CHAPTER IX
A CHAPTER OF LESSONS ABOUT THE AEROPLANE
Early the following morning there was intense activity in the camp, and Ralph was among the first to learn the cause of the excitement. Several army divisions had come up in the night, and were bound for the Verdun sector, and from the information obtained it was the intention of the commander to make a terrific assault in order to break the German lines north of the city.
The lieutenant, when approached, admitted that they were now in for double duty. "Every man in the corps must report and be ready in the morning. There will be two days of observation, and then look out for some business."
"When will we go to Verdun?" asked Ralph.
"We are expecting orders at any moment," was the reply.
During the previous afternoon more than fifty machines had assembled, and some of those were now leaving, a few going directly east, on observation tours, while others were circling about and testing the engines.
"I am expecting a big Farman machine," said Lieutenant Guyon, as he returned from headquarters an hour afterwards, "that is equipped for carrying bombs, but I am told it is one of the speediest machines in the service. It will easily carry six hundred kilos in bombs (1,200 pounds), and we are ordered to wait here until it arrives."
When the boys were alone, Alfred, with a glint of joy in his eyes, remarked: "I think that will give us an opportunity to do some flying with the lieutenant."
"Do you think so?" replied Ralph, elated at the thought.
"I am sure of that," said a voice behind them.
They quickly turned and saw the lieutenant, who had entered unobserved. They saw by the smile on his face that the remark was an agreeable one, for he continued:
"Yes, and the machine is now here; the men are at work setting it up; so we might as well go over and help out."
A second invitation was not necessary. Ralph, who was outside in one bound, rushed across the field, but Alfred accompanied the lieutenant to the commandant's office, where they were provided with the receipt for the machine. The lieutenant remained here while Alfred carried the document to the warehouse. Within two hours the machine was in condition to receive the fuel and the supplies usually carried in the machines for emergencies.
When the lieutenant returned he made a careful inspection, and on this occasion the boys followed every movement of his to learn what were the essential requirements in inspecting. Naturally, the most important thing was to know that every part of the frame is not only properly set up and the wires made taut, but that the fastenings, the turnbuckles, are in good condition. That necessitated a minute examination of every one of them.
Then the planes were sighted to ascertain whether they were properly aligned. Sometimes when the planes are not exactly parallel with each other, the end of one, for instance, being set a little higher or lower than the other, it is usually corrected by letting out one or more sets of brace wires and taking up on others. This observation was followed by a careful look at the control planes. These are the sensitive parts of the plane, and may be likened to feelers, for the slightest warping of the horizontal tail planes will frequently cause the machine to fly with a skidding motion, not dangerous, but exceedingly uncomfortable when flying at a high rate of speed.
"The wires leading to the control levers are always a source of worry to me," remarked the lieutenant, and he drew himself up into the rear part of the chassis. "You will notice that this one rubs along the side of that brace. I could not permit that," he said, as he glanced toward one of the workers.
"Do you think it would weaken the brace?" asked Ralph.
"No, it's not that," replied the lieutenant. "The difficulty is that all these wires are stranded, and as soon as one of the wires wears out by the frictional contact, another will give way, and the control wire is liable to part at the most critical time."
The boys had occasion to remember the lieutenant's warning shortly thereafter. After an examination of the airplane structure an investigation was made of the engine. The mechanic turned it over to be sure that the compression was all right. Self-starters are provided on all these machines, as the French learned at an early day that it would be unwise to depend on cranking.
Then a thorough inspection of the pipes and tubing for the fuel and lubrication was made. The dashboard of an aeroplane is a much more wonderful contrivance than the dashboard of an automobile. The aviator must look out for several things not necessary when traveling on land.
The machine which they were examining had on it the most improved contrivances, which had been found desirable, some of which were entirely new to the boys, one of them being the inclinometer.
"That must be a dandy thing," said Alfred, pointing to it.
"I think there are only a few of the military machines which are supplied with them, but the order has been given to put them on all the new machines," said the lieutenant.
"What are the two rods for?" asked Ralph, as he looked at the inclinometer.
"The two rods which swing past the vertical bar, on which you see the numbers, indicate the angle at which the machine is going. All that is necessary is to observe the crossing point of the rod over the marked bar, and it will instantly tell what the angle of ascent or descent is. You see an aviator now has so many things to think of that he must have devices of various kinds which will constantly tell him anything or any condition without asking for it."
"Why, this also tells how fast the engine turns," remarked Alfred.
"Of what use is that?" asked Ralph.
"Well; if you knew that the engine was capable, under full throttle, to make eighteen hundred revolutions a minute, and the dial showed that the shaft was turning only one thousand, you would quickly get the idea that something was wrong," answered the lieutenant.
"Oh, yes; and then you would start to make an investigation at once without waiting for the engine to stop," said Alfred.
"Exactly; it is there as a warning, just as a headache is a warning that something is wrong, or a pain, which is nature's way to indicate that an investigation should be made without delay," answered the lieutenant with a nod.
Besides the foregoing, the dash had on it a watch. Now, a watch may be a convenient thing to have on an automobile, but it is not a necessity. On a scouting and observation plane it is one of the necessary implements. Alfred laughed, as he looked at the neat little clock face.
"I suppose," he said, "we could get along without that."
"Of course we could," answered the lieutenant. "But why get along without it when we now find it such a necessary element?"
"Necessary how?" asked Ralph, in surprise.
"In determining distances, for one thing," answered the lieutenant.
"A watch to tell the distance?" asked Alfred incredulously.
"Yes, indeed," responded the lieutenant. "If you saw a puff of smoke in the distance, and shortly thereafter heard a boom, the distance could be determined almost instantaneously by roughly calculating 1,200 feet for every second. You see, the clock there has a second hand, which is very plain, for that very purpose."
"But suppose there is a regular battle on, it would be hard to tell about the boom from any particular gun, wouldn't it?" asked Ralph.
"Quite true; in such a case it would be useless for that purpose. Another use is in signaling," continued the lieutenant. "For instance, in sending information to a battery, arrangement is sometimes made to flash the distance by means of second intervals."
"How is that done?" asked Alfred, now growing intensely interested in the details of the dashboard mechanism.
"It is an easy matter to signal numbers," answered the lieutenant and a favorite plan is to fly over the area where the enemy's battery is located, then flash at that altitude. The gunner will take the angle, set his piece and fire, the aviator, meanwhile, noting the course and effect of the shot. By means of the watch he can determine the distance, counting either by the time of flight of the missile, or by the elapsed time between the flash of the gun and the landing of the shot.
The altimeter is another very important part of the equipment. It is a device which tells at a glance how high the machine is flying, and Ralph looked at it with a somewhat doubtful expression. The lieutenant saw the questioning lines on his face, and instantly divined the reason.
"You are in doubt whether the altimeter can be relied on? Am I correct?" he asked.
"Well, I suppose it is all right, but almost every time we have been up and took the readings, we found we were actually hundreds of feet less than the altimeter actually showed, so I am wondering if it is possible really to tell the exact height by that apparatus," remarked Alfred.
"Yes, I understand what you mean," replied the lieutenant. "The other day, when we made the long flight from Bar-le-Duc, the device we had showed 900 meters, for it was an automatically registering barometer, as all of them practically are. When we returned I noted on the report book 872 meters. Did you notice that?"
"Yes, and I wondered at it at the time," said Alfred.
"I knew that the general altitude of the country at that place, as indicated by the topographical charts, was 28 meters above sea level so I merely subtracted 28 from 900, and that showed how far up above the land we really were," said the lieutenant.
"Of course, it's a satisfaction to know how high one is flying," said Ralph.
"It is not only a satisfaction, but it is an absolute necessity for an aviator to know how high he is flying, if his mission is to convey any information to the batteries in the rear," said the lieutenant.
"And how is that done?" asked Alfred.
"By a system of triangulation," he replied. "In a few days we may have an opportunity to use the system, and I will explain it then so you can quickly grasp the subject."
The air speed indicator was another interesting device, but at that the lieutenant shook his head as though doubting its general value.
"Don't you think it's accurate?" inquired Alfred of the officer.
"Oh, yes; it is as accurate as it can be made. In fact all devices, which are used to indicate the speed of the wind, are nearly perfect. That is not the difficulty. When it is used on a flying machine several new things enter into the problem, which makes it difficult for the instrument to be truthful."
"What is the main trouble?" asked Alfred.
"Well, suppose we are starting a flight against a wind, which is moving at the rate of, say, ten miles an hour," answered the lieutenant. "While in flight we note that, going against the wind, the air speed is sixty miles. Now, if we happened to stop suddenly so we were poised in the air, the indicator would show the air speed to be ten miles, so that we were really going only fifty miles. If, now, the machine is turned so that we are going at right angles to the movement of the wind, although we may be going actually through the air at a speed of seventy miles an hour, the indicator does not register the air speed at all, because it is in such a position that the air does not affect it and the only indication we have is the speed of the air relative to the movement of the machine,—or, to put it in a better way, I might say that the instrument only registers, in reality, the speed at which the aeroplane goes through the air, and no more."
"But is that the only way to tell how fast we are going?" asked Ralph.
"The best test is to take the engine revolutions. A certain machine after it has been properly tested in a calm, and also in wind currents of different velocities, will show a record of speed with the engine running at certain revolutions. An experienced aviator can judge pretty well, by experience, what the speed of the wind is, and, knowing the propeller speed, and the direction he is going relative to the wind, he can make a fair estimate of the speed of the machine."
CHAPTER X
A THRILLING EXPERIENCE IN THE AIR
It was with feelings of joy that the boys stepped out of their tent the following morning to learn that the lieutenant had decided on a trial spin in the forenoon, preparatory to the real start, which was to take place at two in the afternoon. The engine was turned over, and the machine held down while the usual hour's running test was going on. Everything seemed to be in order, the engine was stopped and another inspection made when the lieutenant gave the order to mount the machine.
In this type of military machine the swivel gun is at the extreme forward end, and the pilot directly behind the gunner, and at a slight elevation above the gun. Both gunner and pilot are housed in, and in most cases strapped to the body of the machine to prevent any accidental falling out, as there have been numerous accidents due to men being thrown from their perches.
The boys found ample room in the forward pit, and at a word the machine was released and glided forward. The new machine gave them a sensation different from the former one, as it appeared to ride more easily and steadily. In fact, there is just the same difference in the motion of flying machines as there is in autos, some, the small machines, seeming to glide over the ground and impart every bump to the occupants, as might be expected of a light machine.
A heavy flying machine, however, seems to move along with the utmost ease, and does not sway from side to side when sailing through cross currents. Naturally, such a machine is a more stable base for machine guns as well as for observation.
Alfred's particular hobby was kodaking. On this occasion, the first time he had an opportunity, he prepared himself with a camera. The lieutenant, learning of Alfred's penchant in this direction, had a regulation government instrument sent over, and attached to the machine, to Alfred's surprise.
Before starting out, the lieutenant said: "I want to give you some points now, in using the camera. Photographs, in order to have any military value, must be identified,—that is, they must be made at such altitudes, and with reference to certain marked characteristics on the earth, that we may be able to place them on the topographical maps of the particular section, and thus verify them day after day."
"What do you mean by verifying them day after day?" asked Alfred.
"I mean by that to see what changes have taken place in the same view between the taking of the two pictures," replied the officer.
"Well, what possible changes could take place in a day or two?" asked Ralph in astonishment.
"A great many, and very important ones, too," answered the lieutenant. "The camera sees what the eye does not notice. If a picture is taken of a certain section today, and the following day another picture is snapped, a comparison of the two will show whether or not there has been a movement of troops, or, whether or not a certain undistinguishable object was something movable, or not."
"Is that the way the map of the enemy's country is made up?" asked Alfred.
"Yes, and every detail is noted, so that when you commence the work be careful to notice something which will distinguish the exact place where you are located; also put down the direction of the flight over that same area, and the altitude at which we are flying."
As the machine glided over the treetops and the village on the northern border of the Meuse, the sun shone out with intense brilliancy. They were going directly east, and both boys turned toward the lieutenant, their eyes seeming to say: "So you are going to take a peep at the front, by way of experiment?" which was exactly what the lieutenant purposed doing.
The altimeter now registered 1800 meters, considerably over a mile high. From that point they could see to Verdun, and thirty miles east of Verdun, could be noted the blurred outlines and surroundings of Metz, that greatest of all fortified German defences. On they went for nearly three-quarters of an hour until a stream of some magnitude appeared to the east, which they soon crossed.
They afterwards learned that this was the Mosel, which flows through Metz. The latter city now loomed up so it could be plainly seen, and to their right was another town, Nancy, a fortified French place. They were about midway between the two places.
Suddenly an aeroplane appeared to the right, and the lieutenant turned the machine in that direction. The boys were relieved to see the great circle on the control planes of the machine in the distance, which showed them it was a French reconnoitering airplane. In the east several other machines were noticed hovering about, and the lieutenant at first headed directly for them, but he soon turned to the north.
Below were seen numerous flashes of guns, and they knew from this that the fighting lines must be along the river. The most startling thing which occurred was a tremendous explosion that seemed to be right in the machine itself, and they looked around startled at the suddenness of it, for everything seemed peaceful enough to them at that altitude.
The lieutenant turned the machine, however, as he apprehended more trouble, now that the gunners below had so luckily secured a fair range. The first shot was followed in another moment by another, and the lieutenant now began to dart the machine back and forth, and turn it in short, sharp circles.
Another explosion took place, this time remarkably close, and pieces of the flying machine came down, and brushed past the boys. The lieutenant shook his head, as the boys glanced back. The machine was now circling around, a peculiar manoeuver, the boys thought, as they looked at each other for a possible explanation.
Ralph looked back, and noticed that the lieutenant, with an alarmed look on his face, was constantly glancing back to the tail planes. The steering lever seemed to be jammed. Ralph had an idea that something was wrong, and crawled over the body until he was alongside of the lieutenant. The latter pointed to the control lever, and Ralph understood.
Without waiting for instructions from the lieutenant, he cautiously made his way along the chassis, following up the wires which were indicated by the lieutenant. Within four feet of the tail plane Ralph halted. Then, reaching down, he succeeded in grasping a dangling wire, and held up the end for the lieutenant's inspection. After several attempts he found the other end of the wire, which had been severed by a shot from a shrapnel shell.
The ship was still circling around, so without waiting to repair the break Ralph turned the rudder, and, glancing at the lieutenant, saw the latter smile, and then by motions direct him to give the control plane a still further push in the right direction. It was impossible for Ralph to hear anything the lieutenant said, but as soon as the airplane was fairly headed for the west, the power was shut off, and the machine began to descend.
"Good boy!" shouted the lieutenant. "Can you fasten them together?" he asked.
"I am afraid not," replied Ralph. "A piece seems to have been shot away. But I can take care of it if you will only direct me to pull it to the right or to the left."
"All right, then. Do you see that great patch of green, directly beyond the castle?" asked the lieutenant.
"I can see it plainly," replied Ralph. "Shall I steer for it?" he asked.
"Oh, no. We must come up from the south. Note the direction of the wind from the smoke. Make a long sweep. We are now at an altitude of 1200 meters. We can volplane twelve kilometers from this height," remarked the lieutenant.
The turn was made to the south in a long sweep, Ralph continually glancing forward to note the direction indicated by the lieutenant.
"Now straight ahead, and hold steady."
They were now rapidly approaching the earth; the machine gliding over the tops of the trees at the border of the forest that ran along the river bank. To their right, across the river, was a large town, Pont-a-Mousson, and the castle ahead of them was a large school, from which even then hundreds of children were emerging, and excitedly rushing toward the approaching machine.
Down went the machine at a sharper angle; then, when close to the earth, the rear control was sharply turned, and the nose of the ship raised up, but for an instant only, when the machine settled down, and, after running along a hundred feet, stopped.
The agitated children pressed about, and the lieutenant tried in vain to keep them off. Some more venturesome than others, after seeing Ralph and Alfred, began to question them. To the relief of the boys they learned that the French out-posts were less than a mile distant.
"Let us make the repairs as rapidly as possible," said the lieutenant.
An examination showed that not only was the control wire cut in two places, but the vertical plane had its pivot shot away, thus accounting for the peculiar action of the lever, which seemed to jam whenever an attempt was made to turn it to the right. Ralph did not know this, while seated astride the body and manipulating the plane, and it was obvious that even though he had succeeded in splicing the wire, it would have been impossible, with the rudder in that condition, to turn by means of the wire controls.
Assisted by the machinist from the garage belonging to the owner of the school, they completed the repairs in an hour, and, hungry though they were, they again went aloft and sailed for their camp, which was reached after an absence of three hours.
They thus had less than a hour to get a hurried meal and prepare to line up with the squadron, to carry out the orders for the movement to the north. They were now going to that section of the fighting line in France where the most intense struggles up to that time had taken place, and where, ever since the opening of the conflict the most stupendous operations were being carried out to gain the mastery.
Imagine, if you can, the sight that met their gaze, as they took their place on the extreme right of the three squadrons, which were about to launch on this memorable occasion. They were about twenty miles south of the city of Verdun. The extreme northern aviation base was not more than eight miles southwest of the city, located on a level plain east of the forest of Argonne, and close to the Aire river, a tributary of the Aisne.
The trip was a short one, as the actual flying distance was less than fifteen miles. Long before they reached the scene of the great camp, they could see the thousands of vehicles, and the hundreds of thousands of soldiers, on the highways, in the fields, and around the villages along the two main railways which threaded their way along the wide valleys between the Meuse and the Aire.
During every mile of the trip they were under the constant vigilance of the officers, who moved them into echelon, formed them into squares, or caused them to trail in columns of two or three, the object being to accustom the pilots to obey and execute signals while in flight.