Searching Medical Examinations for Service and Commercial Pilots
THERE is no recorded instance in the history of British aviation of an accident due to the physical failure of a commercially-licensed pilot. This is largely due to the high standard of physical fitness demanded in the specialized examinations of the Central Medical Board of the Air Ministry, the headquarters of which are within a few yards of the Law Courts in London. This Board has to ensure that none but pilots of exceptional fitness are licensed commercially to carry passengers or goods by air. The Board represents, in effect, one of British air transport’s greatest safeguards.
The Central Medical Board is, however, considerably more than the guardian of commercial aviation. Not only every commercial or “B” licensed pilot and navigator in Great Britain, but also every prospective and present pilot of the Royal Air Force must pass before it or its representatives. Even the private, or “A” licensed pilot, who may be examined by his own medical attendant instead of appearing before the Board, still comes under its influence, as it is the Board’s experts who compile and supply the detailed medical form upon which the private pilot’s doctor bases his examination.
X-RAY APPARATUS used at the Central Medical Board for examination of suspected cases of heart or lung disease. The candidate is standing between the X-ray tube and the fluorescent upper screen upon which the outline of his heart appears. The examiner, on the left, may either study the living picture, or a photograph may be taken for closer study.
The medical standards for commercial pilots who fly public transport aircraft, and for Royal Air Force pilots, are considerably higher than those imposed upon the private or amateur aviator, whose licence does not permit him to fly for hire or reward. Moreover, whereas the holder of a private pilot’s licence is required to be medically re-examined only once a year, the commercial pilot must submit himself to rigorous re-examination by the Medical Board at least every six months. If he should at any time suffer an accident or an illness which incapacitates him for work for a period of ten days or more, he must again be medically examined and passed as fit by the Board’s doctors before he may resume flying duties.
Another concession afforded the private pilot is that he becomes eligible for a licence as soon as he is seventeen years of age, whereas pilots and navigators of aircraft engaged in commercial flying may not enter upon their duties before eighteen or after forty-five years of age. No upper age limit has yet been set for the private pilot, nor, judging by the skill displayed by septuagenarians who are regularly learning to fly light aeroplanes, is there any need for such a restriction.
The medical standards required of commercial and Royal Air Force pilots, and the method of their examination, are substantially the same, except for some minor differences, which are mainly concerned with the relative significance of various disabilities that may have occurred in the candidate’s life. For the commercial pilot these standards have been set by international agreement and are the same for the commercial pilots of all those countries subscribing to the International Convention for Air Navigation, the virtual charter of international air commerce throughout the world. Having agreed to the standards, however, the Convention leaves each contracting State free to determine its own methods of examination.
BALANCING TEST in which three attempts are allowed wit each arm. Apparatus consists of a metal rod about 5-in long with a narrow baseplate. This is balanced about 1½-in from the end of the board about 12-in long, 4-in wide and weighing 4 oz. The candidate must raise the board to shoulder height without upsetting the rod.
“SHOOTING THE MERCURY”. In this test the candidate’s nostrils are clipped and, having drawn a deep breath, he is required to exhale down a tube. The average person will cause the mercury to rise 110 millimetres, or 4·33-in, and any figure below 80 millimetres (3·15-in) is insufficient.
The methods of examination used in Great Britain are those originated by the Central Medical Board of the Air Ministry. The Board’s experts were among the first to recognize that ordinary clinical methods of examination were not alone sufficient for the selection and care of flying personnel. They required to be supplemented by certain special tests to determine whether a candidate had a degree of mental and physical stamina compatible with the safe handling of aircraft in any conditions for prolonged periods in peace or war.
These tests had to be searching, for modem flying duties involve the guidance and control of a machine moving at much higher speeds than any hitherto experienced by the human body. The performance of manoeuvres, such as aerobatics at high speed, which submit the pilot to dangerously high physical stresses, and the attainment of great heights with exposure to extreme cold and the effects of diminished oxygen pressure, all demand a high physical standard.
Apart from these special considerations, even ordinary “straight” flying calls for certain coordinated limb movements which are initiated from sensory impressions. Of these, vision is easily the most important, as without good visual judgment accurate flying is not possible.
A blindfolded pilot cannot keep an aircraft on an even keel for any appreciable length of time, however highly he may assess his inherent sense of balance. A test under dual control will quickly prove his dependence upon his sense of vision.
Again, when flying in fog or clouds, a pilot has to rely entirely on his eyes for information from his instruments. The same is largely true of night flying, although here a certain amount of visual information may also be available from external sources, such as the horizon, lights on the ground or the stars. Thus in all forms of flying a pilot depends on visual information, gathered either from objects outside the aircraft or from instruments within it.
Thus the Board’s tests of a candidate’s eyesight are searching and comprehensive. The examination covers visual acuity, colour vision and visual judgment. Moreover, the R.A.F. or commercial pilot, unlike the private pilot, is not permitted to wear glasses, except after certain flying experience. Latterly, too, the high speeds now being attained in military flying - well over 350 miles an hour in R.A.F. Fighters - have introduced a new ocular phenomenon which is engaging the special attention of the Central Medical Board’s experts.
A REVOLVING CHAIR is used to test reactions to aerobatics or stunt flying. The candidate is seated in the chair, which is rotated ten times in twenty seconds and suddenly stopped. Pulse rate and arterial pressure are recorded immediately before and after rotation.
It has been found that any sudden alteration of course, when the pilot is travelling at very high speed, subjects him to centrifugal forces of such strength that they momentarily drain the blood from the vessels behind the eyes. The result is a temporary but total blindness, known as a “blackout”. The victim retains full consciousness while “blacked out”, and, so far as experience has yet shown, appears to suffer no ill effects from the temporary disability.
The importance of good eyesight in flying is particularly evident during the training period, when all coordinated movements of the controls have to be initiated consciously. Later, as experience grows, the pilot derives an increasing amount of information from the nerves of “deep” sensation, such as the “feel” of the control column, rudder bar and seat, and he can more or less automatically initiate the appropriate movements necessary for the proper handling of his machine.
The sense of touch plays but little part in flying, though an experienced pilot will be able to derive a certain amount of useful information from the feel of the wind or other air currents upon his face. Similarly, auditory sensations make no major contribution to the art of flying, although good hearing is essential from other points of view, such as for the appreciation of the engine’s “note” and for the proper reception of radio signals.
Of vital importance for the accurate control of an aircraft is the ability to carry out delicately coordinated movements of arm and leg. Some individuals may be found incapable of achieving this lightness of touch and are thus “ham-handed” or heavy-footed, or both. Others, less clumsy, may still not be able to combine leg and arm movements with sufficient speed and accuracy because of their inability to perform successfully two relatively simple movements at the same time.
Lack of aptitude for flying may, therefore, be due either to defective afferent (inward-conducting) impressions - chiefly visual - or to defective coordinated movements. No less important is the possession of good general judgment and the less easily proven quality of coolness in emergency. Tests for nervous stability help to ascertain the presence of these qualities in any particular candidate. It is often found, however, that bad judgment is not associated with any lack of nervous control in the accepted medical sense, but more often with a general temperamental unfitness for flying.
TO DETERMINE EYE MUSCLE BALANCE the Central Medical Board uses, among other methods, the Bishop-Harman test of “desire for binocular vision”. The candidate holds the instrument pressed against his face and looks through a slit of variable width midway along the rod. He is then required to read a set of figures on a card at the far end of the rod. Above his head hangs a portable light which illuminates the card.
With all these varying considerations prominently in mind, the Central Medical Board has drawn up its rules for examination.
The object of the examination required by the Board is not only to exclude the presence of defects or disease, but also to make sure that the candidate has physiological attributes likely to make him an efficient pilot.
The following data form a basis of selection.
(a) A careful personal history of the candidate, with particular reference to nervous stability, respiratory and circulatory efficiency, and past illnesses.
(b) A general medical and surgical examination, including special tests for flying fitness.
(c) An eye examination.
(d) An ear, nose and throat examination.
(e) A careful assessment of all the facts elicited under the foregoing headings.
In the examination are incorporated certain special tests for physical efficiency which are not generally included in a medical examination.
One of the more interesting of these is a breath-holding test in which the subject is asked to exhale as fully as he can, then to fill his lungs and hold his breath for as long as possible with his nostrils clipped.
When the candidate has become almost purple in the face in his determination to secure full marks in this test, and has been finally compelled to exhale, the examiner then asks his reason for giving up. If the reply is the natural one of, “Because I felt I should burst!” or, “I wanted to breathe”, the result is deemed normal and satisfactory, whereas if the answer had been “I came all over funny”, or “Things began to go muzzy”, some abnormality would have been suspected and a closer examination made.
TO TEST THE LUNG CAPACITY of an applicant for a flying licence a spirometer is used. The candidate exhales into a mouthpiece leading to a meter, which records the quantity of air exhaled. The minimum required is 3,500 cubic centimetres (305 cubic inches), the normal for a young man of 5 ft 3-in with a chest measurement of 26½-in.
The normal minimum time for a fit young pilot to be able to hold his breath is one minute. The successful completion of such a test is taken as satisfactory evidence of the stability of the respiratory centre and, indirectly, of the nervous system generally, and of strength of resolution to “carry on” in difficulties.
If the candidate is unable to hold his breath for the minimum period of one minute, or gives an abnormal answer to the examiner’s question, it is generally assumed that he will suffer from lack of oxygen when flying at high altitudes.
The expiratory force of the candidate may next be tested by requiring him to apply his lips to the mouthpiece of a mercury-filled tube and, after having drawn a deep breath through the nose, to blow the mercury in the tube steadily as high as possible. Any attempt to “shoot” the mercury up high by a sudden hard blow is considered a “foul”, and the test must be started afresh. The average height attained by the normal person is about 110 millimetres (4·33-in) of mercury, and if this is not reached at the first trial, two further attempts are allowed. A figure below 80 millimetres (3·15-in) is an indication of incapacity for sustained effort in the candidate.
Yet another important respiratory test is that for determining the candidate’s lung capacity. For this a device known as a spirometer and somewhat resembling a gas-meter is used. The candidate, having filled his lungs to full capacity, is required, while holding his nose, to exhale slowly and steadily through the tubular mouthpiece of the spirometer. Five attempts at this test are allowed, and the best is taken as representing the candidate’s lung capacity. The resultant figure varies with the age, weight and chest measurements of different candidates and may be as much as 5,000 cubic centimetres (305 cubic in.) for a man six feet high with a 36-in chest, or as low as 3,500 cubic centimetres (213 cubic in). This is the minimum required for commercial pilots under the international agreement and corresponds to the normal, vital capacity for a young man of 5 ft 3-in with a 26½-in chest circumference. Several tests are used to determine pulse responses, one of which is popularly known to candidates as the “Jack-in-the-Box” test. In this the subject, placing and keeping one foot upon a chair, stands alternately on the chair and on the floor five times within fifteen seconds. His pulse is taken at intervals by the examiner and normally the increase rate, due to the exertion, should be from twelve to twenty-four seconds, and the time of return to normal from fifteen to twenty-five seconds. Should the time of return to normal exceed thirty seconds, “cardio-vascular insufficiency”, or more simply a “groggy” heart, may be indicated.
HEART IRREGULARITIES which cannot always be precisely located by ordinary clinical methods of examination are nearly always disclosed by the electrocardiograph. Alternative connecting leads are taken either from the candidate’s arms, or from a leg and an arm. The heart action is graphically recorded, by interruptions of a ray of light photographed on the film of the electric box-camera to the right of the candidate’s head.
Pulse pressure is the subject of another distinct test involving the use of an apparatus known as “sphygmomanometer”, similar to the mercury-filled U-tube already described, but fitted with a bulb and armlet in place of a mouthpiece. The armlet is adjusted round the candidate’s upper arm and its pressure slowly increased and then diminished. Meanwhile, with the aid of a stethoscope and the movement of the mercury in the U-tube, the examiner is able to ascertain the pulse pressure and the potential pilot’s liability to fainting.
A sense of balance is tested by the candidate having to stand with his feet close together, heels and toes touching, and arms to the side. He then bends one knee to a right angle without moving the hip and, having obtained his balance, shuts his eyes tightly and tries to keep steady in this position for fifteen seconds - a considerably more difficult achievement than it may sound. Three attempts in all are allowed for this test.
Another balancing test (and perhaps the trickiest ordeal of all) is one in which a rod, 5-in high and with a narrow baseplate, closely resembling the valve of a car engine, is placed upright on, and about 1½-in from, the end of a board about 4-in wide, 12-in long and weighing some 4 oz. The candidate is then asked to take hold of the board between fingers and thumb by the end farthest away from the rod and to raise it, at arm’s length, from the table to shoulder level and then to replace it without upsetting the rod.
Occasionally it may happen that a candidate, though apparently fit for all normal flying duties, would yet be liable to “crack-up” under the exceptional stresses of aerobatics, or stunt flying. For this there is a special test in which the subject is seated in a revolving chair - which resembles a somewhat elaborate swivel chair - and there subjected to most of the sensations afforded by a swiftly spinning aeroplane.
With his eyes open and with his head in the most favourable position, that is, looking inside the knee farthest from the direction of the spin, the candidate is subjected to a relatively fast spin ten times in twenty seconds, and then stopped suddenly. Pulse rate and arterial pressure are taken just before the spin begins, and both are again recorded immediately afterwards.
The methods used in these tests, and the several others which together constitute the present medical examination for commercial and R.A.F. pilots, have all been evolved as the result of the Board’s past examinations of fit and proficient aviators specially chosen for this purpose. They are, therefore, based on substantial grounds. In practice over many years they have proved an almost infallible means of selecting personnel capable of withstanding the stresses of military and commercial flying, and of promptly indicating any falling off in a pilot’s fitness.
TESTING THE COORDINATION of a candidate’s eyes, hands and feet. Seated in the “cockpit” chair with his feet on the rudder-bar and his hand on a control column, the candidate watches a spot of light moving on the face of a cathode ray tube before him. By correctly combined movements of stick and rudder-bar he has to try to keep the spot on the point of intersection of two black lines, bringing it back each time the mechanism throws it off-centre. As additional tests, distractions from an electric buzzer, or red and white flashing lights come into operation from time to time and have to be stopped by the candidate without interruption of the main test.