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#91
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Morgans wrote:
"Matt Whiting" wrote Sure, if the engine quits it will be ugly, but that is a very remote possibility and one that I accept every now and again if the trip is important enough. Matt Do me a favor, and settle a bet. Would you mind telling us how old you are? 45. Who won the bet? :-) Matt |
#92
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#93
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#94
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In article ,
"Peter Duniho" wrote: "Ron Garret" wrote in message ... [...] and have determined the number of trials (flights) in advance. No. That statement is true regardless of whether N is known. Knowing that your chances of having an engine failure are 1-(1-P)^N isn't very useful information if you don't know what N is. As I pointed out before (and will point out again later on -- watch for it) it is useful because you can choose your risk tolerance and then solve for N (assuming of course you know P). It's not a useful calculation for the purpose of this discussion. That is a matter of opinion. Tell me how I'm going to use the information then. Since you think it's so useful. I just did, but here it is again: if you believe that the risk of an engine failure on any particular flight is P1 and you are willing to accept a lifetime risk of experiencing an engine failure at no more than P2, then you can use these two numbers and the formula for cumulative probability to solve for N. You can then choose to stop flying after N flights. No one knows before they've started flying how many flights they will make in a lifetime. That is not necessarily true. My mother, for example, knows exactly how many flights in GA aircraft she will make during her lifetime: zero. For a person who will never make a flight in a GA aircraft, why in the world would I consider at all how many engine failures she'll experience? It's like trying to figure out how many live births I'll have in my lifetime. Duh. No, because in my mother's case the number is zero because she has *chosen* to make it zero. (Perhaps I should have made it clear that I am a pilot, and so my mother can, if she chooses, go flying with me any time she wants.) Your analogy is faulty because you cannot choose to get pregnant. And just in case you're too dimwitted to extrapolate from this example I'll spell it out for you: one can *decide* on the basis of this calculation to stop flying after some number of flight because flying more than that results in a cumulative probability of disaster that exceeds one's risk tolerance. Only if they make that decision prior to flying those hours. I haven't met a single person who has ever done such an analysis of their flying career. I doubt one exists. Just because you are not personally acquainted with someone who has chosen to avail themselves of the utility of this calculation does not mean that such people do not exist. (And even if it were true that no one in the world has availed themselves of this utility (which it isn't) that would not prove that the calculation is without utility.) If you can find me one, I'll stand corrected. I very much doubt that. You seem not to have noticed, but we've actually already done that experiment, and you stubbornly cling to your position regardless. Not only are you wrong, but you are clearly, demonstrably, and self-evidently wrong. If you don't believe me, you can actually *do* this experiment. Don't play the lottery or go flying until your engine fails. Get a die. Pretend that rolling a six means your engine has failed. Now ask yourself: are you more likely to roll a six if you roll it once, or if you roll it 100 times? Clearly if you roll it once your chances are one in six, and if you roll it 100 times the chances of rolling AT LEAST ONE SIX in those hundred trials is very close to 1. (0.99999998792532652 to be precise). Otherwise, you are without a point Whereas you seem to have one on the top of your head. (I'll refrain from any implication that YOU are dimwitted, just 'cause that's the kind of guy I am). Hey, if the shoe fits, I'll wear it. Will you? rg |
#95
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In article ,
"Peter Duniho" wrote: wrote in message ... [...] Of course your odds of having an engine failure with two engines is double of what it would be with one, and quadruple with four. Only approximately. The only reason doubling (or quadrupling) the number of engines doubles (or quadruples) the chance of an engine failure (approximately) is that the failure rate is so low. For example, if the failure rate were 50%, a doubling of that would cause you to expect an engine to fail each flight (a 100% chance of failure), when in fact the chance is actually only 75%. It is somewhat ironic that you should be the one to point this out in light of the argument we are having in another branch of this thread because this is precisely the point I was making. The condition of the probability of failure on a single trial P being low is precisely the condition that allows you to approximate the formula for cumulative failure 1-(1-P)^N as P*N. If you think about it, there is absolutely no difference in the risk calculation between making one flight with four engines and four flights with one engine (except insofar as the probability of failure for one engine over four flights are not quite independent of each other if it's the same engine each time). rg |
#96
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#97
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#98
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#99
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Running out of fuel is not my idea of "engine failure".
Well, statistically, it is THE reason for engine failure. -- Thomas Borchert (EDDH) |
#100
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OK, having read through this thread for awhile, I might as well chime in
with a few observations: 1) Roll the dice often enough, and they will eventually come up snake-eyes. The question is whether they are likely to do that before something else gets you. Most people want to make it more likely that they will die of cancer or heart disease than in an airplane crash. Apparently we want to die slowly and old. 2) Here in the Pacific Northwest, flying at night in the mountains is dangerous, no question about it. Indeed, the mountain ranges around here are possibly some of the most dangerous in the world. The trouble is, flying anywhere around here at night as not much better. The whole area is mountainous, heavily forested, with large tracts of water that is barely above freezing year 'round. Visible emergency landing areas at night are few and far between. Low ceilings, low freezing levels, haze, mountain obscuration, micro-climates with weather wildly different from anything forecast -- these are the norm around here. Many students around here manage to log over an hour of actual IFR before they get their private certificate. On top of that, the days get real short and real dark during the winter, so restricting yourself to daytime flight is difficult. 3) Even if you live through an emergency landing at night in this area, the odds of surviving until you are found are vanishingly small, especially considering that most pilots do nothing to increase their chances of survival. They fly without jackets or coats, take no survival gear, have no way of signaling rescuers, etc. You are going to be wet and cold and probably injured. Not good. OK, if you want to die slowly and old, don't fly at night in the Pacific Northwest, especially in the mountains. If you don't want to kill your son or anybody else, don't take them with you when you fly little single engine airplanes at night in the mountains around here. But even if you don't give a rip about yourself or anybody else, I would ask you not to do it anyway. Too many good people are killed every year trying to rescue selfish, thoughtless bozos who thought they were invulnerable to the laws of averages. |
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