FLYING ALMOST AS FAST AS SOUND

New Zealand Listener, Volume 13, Issue 335, 23 November 1945, Page 14

FLYING ALMOST AS FAST AS SOUND

What Flesh and Blood Can-And Cannot- Bear

BECAUSE the Meteor planes which last week established a new world speed record were stressed for speeds of 600 miles an hour, no attempt to set a new mark substantially higher than that is likely to be made for some time. But though the cables told us so much, they did not refer at all to the risks run by the pilots. Some of these are obvious, others are more insidious, as this article shows.

VERY schoolboy knows (and most adults remember) that an express train travelling 60 miles an hour-when there are no slips on the line-covers 88 feet a second. With that to go on, it is easy enough to figure out that a jetplane, whistling along at about 600 m.p.h. in level flight is covering about 880ft. per second. It is just as easy to appreciate the importance to the pilot of the phrase "in level flight.’ The slightest dipping of the nose of the plane could hurtle one downwards with such tremendous yet imperceptible velocity that the safety margin of 250ft. could be swallowed up in a matter of seconds.

That is obviously possible even in still air and ideal conditions of visibility. The official report that low visibility and seahaze created a serious problem in the preliminary test-flights may properly be regarded as a good example of Ministerial under-statement. Hidden Enemy These, however, are but the mechan-ical-or mathematical-dangers which must be surmounted by those who travel cl to the speed of sound. More perilous still is the hidden enemy, the ebb and flow of blood within their own bodies, and more unpredictable because so little is yet known about it. But of this one can be sure, that each pilot; as (continued on next page)

(continued from previous page) he turned for a second run over the testcourse, knew that too tight a turn would lose him consciousness and almost certainly life itself. Blackouts during turns were reported by Schneider Trophy pilots as long ago as 1922 when the world’s best land and sea planes tortoised round the course at about 200 m.p.h., but little attention was paid to the phenomenon.at the time and it was not until many years later that detailed information was either sought or. obtained. Remember Spain? About 1935, -however, Germany and Italy had awakened to the value of the dive-bomber as a means of hurrying in the. New Order in backward areas like Abyssinia and Spain, and at the Tempelhof..laboratories of the Reich Air Ministry a gigantic centrifuge was built to find out just how hard a.dive-bomber could dive and at the same time confine the damage to the target area. In this Wellsian contraption large animals and human subjects -were rotated (in something: more than the vernacular sense of the word) and simultaneously X-rayed by means of an automatic plant installed in the frame with the subject. In this manner was gathered an im- posing amount of data on the effects of centrifugal force on the body. Vision Suffers First Vision suffers first, for example, when centrifugal force drains blood from the head. This, medical men explain, is because, even under normal conditions,

blood is supplied to the eyes against the resistance of muscular pressure within the eyes themselves. When banking at speed, therefore, the airman is conscious first of spots or a veil, before his eyes, followed by visual blackout. If the turn is violent enough, mental blackout supervenes rapidly, but for this to.occur the Germans discovered that the centrifugal acceleration (as it is called) must be more than five times the pull of gravity, or 5G, and must last for more than four seconds. Along with the reduction of blood pressure in the head and upper body a corresponding build-up of pressure occurs in the lower limbs. Fighter pilots have told of the intense pain in the legs caused by engorged veins and arteries and some have returned from combat bearing the stigmata of high-speed turning in the form of ugly blood-blisters formed by the rupture of vein walls. Nor is blood alone affected by these stresses. All the internal organs tend to be displaced when strains are prolonged and the Tempelhof investigators, gravely spinning a group of anaesthetised monkeys, found that the apex of the heart dropped as much as three inches if the pull reached a strength of 8G. Blood and Iron Yet perhaps stranger than these discoveries was the degree of recuperative power shown in the flesh and blood of the subjects. A number of rabbits, for example, were subjected twice daily for a fortnight to 90-second spells at an acceleration of 15G. In spite of this tremendous strain none of the animals suffered injury and one even gave birth, 14 days later, to a healthy litter. Just one vicious circle after another. And as evidence of what the human body can stand, one German investigator, a Dr. von Diringshofeh, detailed an experiment with a Henschel dive-bomber in’ which a pilot underwent a stress of 8.2G over a period of six-and-a-half seconds. One can only appreciate the strain endured by that airman when it is understood that for the seeming eternity of those seconds his blood had the weight of iron. No doubt Bismarck would have approved thé test. Accelerations beyond 10G, however, are now known to cause concussion, and though reliable scientific data on even greater préssures were gathered by both sides during the War, in most cases neither the planes nor the men who piloted them survived. How "Cobber" Kain Died Blackout octurs, as has been pointed out, when centrifugal force draws blood from the upper part of the body, and sincé in normal aerobatics and combat flying the pilot’s head is towards the centre of the circle round which the plane is flying the blackout is the normal physiological reaction to a fast turn. In the normal loop, for example, if it happens at all blackout will occur when the pilot is climbing up and over after the initial dive to gain speed. But should the loop be made forward, with the pilot on the outside of the curve, or should a pilot bank steeply in the same outer position, then what he suffers is not a blackout, but a "red-out" caused by building up of blood-pressure in Ree chest and head. It was this type of attack which, in the opinion of one medical authority, Captain Ernst Jokl*, killed "Cobber" *A South African, author of Medical Aspects of Aviation, from which most of the scientific detail of the above article was derived.

Kain, the Wellington airman who was the first British ace of World War II. Here is his reconstruction of what happened on that tragic afternoon in June, 1940, when Kain, already posted to instructional duties in England, stunted for the last time over Blois airfield. " ... at 350 mp.h. Kain dived upsidedown towards the aerodrome. Although at this phase the main acceleration impact did not affect his body in the dangerous longitudinal axis, the fact that he flew in an inverted position already implied a considerable strain upon his blood circulation. Missing the ground by a few feet, ‘Cobber’ performed a sharp vertical turn, shooting up to 1,500ft. in less than a minute. The writer has- calculated that during this manoeuvre powerful centrifugal*forces ahout four times the gravity of the earth were produced, affecting him now in the longitudinal body axis .... under such circumstances, Kain must at this moment already have experienced visual disturbance of the ‘reddening-out’ type. Since he was an unusually tough and daring fellow, we may assume that he disregarded this first warning symptom, especially since (unfortunately) its significance had never been explained to him. A few seconds later, when he reached 1,500ft. he turned his right wing up and started rolling. This was a risky and extremely danger-. ous manoeuvre since it brought into operation additional centrifugal impulses shifting more blood from the legs and pelvis towards chest and head. The resisting power of his vascular system became definitely overstrained at’ this point. "Tt is more than doubtful if ‘Cobber’ ever intended to carry out two consecutive rolls from a height of only 1,500ft. We are told that he didn’t straighten out after the first but completed a second and even started a third roll. The writer has no doubt that his conscious control became impaired as early as during his first roll. Before crashing he was handling his controls in an automatic manner, in the same way in which a groggy boxer continues fighting without really knowing what he is doing."