Learning to Fly: A Practical Manual for Beginners

The rules drafted by the Club to govern these flights are set forth herewith:—

These flights as specified to-day, though they present no difficulty to the pupil who has been well trained, are more stringent than they were in the first scheme of tests as prescribed by the Club, and as enforced for several years. In those early rules the distances were the same as they are to-day, but in the altitude flight the height required was only 50 metres (164 feet)—just half the height specified to-day. It was not laid down, either, in the first rules, that the engine should be stopped in this altitude flight when at the maximum height, and that the descent should be made in a complete vol-plané, without once re-starting the motor. As originally framed, indeed, the rule as to the control of the engine in this altitude test was the same as in regard to the distance flights—i.e., that it should be stopped "at or before the moment of touching the ground." What the present rule means, in this respect, is that the pupil must be really proficient at making a vol-plané, without any aid at all from his engine, before he can hope to pass the test; and such a proved skill—say in the making of his first cross-country flight, should his engine fail suddenly—may spell the difference between a safe or a dangerous landing.

The test flights for the certificate, undertaken only in such weather conditions as the pupil's instructor may think suitable, are watched by official observers appointed by the Royal Aero Club. It is the business of these observers, when the prescribed flights have been made, to send in a written report concerning them to the Club; and acting on this report, after it has been considered and shown to be in order, the Club issues to the pupil his numbered certificate. With the successful passing of his tests the pupil's tuition is at an end. He is regarded no longer as a novice, but as a qualified pilot.

CHAPTER VII

PERILS OF THE AIR

There are people, very many people, who still regard flying as an undertaking of an unreasonable peril, essayed mainly by those who are in quest of money, notoriety, or sensation at any price. Such people—still to be met with—have one mental picture, and one only, of the flight of an aeroplane. They imagine a man in the air—and this mere idea of altitude makes them shudder; and they picture this man in a frail apparatus of wood and wire, capable of breaking to pieces at any moment; or even if it does not break, needing an incessant movement of levers to maintain it in a safe equilibrium; while they reckon also that, should the engine of the machine suffer any breakdown, the craft will drop to earth like a stone. Prejudice dies hard; harder no doubt in England than in other countries. There are still people, not few of them but many, who would be ready to declare, offhand, that one aeroplane flight in six ends in a disaster.

It is a truism, but one that has a peculiar truth in aviation, to say that history repeats itself. To-day we find large numbers of people who still cherish the opinion that—save perhaps when on service in war—it is nothing less than criminal foolishness for men to ascend in aeroplanes. That attitude of mind persists; the growing safety of flight has not affected it to any appreciable degree. But those eager for the progress of aviation need not despair, or imagine that their particular industry is being treated with any exceptional disapprobation. They have only to look back a little in our history, no great distance, and read of the receptions that were accorded the first pioneers of our railways. Public meetings of protest have not been held to condemn aviation; yet they were frequent in the days when the first railways were projected. Vast indignation was indeed aroused; it was declared to be against all reason, and a matter of appalling risk, that people should be asked to travel from place to place in such "engines of destruction." But the railways managed to survive this storm. They were placed here and there about the country; they were improved rapidly; and it would be hard, to-day, to find a safer place than the compartment of a railway train.

Motor-cars, when their turn came, had to go through a similar ordeal. There was the same indignation, the same chorus of protest; and when the first of the pioneers, greatly daring, began actually to drive their cars on the public highway, there were people who believed, and who declared forcibly, that to permit such machines on our roads was the crime of the century. Had not these pioneers struggled valiantly, sparing neither time nor money, it is possible that the motor-car might have been driven from the highway. But here again progress, though it was retarded, could not be checked. The motor-car triumphed. It grew rapidly more reliable, more silent, more pleasing to the eye; and to-day it glides in thousands along our roads, a pleasure to those who occupy it, a nuisance neither to pedestrians nor to other wheeled traffic; more under control when it is well driven, and more ready to stop quickly when required, than any horsed vehicle which it may have replaced. At one time the papers were full of such headlines as: "Another Motor-car Accident." Each small mishap received prominent attention: and to the majority of people it seemed the wildest folly to travel in such vehicles. Yet to-day—such is progress—these same people ride in a motor-car, or a motor-cab, quite as a matter of course and without a thought of risk.

When one discusses flying and its dangers, it is essential to maintain an accurate sense of proportion. In the very earliest days, for instance, it must be realised that the few men who then flew—they could be numbered on the fingers of one hand—exercised the greatest caution. They did not fly in high winds; they treated the air, realising its unknown perils, with a very great and a very commendable respect. Thus it was that thousands of miles were flown, even with the crudest of these early machines, and with motors that were constantly giving trouble, without serious accident. But after this, and very quickly, the number of airmen grew. New aviators appeared every day; contests were organised extensively; there were large sums of money to be won, provided that one pilot could excel another. And the spirit of caution was abandoned. Even while they were still using purely experimental machines—craft of which neither the stability nor the structural strength had been tested adequately—there grew a tendency among airmen to fly in higher winds, to subject their machines to greater strains, and to attempt dangerous manœuvres so as to please the crowds who paid to see them fly.

It was not surprising, therefore, that flying entered upon an era of accidents. Such disasters were inevitable—inevitable, that is to say, in view of the tendencies that then prevailed; though it is a melancholy reflection that, had men been content to go ahead with the same slow sureness of the pioneers, many of those lives which were lost could have been saved.

To the public, not aware exactly of all that was going on, it appeared as though the navigation of the air, instead of growing safer, was becoming more dangerous. There were suggestions, indeed, made quite seriously and in good faith, that these endeavours to fly should cease; that the law should step in, and prevent any more men from risking their lives. What people failed to realise, when they adopted this view, was that instead of one or two men flying there were now hundreds who navigated the air; that flights in large numbers were being made daily; that thousands of miles instead of hundreds were being traversed by air—and often under conditions the pioneers would have considered far too dangerous. These facts, had they been realised, would have shown people what was actually the true state of affairs; that, though accidents seemed numerous, and were indeed more frequent than they had been in the earliest days of flying, they were as a matter of proportion, reckoning the greater number of men who were flying, and the thousands of miles which were flown, growing steadily less frequent.

There was this important fact to be reckoned with also. Each accident that happened taught its lesson, and so made for future safety. A considerable number of those early accidents can, for instance, be traced to some structural weakness in a machine. The need in an aircraft then, as now, was lightness; and in those days designers and builders, owing purely to their inexperience, had not learned the art, as they have to-day, of combining lightness with strength. So it was that, as more powerful motors began to be fitted to aeroplanes, and greater speeds were attained, it happened sometimes, when a machine was being driven fast through a wind, that a plane would collapse, and send the machine crashing to the ground; or in making a dive, perhaps, either of necessity or to show his skill, a pilot would subject his machine to such a strain that some part of it would break.

From such disasters as a rule, greatly to be regretted though they were, the industry emerged so much the wiser. The strength of machines was increased; the engines which drove them were rendered more reliable; and gradually too, though none too rapidly, the airmen who piloted them grew in knowledge and skill. But all this time, while flying was being made more safe, there were accidents frequently for the papers to report; and this was due entirely to the fact that there were now thousands of men flying, where previously there had been fifties and hundreds. The public could not realise how rapidly the number of airmen had grown; that practically every day, at aerodromes scattered over Europe, flights were so frequent that they were becoming a commonplace. It was in 1912, as one of its many services to aviation that the Aero Club of France was able to show, by means of statistics which could not be questioned, that for every fatality which had occurred in France, during that particular year, a distance of nearly 100,000 miles had been flown in safety.

The cause of many of the early accidents was, as we have suggested, the breakage of some part of a machine while in flight. In an analysis for instance of thirty-two such disasters, it was shown that fourteen were due to the collapse of sustaining planes, control-surfaces, or some other vital part of a machine. And this risk of breakage in the air was increased, in many cases, by the building of experimental machines by men who had no qualifications for their task, and who erred only too frequently, in their desire to attain lightness, on the side of a lack, rather than an excess, of structural strength.

There are many cases, unfortunately, that might be cited; but one may be sufficient here. A man with an idea for a light type of biplane, a machine designed mainly for speed, had an experimental craft built—this was in the pioneer days of 1909—and insisted on fitting to it a motor of considerable power. It was pointed out to him that his construction was not sufficiently strong, in view of the speed at which his machine would pass through the air. But he was of the quiet, determined, self-opinionated type, who pursued his own way and said little. He did not strengthen his constructional, and he began a series of flying tests. In the first of these, which were short, the planes stood up to their work, and the fears of the critics seemed groundless. But a day came when, venturing to some height, the aviator encountered a strong and gusty wind; whereupon one of his main-planes broke, and he fell to his death.

As a contrast to this tragedy, and a welcome one, there is a humorous story, that is true, told of one experimenter. His knowledge of construction was small, but what he lacked in this respect he made up for in confidence; and he built a monoplane. This was in the days just after the cross-Channel flight, and experimenters all over the world were building monoplanes, some of them machines of the weirdest description. The craft built by this enthusiast seemed all right in its appearance; nothing had been spared, for instance, in the way of varnish. When wheeled into the sun, for its first rolling test under power, it looked an imposing piece of work. Friends were in attendance, photographers also; and the would-be aviator was in faultless flying gear. Mounting a ladder, which had been placed beside the machine, he allowed his weight to bear upon the fusilage, and proceeded to settle himself in his seat. But he, and the onlookers, were startled as he did so by an ominous cracking of wood. It grew louder; something serious and very unexpected was happening to the machine. As a matter of fact, and just as it stood there without having moved a yard, the whole of the flimsy structure parted in the middle, and the machine settled down ignominiously upon the ground, its back broken, and with the discomfited inventor struggling in the débris.

It was far from easy, in the early days, for even an expert constructor to calculate the strains encountered under various conditions of flight. In wind pressure, under certain states of the air, there are dangerous fluctuations—fluctuations which, even with the knowledge we possess to-day, and this is far from meagre, exhibit phenomena concerning which much more information is required. Machines have collapsed suddenly, while flying on a day when the wind has been uncertain, and have done so in a way which has suggested that they had encountered, suddenly, a gust of an altogether abnormal strength. Occasionally, though research work in this field is extremely difficult, it has been possible to gain data as to the existence of conditions, prevalent as a rule over a small area, which would spell grave risk for any aeroplane which encountered them. There is a strange case, verified beyond question, which occurred during some tests with man-lifting kites at Farnborough. These kites are strongly built, and withstand as a rule extremely high winds. On this particular day a kite, when it had reached a certain altitude, was seen to crumple up suddenly. The wind did not seem specially strong—not at any rate on the ground; and there appeared no reason for the breakage of the kite. Another was sent up; but the same thing happened, and at the same altitude. Then the officer who was in charge of the kites sent for a superior. A third kite was flown to see what would happen. This one broke exactly as the others had done, and at just the same height—about five hundred feet. Precise data could not be gained as to this phenomenon; but the breaking of these kites—which had withstood extremely high pressure in previous tests—was reckoned to be due to the fact that, when they reached a certain point in the air, they were subjected to the violent strain of a sudden and complete change in the direction of the wind. To the pilot of an aeroplane, entering without warning some such area of danger, the result might naturally be serious in the extreme.

The air has been, and is still, an uncharted sea. It does not flow with uniformity over the surface of the earth. It is a constantly disturbed element, and one that has the disadvantage of being invisible. An aviator cannot see the dangerous currents and eddies into which he may be steering his craft; and so it was not surprising, in those days when aircraft were frailer than they should have been, and cross-country flights were first being made, that machines broke often while in flight and that the airman's enemy, the wind, claimed many victims.

Wind fluctuations that are dangerous, those which possess for one reason or another an abnormal strength, are encountered frequently when a pilot is fairly near the earth; and his peril is all the greater in consequence. On a windy day, one on which there are heavy gusts followed by comparative lulls, it is when he is close to the ground, either in ascending or before alighting, that a pilot has most to fear. If he is well aloft, with plenty of air space beneath him, and particularly if he has a machine that is inherently stable, he has little to fear from the wind; save, perhaps, should his engine fail him, or should he find—as has been the case in war flying—that the force of the wind, blowing heavily against him, and reducing the speed of his machine, has prevented him from regaining his own lines before his petrol has become exhausted. The modern aeroplane, when its engine-power is ample, and it is at a suitable altitude, can wage battle successfully even with a gale. But it must rise from the earth when it begins a flight, and return to earth again when its journey is done; and here, in the areas of wind that are disturbed by hills, woods, and contours of the land, there are often grave dangers. The wind at these low altitudes blows flukily. Its direction may be affected, for instance, owing to the influence of a hill or ridge. A side gust, blowing powerfully and unexpectedly against a machine, just as it is nearing the ground before alighting, may cause it to tilt to such an angle that it begins a side-slip. If the craft was sufficiently high in the air, when this happened, the pilot would be able, probably, to convert the side-slip into a dive, and the dive into a renewal of his normal flight. But if such a side-slip begins near the ground, and there is an insufficient amount of clear space below the machine, it may strike the ground in its fall, and become a wreck, before there is time for the pilot, or for the machine itself, to exercise a righting influence. The fact that a craft may be forced temporarily from its equilibrium, say by a side-slip, is known now to represent no great risk for the airman, granted always that he has the advantage of altitude. The machine, in such circumstances, falls a certain distance. This is inevitable, and for the reason that it must regain forward speed—which it has lost temporarily in its side-slip—before its own inherent stability can become effective, or its pilot regain influence over his controls. And it is this unavoidable descent, this short period during which the machine is recovering its momentum, and during which the pilot has no power of control, that represents in a heavy wind the moments of peril, should a pilot enter an area of disturbance just as he nears the ground.

An aeroplane, when it sets out to fly in bad weather, may be likened to a boat that is being launched from a beach upon a rough and stormy sea. It is the waves close inshore, which may raise his craft only to dash it to destruction, that the boatman has chiefly to fear; and for the aviator, when he leaves the land and embarks upon the aerial sea, or when he returns again from this element and must make his contact with the earth, there lurks a risk that, caught suddenly by an air wave, and with insufficient space beneath his machine, he may be forced into a damaging impact with the ground. But the skill of designers and constructors, to say nothing of the growing experience of aviators, is working constantly towards a greater safety.

Of the risk attached to engine failure, when he is piloting a craft fitted with only one motor, an airman is reminded frequently, not only from his own experience, but from that of other flyers. With the aeroplane engine, even with types that have gained a high average of reliability, there are many possibilities of a slight mishap—each of them sufficient, for the moment, to put an engine out of action—that the pilot who is flying across country must, all the time he is in the air, have at the back of his mind the thought that at any moment, and perhaps without any warning, he may find that his motive power has gone. A magneto may fail temporarily; an ignition wire or a valve spring break. The aeroplane engine of to-day is, of course, an infinitely more reliable piece of apparatus than it was in those early days when Henry Farman, working with extraordinary patience at Issy-les-Moulineaux, was endeavouring—and for a long time without success—to make the motor in his Voisin biplane run for five consecutive minutes without breakdown. The war has shown us, and under working conditions which have been exceptionally trying, how reliable the aero-motor has become. But until duplicate plants have been perfected, and more than one motor is fitted to aircraft as a matter of course, there must always be this risk of failure.

In the mere stoppage of a motor no great danger is implied. The pilot must descend; that is all. His power gone, he must glide earthward. But where the risk does lie, in engine failure, is that it may occur at a moment when the airman is in such a position, either above dangerous country or while over the sea, that he cannot during his glide reach a place of safety. A study of flying will show how awkward, and how perilous on many occasions, has been the stoppage of a motor while a machine is in the air. Two historic instances, though they did not, fortunately, end in a loss of the pilot's life, were the compulsory descents into the Channel made by the late Mr. Hubert Latham, during his attempts, in 1909, to fly from Calais to Dover. In both these cases—once when only a few miles from the French shore, and on the second occasion when the aeroplane was quite near its destination—the motor of the Antoinette monoplane failed suddenly, and the aviator could do nothing but plane down into the water. On the first occasion he alighted neatly, suffering no injury, and being rescued by a torpedo boat; but in the second descent, striking the water hard, he was thrown forward in his seat and his head injured by a strut.

Less fortunate, in a case of presumed engine failure that will become historic, was Mr. Gustave Hamel. Eager to reach Hendon, so as to take part in the Aerial Derby on May 23rd, 1914, his great experience of Channel flying induced him to risk the crossing with a motor which, on his flight from Paris to the coast, had not been running well. His monoplane was a fast machine, and the flight across Channel would have taken him less than half an hour. But at some point during the crossing, it seems obvious, his engine failed him, and he was unable to prolong his glide either to gain the shore, or the vicinity of a passing ship. His monoplane was never recovered; but the body of the aviator—whose loss was mourned throughout the flying world and by the general public as well—was discovered by some fishermen while cruising off the French coast, and identified by means of a map, clothing, and an inflated motor-cycle tyre; the last-named being carried by the airman round his body to act as an improvised life-belt.

Engine failure, though a fruitful cause of minor accidents, and of the breakage of machines, has led to few fatalities; and this has been due very largely to the fact that, though machines have descended under dangerous circumstances, and have been wrecked in a manner that would appear almost certain to kill their occupants, the pilots and passengers have, as a matter of fact, escaped often with no more than a shock or bruises. An aeroplane does not strike the ground with the impact of a hard, unyielding structure. It is essentially frail in its construction; and this frailness, though it spells destruction for the machine in a bad descent, provides at the same time an element of safety for its crew. Take the case for instance of a machine falling sideways, and striking the ground with one plane or planes. These planes, built of nothing stronger as a rule than wood, crumple under the impact. But in their collapse, which is telescopic and to a certain extent gradual, a large part of the shock is absorbed. By the time the fusilage which contains the pilot touches ground, the full force of the impact is gone. And it is the same, often, if a machine makes a bad landing, say on awkward ground, and strikes heavily bow-first. Granted that the occupants of the machine are well-placed, and prevented by retaining belts from being flung from the machine, they should escape injury from the fact that there is so much to be broken, in the way of landing-gear and other parts, before the shock of the impact can reach them in their seats.

Had it not been for the capacity of the aeroplane to alight in awkward places without injury to its pilot, many lives might have been lost through descents in which motors have failed. Aviators have been obliged to land in most unsuitable places: on the roofs of houses, for instance, in small gardens, and frequently on the tops of trees. If he finds his engine fail him when he is over a wood or forest, and there is no chance save to descend upon the trees, a skilled pilot may save himself as a rule from injury. Planing down, till he is just above the tree-tops, he will then check suddenly, by a movement of his elevator, the forward speed of his machine. The craft will come to a standstill in the air; then, the support gone from its planes owing to the loss of forward speed, it will sink down almost vertically, and with very little violence, on to the tops of the trees. The machine itself will naturally be damaged, seeing that boughs will pierce its wings in many places, and that one or more of its planes may possibly collapse. But the net result of such a landing—and this is the point which is important for the pilot—is that the machine will be caught up and suspended on the trees, making a comparatively light and gradual contact, instead of there being any risk of its driving through the trees and making a heavy impact with the ground.

Humour, sometimes, may be extracted from such a predicament as engine failure, though it needs an aviator with a very deeply ingrained sense of humour to do so. The story is told, however, of a pilot who, flying across difficult country with a passenger, found that his motor failed—as they often will—just at a moment when there seemed no possible landing-point below. Looking over the side of his machine, and glancing quickly here and there, the aviator saw no alternative but to bring his craft down in an orchard that lay below. Pointing downward, to acquaint his passenger with their unpleasant situation, and to call his attention also to the orchard, the pilot said with a smile:

There is a risk in engine failure which has been emphasised more than once; and it is that which may attend the pilot who, while prolonging a glide in order to reach some landing-point, may be struck by a gust, or enter some area of disturbed wind, just before he reaches the ground and while his machine, moving slowly, is not in a position to respond effectually to its controls. In one case an aviator, struggling back towards the aerodrome with a motor which was not giving its power, found that it stopped suddenly when he was not far from a wood. Beyond the wood, which stood on a ridge, there was a stretch of grassland. Endeavouring to reach this promised landing-point, and holding his machine on a long glide, the airman came across above the trees. He had almost reached his goal when his machine entered a sudden down-current of wind—occasioned, no doubt, by the proximity of the trees and ridge. Caught by this eddy, with no motive power to help him and very little speed on his machine, the pilot could not check its sudden dive; and the craft struck ground so heavily that both he and his passenger were killed.

We have mentioned previously, as a fruitful cause of accident, that structural weakness of machines which has led, when conditions have been unfavourable, to a sudden collapse in the air. But apart from weakness in construction, and notably in accidents with early-type machines, there was the risk attached to mistakes in design, which produced machines which were unstable under certain conditions—and the dangers also which were due to inefficient controlling surfaces. It was no uncommon thing, in pioneer days, for a machine to be built which would not respond adequately to its elevator or rudder; though this unpleasant fact might not be discovered by the pilot until he was actually in flight, and perhaps at some distance from the earth. In one case, which is authenticated, a two-seated monoplane of a new type was tested at first in a series of straight flights, and found to be promising in its behaviour. A skilled pilot then took charge of it, and, carrying a passenger, proceeded to some more ambitious flights. Steering the machine away across the aerodrome, and flying at a low elevation, he approached a belt of woods. The machine was too near the ground to pass over the tops of the trees; so the aviator decided to make a turn, and fly parallel with the wood. But when he put his rudder over, so as to bring the machine round in a half-circle, he found to his dismay that there was no response. In the design of the machine, as it was found afterwards, the rudder had been made too small: it would not steer the machine at all. In the little space that was left him, and to avoid crashing into the trees, the pilot had to bring his craft to earth in such an abrupt dive that it was wrecked completely. He and the passenger, though, escaped unhurt.

Carelessness has, fairly frequently, played its part in aeroplane disasters. Sometimes a pilot has been careless, or perhaps in a hurry, and has failed to locate some defect which, had it been seen and attended to, would have saved a disaster when a machine was in flight. Such inattention, which is sufficiently dangerous in the handling of any piece of mechanism, is deadly in its peril when those who are guilty of it navigate the air. A man who brings out a machine time after time, and ascends without examining it carefully, is adding vastly to the risks that may attend his flight; and the same remark will apply to the carelessness of mechanics; though as a class, in view of the arduous nature of their work, and of the long hours they have frequently to be on duty, with no more than hasty intervals for rest, their average of care and accuracy is very high. But there have been cases—mostly in the past though—in which a machine has developed a structural defect, or some defect say in its control gear, which ought to have been observed by its mechanics, but which has not been so detected, and has led to a catastrophe in flight. With machines built lightly, and subjected to heavy strains when at high speeds, it is vital that the inspection of such craft, that the examination of every detail of them, should be carried out in a spirit of the greatest care. The fraying through of a control wire, unnoticed by those in charge of a machine, has been sufficient to cause a disaster; while carelessness in overhauling a motor, a task of supreme importance, seeing that its engine is the heart of an aeroplane, has been another cause of accident. It is vital that, when an airman ascends, both his machine and his motor should be in perfect working trim. He himself, before he flies, and after his aeroplane has been wheeled from its shed, should make it a habit to look over the machine, so as to impose his own personal check upon the work his mechanics have done.

Even when every care has been taken, and a machine ascends in perfect trim, there is the human factor, represented by the pilot, which must be considered always in a study of aeroplane accidents. There is often, when a catastrophe seems imminent, a choice of things that may be done. If an engine fails, for instance, under awkward circumstances, the pilot may have, say, three courses open to him in regard to his descent. Two may spell disaster and the third safety. It is here that the innate judgment of a pilot, combined with his experience, will tell its tale. But this personal element in flying, and particularly in regard to an accident, is often a very difficult one for which to make allowances.

The whole problem of aeroplane disasters is, to the analyst, one of unusual complexity. Take for example the case of a pilot who is flying alone in his machine, and at an altitude of several thousand feet. Suddenly something happens; the machine is seen to fall and the pilot is killed. Experts come to examine the aircraft, but it is wrecked so completely that little which is reliable can be gathered from any inspection; while the man who could explain what has happened—the pilot of the machine—is dead. The statements of eyewitnesses, when taken on such occasions, are often misleading. One person heard a crash, and saw something fall away from the machine. Another declares the engine stopped suddenly and that the machine "fell like a stone." Another says he is sure he saw one of the wings fold upwards and the machine swing and fall. And so on. It is extremely difficult, even for a technical eye-witness, to be sure of what he sees when things happen quickly and at a distance from him; while the statements of non-technical people, who are not trained in observation, are generally so unreliable as to be useless.

It has happened often therefore, far too often, in aeroplane fatalities that have happened from time to time, that the cause of such accidents has, even after the most careful investigation, had to be written down a mystery. But in more than a few cases, though the evidence has been far from conclusive, it has been considered that a pilot has been guilty of some error of judgment. There were puzzling instances, notably in the early days of flying, when airmen began first to make cross-country flights, of engines being heard to fail suddenly, and machines seen to fall to destruction. That engines should break down was not surprising; they were doing so constantly; but there was no reason why, even if they did fail, a machine should fall helplessly instead of gliding. But what was thought to have happened, in more than one of these cases, was that the pilot, through an error of judgment, had failed to get down the bow of his machine when his motor gave signs of stopping. The craft concerned were, it should be mentioned, "pusher" biplanes; and the same rule applied to them, in cases of engine failure, as has been explained in a previous chapter, and as is emphasised nowadays in the instruction of the novice. But in those days the beginner had frequently to learn, not from wise tuition, but from bitter experience; and he was lucky, often, if he learned his lesson and still retained his life. On certain early-type biplanes, for instance, machines with large tail-planes, and engined as a rule by a motor which was giving less than its proper amount of power, it was most dangerous for a pilot if, on observing any signs of failing in his engine, he sought to fly on in the hope that the motor would "pick up" again, and continue its work. Directly there was a tendency of the motor to miss-fire, or lessen in the number of its revolutions per minute, the consequent reduction of the propeller draught, as it acted on the tail of the machine, would cause this tail to droop, and the machine to assume very quickly a dangerous position. And when once it began to get tail-down, as pilots found to their cost, there was nothing to be done. The machine lost what little forward speed it had, and either fell tail-first, or slipped down sideways. Such risks as these, which were very real, were rendered worse owing to the fact that, in much of the cross country flying of the early days, pilots flew too low. They lacked the confidence of those who followed them, and were too prone to hug the earth, instead of attaining altitude. It was not realised clearly then, as it is now, that in height lies safety. And so when a machine lost headway through engine failure, and was not put quickly enough into a glide, it happened often that it had come in contact with the earth, and had been wrecked, before there was any chance for the pilot to regain control, or for the machine itself to exhaust its side-slip, and come back to anything like a normal position.

But the failure of the human factor in flying, the lack of skill of a pilot that may lead to disaster, is shown by statistics to play no more than a small part, when accidents are studied in numbers and in detail. Some time before the war, in an analysis of the accidents that had befallen aviators in France—accidents concerning which there was adequate data—it was shown that only 15 per cent. of them could be attributed to a failure in judgment or skill on the part of the pilot.

Apart from errors, however, in what may be called legitimate piloting, there have been regrettable accidents due to trick or fancy flying. Putting a machine through a series of evolutions, to interest and amuse spectators, is not of course in itself to be condemned. In such flying, and notably for instance in "looping the loop," facts were learnt concerning the navigation of the air, and as to the apparently hopeless positions from which an aeroplane would extricate itself, which were of very high value, from both a scientific and practical standpoint. Public interest in aviation was increased also by such displays; and it is very necessary that there should be public interest in flying, seeing that it is the public which is asked to pay for the development of our air-fleets. But the man who undertakes exhibition flying needs not only to be a highly-skilled pilot, but a man also of an exceptional temperament—a man whose familiarity with the air never leads him into a contempt for its hidden dangers; a man who will not, even though he is called on to repeat a feat time after time, abate in any way the precautions which may be necessary for his safety. In looping the loop, for instance, or in upside-down flying, it is necessary always that the aeroplane should be at a certain minimum height above the ground. Then, should anything unexpected happen, and the pilot lose command temporarily over his machine, he knows he has a certain distance which he may fall, before striking the ground; and during this fall the natural stability of his machine, aided by his own operation of the guiding surfaces, may bring it back again within control. But if he has been tempted to fly too near the ground, and has ignored for the moment this vital precaution, and if something happens for which he is not prepared, then the impact may come before he can do anything to save himself.

In the early days of flying, when aviators attempted an acrobatic feat, they ran a far heavier risk than would be the case to-day; and for the simple reason that their machines, not having a strength sufficient to withstand any abnormal stresses, were likely to collapse in the air if they were made to dive too rapidly, or placed suddenly at any angle which threw a heavy strain on their planes. A machine for exhibition flying needs to be constructed specially; but this was not realised till accidents had taught their lesson.

It is a regrettable fact, one which emerges directly from a study of aeroplane accidents, that many of them might have been avoided had men been content to follow warily in the footsteps of the pioneers, and not run heavy risks till they themselves, and the machines they controlled, had been prepared, by a long period of steady flying, to meet such greater dangers. The first men who flew realised fully the risks they ran. But when flying became more general, and men found machines ready to their hands, machines which it was a simple matter to learn to fly, this early spirit of caution was forsaken, and feats were attempted which brought fatalities in their train, and which seemed to emphasise the risks of aviation, and did it the very bad service that they fixed in the public mind a notion of its dangers, and prevented men from coming forward to take up flying as a sport.

CHAPTER VIII

FACTORS THAT MAKE FOR SAFETY

It has been calculated that nearly half the aeroplane disasters of the early days were due to a structural weakness in machines, or to mistakes either in their design, or in such details as the position, shape, and size of their surfaces. To-day, thanks to science, and to the growing skill and experience of aeroplane designers and constructors, this risk of the collapse of a machine in the air, or of its failure to respond to its controls at some critical moment through an error in design, has been to a large extent eliminated. That such risks should be eliminated wholly is, as yet, too much to expect.

One of the factors making for safety has been the steady growth in the general efficiency of aircraft: in the curve of their wings which, as a result largely of scientific research, has been made to yield a greater lift for a given surface and to offer a minimum of resistance to their passage through the air; in the power and reliability of their engines; in the efficiency of their propellers; and in the shaping of the fusilage of a machine, and in the placing and "stream-lining" of such parts as meet the air, so as to reduce the head resistance which is encountered at high speeds. Such gains in efficiency, which give constructors more latitude in the placing of weight and strength where experience show they are needed, have gone far to produce an airworthy machine. In the old days, when machines were inefficient, a few revolutions more or less per minute in the running of an engine meant all the difference between an ascent and merely passing along the ground. But nowadays, through the all-round increase in efficiency that has been obtained, a machine will still fly upon its course without losing altitude, and respond to its controls, even should the number of revolutions per minute of its engine be reduced considerably.

When given a greater efficiency in lifting surfaces and power-plants—and profiting also from the lessons that had been learnt in the piloting of machines—constructors were able to devote their attention, and to do so with certainty instead of in a haphazard way, to the provision of factors of safety when a craft was in flight. With a machine of any given type, if driven through the air at a certain speed, it is possible to estimate with accuracy what the normal strains will be to which it is subjected. But even if such data are obtained, and the machine given the strength indicated, this factor of safety is insufficient. It is not so much the normal strains, as those which are abnormal, that must be guarded against in flight. A high-speed machine, if piloted on a day when the air is turbulent, may be subjected to extraordinarily heavy strains; rising many feet in the air one moment, falling again the next, and being met suddenly by vicious gusts of wind—in much the same way that a fast-moving ship, when fighting its way through a rough sea, is beaten and buffeted by the waves. Air waves have not of course the weight, when they deliver a blow, that lies behind a mass of water; but that these wind-waves attain sometimes an abnormal speed, and have a tremendous power of destruction, is shown in the havoc that is caused by hurricanes.

It seems astonishing to many people that such a frail machine as the aeroplane, with its outspread wings containing nothing stronger often than wooden spars and ribs, covered by a cotton fabric, should be capable of being driven through the air at such a speed, say, as 100 miles an hour, encountering not only the pressure of the air, but resisting also the fluctuations to which it may be subjected. But, underlying the lightness and apparent frailty of such a wing, when one sees it in the workshop in its skeleton form, before it has been clothed in fabric, there is a skill in construction, and an experience in the choice, selection, and working of woods, that produces a structure which, for all its fragile appearance, is amazingly strong. And the same applies, nowadays, to all the other parts of an aeroplane. That it should have taken years to gain such strength, and to reduce so largely the risk of breakage, is not in itself surprising. Men had to devise new methods in construction—always with the knowledge that weight must be saved—and to create new factors of safety, before they could build an airworthy craft.

To-day, when a man flies, he need have no lurking fear, as had the pioneers, that his craft may break in the air. Even when it is driven through a gale, plunging in the rushes of the wind, yet held straining to its task by the power of its motor, the modern aeroplane can be relied upon; and not in one detail of its construction, but in every part. Experience, the researches of science, and the growing skill with which aircraft are built, stand between the airman and many of his previous dangers. The aeroplane to-day, one of the structural triumphs of the world in its lightness and its strength, has a factor of safety which is sufficient to meet, and to withstand, not merely ordinary strains, but any such abnormal stresses as it may encounter—and which may be many times greater than the strains of normal flight.

The aviator knows also that his engine, as it gives him power to combat successfully his treacherous enemy, the wind, represents the fruit of many tests and of many failures, and of the spending of hundreds of thousands of pounds. Many of its defects have revealed themselves, and been rectified; it is no longer light where it should have weight of metal, nor weak where it should be strong. So far as any piece of mechanism can be made reliable, consisting as it does of a large number of delicate parts, operating at high speed, the aeroplane motor has been made reliable. But, so long as one motor is used, there must always, as we have said, remain a risk of breakdown. It is for this reason that, thanks largely to the stimulus of the war—which has created a practical demand for such machines—aeroplanes are now being built, and flown with success, which are fitted with duplicate motors. With such machines, which give us a first insight as to the aircraft of the future, engine failure begins to lose its perils—particularly in regard to war. More than once during the great campaign, when flying a single-engine machine, an aviator has found his motor fail him, and has been obliged to land on hostile soil; with the result that he has been made prisoner. But with dual-engine machines it has been found that, when one motor has failed mechanically, or has been put out of action by shrapnel, the remaining unit has been sufficient—though the machine has flown naturally at a reduced rate—to enable the pilot to regain his own lines.

In peace flying, too, as well as in war, the multiple-engined aeroplane brings a new factor of safety. If one of his motors fails, and he is over country which offers no suitable landing-place, the pilot with a duplicate power-plant need not be concerned. His remaining unit or units will carry him on. There are problems with duplicate engines which remain to be solved—problems of a technical nature—which involve general efficiency, transmission gear, and the number and the placing of propellers; but already, though this new stride in aviation is in its earliest infancy, results that are most promising have been obtained.

To those who study aviation, and have done so constantly, say from the year 1909, one of the most striking signs of progress lies in the fact that, though unable at first to fly even in the lightest winds, the aviator of to-day will fight successfully against a 60 miles-an-hour wind, and will do battle if need be, once he is well aloft, with a gale which has a velocity of 90 miles an hour. He will ascend indeed, and fly, in any wind that permits him to take his machine from the ground into the air, or which the motor of his craft will allow it to make headway against. And here, though machines are still experimental, there is removed at one stroke the earliest and the most positive objection of those who criticised a man's power to fly. When the first aeroplanes flew the sceptics said: "You have still to conquer the wind, and that you will never do. Aeroplanes will be built to fly only in favourable weather, and this will limit their use so greatly that they will have no significance." But to-day the aviator has ceased, one might almost say, to be checked or hampered by the wind. If the need is urgent, as it often is in war, then it will be nothing less than a gale that will keep a pilot to the ground, provided he has a sufficiently powerful machine, and a suitable ground from which to rise—and granted also that he has no long distance to fly. Wind-flying resolves itself into a question of having ample engine-power, of being able to launch a machine without accident, and get it to earth again without mishap; and of being able to make a reasonable headway against the wind when once aloft; and these difficulties should solve themselves, as larger and heavier machines are built.

Apart from the growing skill of the aviator, which has been bought dearly, science can now give him a machine, when he is in a wind, that needs no exhausting effort to hold it in flight. Craft are built, as a matter of certainty and routine, which have an automatic stability. Science has made it possible indeed, by a mere shaping and placing of surfaces, and without the aid of mechanical devices, to give an aeroplane such a natural and inherent stability that, when it is assailed by wind gusts in flight, it will exercise itself an adequate correcting influence. To understand what this means it should be realised that, when such a machine is in flight say in war on a strategical reconnaissance, and carries pilot and passenger, the former can take it to a suitable altitude and then set and lock his controls, and afterwards devote his time, in common with that of his passenger, to the making of observations or the writing of notes. The machine meanwhile flies itself, adapting itself automatically to all the differences of wind pressure which, if it had not this natural stability, would need a constant action of the pilot to overcome. All he need do is to maintain it on its course by an occasional movement of the rudder. With such a machine, even on a day when there is a rough and gusty wind, it is possible for an airman to fly for hours without fatigue; whereas with a machine which is not automatically stable, and needs a ceaseless operation of its controls, the physical exhaustion of a pilot, after hours of flight, is very severe.

So, already, one sees these factors of safety emerge and take their place. There is no longer a grave peril of machines breaking in the air; there need be no longer, with duplicate power-plants, the constant risk of engine failing; while that implacable and treacherous foe, the wind, is being robbed daily of its perils.

CHAPTER IX