While the “joy-stick” type of control is greatly in favour, there are various forms of wheel control in use. American machines are almost entirely fitted with wheel controls, and all things considered, it appears that modern practice is evenly divided between the two types. The sequence of movements of the wheel type may be varied in a number of ways, the general arrangement shown by [Fig. 101] being typical of an average system. In this case the hand-wheel is mounted on a central column, which in turn is rigidly fixed by some form of Tee joint to a transverse rocking shaft. A sprocket attached to the wheel centre engages with a short length of chain, which connects to the aileron control, while the elevator wires are connected to short tillers, arranged to work on the outer side of the fuselage. With this system the hand-wheel is rotated for the aileron movements, a fore-and-aft rocking motion for the elevation, and the rudder is actuated by an outward movement, with either foot on the rudder bar. A development designated “three in one” embodies all these movements in the wheel column, which in this case is pivoted at its base: a to-and-fro motion in the column for the elevators, sideways for the ailerons, while the rudder control is effected by the rotation of the wheel. This system is fitted to a number of American machines, but it is a moot point whether the rotation of the wheel for warping or steering is quite such an instinctive action, as the sideways movement of the lever combined with the movements of the foot on the rudder-bar; in any case, there is just a suspicion of complication in its working which is undesirable, that is, for machines intended for popular use.
The “Dep” Control.
Fig. 102.—“Dep” type control.
The type of control used on the Deperdussin monoplanes of 1910 and onwards has survived until the present day, and forms a distinctive arrangement. Its chief attribute is that, compared with other systems, much greater room and freedom is afforded the pilot, which is evident by a consideration of the diagrammatic sketch, [Fig. 102]. The inverted U-shaped lever is composed of either ash, bent to shape, or steel, or duralumin tube, the general system of its working being the same as the wheel control shown by [Fig. 101]. Incidentally, passing reference may be made to the fact that the usual close proximity of the compass to the controls precludes the use of steel in any great quantity for the construction of the lever, as the various movements adversely affect the compass readings.
The Wright System.
Another variant of the wheel control is instanced by the Wright system, this consisting of a general lay out similar to that shown by [Fig. 101], but no rudder-bar is fitted. The rudder control is provided by a small lever, mounted concentric with the wheel, the latter carrying a rigidly attached sprocket. The hand-lever is also connected to a sprocket, this running free on the wheel shaft, so that by gripping both hand-lever and wheel it is possible to operate the ailerons and rudder simultaneously, this action being a characteristic feature of all the Wright productions. Although there are many types of control in use, those described in the foregoing chapter are illustrative of general practice.
CHAPTER XIII.
WIRES AND CONNECTIONS.
In all aeroplanes the question of wires and the terminal connections associated therewith is a matter of some importance, and while this may vary in degree, there is little doubt that the efficiency of modern wiring systems is largely responsible for the structural efficiency of the aeroplane as a whole.
Aeroplane construction consists almost exclusively of a framework of wood braced by wires, a condition of things which has obtained since the inception of flight; as may be judged by the various engravings of Henson’s projected monoplane of 1842. This machine incorporated an arrangement of king-posts and wires approximating very closely to modern practice, and the natural sequence of improvements have tended towards the gradual elimination of exposed wiring.