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Aviation History
1921
1921 - 0073.PDF
FEBRUARY 3, 1921 THE AVELINE "AUTOMATIC PILOT FROM the earliest days of flying, inventors have occupied their minds with mechanical apparatus whereby the equilibrium of an aeroplane could be maintained without the aid of the pilot. One of the first, and most obvious, solutions of this problem was the pendulum, and inventions out of number utilising the pendulum principle have been patented. Some of these have been very ingenious, but when reduced to ele- mentary principles have proved to be but some form of pendu- lum gear after all. Now the pendulum control is taboo on account of the fact that, although under certain conditions it will do what is required of it, it suffers from the disadvantage that it is acted upon by centrifugal force and by acceleration. This results in incorrect readings when the instrument is used as an indicator, and may mean a crash if the pendulum is used for operating, directly or indirectly, the controls. As a variation of the pendulum type of stabiliser, gyroscopes have been suggested, and several types have in fact been made and have proved to work satisfactorily. Perhaps the best- known of gyroscopic stabilisers is the Sperry, an American invention, which was used with success on several machines, notably large flying boats. Although this instrument worked very well, it never came into general use, probably because a gyroscope is, at the best of times, a delicate piece of machinery likely to get out of action. Moreover, the gyroscope with its machine is electric, part pneumatic, and part aerodynamic. The pendulum portion, which is only partly to be regarded as a pendulum, coasists of an inclinometer in which the fluid is mercury. This mercury is contained in a disc with a narrow circular groove, and serves to make and break an electric con- tact which operates the valves that admit compressed air to the air cylinder whose pistons actuate the control cables. A reference to the accompanying diagram should help to give an idea of the fundamental principles involved. This diagram, by the way, is not meant to represent the actual mechanism except in so far as concerns elementary principles, being neither to scale nor representing in component details the actual machine. It has been drawn solely in order to assist in fixing ideas, and deviates in many respects from the machine itself. We have thought this would form a better explanation of the idea of the invention than a more acciirate and compli- cated set of drawings of the actual details, and presently we shall attempt to indicate wherein the machine itself differs from the diagram. , Having made this proviso, one may proceed to a description of the apparatus. To begin with the inclinometer, and taking first that for aileron controls (there is a separate one for the elevator). This consists of a fibre disc in which is a circular groove approximately half filled with mercury. Passing into THE AVELINE STABILISER : Elevation, side view and plan attendant servomotors and other paraphernalia weighs a good deal, and .this, coupled with the various complications, has probably prevented the Sperry gyroscopic stabiliser from becoming as popular as it otherwise would have done, Recently a form of " automatic pilot " has been introduced in this country, in which the pendulum principle is involved, but in which the objectionable features of the pendulum control have been avoided, or rather countered. This machine is the invention of a young Frenchman, M. Georges Aveline, who has succeeded in forming a company for exploit- ing his patents in this country. This firm is established as Automatic Controls, Ltd., with offices at 19, Regent Street, and at the present moment Messrs. Handley Page, Ltd., are carrying out a series of practical tests of the invention at their Cricklewood aerodrome. We understand^ that previously the " automatic pilot " has been tested by Air Ministry pilots, but the Handle ' Page tests are the first to be carried out by a private firm. During a series of tests by Major H. G. Brackley, D.S.O., the well-known H.P. pilot, the Aveline stabiliser has functioned very well indeed, and although there arc still minor adjustments to be made the invention has already proved extremely promising. The Principle of the '' Automatic Pilot '' As has already been mentioned, the Aveline stabiliser employs a form of the pendulum principle, and part of the this circular groove, and a small distance above the level of the two ends of the mercury, are two electric contacts while a third contact is placed at the bottom of the disc. To these contacts are passed wires from a 4-volt electric battery. In the actual machine one only is employed, but in order to keep the wiring diagram as simple as possible we have shown a battery for each side. It will now be seen that if the disc is tilted the mercury will rise on one side, thus closing the electric circuit on that side. The relay current of 4 volts on being closed actuates a solenoid switch, which closes a stronger circuit of 12 volts. This in turn actuates the valve mechanism of the working cylinder, which is supplied with air from a container. Two turbine pumps running at 2,000 r.p.m. keep up a pressure of about 50 lbs. per sq. in. in the air container. These two pumps are driven bv two windmills, mounted under the front portion of the fuselage. Suppose the left wing of the machine is tilted downward by a gust or through some other cause. The mercury will then rise in the left-hand side of the disc, and will make contact with the left-hand circuit. This closes the left-hand 12-volt circuit, and the solenoid shown at the left end of the working cylinder closes the* exhaust valve and opens the inlet valve, thus admitting air from the container to the cylinder. The pressure of the air forces the piston to the right, and as the rigid connecting rod is provided with a rack engaging with the teeth of the quadrant above it, the quadrant is turned 73
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