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Aviation History
1912
1912 - 0191.PDF
MARCH 2, 1912. The vane, A, therefore, would become positively incident to the relative wind and would consequently lift, deforming the framework, B, and operating the three-way valve, D. This valve controls the admission and escape of compressed air to and from the relay motor, F, which is represented in section by the inset sketch. The result of the particular valve movement that the lifting of the vane, A, would make, would be to return the piston of the motor, F, to the top of its stroke, thus arranging the elevator, G, connected by rope and pulleys to the motor, in the position for ascent. If the head were to tilt, the relative wind would blow on the top of the vane and the action of the pneumatic relay would be to set the elevator for descent. A very ingenious device was that suggested by M. Orlando, of Rome (Fig. 5), but although at first sight it appears so evidently simple and convenient VV on the score that it is entirely automatic and , • "\ does away with the extra complication of a relay mechanism, it is doubtful if the system would give good results when put to practical l/l»C"T o>i**~oc> siM&t-'Z&i Fig. 5.—The Orlando anemometrlc stabilizer. test. At the end of the extension, E, of the elevator is hinged a flap, F, which is retained in position by the spring, S. Should the aeroplane to which this apparatus is fitted tend to dive, the relative wind will increase in velocity with the result that the incidence of the flap, F, will tend to increase, thus raising the rear of the elevator, and arranging it in the position for ascent. Should, on the contrary, the head be inclined to rise, the relative speed will drop, and the strength of the spring, S, will overcome the lift on the flap, F, and the elevator will thus be thrown into a position for descent. The system is based on the state of equilibrium between the positive and negative lifts pro duced by the relative wind in the rear elevator and on the hinged flap. operates the longitudinal rudder according to the indications of the former two members. The pressure-vans, P, is mounted on arms proceeding from the tubes, A, which are free to slide in a longitudinal direction through bearings in the aluminium casting that forms the outside of the instrument. When the relative speed of the machine is equal to or greater than its flying speed the pressure-vane is forced back against a stop, but as soon as the relative speed drops below the flying speed, the springs, IV, come into action, and press the tubes, A, together with the vane, forward. By their connection with the rods, E, they withdraw the slide-valve rod, T, so that the pneumatic relay im mediately sets the elevator for descent. The action of the relay mechanism will be explained later. As the speed of the machine in creases towards that necessary to sustain the aeroplane, the vane will gradually recede until it returns to its normal position, by which time the elevator will have gradually moved from the descent position to the position of normal horizontal flight. Thus the function of the pressure vane, P, is to detect any diminution of speed below that necessary to sustain the aeroplane to which the apparatus is attached. Any increase of speed is detected by the movable weights, M and M1, which are kept in position with regard to the rod, A, by means of springs, R, on each side, and which are keyed to the rods, E, by means of set screws. Should the front ot the aeroplane tend to dip the speed will increase, and this will cause the weights, M and M\ to^lag behind, drawing with them the rods, E, and causing the side- valve-rod, T, to operate the relay so that the elevator is arranged for ascent. As normal speed is regained, the springs, R, will return the temporarily-displaced weights, M and M1, to their normal positions, and the elevator will, at the same rate, be brought back to its horizontal flying position. The movable weights also assist the pressure-vane, P, in the detection of any decrease in speed. Thus it will be seen that any deviation of the aeroplane from the horizontal path, an event which is accompanied by either a rise or a fall in the relative speed, will be detected by the combined action of the accelerometer and anemometer, and correcting adjust ments of the elevator will simultaneously be effected by the relay mechanism. This latter itself is not by any means the least interesting section of the device, and is the evidence of much ingenuity on the part of the inventor. Sliding along the inside of the cylinder, C, is the double-ended piston, B, and from this piston proceed rigidly at tached connecting rods, passing through stuffing boxes at either end of the cylinder. The rod, T, essentially a slide valve, Fig. 6.—The Doutre automatic stabilizer. S7*<gn-iZ£f^_ 4. Devices Depending on both Velocity Pressure and Inertia Principles for their Action.—Undoubtedly the most noteworthy device for maintaining longitudinal stability, combining both velocity-pressure and inertia actions, is the Doutre stabilizer, for not only is its operation sound on theoretical grounds, but it has fully demonstrated its practical value as applied to a Maurice Farman biplane, piloted by Didier. Some photographs of this device appeared in FLIGHT some months ago, but as the description accompanying them was necessarily short, in view of the information available at the time, it may be of some interest to describe the device at fuller length. Fig. 6 represents a section of the apparatus. It has three essential members, an anemometer, represented by the pressure- vane, P, an accelerometer, represented by the movable weights, M and M1, and a relay device which, by means of compressed air, K> CcC^To^ which moves integrally with the two rods, E and E1, is allowed to slide with a certain amount of latitude along a cylindrical hole bored in the centre of the front end of the piston, B. Those portions of the rod, T, marked K and L, are machined to be a perfect fit in the slide valve cylinder, while those portions between and on each side of them are turned down so that there will be left an air space between the rod itself and the walls of this slide valve cylinder. Compressed air is admitted to the compartment, D, and is carried thence by the duct, Q, to the air space between K and L. Let us imagine tnat the rod, T, is being withdrawn by the combined action of the plate, P, and the weights, M and M1, in the event of a diminution of the relative speed of the machine. As the withdrawal takes place the movement of the piston, K, will uncover the end of the port, N, and admit air into the cylinder, I, with the result that the piston, B, will travel in the same direction as the rod, T, which movement automatically cuts off the supply of compressed air to the cylinder, I. At the same time the piston, L, wili uncover the end of the port, O, and will release any compressed air that had previously been admitted to the cylinder, H. The compressed air ipi C 2
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