varies with circumstances. Provided that it moves in the right direction, this differential action is, of course, all to the advantage of the natural stability of the machine. Natural stability is the great aim, we might almost say the raison tt&tn, of the Dunne aeroplane, and, so far as the longitudinal stability is concerned, the simple principle of the fore and aft dihedral is apparently a sufficient explanation of the system. In many modern machines the principle of the dihedral is also used for lateral stability, but in the Dunne machine this equilibrium is arranged in a different way. As a glance at the accompanying illustrations shows, the wings are arched rather than upturned, and it is therefore to the principle of the gull's wing, and not to the dihedral angle, that the lateral stability of the machine is due. Unfortunately, this principle does not lend itself to any very precise explanation, but as a general description it may be pointed out that the down-turned extremities are so arranged that if the relative wind veers from an initial position, which may be assumed to be in the line of flight, the near wing will be partially shielded and may even have a downward pressure on its extremity. Simul- "Flight" Copyright. Sketch illustrating the pilot's seat and two control-levers en the Dunne monoplane. Three-quarter view of the Dunne monoplane from behind, 544 " Flight" Copyright.
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