Part 8 (2/2)

Occasionally instead of a series of photographs of a trench line or limited area, a continuous set of pictures of a broad s.p.a.ce of country is desired. Then instead of a single machine as described above, a squadron of reconnaissance machines set forth, flying in V formation, with the leader of the squadron flying in front at the point of the V.

The moment he reaches the area to be photographed, he notifies the machines behind him by firing a smoke rocket with a signal pistol. At that signal the V broadens instantly, so that it becomes almost a straight line, the commander keeping only slightly ahead so that he may lead the way. On and on that broad V formation of airplanes sweeps, every camera registering, and all keeping close enough together to produce slightly overlapping photographs. Each machine will bring home a long line of pictures of the country over which it pa.s.sed, and those lines, pieced together, will make a large military map of the entire region. That is if everything goes smoothly, which in war time it seldom does. More likely that plucky V will be pounced upon by a herd of fast fighting machines whose duty it is to see that none ever return with their information to headquarters. There will follow a terrific contest; the observer in the reconnaissance machine becomes a gunner, and fires away at his pursuers, while the never-failing camera keeps steadily on with its job of recording. As nearly as possible the V formation is held, for much depends upon it, but suddenly a great gap appears in the line. ”Done for” with a direct hit, one brave machine goes cras.h.i.+ng earthward. That will mean a gap in the ”map” that is in the making.

Still the V presses on relentlessly. One of the planes begins to lag behind. There is something wrong with its engine. It does its best to keep up with its fellows, but soon it is left behind, and the enemy craft dive after it. Battered and torn, its numbers depleted sadly, several of its crew wounded, its wings perhaps riddled with bullets, the photographing squadron turns its face toward home, and, flying now as high as possible to keep out of sight, puts on all speed for the safe side of No Man's Land. Military photography _sounds_ easy and comfortable. It _demands_ the type of courage which can make a man stick to a given line of flight, even when certain death lies straight ahead.

Sometimes a machine carries both bombs and a camera, and, as it drops its missiles, keeps a continuous record of its ”hits” to carry home. And that brings us to the bombing machine, last but not least of the trio of military airplanes.

The bomber that works by day and near to its own lines, is similar to the reconnaissance machine, except that it does not usually carry a radio apparatus or a camera. Instead, the greater part of its cargo consists of bombs, dread instruments of destruction which will fall on the railroad junctions, troop trains, staff headquarters or ammunition dumps of the enemy. The day bomber is never used for long distance work, and so it does not need to be of tremendous size, as the machine which must carry fuel for an all night run as well as a large quant.i.ty of bombs to drop on a far away important objective.

The night bomber is the giant of the sky. The greatest genius of the cleverest designers has been expended upon its construction. More and more its tremendous importance is being recognized. Its activities precede every great offensive movement, for it flies over the enemy's country, leaving a trail of terrible destruction in its wake, and ”preparing the soil” for the infantry advance. Deep in the territory of the foe it searches out the great supply centers and railway terminals and there it unloads its cargo of bombs.

If the Allies had possessed a sufficient number of these huge bombing planes they could have carried on an aerial warfare against Germany which would have defeated her without nearly so great a sacrifice of the lives of the infantry. The work is dangerous, but a single bombing plane could have wreaked more vengeance upon the Hun than perhaps a whole regiment of the bravest fighters. Consequently its use would have meant economy of human lives.

These fearful shadows that walk by night require pilots of the utmost skill to navigate the sea of darkness, as well as bomb droppers and gunners whose training has been perfect. The largest of them are equipped with either two or three powerful engines, each working a separate propeller. Such a machine can carry as much as five tons of explosives, with fuel for a twelve hours' flight.

The night bomber is very often a huge triplane, for the extra wing surface gives greater lifting power. At the same time the triplane has greater stability and has a fair chance of reaching home even when one of its planes has been badly damaged. It is the same with a machine which has two or more engines: even when one of these has been put out of order by the shots of the enemy the airplane can still reach home.

The night bombers must travel long distances, carry great cargos, bomb their objectives and make their escape, and so in the construction of their machines as much stability, lifting power and speed as possible has been the aim.

Usually it is some important munition base or factory center that is supplying the German troops, which the airmen set out to bomb. They travel in squadrons not only for safety, but because in this way an almost unlimited number of bombs can be carried and dropped simultaneously. Often a second squadron follows the first at a short distance. By the light of the terrible fires that the first set of explosives dropped are bound to start, this second squadron can drop its bombs with greater precision directly on important buildings that must be destroyed.

Moving slowly under their great load of explosives, and flying low, these two squadrons of destroyers start for some point in the heart of the German Empire. Like ghosts they ”feel their way” mile after mile.

They are not anxious to invite detection, for under the great weight of their ”messages” to Germany, they would not be able to maneuver quickly or to climb to safety.

Once those tons of explosives have been released and the noise of their dreadful havoc has aroused the anti-aircraft gunners of the enemy, those bombing planes will find the earth an uninviting sort of region and they will be glad to spring into the protecting silence and darkness of the upper air. And this they can do easily, for, rid of their load, they possess unusual climbing powers. The second squadron of bombers, flying over the same territory may expect a warm reception, and they will need to do their work quickly and beat a hasty retreat.

Such are the mysterious doings of the night. When the early dawn appears, gray and heavy eyed, it will find the bombing planes tucked away drowsily in their hangars, scarcely knowing themselves whether the journey up the Rhine was a reality or merely a terrifying dream.

And with the dawn their daylight sisters will take up the work near home. Word has just come that enemy reinforcements are moving up to the front along certain roads. ”Fine,” sings out a young lieutenant, appearing unexpectedly on the field from a small, carefully camouflaged office. ”We will make them dance for us this morning!” He talks quickly and determinedly with a group of pilots, giving instructions, charging all to keep the formation. Machines are gone over to make sure that everything is in perfect condition. Then the first bombing plane, bearing the flight leader, ”taxis” across the field, appearing to stagger under its great burden. Suddenly it takes to the air, and like a large graceful bird, its clumsiness all gone, it soars up into the blue.

Rapidly the other big birds follow suit, and at a signal they are off, the flight commander heading the group, and the others following in close formation, like a huge flock of wild geese.

On and on they fly, until beneath them appears the winding ribbon of road that is their objective. It is crowded with marching troops, gun wagons, supplies. As they swoop close to the earth they catch a swift glimpse of white faces turned up at them with terror. Then panic falls upon the marching column and, helter-skelter, every man tries to break away to a point of safety. In another moment guns are turned upon the bombers, but they dodge the flying sh.e.l.ls and let go their heavy explosives, which crash to earth with dreadful uproar. Where a few moments before the Huns were following their way undisturbed there is now a road in which great furrows are plowed; huge holes gape open and a hopeless ma.s.s of debris covers the earth. The columns of the enemy will be blocked for many hours while the ma.s.s is being cleared away.

Satisfied with the results of their exploit the bombing squadron turns swiftly toward home.

How simple a matter it seems at first glance to release a bomb and hit a given point below. Actually it requires the very highest skill. To begin with, the airplane is moving at tremendous speed, and the bombardier (as the man who drops the bombs is called) has to know exactly how the forward motion of the airplane will affect the direction that the bomb takes on its course toward the earth. Moreover the bomb has a speed at starting equal to the speed of the airplane, and this beginning speed is increased by the action of gravity drawing it down. It may be aided in its journey by the wind or r.e.t.a.r.ded, according to the wind's direction, and this too must be taken into account, if the target is to be hit.

Bomb dropping can only be carried out successfully with the aid of the most delicate and complicated range-finding mechanism, with which every bombing plane is equipped. The Germans have led the way in inventions for this purpose, and their Goertz range finder is perhaps the best in the world.

The bombs themselves are generally carried in vertical position, one-above another, in the body of the airplane, and by an automatic arrangement, as one is released, another slips into place, ready to be dropped.

Now that we have made the acquaintance of the three types of machines that are used over the trenches--the ”speed scout” or small fighting machine; the larger armed reconnaissance plane; and largest of all, the bomber--let us go back and give just a hasty glance at the main points of their construction.

First we must recall the ”A B C facts” we learned about wing construction. A wing gains lifting power from two sources: the upward pressure of the air current underneath it, and the force of the vacuum above it which is created by the arch of the wing. If a wing is only slightly arched it can move _forward_ through the air more swiftly, but it will not have the _lifting power_ of the high arched wing. This is the reason that an airplane which must be a weight carrier cannot be as fast in flight as the ”speed scout,” which has only its pilot and a machine gun to carry.

The ”speed scout” is always a small machine, usually a single-seater, with a gun in front that fires over or through the propeller. In the early part of the Great War it was most often a monoplane, but the smaller biplane took its place, because, with practically the same speed, it combines greater stability.

The planes of the speed scout are very flat as compared with those of the reconnaissance craft. This airplane must carry machine guns, photography apparatus, radio, and a pilot, an observer, and often a gunner. Its wings must therefore be arched to give it lifting power, but at the same time it becomes a much slower flying machine than its smaller sister.

Lifting power of a wing can of course be increased _up to a certain point_ by increasing the wing area, so that a greater air pressure is created below. Beyond that certain point the machine would become unwieldy and would lose its balancing properties. Yet this idea has been put into practise in building the latest types of aerial dreadnaughts used for reconnaissance. These airplanes have gained their lifting power partly by increasing the wing spread and partly by arching the wing.

Thus a wing has been secured which offers the minimum resistance to forward motion through the air, together with the maximum weight carrying ability. Biplanes of this type are by far the most popular of those designed for general service, for they combine speed, climbing ability, and lifting power,--thanks to their strong armament they can defend themselves or run away quickly as the situation demands.

But there is one other method which has not yet been mentioned of increasing the lifting power of an airplane. It is simply to add a third wing. When we have made the wings of the biplane as large as we dare, and have curved them to make them weight-bearers, if the resulting machine is still not strong enough to carry as many tons of explosives as we desire, there is only one thing left to do and that is to add a third wing. Thus the triplane made its appearance in answer to the call for planes which could carry vast cargoes of explosives and fuel for journeys of many hours over the enemy's country. The huge night bombing machine of the present time is almost always of the triplane type.

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