But there is another force the airman can use, even when his motor fails entirely; and this is the downward pull of gravity, which acts unceasingly upon his machine. He must, at all costs, restore the speed of his craft; not only that its main-wings may bear their weight, but that its controlling-planes may continue operative, and enable him to steer towards a landing-point. What he does, therefore, when he hears his motor stop, is to tilt his elevating lever and send his machine upon a dive. Thus, even with no motor to propel him, he can still fly. It is gravity now that moves his machine, and so long as he keeps his lever forward, and sends his craft downward upon a gradually sloping path, he has perfect control and need not fear a fall. Air is still being forced under his planes; therefore, they bear their load; and, seeing that the machine is moving forward, its rudder and other controlling planes are able to do their work. The airman is, in fact, as much in command of his machine as he was before its motor stopped--save for one vital difference. While his motor ran he could fly where he pleased; but now he is obliged to glide downward. He is, indeed, in the same position as was Lilienthal, or any of the men who soared from hilltops. But, being say 1000 feet or more high when his engine stops, he has the advantage of a long glide before he reaches ground; and this gives him a chance, surveying the land below him, to pick a smooth landing-point that may lie in his path. If well-designed, an aeroplane will glide a long way after its motor has failed, as is indicated by Fig. 54. In this case, representing an actual test with a military machine, the motor has stopped at an altitude of between 1200 and 1400 feet, and the craft glides, before touching ground, a distance of nearly 9000 feet. [Illustration: FIG. 54.--The gliding angle of a plane. The motor is switched off at a height of between 1200 and 1400 feet, and the craft glides nearly 9000 feet before landing.] This gliding without motive power is a safeguard to the airman when he flies across country. Should he attain a sufficient altitude, he has little to fear, even if his engine does fail. As he glides down, he can steer from side to side, or make a half circle and land upon a spot that lies behind him. An aeroplane with a gliding path of 1 foot in 10, and at a height of a mile when its engine stopped, would glide ten miles before alighting. Taking an extreme case, one might imagine an airman flying over a city. Suddenly, while above a network of streets and houses, his engine stops. But even in such a quandary as this, granted he has the wisdom to be several thousand feet high, he need not fear disaster. Glancing keenly below him, he sights some park or open space like an oasis among the close-packed buildings, and glides swiftly and accurately towards it, landing without difficulty or injury to his machine.