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.