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Aviation History
1910
1910 - 0684.PDF
By SIR RICHARD PAGET, BART. THE problem of controlling the movements of an aero plane may be viewed by the driver from two diametrically opposite standpoints. He may consider the direction in which he wants the machine to move, and obtain that motion by moving the levers in the same direction; or he may consider the direction in which he wants to move himself, and obtain that motion by pressing against the levers so that they move in the opposite direction. At present, these two methods of control are com bined indiscriminately in many machines. The method of direct action, in which the levers are moved in the direction in which it is desired to move the aeroplane, is seen, for example, in the warping of a Wright or a Farman biplane, while cases typifying the other system, in which the operator pushes himself in the direction in which he wants to go by thrusting against the lever, are those of the foot-steering in the Farman, Bleriot, and other machines. In some cases these methods are combined with a third, in which the direction of the movement of the controlling-handles is purely arbitrary, and bears no direct relation to the direction in which the machine is desired to move, as, for instance, is the case in the steering of a Wright machine by means of a to-and-fro motion of the lever. If it is granted that the method of control should be such as requires the minimum of conscious thought and the maximum of automatic action on the part of the operator, it' must almost necessarily follow that the method of control should be the same for all required movements. It can hardly be sound practice to steer by the method of reaction, and to warp and elevate by the method of direct action, while still less can it be right to combine either of these with an arbitrary motion. Thus the question arises, which method is preferable, that of direct action or that of reaction ? Modern systems of aeroplane control by direct action are the descendants of the control of the bicycle and the motor car, in which, for reasons of mechanical simplicity, the direct system of control has been adopted, and it would appear that for this reason the claims of the re action system have been largely overlooked. It may be admitted that when once a beginner has practised and learnt the movements, he can, without thought, operate the control handles by the direct method without difficulty, so that it becomes perfectly natural for him. to move these handles in the direction in which he desires the machine to go. The same can undoubtedly be said for the reaction method, for in that case the operator has only to think of the direction in which he himself wishes to go, and to push himself into the desired position by pushing or pulling at the handles, which are thus moved in an opposite direction. That this is the case is proved by the fact that there is no difficulty in learning to steer a boat by means of a tiller or to maintain the balance of a canoe by means of a paddle, this latter being an excellent instance of control by steering and balance by the reaction method. It may be admitted, therefore, that so far as normal operation is concerned, there is probably nothing to choose between the method of direct action and the method of reaction. But, ultimate safety in flight depends not on what the operator does normally, but what he will do instinctively under abnormal conditions, such as when his balance is upset by a sudden gust of wind, an " air-hole," or the draught from another machine. In such cases, a point is easily reached in which the operator can no longer maintain his balance indepen dently of the machine, and it is then that the method of direct action seems to fail. Direct action control essentially presupposes that the operator himself always represents a fixed point, from which the machine may be controlled by moving the various handles in the direction required, hence the system must fail if the operator loses his balance and ceases to be fixed in space. It also presupposes that the operator never loses his head, for in that case general experience shows that the operator makes an instinctive effort to redress his balance by endeavouring to pull or push himself upright by means of whatever handles or supports are available. Just as a man in a canoe, feeling himself falling over to the left, would instinctively press his paddle down on the water on the left, so a man in an aeroplane, feeling himself in danger of falling to the left, will press down on the left or endeavour to pull himself up to the right. It has, for example, been observed by the pilot of a Bleriot monoplane, that if the engine stops in mid-air, his instinctive action has been to pull the control-handle towards himself, the unconscious underlying idea being doubtless to pull himself and the machine forwards. As matters are at present arranged, the Bleriot elevating mechanism is operated by direct control, and the instinctive movement results in elevating the head (or rather depressing the tail) of the machine, which is the reverse of the action desired. If the reaction method were adopted for the elevator control, the instinctive action would depress the head and elevate the tail of the machine, and cause it to glide down safely. Instinctive action is, indeed, the whole cause of the initial difficulty to ride a bicycle, for when the rider begins to fall over to the right he instinctively tries to readjust his own balance by pulling on the left handle of the machine. Unfortunately for him, the control of bicycle balance is by the method of direct action, and not that of reaction, and the instinctive movement only accentuates the evil. The risk of learning on a bicycle is very small, while that of learning on an aeroplane is very great; so that, for flying, the advantage of automatic action associated with the indirect system of control is worth obtaining, especially when it is remembered that this advantage is again apparent in the last resort, when the operator has lost his balance and returns once more to the condition of a drowning man clutching at a straw. In this latter case every instinctive effort made by the operator to readjust his own balance, by pressing or pulling at the available supports, automatically tends to readjust the balance of the machine; whereas, if the method of control is direct, these instinctive actions accentuate the loss of balance. It is most desirable that an experiment should be made as to the practical effect of linking up the various controlling-handles so that each of these controls is operated on the reaction system, for it seems highly probable that the system will be easier to learn initially, as easy to operate normally, and much safer in an emergency, than the system of direct control. 682
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