Claude Grahame-White

Biplanes and monoplanes with floats—A flying boat—The airship—Its growth from the balloon and development into types—Large craft with rigid hulls.

As military flying produces special forms of aircraft, so the needs of the Navy make themselves felt; and the first task set the designers of aeroplanes was to provide a machine which should alight upon water. They did so by fitting floats, or pontoons, below an ordinary land aeroplane, these taking the place of the wheeled chassis; and then by degrees a special type of air and water craft was developed, and came to be known as the flying boat.

In Fig. 39, it may be remembered, was illustrated a biplane which would rest on wooden pontoons, and so ride upon the water; and this method of a hollow float was adopted and improved by the modern builders. In Fig. 68 will be seen a typical hydro-biplane, water-plane, or sea-plane—the name last mentioned being that adopted by our Admiralty when referring to such craft. The machine is an Avro, and its appearance is that of a land aeroplane, save that it has a set of three pontoons to support it on the water—two main floats beneath the sustaining planes, and a third to bear the weight of the tail. Several needs have to be considered when such floats are built. One is that they should be buoyant enough to bear upon the water the weight of the machine, and its pilot, passenger, and fuel. In the case of the craft shown, this represents a total of 2200 lbs. Another point is that the float should detach itself readily from the surface of the water.

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Fig. 68.—An Avro Sea-Plane.

A. Propeller; B. 100-h.p. Gnome motor, hidden by shield; C.C. Main-planes; D. Observer’s seat; E. Pilot’s seat; F. Rudder; G. Elevating-plane; H. Float to support tail; I. Main floats to bear the weight of the machine.

The sea-plane, when a flight is made, is launched upon the water down a slipway; then the pilot and his passenger embark, the motor is started, and the propeller draws the machine across the water at a rapidly increasing pace. The floats raise themselves higher and higher upon the water, as the air-planes exercise a growing lift, until they only just skim the surface. And now comes the moment when the airman, drawing back his elevating lever, seeks to raise his craft from the water into the air. At first only the front of the floats rise, the rear sections clinging to the surface; then, in another instant, the whole float frees itself from the water in a scatter of spray, and the craft glides at a gently-sloping angle into the air. It is the aim of builders, by the curve they impart, to make the floats leave the water with as little resistance as possible. In the floats of the Avro (Fig. 68) will be noticed a notch, or cut-away section, which occurs at about the centre of the float upon its lower side. This is called a “step,” and is to help the float to lift from the water. When the main-planes draw upward, as the craft moves prior to its flight, the floats tend, as has been said, to raise themselves in the water; and as they do so, lifting first towards the bow, there comes a space between the upward-cut “step” and the surface of the water. Into this space air finds its way and, by helping still further to free the float from the surface, aids greatly at the moment when the pilot—operating his hand-lever—seeks the final lift which will carry him aloft.

When in flight, as when skimming upon the surface of the water, a sea-plane must carry its floats with it; and this introduces a complication, inasmuch as the floats offer a resistance to the air and tend to reduce speed. Another need is thus shown; the builder of a float must so shape it that it will move through the air with the least possible friction. This is accomplished by making it long and tapering in form and by curving and polishing its surface.

England, in the building and handling of sea-planes has come well to the fore, and our machines are more advanced than those of other countries. The Admiralty has recognised that, acting as a coastal scout in time of war, such craft would be of the utmost value; thus we find air-stations dotted round our seaboard, from which machines may fly in a regular patrol. By the employment of hundreds of craft, operating upon a well-ordered plan, it will be possible in the future to girdle our shores completely; and such machines would not only spy out the approach of an enemy’s fleet, but give battle to hostile aeroplanes or airships which might seek to pass inland. The type of machine we have just described was a biplane, but there are monoplane sea-craft, and a Bleriot fitted for alighting upon the water is shown in Fig. 69.

Fig. 69.—A Bleriot Sea-plane.

Another form of craft is being developed successfully—the flying boat. This is not merely a land aeroplane with floats instead of wheels; it is a boat with a sea-going hull, which has lifting planes upon it; and it assumes the distinctive form seen in Fig. 70. When on the surface of the water the machine floats like a ship; then, when driven rapidly across the surface, its planes raise it into the air and it flies. A closer view of the hull of such a craft is given in Fig. 71.

Flying boats are at present small and lightly built, and they have difficulty in weathering rough waves when floating upon the water; but already the tendency is to make them larger, and to give them more powerful motors, and such machines for naval work, as developed in the future, may be as large as a torpedo-boat-destroyer and capable of high speeds both on water and in the air.

There is another type of craft that is being adapted and improved for naval use, and this is the airship. Although it is costly to build, requires a huge shed in which to house it, and needs also the service of trained crews to handle it when ascending or alighting, the airship is a vastly important machine for the purposes of war. Its ability to make flights lasting several days, and the power of its pilot to manoeuvre it at night, render it particularly suitable for naval use. Our Admiralty is buying large machines, aiming at a preliminary fleet of fifteen, and the German Navy is organising a squadron of Zeppelins.

The airship, although in use before the aeroplane, has developed more slowly, and is even to-day in a crude form. This has been due to the cost of experiments. Whereas a new aeroplane may be built and tested for £1000 or so, the construction of an airship and the provision of its shed spells an expenditure of many thousands. This money may, as in the case of the aeroplane, be lost as a result of one mishap. In Germany Count Zeppelin spent a fortune upon airships, before the Government and the nation helped him with funds. With very few exceptions, none but Governments—which have long purses to draw upon—can afford to build large airships.

The airship is a development of the balloon; and the balloon we owe to Stephen and Joseph Montgolfier—two French brothers who, after watching clouds floating in the sky, had the notion that if they could fill a light envelope with “some substance of a cloud-like nature” it would raise itself into the air. Their father was a paper manufacturer, and so they had facilities for making a number of very large paper bags. Under these they lit fires of chopped straw, allowing the hot air and smoke to rush up into the bags, and, when they were released the bags ascended, carried up by the lifting influence of the heated air within them. Thus was invented the hot-air balloon; and we buy paper replicas of it to-day.

Delighted with their first success, the Montgolfiers built a paper balloon 30 ft. in diameter, and this was sent up at Annonay, in France, on 5th June 1783. It flew for ten minutes before the heated air inside it became cold, and reached a height estimated at more than a mile. After this came the ascent of a spherical balloon—one, that is to say, the shape of a modern-type balloon. It was made of linen, covered with paper, and had a small car attached. At Versailles, in France, on 19th September 1783, this balloon was sent up with passengers in the car; not human beings, though, for no man cared to ascend, fearing that the upper atmosphere might have some strange effect upon him. The actual occupants were a sheep, a cock, and a duck; and these three unwilling voyagers made a flight which lasted eight minutes. When they descended the sheep and the duck were found to be unharmed, although greatly perturbed; but the cock showed symptoms of not being well! At first, when learned men examined him, it was thought the rarefied atmosphere had in some way affected him, and this view was held until practical folk were able to show that the bird had been trampled upon by the sheep.

From this, of course, the next step was the ascent of a man, and on 15th October 1783 an adventurous youth named Pilatre de Rozier went up in a balloon built by the Montgolfiers. The balloon was attached to a rope and not allowed to ascend more than 100 feet; and at this altitude the aeronaut remained for about four minutes. A month later de Rozier and a passenger—the Marquis d’Arlandes—were bold enough to risk a flight in a Montgolfier balloon. This time the ascent was made from Paris, and the balloonists flew for five minutes before descending, reaching a height of 500 feet.

Coal-gas superseded hot air in the filling of balloons, the latter being unsatisfactory, seeing that it cooled rapidly and allowed the balloon to descend; the only alternative being to do what some of the first aeronauts did, and burn a fire below the neck of their balloon even when in the air. But the dangers of this were great, seeing that the whole envelope might easily become ignited. With balloons filled with coal-gas—modern examples of which are seen in Figs. 72 and 72A—long flights were possible, but they had always this disadvantage—the voyagers were at the mercy of the wind, and could not fly in any direction they might choose. If the wind blew from the north then they were driven south, the balloon being a bubble in the air, wafted by every gust. Aeronauts became disgusted with this inability to guide the flight of a balloon, and many quaint controls were tested; such, for example, as the use of a large pair of oars with which the balloonist, sitting in the car of his craft, rowed vigorously in the air. But this method found little favour; and it was followed in due course by the use of small steam engines and electric motors, which were made to turn propellers such as are used in aeroplanes. For such experimental craft, the rounded form of gas-container was abandoned and a cigar-shaped envelope adopted, pointed at both ends, which could be more easily driven through the air. An airship of a crude and early type is seen in Fig. 73. It was built by an experimenter named Gifford, and in 1852 it flew at the rate of seven miles an hour.

When petrol engines became available, they gave an impetus to the building of airships; for, like the aeroplane, the airship needed a motive agent which gives a high power for a low weight. One of the first to use a petrol motor in an airship with success was M. Santos-Dumont, whose name has been mentioned in connection with aeroplanes. He tested small, light airships, driven by petrol engines and two-bladed propellers—as illustrated in Fig. 74; and with one of these, on a calm, still day, he flew over Paris and round the Eiffel Tower.

Then by degrees came larger craft, more powerfully engined, and built to attain greater speed. Hydrogen, far more buoyant than coal-gas, was used to inflate their envelopes, and so they obtained a greater “lift.” Speed with the airship was recognised as vital. If it could not fly fast it was at the mercy of the wind, gusts striking powerfully against its envelope, and driving it off its course.

A typical craft, representing the first of those navigated with any certainty, is shown in Fig. 75. A gas-containing envelope, made of a light, strong, varnished fabric, is kept taut by the pressure of the gas within; the car, constructed of wood or metal tubing, is suspended by ropes from the envelope, and contains engine and crew, with a two-bladed propeller revolving astern. Such a machine, in its control, had an elevating-plane and rudder, upon the same principle as those of the aeroplane. One of the difficulties to be overcome was the expansion and contraction of gas in the envelope owing to differences in altitude and temperature. When the craft ascended, its envelope completely inflated, the gas began to dilate owing to the outer air becoming less dense; and some had to be allowed to escape through automatic valves. Then, should the machine descend to a lower level, there was not sufficient gas in the envelope to keep it tightly stretched, and it tended to sag at the bow as it was driven through the air. To prevent this kinking, which would have reduced the speed of the airship, and made it difficult to control, an interior chamber, called the “ballonette,” was fitted to the envelope, as shown in Fig. 76. When the gas-container was tightly filled, this ballonette lay empty upon its lower surface; but, should the envelope tend to become flaccid, through a loss of gas, a fan pumped air into the ballonette; and, swelling out within the balloon, it compensated for the gas which had escaped, and prevented the envelope from losing its shape.

The craft shown in Fig. 75 is of the non-rigid type; its car, that is to say, is hung by ropes from the envelope; and when the envelope is deflated it can be detached from the car and the machine packed away in a relatively small space. But as airships were built larger, and greater speeds were obtained, it became necessary to strengthen the envelopes with some form of keel; and this led to a type which is known as the semi-rigid, and is developed successfully in France. Fig. 77 illustrates an airship of this build. Along the lower side of its envelope is placed a light, rigid framework or keel, and from this is suspended the car which contains engines and crew.

The car of an airship, showing its construction and the disposition of motors and propellers, is sketched in Fig. 78; while in Fig. 79 may be seen the pilot’s driving platform with wheels, dials, and speaking-tube to the engineers.

Craft of the semi-rigid type provide a link between small, non-rigid ships and the very large machine which is built with an entirely rigid framework, and has its example in the Zeppelin. The maker forms a skeleton hull of aluminium or some light metal alloy, a method that is shown in Fig. 80. The hull of a Zeppelin, slightly more than 500 feet in length, is sheathed with tightly stretched fabric; and within it are the gas-containers—a row of seventeen separate balloons, each in a compartment by itself, and containing a total of nearly 1,000,000 cubic feet of gas—which give these airships a lifting power of close upon 30 tons. The arrangement of the gas-holders, and the general outline of the machine, may be observed from Fig. 81. The vessel offers comparatively little resistance to the air, despite its size, and this is due to the finely tapering shape of the hull; while its rigidity allows it to be driven at speeds of more than 50 miles an hour. The lifting capacity, also, enables long flights to be made. Taking up crew and petrol, such a craft can remain aloft for several days, and travel distances of more than 1000 miles.

At first, flying slowly and with unreliable motors, these very large airships were at the mercy of the wind, particularly when manoeuvring near the ground. Trained crews were necessary to handle them, and they had to be housed in huge and expensive sheds, as will be realised from a glance at Fig. 82. But for the one ardent pioneer, Count Zeppelin, it is doubtful whether large, rigid craft would have been built at all. After costing many thousands, they ran the risk of being dashed to earth in a squall and hopelessly wrecked. Such a fate, indeed, befell one ship after another that Count Zeppelin launched. But he refused to be discouraged, and went on doggedly until his private fortune was gone. Then, magnificent flights having been made, the Government came to his aid; while the German people, immensely proud of his achievements, subscribed more than £300,000 for the furtherance of his tests. And so now the Zeppelin—powerfully engined, better built, and handled by expert crews—is the Dreadnought of the German air-fleet, flying hundreds of miles over the North Sea, co-operating with warships as a scout, and flashing messages by wireless for distances of 300 miles.

The airship, for long-distance reconnoitring, stands at present unrivalled. It can remain in the air for days, sweeping over sea or land, and reporting constantly to its headquarters. For night flying, also, it is at present the superior of the aeroplane, being navigable in darkness, and having an ability to hover above a given spot, its engines silent, and its presence undetected by those below.