William D. Ennis

“ The flying machine is no longer the delusion of the “crank,” because it has developed a great industry. A now antiquated statement put the capitalization of aeroplane manufactories in France at a million dollars, and the development expenditure to date at six millions. There are dozens of builders, in New York City alone, of monoplanes, biplanes, gliders, and models. A permanent exhibition of air craft is just being inaugurated. We have now even an aeronautic “trust,” since the million-dollar capitalization of the Maxim, Blériot, Grahame-White firm. ”

“ Let armed international strife be viewed as it really is—senseless as the now dying duello. Let the navy that represents the wealth, the best engineering, the highest courage and skill, of our age, be powerless at the attack of a swarm of trifling gnats like Gulliver bound by Lilliputians—what happens then? It is a reductio ad absurdum. Destructive war becomes so superlatively destructive as to destroy itself. ”

“ A drifting balloon is like a becalmed ship or a dead fish. It moves at the speed of the aerial fluid about it and the occupants perceive no movement whatever. The earth’s surface below appears to move in the opposite direction to that in which the wind carries the balloon. With a dirigible balloon or flying machine, the sensation is that of being exposed to a violent wind, against which (by observation of landmarks) we find that we progress. ”

“ A vessel in the air may be at any elevation in the surrounding rarefied fluid, and great attention is necessary to keep it at the elevation desired. The air has no surface. The air ship is like a submarine—the dirigible balloon of the sea—and perhaps rather more safe. An ordinary ship is only partially immersed; the resistance of the fluid medium is exerted over a portion only of its head end: but the submarine or the flying machine is wholly exposed to this resistance. The submarine is subjected to ocean currents of a very few miles per hour, at most ”

“ If aviation is to become a popular sport, the latter ideal must prevail. The machines must be more automatic and the aviator must have time to enjoy the scenery. In France, where amateur aviation is of some importance, progress has already been made in this direction. The universal steering head, for example, which not only revolves like that of an automobile, but is hinged to permit of additional movements, provides for simultaneous control of the steering rudder and the main plane warping, while scarcely demanding the conscious thought of the operator. ”

“ What happens when the motor stops? The velocity of the machine gradually decreases: the resistance to forward movement stops its forward movement and the excess of weight over upward pressure due to velocity causes it to descend. It behaves like a projectile, but the details of behavior are seriously complicated by the variation in head resistance and sustaining force due to changes in the angle of the planes. The “angle of inclination” is now not the angle made by the planes with the horizontal, but the angle which they make with the path of flight. ”

“ The aeroplane soldier takes tremendous risks; but perhaps not greater risks than those taken by the crew of a submarine. There is never any lack of daring men when daring is the thing needed.
All experience goes to show that an object in the air is hard to hit. The flying machine is safer from attack where it works than it is on the ground. The aim necessary to impart a crippling blow to an aeroplane must be one of unprecedented accuracy. The dirigible balloon gives a larger mark, but could not be immediately crippled by almost any projectile. ”

“ We are very sure to be informed of the fact when an aviator is killed. Comparatively little stir is made nowadays over an automobile fatality, and the ordinary railroad accident receives bare mention. For instruction and warning, accidents to air craft cannot be given too much publicity; but if we wish any accurate conception of the danger we must pay regard to factors of proportion. There are perhaps a thousand aeroplanes and about sixty dirigible balloons in the world. About 500 men—amateurs and professionals—are continuously engaged in aviation. ”

“ A slight downward direction of this stroke serves to impel the flight sufficiently upward to offset the effect of gravity. Any man can learn to swim, but no man can fly, because neither in his muscular frame nor by any device which he can attach thereto can he exert a sufficient pressure to overcome his own weight against as imponderable a fluid as air. If air were as heavy as water, instead of 700 times lighter, it would be as easy to fly as to swim. The bird can fly because of the great surface, powerful construction, and rapid movement of its wings, in proportion to the weight of its body. ”

“ With the aeroplane, higher speed means less sail area for a given weight and a stronger machine. Much higher speeds are probable. We have already a safe margin as to weight per horse-power of motor, and many aeroplane motors are for stanchness purposely made heavier than they absolutely need to be.
The Cost of Speed
Since the whole resistance, in either type of flying machine, is approximately proportional to the square of the velocity; and since horse-power (work) is the product of resistance and velocity, the horse-power of an air craft of any sort varies about as the cube of the speed. ”

“ If there is no string, and the wind blows the kite with it, the kite comes down, because the pressure is wholly due to a relative velocity as between kite and wind. The wind exerts a pressure against the rear of a railway train, if it happens to be blowing in that direction, and if we stood on the rear platform of a stationary train we should feel that pressure: but if the train is started up and caused to move at the same speed as the wind there would be no pressure whatever. ”

“ Even on a mountain top, the direction and speed of the wind are less steady than in the open where measured by a captive balloon. The stronger the wind, the greater, relatively, is the irregularity produced by surface conditions. Further, the earth’s surface and its features form a vast sponge for sun heat, which they transfer in turn to the air in an irregular way, producing those convectional currents peculiar to low altitudes, the upper limit of which is marked by the elevation of the cumulus clouds. ”

“ Travel in an aeroplane is like skating rapidly over very thin ice: the air literally “doesn’t have time to get away from underneath.”
Direct, Lifting, and Resisting Forces If the pressure is 10 lbs. when the wind blows directly toward the surface (at an angle of 90 degrees) , then the forces for other angles of direction are as shown on the diagram. The amounts of all forces depend upon the wind velocity: that assumed in drawing the diagram was about 55 miles per hour. But the relations of the forces are the same for the various angles, no matter what the velocity. ”

“ It is true that the resistance to propulsion decreases at high altitudes, just as the supporting power decreases: and on this account, given only a sufficient [Pg 7] margin of supporting power, we might expect a standard machine to work about as well at a two-mile elevation as at a height of 200 feet; but rarefaction of the air at the higher altitudes decreases the weight of carbureted mixture drawn into the motor, and consequently its output. Any air-man who attempts to reach great heights in a machine not built for such purpose is courting disaster. ”

“ Broadly speaking, designers may be classed in one of two groups—those who, like the Wrights, believe in training the aviator so as to qualify him to properly handle his complicated machine; and those who aim to simplify the whole question of control so that to acquire the necessary ability will not be impossible for the average man. ”