making use of the variations in position of the center of pressure a semi-automatic balance is obtained. The planes are 6 feet apart, 6 feet in depth, and spread 20 feet 41⁄2 inches longitudinally and 46 feet laterally. The total area is 527 square feet. Elevation.-At the rear ends of each plane are hinged flaps, each feet wide and 12 square feet in area, controlled by a left-hand and a right-hand lever. They are so connected that when the right-hand lever is pulled back, and the left-hand lever is A REAR THREE-QUARTER VIEW OF THE DUNNE BIPLANE This photograph is worthy of study because it gives the correct impression of the shape, and slope of the main planes. pushed forward, then the left ailerons are pulled down, lifting up that side and the right ones are turned up. When both levers are pulled back together, both flaps are turned up, and since they are to the rear of the center of support, the entire machine will be turned up for ascent. Direction. When steering to the right, for example, the right lever is drawn back and the left pushed forward, thus pulling up the right flap and pulling down the left. The angle of incidence of the ends is always negative. Therefore turning up the right flap increases still further the negative incident angle, and consequently greatly increases the negative drift, thus causing the right side of the machine to slow down, at the same time as it is depressed. But since the flaps are at the rear of the center of gravity, and since turning up the right flaps causes this end to sink (like the tail of a Blériot, for example), there is a tendency for the entire machine to ascend. To counteract this, the left lever is pushed over, thus increasing the lift on this end and decreasing the negative incident angle. This now results in a decrease of drift on this side, and causes the machine to “skew” around faster and to "bank" with the right down and the left up. Transverse Control.-The character of the planes on this biplane give it practically an automatic transverse equilibrium, so that there is no distinct and separate manner of controlling the lateral inclination of the machine. The manner in which this aeroplane is artificially inclined when making turns, however, has already been described. Keels. The end panels of the main cell are covered-in, giving a vertical keel at each side, which aids materially in the various movements for equilibrium and holds the machine to its course, preventing any skidding sideways, etc. Propulsion.-Two wooden propellers are mounted on a frame built out on either side of the central body. These propellers are 7 feet in diameter, 7% feet pitch, and rotate at 669 r.p.m. They are driven by chains from a 50 horse-power four-cylinder Green engine, and are rotated in the same direction. To counteract the torque resulting from this, a weight is fixed on one end of the machine. This is not a very good provision. Mounting. The mounting is similar to the old Voisin type, and consists of two rubber-tired wheels mounted on a steel-tube chassis fitted with coiled steel springs at the front and a single wheel and skid at the rear. Weight, Speed, Loading and Aspect Ratio.— The total weight in flight is about 1,700 pounds, 34 pounds are lifted per horse-power, and 3.2 per square foot of surface. The aspect ratio, considering the actual width of the planes, is 9 to 1, and considering the projected span of 46 feet, is 7.6 to 1. References.-Flight, June 4th, 1910; June 18th, 1910, p. 459; June 25th, 1910; Flugsport, July, 1910. 7. THE FARMAN BIPLANE (1909) Henri Farman, in 1907, began his career as an aviator by making short flights of a few seconds duration on a biplane constructed for him by the Voisin brothers. On January 13th, 1908, he succeeded in flying one kilometer in a closed circuit, thereby winning the Deutsch-Archdeacon prize, the first great prize offered for an aeroplane flight. Until the end of that year Farman flew this machine and with it conducted a series of experiments on stability. In the early part of 1909, having severed his connection with the Voisins, Farman opened an aeroplane factory at Chalons, France, and began manufacturing aeroplanes himself. His design was original in many ways, and embodied several practical innovations that his previous experience had suggested. The Farman biplane has been used extensively in Europe, and notably by the well-known aviators Paulhan, Weyman, White, etc. More than one hundred of this type are in use or under construction, and for a slow but trustworthy machine it has been found very satisfactory. The Frame. The frame consists essentially of a main box cell, somewhat similar in design to a Pratt truss, counterbraced throughout, with identical upper and lower chords, uprights of wood acting as compression members and cross wires as tension. members. The supporting planes are analogous to the upper and lower decks of such a truss. The Supporting Planes.-There are two main carrying surfaces, identical and directly superposed. Their sectional curvature is of the cambered shape, used so generally in present day aeroplanes. The curvature is concave on the under side, and of parabolic character. The surfaces are made of "Continental" cloth, a special rubber fabric, stretched tightly over ash ribs. The spread of the surfaces is 33 feet; the depth, 6.6 feet, and the total area, 430 square feet. The distance between planes is 7 feet. The Elevation Rudder.-The elevation rudder originally consisted of a single surface, about 43 square feet in area situated well out in front. It was hinged and braced to two sets of outriggers, firmly attached to the main cell, and was controlled by |