CHAPTER XVI
AT A MODERN AERODROME
The workshops—Some problems of construction—The building of a wing—Aeroplane races—The Aerial Derby—Passenger flights.
The first flying grounds were merely open tracts of land, chosen more or less haphazard, and offering no more than a smooth landing-point and an absence of treacherous gusts. But as flying developed, men came together with their machines, and groups of sheds were built. Then pupils arrived to learn to fly, and gradually an organisation was evolved. From a single rough shelter, perched perhaps at the brink of some stretch of waste land, pilots found themselves promoted to a row of neatly-built sheds, with a workshop attached to them in which aeroplanes might be built or repaired. And from this stage, not being contented with what could be found in the way of natural flying grounds, men uprooted trees, filled up ditches and hollows, erected fences, barriers, and gates, and created what we know as the modern aerodrome—a centre, that is to say, where machines are designed, constructed, and flown, where there are regular schools for pupils and apprentices, and to and from which the airmen pass when making cross-country flights. Public interest has also aided the growth of aerodromes; people are eager to see aeroplanes fly, and will come in thousands to an air meeting. So, as at the London Aerodrome, Hendon, there are public enclosures and pavilions, in addition to the buildings concerned solely with flight; and flying races and other contests are arranged, in which the pilots at the aerodrome, as well as those who come from other grounds, meet each other in friendly rivalry.
To-day, the aerodrome is the rendezvous of those who fly, or build machines, or seek to learn the art; while the general public, thronging the stands on racing days, learns more of aviation in an hour than it would in a month by merely reading of flights that have been made. All day, from the moment it grows light until the final dusk, there is activity upon the aerodrome. Machines are brought out and tested; pilots arrive from other flying grounds; there is a hum of activity in the workshops; and in regular batches, with this instructor and that, are pupils taught to handle a craft in flight. It is, to those who have only a vague knowledge of aviation, a surprise indeed to spend a day at an aerodrome. They imagine that the industry is no more than haphazard; that a few machines are built—mostly in small workshops, and that there is neither method nor organisation in their making. And then, perhaps, they are taken through a modern factory, and hold such views no more.
By the work of trained men, who have become highly skilled in their art, are the parts of a flying machine built and assembled; and no sooner is one machine wheeled from the shops and takes the air, than another is being made ready. Governments give orders for large batches of craft; aeroplanes of new types are built and tested. And, in all departments of the factory, the output of work is constant and well ordered.
First, of course, the machine is designed; and those in the drawing office are specially trained men. The planning of an aeroplane is a matter of no simplicity. First of all there is to be considered what may be termed the main feature of the machine; whether, that is to say, it is to be built for speed, for weight-lifting, or for aerial touring. For high-speed flying it will need small sustaining wings; for weight-lifting, its area must be large; while in aerial touring there is need for a medium-paced, highly reliable craft, which will ascend quickly or plane slowly to earth. The characteristic of the machine determined, there are other problems to be studied—such, for example, as the placing of the engine and propeller, the position of the body containing the pilot and passenger, and the arrangement of the control surfaces. And, above all, the craft must be built strongly. No matter how well a machine may fly, or how skilled its pilot, there is peril should its structure have a weakness, or some hidden defect. For months, perhaps, in the early days of aviation, a faulty machine would fly; and then some day, subjected to an abnormal strain, a wing or a tail would break, and the airman would fall to his death. Should an aeroplane dive suddenly, there may be a tremendous strain upon its planes; and in a violent wind, while its motor is thrusting it through the gusts, it is sustaining shocks and jars which may be of tremendous force. It is not, indeed, the ordinary wear of flying that a designer needs to guard against, but those excessive strains—caused perhaps by reckless flying, or the onslaught of a gale—to which a machine may be exposed.
Security lies in one direction only; and that is to give a machine such a factor of safety as may be equal to all demands—normal or abnormal. So a designer calculates, before he draws out the plan of a wing, just what pressure it may have to resist in ordinary flight; and then to this he adds such strains as might be caused by diving or by violent gusts. To be completely on the safe side, to be guarded beyond question from any excessive shock, a modern-type aeroplane will be given a factor of safety that may be ten or twelve times more than is necessary in the ordinary passage of the machine through the air; and this security lies not only in its planes, say, or its controlling gear, but in every wire and bolt and stay which goes to its construction. And, by this precaution alone, has one of the gravest risks of aviation been removed. Formerly, when men built machines, they did so by what is termed rule-of-thumb; the builder, that is to say, relied upon his own judgment and experience—small though these were—and submitted his plans to no rigorous or scientific test. And so lives were lost. But now, even when he “loops the loop,” or fights a 60-mile-an-hour gale, a pilot has confidence in the machine he flies. He knows it is strong as a whole; that it has no hidden weakness or faulty spar; that he may rely upon it implicitly, even under the acutest strain.
The building of an aeroplane is a problem of great difficulty—such a problem, in fact, as no other designers of craft, either for land or sea, are called upon to face. The machine must be immensely strong, and yet it is essential that it should be light. Its planes cannot bear through the air more than a certain number of pounds per square foot; and so if it is to be a practical craft, and raise a useful load, every pound that can be saved in its construction has a definite value. It is because such work is so intricate that there is special interest in a visit to an aeroplane factory. Here, in large, well-lighted workrooms, are skilled craftsmen employed. Some of the men, now risen to be foremen of their departments, made their first acquaintance with aviation in the very early days. Then there were no factories, and an inventor, regarded invariably as a “crank,” found a mechanic who was intelligent to help him, and built his craft humbly in some outhouse or shed. Now these handy mechanics, who perhaps forsook a post in a motor works to join some scheme to build an aeroplane, find themselves in positions of trust in a large and flourishing factory—turning out aircraft for Governments and for private use, and with a staff of workers under their control.
An impression of one of the workrooms in a modern factory may be gained from a study of the photograph on [Plate XIII]. This was obtained in the Grahame-White factory at Hendon. In the foreground of the picture, resting upon trestles, is one of the sustaining planes of a machine. It is in its rough stage, prior to being covered with fabric, and the method of construction may be seen. The system is to use two or more main-spars, which run the whole length of the wing; and above and below these pass the thin wooden strips which form a series of ribs. [Fig. 90], representing a monoplane wing in skeleton, should make clear this method of building. Although such a wing may appear frail, it has in reality a surprising strength. English ash and silver spruce, in carefully selected lengths, are the woods used chiefly in aeroplane construction, and calculations have shown them able to bear a greater strain, weight for weight, than would a framework made of mild steel. In the future, of course, when aircraft are built far larger, wood will cease to be employed—and partly for the reason that, when wing constructions of great sizes are needed, it will be impossible to obtain timber that can be cut into spars of a sufficient length and soundness. Then, probably, will come the day of high-tension steel, and we shall have a liner of the air built almost after the fashion of a leviathan of the sea; but for the making of a small machine, at any time, there should be an advantage in the use of wood.