1.1111 GLIDERS.
Tuft' performances in gliding, or perhaps one should rather say in soaring, which have just been accom- plished in Germany would have seemed quite incredible a few years ago. A young student named Hentzen, of the Hanover Technical High School, stayed in the air In a motorless aeroplane for a few seconds over two hours. For about an hour and three-quarters he moved more or less over the same spot, sometimes ascending and some- times desoending—varying his height apparently between 300 and 600 feet—and finally he set off to satisfy the test of gliding five kilometres in a straight line. He did much more than that. He glided ten kilometres and landed precisely at the point which he had said he would reach. We confess that the descriptions of all this have thrilled us more than anything we have read about the air for a long time. The chilling criticisms of experts who tell us, truly enough, that the motorless plane will not be able to compete with the power-driven plane and that, therefore, not very much is to be learned from the feats in Germany, leave us unmoved. No expert will be able to convince us that if gliding and soaring are made continually easier by means of improved planes and knowledge of the air, there will not be great resulting improvements in flying under power. The machine that can sail along with no power at all will sail to much better effect than the older planes when power is applied. Another reflection which instantly occurs to us—and it is not the less striking because it is moral rather than mechanical—is that the great German advance in gliding which has quite eclipsed the French experiments is a real instance of necessity being the mother of invention. Under the Peace Treaty the Germans were forbidden_ for a time to build aeroplane engines at all, and later, though they were allowed to build engines, the power of them was restricted. Consequently, the Germans wanted to lay out the permitted power to the greatest possible advantage. Thus they took to experi- menting in bringing the air currents more skilfully under contribution and discovering the maximum of supporting power which could be obtained from the air without the use of any engine. The feats have been performed by youths at the Technical Universities and High Schools. It only shows that when necessity rules ploughshares might be turned into swords as easily as swords can be turned into ploughshares. What exactly is this new form of so-called gliding? The pilot in the simplest form of glider adjusts the planes to the air currents by the mere movement of his body, but in the more improved types he controls the planes by levers just as in a power-driven aeroplane. Up till recently the pilot obtained an original momentum by lumping from high ground, where there was a very abrupt descent, or by being projected forwards by some mechanical Instrument hke_a catapult, or by choosing for his starting- point sloping ground up which a strong breeze was blowing. The scene of the latest German experiment was a large open grass down with an appreciable gradient. But the art of gliding has already been brought to such a pitch that some of the gliders can start from level ground though being towed for a few yards till they rise as a kite rises when the string is pulled. When once the pilot is in the air he has to make use of the variations in the force of the wind. He must judge these largely from the for- mation of the ground, though he is also helped by the feel of the wind on his face. A bird sails down the wind or rises against it by instinct, but the human glider does it by intellect and practice. It is admittedly a great strain, though it must be grand sport for a short time. Irregular gusts which are an impediment to the power- . driven aeroplane are the wherewithal of the glider. It is upon the gusts that it mounts higher, though gravity is always tending to pull it down to the earth. Of course the pilot can come down slowly, as the arrangement of his weight under the plane serves the purpose of the string upon the kite—it keeps the air pressure well applied under- neath to sustain him. But down he must come if the wind dies away or even if it is perfectly regular. The wind, however, is practically never regular, and sooner or later during his descent to earth he will feel a gust and will make use of it. Everybody has seen a soaring bird turn and mount upwards without actually moving its wings. Some critics have remarked that for gliding England is one of the worst countries in the world owing to the unsettled conditions. We write with diffidence, but again the critics seem to 1113 to be wrong. Would anyone say that the British seas are the worst training place for seamen because they are so boisterous ? Very likely one of the original builders of war canoes who launched his vessel on a placid lake was thankful for such favourable con- ditions and remarked that the gentle art of war-canoeing could not be practised in more dangerous places. A race of seamen would at all events know what to think of such a sentiment. Our seamen are good because they have overcome the conditions. For the same reason we expect our gliders to be similarly proficient. Someone has remarked that the reason that Scotch gardeners are so capable is that it is a miracle that there should be a garden in Scotland at all.
It is almost humiliating to think that we so often take it for granted that finality has been reached when we ought really to consider ourselves to be at the beginning.
Probably if these young men in Germany had not made a virtue out of necessity and experimented so earnestly it would have been assumed for many more years to come that we knew all that was necessary about the lifting and sustaining power of planes. Many flying men would have gone on talking, as some are talking now, about gliding being a retrograde movement—rather as though ships had given up steam and oil and had confined them- selves to sails. The suspicion follows that in many arts or sciences we may be only at the beginning when we think we are at the end. What about the arrangement of sails on ships ? Sail-plans in general have undergone no essential change for generations. Of course, a ship under properly balanced sail must spring to the wind when not directed by the helm ; she must, as sailors say, "take weather helm," otherwise she would be uncontrollable and therefore unsafe. But within that reservation there may be room for developments which have not yet been dreamed of. When a ship is sailing "on the wind" she must be deep in the water if she is to resist the tendency to sag to leeward, but when she is running before the wind the keel or even the natural depth of the vessel is a hin- drance. Has nobody ever tried to apply, at least to small vessels, the lifting power of sail ? The tendency of a vessel running before the wind is to bury her head. Could that tendency be in any way modified by a sail so set that the wind would blow under rather than against it I Soon we shall see gliders in England. Though gliding may remain chiefly a sport, its developments will make great contributions to flying under power. How finished and delicate an accomplishment gliding already is in Germany is proved by the fact that several pilots when coming to earth alighted at the exact spot, within inches, which they were told to aim at. One of them coming down wind turned against the wind just before landing and gently dropped down vertically at the appointed spot as though the glider were a lift descending. In an article in the Manchester Guardian of Tuesday Mr. C. G. Grey says that there is no reason why a clever pilot should not follow a cross-Channel steamer from Dover to France "simply sitting on the top of the air wave thrown up by the progress of the steamer," as gulls follow a steamer using the upward draught without flapping their wings.
Previous page
