Dick Hamilton's Airship Part 10

The captain and Lieutenant Larson took their places, one on either side of d.i.c.k. Some of the orderlies at the Academy had been detailed to a.s.sist in the start, holding back on the biplane until the engine had attained the necessary speed.

There was an arrangement whereby the machine could be held in leash, as it were, by a rope, and when the necessary pressure developed from the propeller blades, the rope could be loosed from the aviator's seat.

But that attachment was not in use at Kentfield then.

The powerful motor hummed and throbbed, for a m.u.f.fler was temporarily dispensed with on account of its weight. Every unnecessary ounce counts on an airship, as it is needful to carry as much oil and gasolene as possible, and the weight given over to a m.u.f.fler could be more advantageously applied to gasolene, on the smaller craft.

Faster and faster whirled the big blades, cutting through the air. The captain kept his eyes on a balance scale, by which was registered the pull of the propellers.

"That's enough!" he cried. "Let her go!"

d.i.c.k felt the machine move slowly forward on the rubber tired bicycle wheels over the gra.s.sy starting ground, gradually acquiring speed before it would mount upward into the air.

Perhaps a word of explanation about airships may not be out of place.

Those of you who know the principle on which they work, or who have seen them, may skip this part if you wish.

The main difference between a balloon and an aeroplane, is that the balloon is lighter than air, being filled with a very light gas, which causes it to rise.

An aeroplane is heavier than air, and, in order to keep suspended, must be constantly in motion. The moment it stops moving forward it begins to fall downward.

There are several kinds of airships, but the principle ones are monoplanes and biplanes. Mono means one, and monoplane has but one set of "wings," being built much after the fashion of a bird.

A biplane, as the name indicates, consists of two sets of planes, one above the other. There are some triplanes, but they have not been very successful, and there are some freak aeroplanes built with as many as eight sets.

If you will scale a sheet of tin, or a thin, flat stone, or even a slate from a roof, into the air, you will have the simplest form of an aeroplane. The stone, or tin, is heavier than the amount of air it displaces, but it stays up for a comparatively long time because it is in motion. The moment the impulse you have given it by throwing fails, then it begins to fall.

The engine, or motor, aboard an aeroplane keeps it constantly in motion, and it glides along through the air, resting on the atmosphere, by means of the planes or wings.

If you will take a clam sh.e.l.l, and, holding it with the concave side toward the ground, scale it into the air, you will see it gradually mount upward. If you hold the convex side toward the ground and throw it, you will see the clam sh.e.l.l curve downward.

That is the principle on which airships mount upward and descend while in motion. In a biplane there is either a forward or rear deflecting rudder, as well as one for steering from side to side. The latter works an the same principle as does the rudder of a boat in the water. If this rudder is bent to the right, the craft goes to the right, because of the pressure of air or water on the rudder twisted in that direction. And if the rudder is deflected to the left, the head of the craft takes that direction.

Just as the curve of a clam sh.e.l.l helps it to mount upward, so the curve of the elevating or depressing rudder on an airship helps it to go up or down. If the rudder is inclined upward the aeroplane shoots toward the clouds. When the rudder is parallel to the plane of the earth's surface, the airship flies in a straight line. When the rudder is tilted downward, down goes the craft.

I hope I have not wearied you with this description, but it was, perhaps, needful, to enable those who have never seen an aeroplane to understand the working principle. One point more. A gasolene motor, very powerful, is used to whirl the wooden propeller blades that shove the airship through the air, as the propeller of a motor-boat shoves that craft through the water.

Faster and faster across the gra.s.sy ground went the biplane containing d.i.c.k Hamilton and the army officers. It was necessary to get this "running start" to acquire enough momentum so that the craft would rise, just as a heavy bird has sometimes to run along the ground a few steps before its wings will take it up.

"Here we go!" suddenly exclaimed the captain, and as he raised the elevating rudder the big craft slowly mounted on a slant.

d.i.c.k caught his breath sharply as he felt himself leaving the earth. He had once gone up in a captive balloon at a fair, but then the earth seemed sinking away beneath him. This time it seemed that he was leaving the earth behind.

Higher and higher they went, and d.i.c.k could feel the strong wind in his face. His eyes were protected by goggles, made of celluloid to avoid accidents from broken gla.s.s in case of a fall, and on his head he wore a heavy leather helmet, not unlike those used by football players. He was strapped to his seat, as were the others, in case the machine should turn turtle. The straps would then prevent them from falling out, and give them a chance to right the craft.

For this can be done, and now some aviators practice plying upside down to get used to doing it in case they have to by some accidental shift of the wind. Some of them can turn complete somersaults, though this is mostly done in monoplanes, and seldom in a biplane, which is much more stable in the air.

"Feel all right?" asked Captain Grantly of d.i.c.k. He asked this, but d.i.c.k could not hear a word, on account of the great noise of the motor.

But he could read the officer's lip motions.

"Yes, I'm all right," the young millionaire nodded back.

He was surprised to find, that, after that first sinking sensation at the pit of his stomach, he was not afraid. He now felt a glorious sense of elation and delight.

He was actually flying, or the next thing to it.

"We'll go a little higher," said the captain, as he elevated the rudder a little more. The aeroplane kept on ascending. d.i.c.k looked down. He did not feel dizzy as he had half expected. Far below him were the buildings of Kentfield, and the green parade ground. But what were those things like little ants, crawling over the campus?

Why the cadets, of course! They looked like flies, or specks. d.i.c.k was ready to laugh.

On a level keel they now darted ahead at greater speed as Lieutenant Larson turned on more gasolene. Then, when d.i.c.k had become a little used to the novel sensation, they showed him how to work the different levers. The motor was controlled by spark and gasolene exactly as is an automobile. But there was no water radiator, the engine being an up-to-date rotating one, and cooling in the air. The use of the wing-warping devices, by which the alerons, or wing-tips are "warped"

to allow for "banking" in going around a curve, were also explained to d.i.c.k by means of the levers controlling them.

You know that a horse, a bicyclist, or a runner leans in toward the centre of the circle in making a curve. This is called "banking" and is done to prevent the centrifugal force of motion from taking one off in a straight line. The same thing must be done in an airship. That is, it must be inclined at an angle in making a curve.

And this is accomplished by means of bending down the tips of the planes, pulling them to the desired position by means of long wires. It can also he accomplished by small auxiliary planes, called alerons, placed between the two larger, or main, planes. There is an aleron at the end of each main wing.

Straight ahead flew the army men and d.i.c.k, and then, when the cadet was more used to it, they went around on a sharp curve. It made the young millionaire catch his breath, at first, for the airship seemed to tilt at a dangerous angle. But it was soon righted and straightened out again.

Suddenly a shadow seemed to pa.s.s over d.i.c.k's head. He looked up, thinking it was a dark cloud, low down, but, to his surprise, it was the other army craft flying above them.

"A race!" thought d.i.c.k, and he wondered how his chum Paul was faring.

There was an impromptu race between the two aircraft, and then they separated, neither one gaining much advantage. Back and forth they went, over the school grounds, and then in circles. d.i.c.k was rapidly acquiring knowledge of how to operate the big biplane.

"We'll go down now!" spoke the captain, though d.i.c.k could not hear the words. The young millionaire made up his mind that he would have a m.u.f.fler on his airship, and also more room to move about. He intended to make rather a long flight.

The deflecting rudder was tilted downward, and the descent began. They were some distance out from the Kentfield grounds now, but were headed for them on a long slant. d.i.c.k wondered if they would reach them.

At a nod from the captain, Lieutenant Larson reached up and shut off the motor. The sudden silence was startling.

d.i.c.k understood what was to be done. They were to glide, or as it is called "volplane" (p.r.o.nounced vol-pla-nay, with the accent on the last syllable) to the ground.

"I hope we make it safely," mused d.i.c.k. But it did not look as though they had been near enough the landing place when the motor was cut off.

d.i.c.k saw the two army men glance rather apprehensively at one another.

Was something wrong?

d.i.c.k was sure of it a moment later when, as Captain Grantly pulled the lever of the deflecting rudder toward him, there was a snapping, breaking sound.

"Lost control!" cried the captain. "Wire snapped! Look out, everybody!"

d.i.c.k wanted to jump, but he knew that would be rash, as they were still some distance above the ground.

"Can't you guide her?" asked Larson.

"No! We've got to land the best we can!" was the answer.

They were right over a little farm now, and seemed to be headed directly for a small, low building.

"Something is going to smash!" thought d.i.c.k grimly.