GRAHAME-WHITE SCHOOL BIPLANE (TYPE XV.)
Photo by Topical Press Agency.
A.—The front elevating plane, which acts in conjunction with the rear-plane marked A1; B.—The landing-chassis; C.C.—The main-planes; D.D.—The ailerons; E.E.—The rudders; F.—Engine (a 60-h.p. Le Rhone) and propeller.
A reverse movement of the elevator reduces the lift of the main-planes; hence, when an aviator wishes to descend, he tilts down his elevator, bringing his machine at such an angle that it is inclined towards the ground. Then, switching off his engine so as to moderate the speed of his descent, and by such manipulations as may be necessary of his elevator, he pilots his craft to earth in a vol-plané, during which gravity takes the place of his motor, and he is able—by steadying his machine and bringing it into a horizontal position just at the right moment—to make a gentle contact with the ground.
A pilot must be able to do more than cause his aeroplane to ascend and to alight: he must have means to check the lateral movements which, under the influence of wind gusts, may develop while the biplane is in flight. At the rear extremities of the main-planes as illustrated in the photograph [facing page 34]—and marked D.D.—are flaps, or ailerons, which are hinged so that they may be either raised or lowered. These ailerons are operated, through the medium of wires, by the same hand-lever which governs the movement of the elevator. This lever is mounted on a universal joint, and can be moved from side to side as well as to and fro. Should the biplane tilt, while flying, say towards the left, the pilot moves his hand-lever sideways towards the right. This is a natural movement, the instinct being to move the lever away from the direction in which the machine is heeling. This movement of the lever has the effect of drawing down the ailerons on the left-hand side of the machine; on the side, that is to say, which is tilted down; and the depression of these auxiliary surfaces, increasing suddenly as they do the lifting influence of the main-planes to which they are attached, tend to thrust up the down-tilted wings, and so restore the equilibrium of the machine.
In the operation of his ailerons, combined with the use of his elevator, a pilot is given means to balance his craft while in flight. One should not gain the impression that an aeroplane is threatening ceaselessly to heel this way and that. This is not so. The machine has a large measure of stability, apart from any manipulation of its controls, and needs balancing only when some disturbance of the atmosphere affects its equilibrium. Under favourable conditions, such as a pupil will experience in his first flights, nothing more is necessary with the hand-lever than a very slight but fairly constant action; a similar motion, in a way, as is made by the driver of a motor-car when he maintains, by his "feel" on the wheel, his sense of control over the machine. In the controlling actions of an aeroplane—and this is a fact which tends sometimes to the confusion of the novice—nothing more is required, normally, than the most delicate of movements. The difference say between ascending, and skimming along the ground, is represented by a movement of the hand-lever of only a few inches. Delicate, sure, quick, and firm; such is the touch needed with an aeroplane.
With the one hand-lever, as we have shown, it is possible for a pilot to control the rise and descent, and also the lateral movements of his machine; and there remains only the steering to be effected—the movement from side to side, from right to left, or vice-versa. At the rear of the biplane, as shown, [facing page 34] will be seen two vertical planes, E.E. These, being hinged, will swing from side to side; and they exercise a sufficient influence, when working in the strong current of air that blows upon them when a machine is in flight, to steer it accurately in any direction. The pilot, to operate this rudder, rests his feet on a conveniently-placed bar, which is mounted on a central swivel, and allows the bar to be swung by a pressure of either foot. When the pilot needs to make a turn say to the left, as he is flying, he presses his left foot forward. This swings the bar in same direction; and, by a simple connection of wires running to the tail of the machine, the rudders are made to swing over to the left also, and the machine turns in response to them. A similar movement to the right produces a right-hand turn. This foot rudder bar, being numbered 2, is shown in the picture [facing page 36].
THE CONTROLS OF A SCHOOL BIPLANE.
Photo by Topical Press Agency.
1.—The upright lever which, working on a universal joint, operates the elevator and ailerons; 2.—The bar, actuated by the pilot's feet, which operates the rudders of the machine; 3.—The pilot's seat; 4.—The passenger's seat.