Opportunities in Aviation

by Arthur Sweetser; Gordon Lamont

There must be a large field, broad in every dimension, to permit the landing and taking-off of airplanes. A machine must get up flying speed running across the ground before it gets into the air. The flying speed varies with the type of machine, and it may be estimated that most machines take-off and land at a speed of from forty-five to sixty miles an hour. The air must be passing through their planes at this speed before they will begin to fly, and it takes a little run to get up flying speed. Similarly, when an airplane lands, it must lose its flying speed gradually. It may glide to within a few feet of the ground, and then "flatten out" just off the ground and run along until it loses its speed, the air no longer passes over its planes fast enough to support it, and it drops to the ground.

Such are the limitations which the necessity for speed in airplane flight imposes. Compare the paper dart flying through the air. As long as it moves quickly it will fly. Or a kite, that will fly when the wind is strong enough. The airplane creates its own wind to support itself.

There are four forces acting on an airplane in flight, and they must be properly overcome and balanced. There is lift, the upward force exerted on the planes by the passage of air over their surfaces; and drift, the resistance to the passing of an airplane, the retarding force acting opposite to the direction of motion. Then thrust, the forward effort of a machine exerted by a propeller pushing or pulling. And finally gravity.

The primary conditions of flight are that lift made by the planes shall be equal to the force of gravity, and that the forward thrust must be equal to the drift. At that point a machine will sustain flight—a fairly simple thing on paper. But the times that machines have stalled in the air, with their motors full on because their pilots have failed to sustain flight, have let the force of gravity overcome lift, are too numerous to mention.

That dart, if pointed at a proper angle and let loose, will fly; its lift will overcome the force of gravity, even though it has no motive power of its own. An airplane without an engine could be pushed off the Palisades at flying speed, and a skilful pilot could bring it to a reasonably safe landing at the foot. Flight does depend on motion, but motion does not depend on motive power. Given a sufficiently high altitude, the mere act of dropping through the air creates motion, and this motion will sustain flight.

An airplane is in no particular danger in the air if the motor stops—provided it is in an open stretch of country with plenty of fields. Instinctively the pilot will nose down and glide, and on that glide he will find himself maintaining flying speed. He can turn and maneuver his machine, and pick out almost any field near at hand. The only limitations are that he cannot glide more than five times his height, and when he comes down to the ground he must stop gliding and land. He must land on anything that presents itself, a field if he has good judgment; if not, then a barn or swamp or woods. He must land when the end of his glide brings him to the ground.

This is commonly termed a "forced landing," and in every sense of the word it is one. There is no pilot of any extensive flying experience who has not had to make a forced landing. Ninety out of a hundred are perfectly orderly safe landings; the odd ones are occasionally crashes. Incidentally it may be said that forced-landing practice by flying pupils is the most beneficial which may be imagined. It teaches control over a machine as nothing else will. It may be carried out from any height, shutting off the motor, picking out a field, gliding for it, turning and twisting to get into proper position as regards the wind, and "giving her the gun" just at the fence and flying on.

A forced landing over the country is safe, but over a city it is the most deadly thing imaginable. For a machine caught with a "dud" engine over New York there is no escape but a terrific crash in the city streets, against the side of some building, with danger to the pilot and the people in the street below. There has been no motor made by the hand of man which would not let a pilot down at some unexpected time. The instance of Major Woods, starting on his flight across the Atlantic, and forced to come down to the Irish Sea is one example. The NC-4, American naval seaplane, had a forced landing at sea, a hundred miles from Chatham, Massachusetts, on the first leg of the Atlantic flight from this side. Its engines had been carefully cleaned and tested, and yet they failed. Harry G. Hawker's engine failed him half-way from Newfoundland to Ireland and let him down into the sea, from which he was picked up by the greatest good luck.

That is one of the most exasperating and human things about a gasolene-engine. It is efficient, but not thoroughly dependable. The best of them are liable to break down at the most needed moment, due to a hundred causes outside of the control of a mechanic or pilot. Care and rigid inspection will reduce the possibilities, but engine failure cannot yet be eliminated.

That is one of the principal reasons why the roofs of buildings around big cities are so dangerous. The sides of a building drop away from the roof. An error in judgment and the machine is over the edge.