The Challenge of High-Speed Flying

by COL. II. G. MOSELEY, USAF (MC)

1

FLYING has become a challenge: an exquisite challenge to man’s ability to design, to engineer, and to build; a provoking challenge to his skill and daring in a realm of new and formidable frontiers. In meeting this challenge, he has been amazingly successful: so successful, in fact, that like a precocious youth he is hurtling past all known concepts and confounding his professors by asking the solution of thermal barriers, cosmic rays, and other riddles which are not yet included in the textbooks.

However, an unexplained complication has arisen that is causing him to pause in his bludgeoning progress. It is a matter of tolerances which cannot be improved and of design which cannot be changed. It is the design of man himself, who must fly these fabulous products of his ingenuity. And the limitation of concern is not his physical frailty, but an unexpected inadequacy in the very method by which he has been able to survive through these many millenniums.

The human animal has survived by virtue of his ability to perceive, decide, and react. He perceives existing conditions, decides whether they are hostile or friendly, alluring or distasteful, and reacts in the way best calculated to ensure his survival. From prehistoric times to the present, this basic behavioral sequence has not changed, not even when man solved the riddle of lift and energy and undertook the conquest of space. This is the more amazing because man is placing himself in competition with ever more awesome machines and dangerous environments. Were the modern pilot placed side by side with Cro-Magnon man and confronted with a mutually understandable situation such as the sudden appearance of a saber-tooth tiger, both would perceive the situation with the same speed, interpret it as being hostile at approximately the same instant, and react by withdrawal with about the same alacrity. However, in modern high-speed flying, man is pitting himself against opponents that are immeasurably more hostile than a saber-tooth tiger. These are gravity, space, and velocity.

Of the three, velocity is emerging as the most implacable foe. Gravity and space are rather effectively held at bay by aerodynamics and by man’s ability to carry his necessary environment in the bubble of his canopy or the enclosure of his cabin. But in the velocity of flight, man finds himself continually pilling his wits against a course of events which transpire with unbelievable rapidity. And here, perhaps for the first time in all his occupations, man finds that he has placed himself in a true enigma, and that his physical limitations are completely inadequate for the demands of the game. As a result, he is frequently in jeopardy, and even slight errors can be attended with results that are enormously traumatic.

Successful flight is absolutely dependent upon the pilot’s ability to 1) perceive his world and cockpit about him, 2) recognize the meaning and significance of what he perceives and decide from such observations the course of action which will best guarantee unhampered continuance of his flight, and 3) react in a manner that will not only make the aircraft respond to his decisions, but maintain it in flight during his preoccupations and distractions. In modern high-speed aircraft, he frequently finds himself performing these tasks while he is traveling at speeds slightly below Mach 1, or approximately 600 miles per hour. At this speed he is traversing space at 880 feet per second.

Here is where it is quite appropriate to contemplate a small measure of time — one tenth of one second, to be exact. This is the amount of time it takes, on the average, for the optic nerve and its ramifications to carry any image the retina of the eye picks up to the brain. In other words, we “sec” an object approximately one tent h of a second after our eye beholds it.

This delay, so insignificant in our normal lives, obt ains startling stature in the occupation of flying.

While flying at 600 miles per hour, the pilot traverses 88 feet in that instant. Thus he is 88 feet closer to an object in front of him than he thinks he is when he sees it. And this is as unchangeable as the laws of nature, because no known drugs or electronics or forces can reduce this lag. It is an integral part of the human design.

Yet visual perception is one of the fastest processes upon which man depends for his survival. Reaction is much slower. It takes on the average four tenths of a second before a decision from the brain can be transmitted into useful action. Four tenths of a second for the nerves to carry the impulses and to stimulate the hands or feet into effective movement. Four tenths of a second before the pilot, having decided to turn his aircraft, can put such a decision into action. At 600 miles per hour, this can be converted into an absolute forward displacement of 352 feet.

But the most confounding of all are the requirements for interpreting and deciding. When the pilot’s eyes behold an object before him in the sky and the message is carried to the seeing center of his brain, it takes a definite measure of time for the significance of that object to be catalogued. Is it a star or a spot on the windshield, and thus unimportant to the course of his flight ? Or is it a weather balloon or another aircraft, and thus a potential threat to his survival? In other words, what is seen must be recognized and evaluated. Even with the maximum of alertness and the greatest of familiarity with objects to be encountered in the sky, such recognition is computed to take at least onehalf second, and probably takes longer.

The decision of what to do after the significance of an object or event is understood is the most variableof all. Ordinarily, decisions which must be made when life and death are at stake require a profundity of reflection, a weighing of factors, and the eventual distillation of a choice. But the pilot who holds his own life and often the lives of many others in the balance has no time for reflection. When a hostile object appears in the sky before him, he must decide instantly whether or not he should turn his aircraft, and if so whether he should turn up or down, or right or left, and whether he should slow his speed or accelerate, and even whether or not his plane can structurally stand the maneuver he is about to attempt. His decision must be correct. It is difficult to compute the minimum time in which a pilot can conjure up the important factors to be considered in making such a decision, weigh them, and arrive at a choice. It is probable that four or five seconds will elapse. It is possible that he can decide within two seconds, although such instant decisions must be attended with an element of luck to be successful.

Thus, in the alert and fortunate pilot we can expect a minimum of two and a half seconds for his recognition and decision. When we consider the added time of his perception and reaction, we are faced with an absolute minimum requirement of three seconds of time. During this period, while flying at 600 miles per hour, he irrevocably traverses 2640 feet of space or one-half mile, regardless of impediments or danger, regardless of desire, decision, or action to avoid it.

If he is on a collision course with another aircraft, this space deficit will be doubled. The significance of man’s inability to cope with such rates of closure was dramatically illustrated last year by two young pilots. They were flying high-performance jet fighters and had been practicing simulated air-to-air combat maneuvers. Apparently tiring of chasing one another, they announced that they were going to separate a few miles and try a head-on pass. Another pilot who heard this statement immediately warned them against such a maneuver. Whether they did not hear him or whether they simply disregarded instructions will never be known. The only certainty is that it was their last mortal decision. They collided with the explosive impact of two gigantic bullets. Yet little else could be expected. Their closing speed was over 1700 feet per second! Paradoxically, it was their acuity of vision and sureness of action which allowed them to establish their tragic course. They simply failed to reckon with their own physiological inertia.

2

THIS brings up another consideration which is difficult to compute, but which isgrowing in significance as the speeds of flight increase. This is the probability of perceiving the warnings of instruments or of seeing outside obstacles which are detrimental to flight. It is obvious that instruments telling of the flight path, fuel reserve, and other items cannot all be watched constantly or thus interpreted instantly when dangerous situations or levels are reached. Therefore, the pilot sometimes finds that he has placed himself in an untenable position, such as running out of fuel, through oversight or while having his attention diverted to other things. But of great er concern and of ever-increasing magnit ude as the speeds of flight increase is the probability of seeing a collision object outside the aircraft. It is obvious that the pilot cannot see a mountain in front of him while flying in the clouds, or unlighted obstacles while flying at night. However, less obvious is the improbability of seeing an object outside of the cockpit even on a clear day. The following event is revealing: —

A pilot of a jet bomber was recently flying at 30,000 feet at eleven in the morning on a clear day. He made a slow turn and was startled to see three other jet bombers approximately one mile away and on a collision course toward him. He did not have time to react or alter the course of his aircraft during the three or four seconds of closure, and shot through the formation, missing the nose of the first aircraft, flying under the second, and flying over the third. As he went over the third bomber, one of his engines hit the upper portion of this bomber’s tail and knocked it off. The pilot who flew through the formation then returned to his home base, landed, and recounted his experience. Inasmuch as no report had been received from the formation he had flown through, it was called and requested to land. When it landed it was found out that the formation consisted not of three aircraft, but of six. The aircraft whose tail had been hit was not significantly damaged; it was a matter of small concern. However, of great amazement was the fact that neither the pilot, the co-pilot, nor the observer in any of the six aircraft of the formation had seen the other bomber fly through them!

How is such a phenomenon explained? It is partly explained by the fact that modern flying requires a great breadth of attention to a great many instruments and objects, and it is not possible to be constantly on the alert for a collision object. Hut mostly it is explained once more by the lag of the human mechanism. It is seldom that an image falls directly upon the fovea or the central visual point of the eye. Instead, the stimulus falls on some off-center area and the eye responds by turning toward the stimulus. This takes time. And then after the eye is directed toward the stimulus, it must be focused. Like a camera lens, the eye needs time to bring the image sharply upon the fovea. And in the vastness of space where there is little in the outside realm to command attention, eyes tend to become focused on recognizable things in the cockpit or to be relaxed and follow the effortless pattern of looking at the nothingness that lies a few feet ahead. For in the concealment of the cockpit it is impossible to grasp the magnitude of conditions outside. Only an occasional individual such as test pilot George Smith, who ejected at 700 miles per hour and miraculously survived, can give us some clue as to the real meaning of flight, and of nature’s monstrous resentment.

These events signal an era of new and changing conditions. And when conditions change, life must adapt or die. Fortunately man is a highly adaptable animal, and it is his ability to adapt which will undoubtedly allow him to inhabit the missiles of the future and survive. But inasmuch as the penalty for error is extremely harsh in the occupation of flying, we might do well to anticipate some of the future requirements and lower the cost. Although all of the dangers which lie ahead cannot be foreseen, a few at least are obvious.

The most apparent of these is that as speeds increase and as the number of aircraft multiplies, the age-old method of survival by seeing and evading will become completely obsolete. Closing speeds will be so great that a pilot will be committed to a mid-air collision even as, or before, he sees another aircraft. Uninterrupted flying will thus become completely dependent upon strict, accurate air traffic control. And unless man soon makes these laws, and keeps them inviolate, nature will exact the death penalty.

Another fairly obvious conclusion is that the speeds of future flight will commit an aircraft and its occupants to a definite and unalterable course that will involve irrevocable miles of distance in the few seconds required for the human operator to perceive, to decide, and to react. These requirements are absolute and can in no way be eliminated from the occupation of flying. However, there is an evasion which is not only possible but highly practical. This is taking the requirement of decision and accomplishing it before the flight takes place. It is current practice to plan carefully the anticipated course before each flight. This is the only sensible method of avoiding fixed obstacles. However, there are count less additional decisions the pilot still must make in flight, and he sometimes errs and accidents result. 1ft he majority or all of such decisions could be made before he leaves the ground, they could be attended with greater thought, be more accurate, and not. demand the irrevocable block of space which accompanies in-flight decisions. Although this may seem to deprive the pilot of much of his independence, it is nevertheless highly practical. Successful flying operations, both commercial and military, are resorting more and more to this rigid discipline. Furthermore, it is the gospel of test pilots. More than anyone else, they endeavor to preconceive every hazard or hazardous condition before it arises. Then when emergencies occur, they only need to perceive them and react. The decision has already been made, and their immediate reaction is unequivocal and life-sax ing. And this is a peculiar txxist in the pattern of survival, for the lifesax ing decisions do nol come between what man sees and what he does, but the decision comes first of all. This altered sequence might well become the law of future flight.

However, if airborne man is to survive, the greatest responsibility of all falls upon those who design and engineer and produce aircraft. For the man in the cockpit is mortal and he is limited. Therefore, aeronautical science must understand him well and adjust the miracles of progress to his slow chemistry and his propensity for error. Thus the challenge. It is a challenge to develop and provide simplicity of perception, clarity of interpretation, and case of manipulation, even as the aircraft themselves become ever more complex. And the requirement is absolute. If design should neglect or complicate the human lot, man cannot help destroy ing the fabulous machines of the future, and all who occupy them.