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#1
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I don't see the parallel here. Pilot parachutes were never
intended to reduce injury during a glider impact with terrain. Parachute presence during such an impact certainly doesn't DECREASE injury. Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit. In article , John Galloway wrote: . like being better not to wear seat belts in a car - or have an air bag - because they have been known to cause injury? John Galloway At 23:30 21 January 2005, Mark James Boyd wrote: In article , Stewart Kissel wrote: Does having an extra 20 pounds behind you during an impact of more than 20 Gs cause enough additional stress to measurably increase the chance of death in an accident? As opposed to that 20 pounds of silk over your head allowing you to float down? EXACTLY! If you are more likely to be in a impact where the extra 20 pounds is the difference between life and death, than to be in a situation where parachuting is the only option, then wearing a chute is something to consider. So how many chute saves have there been compared to fatal accidents where the pilot almost survived? If a 20 pound chute adds 4% to impact morbidity, and lifesaving use of the chute only happens one time for every 50 impact crashes, then there are things to consider. I'm not talking about situations where wearing or not wearing seems pretty clear. Competitions, aerobatics, test flights, formation flight may be pretty hard to argue. And pattern tows, winch launches in unsoarable weather seem the same way. But what about ridge soaring alone on a day away from MTRs, nobody else around, in a well established sturdy glider? I wonder, because I have a parachute, and I tend to fly in an isolated area, with no MTRs and no company. And I read Kempton Izuno's stuff about wearing a chute on a wave day and wondering about being dragged at 40 knots along the ground if he bailed. Sure, if you gotta have it to save your life, then you got to have it. But for every chute save, how many impact fatalities have there been? How many of these had a chute as a contributing factor because they increase effective BMI? I don't know the answer. But one part of it comes from the ratio of bailouts to fatal impacts. I'd really like to see stats on that... -- ------------+ Mark J. Boyd -- ------------+ Mark J. Boyd |
#2
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Mark,
'Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit' When you said that it was precisely the parallel. The number of motor accidents of a type where the seat belt or airbag causes more injury than they prevent is dwarfed by the number in which they save injury - and I would be totally amazed if the same were not true for parachutes in gliders. Apart from anything else far more glider impacts are closer to the line of the pilot's back than at right angles to it. That's why the cockpit crash tests are done in roughly that direction and why submarining is a major issue. I think this is your parallel to my recent String Theory:-) John At 08:00 22 January 2005, Mark James Boyd wrote: I don't see the parallel here. Pilot parachutes were never intended to reduce injury during a glider impact with terrain. Parachute presence during such an impact certainly doesn't DECREASE injury. Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit. In article , John Galloway wrote: . like being better not to wear seat belts in a car - or have an air bag - because they have been known to cause injury? John Galloway At 23:30 21 January 2005, Mark James Boyd wrote: In article , Stewart Kissel wrote: Does having an extra 20 pounds behind you during an impact of more than 20 Gs cause enough additional stress to measurably increase the chance of death in an accident? As opposed to that 20 pounds of silk over your head allowing you to float down? EXACTLY! If you are more likely to be in a impact where the extra 20 pounds is the difference between life and death, than to be in a situation where parachuting is the only option, then wearing a chute is something to consider. So how many chute saves have there been compared to fatal accidents where the pilot almost survived? If a 20 pound chute adds 4% to impact morbidity, and lifesaving use of the chute only happens one time for every 50 impact crashes, then there are things to consider. I'm not talking about situations where wearing or not wearing seems pretty clear. Competitions, aerobatics, test flights, formation flight may be pretty hard to argue. And pattern tows, winch launches in unsoarable weather seem the same way. But what about ridge soaring alone on a day away from MTRs, nobody else around, in a well established sturdy glider? I wonder, because I have a parachute, and I tend to fly in an isolated area, with no MTRs and no company. And I read Kempton Izuno's stuff about wearing a chute on a wave day and wondering about being dragged at 40 knots along the ground if he bailed. Sure, if you gotta have it to save your life, then you got to have it. But for every chute save, how many impact fatalities have there been? How many of these had a chute as a contributing factor because they increase effective BMI? I don't know the answer. But one part of it comes from the ratio of bailouts to fatal impacts. I'd really like to see stats on that... -- ------------+ Mark J. Boyd -- ------------+ Mark J. Boyd |
#3
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So from the broader perspective of whether a "safety" device
contributes to safety ultimately or reduces it, yes, I see there is a parallel. I was thinking you were drawing a parallel in another way, which you weren't. From reviewing the articles, and what you and Eric said, I think the combined ideas are that: 1) The spinal compression axis is far more of a factor than the forward momentum. 2) Parachute weight doesn't increase compression noticably along the spinal axis (parachute weight doesn't contribute to submarining significantly). 3) During the impact along that axis, the paracute weight forces are borne almost entirely by the seat frame under it rather than by the pilot. So based on this, the extra weight of a parachute has perhaps some effect, but this effect is negligible in sailplane terrain impact accidents. The key difference here is how the weight causes effects differently in a car vs. a sailplane. The semi-reclined sailplane seat position is significantly different than in most automobiles. Does this sum up what you all seem to have said? Is there anything else I missed? In article , John Galloway wrote: Mark, 'Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit' When you said that it was precisely the parallel. The number of motor accidents of a type where the seat belt or airbag causes more injury than they prevent is dwarfed by the number in which they save injury - and I would be totally amazed if the same were not true for parachutes in gliders. Apart from anything else far more glider impacts are closer to the line of the pilot's back than at right angles to it. That's why the cockpit crash tests are done in roughly that direction and why submarining is a major issue. I think this is your parallel to my recent String Theory:-) John At 08:00 22 January 2005, Mark James Boyd wrote: I don't see the parallel here. Pilot parachutes were never intended to reduce injury during a glider impact with terrain. Parachute presence during such an impact certainly doesn't DECREASE injury. Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit. In article , John Galloway wrote: . like being better not to wear seat belts in a car - or have an air bag - because they have been known to cause injury? John Galloway At 23:30 21 January 2005, Mark James Boyd wrote: In article , Stewart Kissel wrote: Does having an extra 20 pounds behind you during an impact of more than 20 Gs cause enough additional stress to measurably increase the chance of death in an accident? As opposed to that 20 pounds of silk over your head allowing you to float down? EXACTLY! If you are more likely to be in a impact where the extra 20 pounds is the difference between life and death, than to be in a situation where parachuting is the only option, then wearing a chute is something to consider. So how many chute saves have there been compared to fatal accidents where the pilot almost survived? If a 20 pound chute adds 4% to impact morbidity, and lifesaving use of the chute only happens one time for every 50 impact crashes, then there are things to consider. I'm not talking about situations where wearing or not wearing seems pretty clear. Competitions, aerobatics, test flights, formation flight may be pretty hard to argue. And pattern tows, winch launches in unsoarable weather seem the same way. But what about ridge soaring alone on a day away from MTRs, nobody else around, in a well established sturdy glider? I wonder, because I have a parachute, and I tend to fly in an isolated area, with no MTRs and no company. And I read Kempton Izuno's stuff about wearing a chute on a wave day and wondering about being dragged at 40 knots along the ground if he bailed. Sure, if you gotta have it to save your life, then you got to have it. But for every chute save, how many impact fatalities have there been? How many of these had a chute as a contributing factor because they increase effective BMI? I don't know the answer. But one part of it comes from the ratio of bailouts to fatal impacts. I'd really like to see stats on that... -- ------------+ Mark J. Boyd -- ------------+ Mark J. Boyd -- ------------+ Mark J. Boyd |
#4
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Mark James Boyd wrote:
So from the broader perspective of whether a "safety" device contributes to safety ultimately or reduces it, yes, I see there is a parallel. I was thinking you were drawing a parallel in another way, which you weren't. From reviewing the articles, and what you and Eric said, I think the combined ideas are that: 1) The spinal compression axis is far more of a factor than the forward momentum. 2) Parachute weight doesn't increase compression noticably along the spinal axis (parachute weight doesn't contribute to submarining significantly). 3) During the impact along that axis, the paracute weight forces are borne almost entirely by the seat frame under it rather than by the pilot. So based on this, the extra weight of a parachute has perhaps some effect, but this effect is negligible in sailplane terrain impact accidents. The key difference here is how the weight causes effects differently in a car vs. a sailplane. The semi-reclined sailplane seat position is significantly different than in most automobiles. Does this sum up what you all seem to have said? Is there anything else I missed? It does for me. -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#5
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Just for the interest of those who are not aware of
the work of English pilot, Dr Tony Segal, on glider pilot fatalities and injuries - there is a series of 6 very detailed articles written by him on the basis of his research in the Gliding Magazine archive starting he http://www.glidermagazine.com/FeatureArticle.asp?id=68 This series is well worth revisiting. Statistically, spinal injuries from downward impacts are the main concern for we (aging) glider pilots. He is still the man to ask and is presenting a lecture on the subject in a couple of weeks at Boscombe Down: http://www.raes.org.uk/raes/division...nch.asp?sessid =&branch=12 John Galloway |
#6
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Mark,
Sorry for the slow reply. Yes - that seems to be a fair summary. John At 05:00 23 January 2005, Mark James Boyd wrote: So from the broader perspective of whether a 'safety' device contributes to safety ultimately or reduces it, yes, I see there is a parallel. I was thinking you were drawing a parallel in another way, which you weren't. From reviewing the articles, and what you and Eric said, I think the combined ideas are that: 1) The spinal compression axis is far more of a factor than the forward momentum. 2) Parachute weight doesn't increase compression noticably along the spinal axis (parachute weight doesn't contribute to submarining significantly). 3) During the impact along that axis, the paracute weight forces are borne almost entirely by the seat frame under it rather than by the pilot. So based on this, the extra weight of a parachute has perhaps some effect, but this effect is negligible in sailplane terrain impact accidents. The key difference here is how the weight causes effects differently in a car vs. a sailplane. The semi-reclined sailplane seat position is significantly different than in most automobiles. Does this sum up what you all seem to have said? Is there anything else I missed? In article , John Galloway wrote: Mark, 'Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit' When you said that it was precisely the parallel. The number of motor accidents of a type where the seat belt or airbag causes more injury than they prevent is dwarfed by the number in which they save injury - and I would be totally amazed if the same were not true for parachutes in gliders. Apart from anything else far more glider impacts are closer to the line of the pilot's back than at right angles to it. That's why the cockpit crash tests are done in roughly that direction and why submarining is a major issue. I think this is your parallel to my recent String Theory:-) John At 08:00 22 January 2005, Mark James Boyd wrote: I don't see the parallel here. Pilot parachutes were never intended to reduce injury during a glider impact with terrain. Parachute presence during such an impact certainly doesn't DECREASE injury. Rather we are discussing whether the increase in impact injuries is so small, or negligible, as to be overcome by the benefit of wearing parachutes for situations where they are a benefit. In article , John Galloway wrote: . like being better not to wear seat belts in a car - or have an air bag - because they have been known to cause injury? John Galloway At 23:30 21 January 2005, Mark James Boyd wrote: In article , Stewart Kissel wrote: Does having an extra 20 pounds behind you during an impact of more than 20 Gs cause enough additional stress to measurably increase the chance of death in an accident? As opposed to that 20 pounds of silk over your head allowing you to float down? EXACTLY! If you are more likely to be in a impact where the extra 20 pounds is the difference between life and death, than to be in a situation where parachuting is the only option, then wearing a chute is something to consider. So how many chute saves have there been compared to fatal accidents where the pilot almost survived? If a 20 pound chute adds 4% to impact morbidity, and lifesaving use of the chute only happens one time for every 50 impact crashes, then there are things to consider. I'm not talking about situations where wearing or not wearing seems pretty clear. Competitions, aerobatics, test flights, formation flight may be pretty hard to argue. And pattern tows, winch launches in unsoarable weather seem the same way. But what about ridge soaring alone on a day away from MTRs, nobody else around, in a well established sturdy glider? I wonder, because I have a parachute, and I tend to fly in an isolated area, with no MTRs and no company. And I read Kempton Izuno's stuff about wearing a chute on a wave day and wondering about being dragged at 40 knots along the ground if he bailed. Sure, if you gotta have it to save your life, then you got to have it. But for every chute save, how many impact fatalities have there been? How many of these had a chute as a contributing factor because they increase effective BMI? I don't know the answer. But one part of it comes from the ratio of bailouts to fatal impacts. I'd really like to see stats on that... -- ------------+ Mark J. Boyd -- ------------+ Mark J. Boyd -- ------------+ Mark J. Boyd |
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