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Aviation History
1953
1953 - 1038.PDF
192 THIS WAY OUT . . . having reached what the subjects felt to be a high rate of rotation, has persisted in spite of any attempts to "unspin." There are several well-authenticated instances in which a violent spin quickly produced in the subject inability to read a! stopwatch—used to check distance fallen—or to judge height above ground. One very experienced parachutist said that he believed himself to be approaching unconsciousness when he pulled the ripcord. His parachute lines twisted and collapsed his canopy, which developed again as the lines unwound. Another parachutist, taking part in a recent competition, pulled his para chute while spinning, and when he felt that the physiological effects were becoming serious. Having personally experienced a slow spin of approximately one minute's duration of which the only effect was sickness, I later encountered a much faster spin; in about half a minute it resulted in a feeKng of sickness and an inability to read the figures of a stopwatch or judge height above ground. Opening the parachute resulted in twisted lines and partial malfunction of and damage to the parachute canopy. A spin, incidentally, was reported in the technical Press as far back as 1935. There have been a number of cases where the parachutist struck the ground having, apparendy, made no effort to open his parachute. Some of these cases were probably due to over- confidence, where the parachutist tried to get as close to the ground as possible before pulling his ripcord. There seems to be no feeling of urgency or danger when falling freely at very low altitude. The stopwatch, the parachutist's favourite means of determining opening height, has its limitations. Rate of descent at a given altitude varies from one parachutist to another due to differences in weight/drag ratio. Where attitude is not constant during the descent, the calculation of distance fallen on a time-elapsed basis is not on'y inaccurate, but may be highly dangerous. Should the parachutist become stabilized in a head-down position, whereas he has estimated for constantly changing attitude, he may reach the ground in less time than that which he calculated to his opening height. The world parachuting championship in Yugoslavia showed parachutes opening at between approximately 1,500 and 1,600ft, against an estimated opening height of 1,000ft. Head down, at a speed probably approaching 200ft per second, things happen quickly. Inclusion of an altimeter in the parachutist's equipment would seem to be of little use in delays terminating as low as 1,500ft. Reading and instrument errors may easily place the parachutist in a difficult situation. And with a very "unclean" and unstable body—"where," as an aeronautical engineer recently asked, "does one locate the static head?" If it is found possible to stabilize a body in all planes during the free fall—that is, between the time of separation from the aircraft and deployment of the parachute—then some of the prob lems found in delayed-opening descents should be capable of solution. With the body held in a favourable attitude at the time of parachute deployment, and with a calculable rate of descent, long delays should be comparatively safe. There are two main schools of thought, the one believing that suitable body-control technique will achieve the desired results, the other (mainly composed of those who have experienced fast spins) firmly convinced that it will not. The battle continues. But how about the aviator who is forced to bale out at high altitude, where immediate parachute-opening may result in serious damage to the parachute perhaps, plus anoxia or frostbite? How is he affected by this state of affairs? For the purpose of this discussion, I will discount the fully automatic ejection seat, which may prove to be a very satisfactory answer, and deal with the occupant of a static seat. Cleverly avoiding all the more difficult problems by starting this jump at 30,000ft or less, and assuming a satisfactory oxygen supply, the man making an emergency bale-out can be quite well catered for. Given a barometric parachute-opening device set for, say, 10,000ft, it matters very little whether or not he is able to read an altimeter or other visual instrument during his free fall. Should he lose consciousness for any reason, the automatic release may be expected to deploy the. parachute at the correct height, or within acceptable limits. A conventional para chute—the design of which has been well tried in its 27 years of service with the R.A.F., will then deposit him, one hopes, on a nice stretch of springy turf. But how about the spin? It is unreasonable to expect an aviator—possibly damaged, and almost certainly feeling unhappy, to put into practice the technique recommended for body-control in free fall. It is not absolutely certain that he will spin or that, if he does, the result will be more serious than temporary sickness. During a long descent with the parachute inflated the sickness is likely to occur anyway. There does, however, remain the risk of FLIGHT "Guide surfaces"—designed to reduce opening shock, stabilize the descent and slow down landing-speed—identify the Pioneer series of para chutes. This model, the P9-B, embodies an automatic barometric release. a parachute malfunction, where arms and legs are spread during deployment; or possibly—though this is less likely—as a result of airflow characteristics peculiar to the spin. Because in parachuting things happen quickly, I believe in storing away in my mind stock answers to many of the obvious snags that may arise. They are useful when there is no time to work out ways and means on the spot, and here are a few of them. When opening a parachute in a spin, keep legs firmly together and arms as close to the chest as possible. Try not to throw the ripcord-operating hand wildly outward when opening the para chute, as some part of the canopy may sneak in between the arm and body. If spinning, do not panic. Try to stop the spin by curling into a ball, waiting for a short period, and then shooting out arms and legs. It may be difficult to pull the legs in due to centrifugal force. Try "paddling" in the opposite direction or attempt to throw the shoulders round into a face-down position. If none of these dodges is successful, remember that the back-down position is sometimes quite comfortable, and keeps the wind out of your eyes. If the parachute is not fitted with an automatic opening device, try to keep watch on the physiological effects of the spin. If there is any really serious tendency to pass out, pull the ripcord and take a chance on the opening shock. There is no guarantee that unconsciousness does occur, even in a fast spin; but, had it done so in the past, the subject would hardly have been in a position to return with the evidence. If as a result of a spin the canopy has an unusual appearance on deployment, do not automatically assume that all is lost. Even a large number of twists can be harmless, and untwisting can be encouraged by leg exercise in the opposite direction. Given a little height, and perhaps some manual assistance, snags have a habit of sorting themselves out.
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