“They also serve who only stand and wait."—Milton.
Why doctor, I can pick up a light as quickly as anybody on the bridge!” “I never had the slightest thing wrong with me!” “Not qualified for aviation! I’ve been flying for months!”
Such comments are all too familiar to the flight surgeon. Unfortunately for the peace of mind of the rejected applicant, they are not always answered. There is seldom time to explain carefully. Unanswered they leave room for the impression that qualifications are arbitrary and senseless and just another effort on the part of the Medical Department to exercise unwarranted, empirical dicta.
But there are good reasons for all causes for rejection in the regulations governing flying qualifications. They are based on sound, general principles. They are neither secret nor needlessly couched in cryptic Latin terminology unintelligible to the lay mind. And there is no reason in the world why a rejected candidate should not know why he has been found not qualified.
It is difficult to generalize on a subject so complex, but in an effort to express simply and in general terms the reasons for the regulations the following is offered.
In general there are two criteria used by flight surgeons: (1) We have very good reason to believe that if an individual is endowed with certain physical deficiencies or defects he is more apt to crash than one who is free from these defects. If he is more apt to crash he is more apt to be injured or killed. In rejecting for these reasons we act solely in the capacity of doctor—to save life. (2) For naval aviation it is not sufficient that an individual be free from defects at the present moment. Will he be fit ten, twelve, fifteen years from now? With how much of the strain of flying under any and all conditions can we burden him without reducing his reserve to a dangerous or disqualifying level? We must weigh the investment. In rejecting because of deficiencies on this score we do so as “budget officers.”
The first is quite understandable. Defects coming within this category include defective vision, defective hearing, impaired heart action, diseases of the ear, nose, and throat, general systemic diseases, etc. Let us consider these in some detail.
Excellent vision is by far the most important single attribute for flying. This statement sounds like a platitude. But there are other respects in which vision plays an all-important part besides simply seeing things correctly.
The perception of depth and distance must be rapid and infallible. This is not a purely physiological function, being largely dependent upon experience in terrestrial association, motion parallax, size of objects, etc. But it is based primarily upon the accuracy of the receptor—good vision.
Why good color perception has so much significance in aviation is not always understood, especially in those rare cases in which the defect is adjudged sufficient to disqualify for flying but not for general line duties. That color perception should be more important to the aviator than to the navigator seems at first glance farfetched. But when it is remembered that color perception plays an important part in estimating terrain, that defective color vision means reduced fields of peripheral color sense which is somehow associated with “night blindness,” and that the rapidity of an aviator’s changes in relation to other objects precludes deliberation, the importance of unhesitatingly accurate color perception becomes apparent.
The accommodative function of the eye must be efficient and accurate. This is the power to adjust the refractive power of the eye for near vision. The aviator must be able to rapidly adjust his vision between distant objects and his instruments, charts, codes, etc., and without bifocals.
Among the most important reasons for good vision is the fact that it is the sine quo non of the aviator’s determination of his position in space. All the other senses of equilibration, the semicircular canals, muscle sense (so-called “seat-sense”), etc., help him to maintain a satisfactory relationship to his airplane, but his only means of determining his relationship to the earth is by vision. He must have visual contact with gravity. This is particularly significant in instrument flying, in which this visual contact is entirely through instruments. The strain of instrument flying is always referred directly to eyestrain.
“Why require good hearing? The noise of the motor makes it impossible to hear anything, anyway!” All the more reason. Very often a failing motor will give its first warning in the form of a change in sound. These sounds as well as radio and voice sounds must be perceived in the presence of and in spite of the noise of the motor. Furthermore, the disease which produced the deafness may have been associated with disease somewhere else, such as the semicircular canals.
Certain disabilities are incompatible with flying but should not necessarily interfere with terrestrial existence. Any condition which might be aggravated by the changes encountered at high altitudes, rapid changes in altitude, or the acceleration of rapid maneuvers must be considered cause for rejection. Any heart findings or even the history of conditions which are often peculiarly associated with heart disability and which would indicate that there had been damage to the heart muscle must be interdicted. The physiological changes incident to low oxygen at altitudes produce an unusual strain upon the heart and circulation. Blood pressure which is perfectly consistent with normal sea-level activity but is persistently above what might be dangerously aggravated by flying makes the possessor a potential crash—a potential casualty.
Some diseases are characterized by periods during which they lie dormant but are apt to manifest themselves at unforeseen times or under adverse circumstances. They should constitute cause for rejection. Malaria is one of these. Exposure to cold may precipitate an attack in one who has been apparently free for a long time. Hay fever and asthma may be precipitated and are particularly undesirable at altitudes where increased breathing is a normal compensatory reaction. Syphilis may be quiescent for years and then take one of the central nervous system forms which insidiously reduce neuro-muscular functions or mental balance.
When a candidate for aviation presents any of the above conditions the examining flight surgeon is faced with the problem of endorsing someone in whom he recognizes conditions which make him a potential crash. He rejects in all professional conscience and unequivocally.
Certain other findings are not so immediately indicative of potential casualty but are more in the nature of impaired or deficient reserve. They indicate that as a result of increasing age or the peculiar rigors of flying they might reduce the individual’s physiological efficiency to a level at which continuance of flying might be unduly hazardous. These govern the second criterion.
It is not sufficient that an applicant have 20/20 vision. How much of the potential strength of his eyes does he use in seeing 20/20? At the expense of how much strain of the muscles of the eyes does he maintain normal binocular fixation? How much may his eyes be burdened and he still see 20/20? By the same token, not that his pulse rate and blood pressure are within certain limits but how about the efficiency of his circulation under a load? These and many other similar questions must be answered before it can be asserted that he is a good aviation investment. A considerable portion of the aviation physical examination is designed to determine just these things.
In estimating the general physique of the candidate there are, of course, certain definite mensurable limits which must not be exceeded. In general they conform very closely to the requirements for general service. It has been said that the ideal aviator is of the tall, short, thin, stout, lanky, thick-set, etc., type. There is no optimum type. Apparently ideal physique may be negatived by other attributes. However, one thing is essential. There must be reserve, be it either wiry or husky reserve. This requires a rather general estimation and is based upon the impressions created by the physique as a whole.
In this connection there are certain limits of stature which are required by purely military considerations. For uniformity of cockpit dimensions, lengths of controls, blind angles, etc., it is essential that height and weight come within certain limits. It has been said, somewhat facetiously mayhap, that after all “we can’t build naval aircraft on kiddycar dimensions.”
Estimation of heart reserve is made by determining the “circulatory efficiency rating,” the so-called Schneider Index. This consists of placing a uniform load on the circulation and measuring the response in terms of change in pulse rate and blood pressure. An efficient circulation is characterized by comparatively slow basic pulse, moderate response to change in posture and exercise, quick return to normal after exercise, and a rise in blood pressure on standing. Of course a low rating may be caused by a great many conditions. Pulse may be rapid because of a fever or because of the tension engendered by being examined. Circulatory efficiency is variable and subject to circumstances in the more or less recent past. The most valuable use of its estimation is as a current frequent index of general fitness. It is used as a quick, ready, numerically expressed guide.
Among the commonest causes for rejection are those indicating deficient reserve in the eyes. “Extra-ocular imbalance,” “high refractive error,” “deficient accommodation” are some of the high sounding terms used. “Exophoria,” “hyperphoria,” “diopters” are words that have resounded unpleasantly in the ears of many readers. What do they all mean?
In order to place the eye in such a position that the rays from a desired point of fixation will fall on the point on the retina of maximum vision, each eye is moved by six voluntary muscles which are capable of moving the eye in practically all directions —even rotating it about its fore-and-aft axis. Each muscle has a specific function determined by its origin on the orbit and its insertion on the eyeball but they are arranged so as to function as groups for specific movements. Thus there are converging and diverging groups, elevating and depressing groups, etc.
These groups vary in their individual and composite strengths, the converging group being strongest because convergence is necessary for near fixation. The nerves controlling the movements of the eyes constitute a most intricate arrangement, being associated with a number of senses and functions.
Easy, symptom-less fixation of both eyes on the same object is dependent upon an extremely delicate balance between these mutually opposing groups. If one group is comparatively weaker than its opponent fixation is possible only at the expense of strain on the weaker group. Such strain may be an insidious besetment. It shows itself in symptoms varying from a slight feeling of fatigue, through pain and headache, to nausea and general systemic disability. When the strain exceeds the capacity of the muscles, the eyes assume an abnormal relative position depending on the imbalance, binocular fixation fails and there is diplopia or double vision.
Balance of the eye muscles is measured on the phorometer. This is an apparatus consisting of small cylinders and prisms arranged in such a way that the relationship of the two eyes may be measured when fixation is artificially relieved. If the relative strength of opposing groups of muscles is such that the eyes will balance in convergence, the condition is expressed as “esophoria.” If balance is reached in divergence it is “exophoria” and if the eyes tend to come to rest with one elevated above the other the condition is called either “right or left hyperphoria,” depending on which is elevated. The degree of phoria is expressed in prism diopters.
Perfect balance is an extreme rarity. It is dependent upon so many other associated conditions that perfection should hardly be anticipated. Esophoria is apt to be associated with farsightedness because the extra energy required to focus for near vision extends to produce an excessive impulse to convergence. Exophoria is more apt to be associated with nearsightedness. Hyperphoria may be the result of habit— tilting the head to balance a hat habitually cocked over one ear.
In setting allowable limits of the phorias, consideration is given to these various associated conditions. Certain degrees of esophoria are allowed when not associated with farsightedness near the allowed limits. Exophoria is not so damning if the angle of convergence is high. Sometimes it is necessary to measure the actual strength of all groups of muscles to determine whether a phoria is the result of weakness of one group or overdevelopment of its opponent.
Certain aspects of flying qualify the significance of the phorias. Unquestionably the aviator uses his extra-ocular muscles more than the individual whose movements are not so restricted. The cramped position in the cockpit together with restrictions of movement of the head make it necessary for him to effect binocular fixation by movement of the eyes rather than by turning the head or body. In open planes it is necessary to wear goggles. These are never perfect and it may be necessary for an aviator to assume an abnormal inter-relationship of his eyes to compensate for refractions in the goggles. Blind angles because of the goggles restrict normal associated movements. The restriction to vision across the midline tends to overdevelop the diverging groups —to exaggerate an exophoria. High altitude is particularly apt to impair the strength and co-ordination of eye muscles.
All these qualifying conditions are taken into consideration in evaluating the significance of the heterophorias. In general it may be said that exophoria is less to be desired than esophoria, and hyperphoria is definitely not acceptable. The fact remains that diplopia, double vision, is of very little help to an aviator.
A word about the accommodative power of the eyes. The normal eye at rest has a refractive index which focuses at infinity, for practical purposes, beyond 20 feet. In order to secure a clear image of a closer object it is necessary to increase the refractive index by decreasing the radius of the lens. This is done by the involuntary ciliary muscles. These muscles operate in a negative way. Contraction of the muscle reduces the diameter of the suspension of the lens and permits it to elongate fore and aft and thereby increase its optical strength. But this elongation is limited by the inherent elasticity of the lens which is determined by age, consistency, etc. No amount of muscular effort can increase the power of the lens beyond its elastic limits.
The accommodative power of the eye is measured by determining the nearest point at which vision can be focused and by refraction. Near vision is expressed in lens diopters and the qualifying limits are on a scale in which age is a variable factor. Refraction consists of paralyzing the ciliary muscles and measuring the refractive index of the eye at rest by the retinoscope and determining the smallest correction required for distant vision. Refraction in the flight physical examination is not designed to determine the best correction such as might be used in the prescription of glasses but only the least necessary correction.
Again the object is to determine the value of ocular reserve. Not that the candidate can see the familiar 20/20 without glasses, but at the expense of what proportion of his seeing strength does he do so or how much can we load on those eyes without reducing his vision below 20/20?
Because of the emphasis placed upon temperamental adaptability, psychological aptitude, personality, etc., flight surgeons have found themselves pretty generally classed in that much to be shunned group of “psychologists,” “psychiatrists,” etc. Service lore is now rife with the stories of the embarrassing questions sometimes asked and the results of some answers. It is unfortunate that antipathy should have developed toward this part of the examination. It is natural enough because no one enjoys the feeling that he is being “measured for the nut house.” It is unfortunate because such is not really the criterion.
Of course it is important to disclose any definite psycho-pathological tendency if such should exist. If an individual should be burdened with trials and tribulations, complexes and conflicts undermining an inherently deficient mental reserve enough to make him a potential mental patient, this should be known not only to evaluate his adaptability to aviation but to service requirements in general. But this is not all. Within the limits of normality covered by the Bard’s “me and thee,” the variations are almost infinite. Fortunately we are not all Caesars, nor Edisons, nor even Lindberghs. We are combinations of attributes arranged in varying combinations and permutations which by their proportionate concentrations determine our peculiar aptitudes and fortes. Certain of these make us adaptable to certain specific endeavors while certain others make it highly undesirable for us to commit ourselves to an existence for which we are not suited. No one will deny that certain temperamental attributes are desirable for flying while others are not. In estimating the applicant’s investment value for naval aviation the flight surgeon must consider these things. Hence the so-called “psychological” examination.
The aviator is not a superman nor is he “born to fly.” There is no specific best type. Nor is every aviator suited for all types of flying. The peace-time aviator differs in some characteristics from the wartime ace. In peace time there is no place for sky gun-fodder.
Considering all these features, these peculiar attributes and personality trends, there remains a certain percentage of otherwise perfectly normal individuals who cannot master the art of flying or, having mastered the art, adapt it to the profession of arms. It is the flight surgeon’s mission to reduce the percentage of failures to a minimum.
In actual practice in peace time, the “proof of the pudding” remains the ultimate criterion. The psychological part of the flight physical examination is still largely in a state of study and research and is essentially a war plan. We must have some yardstick to give our recruiters by which to eliminate the manifestly unfit on whom we cannot afford to expend the time and effort necessary to train them during a war. That yardstick is not yet carefully calibrated or verniered.
The important point to remember about this feature of the examination is that in finding an individual “not temperamentally adapted for duty involving the actual control of aircraft,” the flight surgeon makes no quantitative evaluation. His findings have nothing to do with grading that individual’s adaptability for life in general or any other specific endeavor. He decides only that he is not qualitatively suited for naval aviation. The unfortunate fact remains that it is very often impossible to impart this fact to the individual’s commanding officer without engendering an impression of inaptitude toward the service in general. With the present necessity for unblemished escutcheons this is too great a risk to take and, accordingly, rejection for temperamental inaptitude is practically never made. In all fairness the original examining flight surgeon gives the applicant the benefit of the “proof of the pudding” at Pensacola.
So much for the most frequent causes for rejection for aviation training. To reiterate, the flight surgeon must reject the manifestly potential crash and those whose continuance in flying fitness cannot be anticipated for a sufficiently long career to warrant their training.
Although experience has not been sufficient to remove all empiricisms from all the criteria they are by no means arbitrary. It is much more pleasant for the flight surgeon to wish a successful candidate a cheery “happy landings.” But in his own interest and for the good of the service it is often necessary to express a genuinely sincere “Sorry!”
I end with an apposite quotation from the Archduke Charles:
“A General often does not know the circumstances upon which he has to decide, until the moment in which it is already necessary to proceed at once with the execution of the necessary measures. Then he is forced to judge, to decide, and to act with such rapidity that it is indispensable to have the habit of embracing these three operations in a single glance, to penetrate the consequences of the different lines of action which offer, and to choose at the same time the best mode of execution. But that piercing perception which takes in everything at a glance is given only to him who by deep study has sounded the nature of war, who has acquired perfect knowledge of the rules, and who has, so to speak, identified himself with the “science.”—Mahan, Naval Strategy.