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#81
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"Kyler Laird" wrote in message
... Correct, genius. Similarly, there are engine problems that are quite independent of the number of engines on a plane. Such as? Other than fuel exhaustion, I'm at a loss to think of any. |
#83
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Big John wrote: It basically came out that there were two spikes, one around 500 hours and the other around 1000 hours. The 500 hour accidents were attributed to cocky over confidence. I read the same thing about ten years ago. As I recall, the 1000 hour spike was also tentatively attributed to overconfidence. George Patterson A man who carries a cat by the tail learns something that can be learned no other way. |
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#85
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Geez Michael, settle down! So much stress in the cockpit cannot be
conducive to learning or safety... (Michael) wrote in message . com... (Rich Stowell) wrote Really? If that were true, then there would be hard data. Yes, really No, not really. No hard numbers on actual engine failures (or stall-spins for that matter) - only the ones that led to an NTSB reported accident. Interesting that I cited a specific source for my statement, which you summarily ignore as either irrelevant or incapable of leading to numbers that might be relevant to the concerns that started this post. Have you read the study I cited? Have you followed up on the references cited in that study to see where it might lead in the quest for hard numbers on this issue? Or is it easier to just tell everyone else that they're idiots rather than trying to make a serious contribution to the discussion? True, but that's stating the obvious since NTSB only gets involved in, and thus only reports on, those encounters that have led to actual accidents. But this hideously skews the picture. The only way the events are comparable is if the probability of an engine failure leading to an accident is approximately equivalent to the probability of a stall-spin leading to an accident. This is exactly what I am disputing. If it "hideously skews the picture" wouldn't that apply to all accident numbers from NTSB? Each stall/spin accident represent the tip of the stall/spin problem. Each engine failure accident represents the tip of the engine failure scenario. Accident stats are a poor measure of our overall stall/spin awareness, and of our ability to cope with engine failures precisely because accident numbers represent the relatively few pilots who have had an accident. But useful information can be gleaned. Insight into the broader problems might be found as well. And yes, some kind of logical extrapolation may then be possible to assess the overall magnitude of the issue. Define "rarely." From an industrial accident prevention standpoint, the theoretical ratio 1:30:300 is often applied wherein for every 331 hazardous encounters of a similar type, only one will progress as far as an actual accident (significant damage and/or injury). The rest fall under "incidents" and "hazards." That ratio is nothing more than an expression of ignorance. In reality, depnding on the hazard the numbers can be very different. You neglected to define "rarely." And which "numbers" can be very different -- total numbers, ratios, what? Granted, total raw numbers can be significantly different between different accident types, but--as the study of industrial accident prevention postulates--they may be linked by comparable ratios or some other normalizing parameter. Industrial safety types love to quote statistics like this to scare people, but in reality there is usually a reason why some hazardous encounters lead to accidents or incidents while most do not. It's not random. These reasons generally have to do with individual skill, knowledge, and experience as well as factors the industrial safety people are never told because they involve routine violations of safety rules. Often the same dynamic plays out in NTSB investigations. The intent was not to scare anyone, but to try to add some perspective tying the comparatively rare accident to the unknown (perhaps unknowable) number of hazardous situations that are dealt with without further incident. And yes, there are always reasons why aviation accidents happen, be it attributable to Software (checklists, SOP's, etc.), Hardware (airplane, systems, cockpit layout, etc.), Liveware (the pilot, pax, ATC, etc.), Environment, or the interaction of some or all of these. In other words, typically 1 out of 331 encounters of a similar type results in an accident, whether it's precipitated by an engine failure or an inadvertent stall/spin. No, this is total nonsense because stall-spins and engine failures are not similar. First of all, a mechanical failure generally occurs in a manner that is beyond the pilot's control. When the main seal blows out, or the engine swallows a valve, or a rod goes through a cylinder, or the fuel injectors clog with rust - that's almost always completely independent of pilot skill, knowledge, and judgment. On the other hand, an inadvertent stall-spin is caused by the pilot. Therefore, we're not even looking at the same population. OK, Michael knows best, everyone else is an idiot. The point of the pyramidal accident ratio is not to compare engine failures with stall/spins. Yes, they are two dissimilar accident types in terms of the driving mechanisms -- the engine in one case vs. the pilot in the other. But that does not preclude the mix of accidents, hazards, and incidents within each population from sharing a common relationship. From that standpoint, so what if a hole is blown through the crankcase and the windscreen gets covered with oil, obscuring the pilot's ability to see well enough to land under control. The airplane still gets busted and it's still labelled an engine failure accident. Likewise, so what if the pilot skids a turn and causes the airplane to spin into the ground. It's still a stall/spin accident. But for each one of those accidents, there are many more pilots who, with an oil-slicked windscreen, were able to land under control; there are many more pilots who recognized the developing skid, corrected it, and continued under control. The industrial accident maxim only attempts to quantify how many within each group were able to avert the accident. You can disagree with the theory or its application (in which case, it would be beneficial to put forth an alternative), but can't you do it without denigrating? This is supposed to be a forum for learning -- is this how you treat your students? Just by virtue of the fact that the pilot allowed the inadvertent stall-spin situation to develop, we can expect that he is less likely to handle it properly. The same is not true of engine failure. I would disagree thusly: the pilot who does not routinely ("routinely" meaning at least 50% of the time) simulate an engine failure followed by a glide to landing (even from abeam the numbers would be beneficial) is equally as likely not to be able to handle an engine failure to a successful landing (i.e.: no accident) as a pilot who allows the development of an inadvertent stall/spin. I would postulate that the majority of active pilots (except maybe for students) practice simulated engine outs far less than 50% of the time. In the case of NTSB data, one could extrapolate to get a feel for the order of magnitude of problems pilots deal with in a particular category by multiplying the number of accidents by 331. This is absolutely ridiculous. In addition to the issue of hazard exposure (mechanical engine failures don't discriminate but stall-spins do) there is also the issue of hazard magnitude. Off field landings in gliders, for example, are VERY rarely fatal. The ratio there is 5000:1. On the other hand, I would be amazed if the fatality ratio for midairs was much better than 3:1. 331 may be a good all-around average in aviation (or it may not - data are not available) but to apply it indiscriminately to all types of hazards makes no sense at all. Be gentle, you're dealing with an idiot after all Please explain how an engine failure does not discriminate, yet stall/spin accidents do. The typical stall/spin profile involves a typical pilot on a typical flight -- sounds pretty indiscriminate to me. Please cite your source for the 5000:1 ratio for gliders. Also, glider pilots are always performing engine-out landings, so it would seem to make sense that they'd be better at it than those of us who fly powered airplanes. As for mid-airs, during the period 1977-1986, 40 percent of the mid-airs ended without injury. As for fatality ratio -- yes, the fatality rates between accident types is not at all equal. But for the purposes of counting accidents, a situation in which the pilot walks away unhurt, but the airplane's wing is torn off, is still an "accident" and is therefore equivalent to a case where a pilot lands in a field with the only damage being a tree branch through the windscreen, which kills the pilot. They are both accidents per the definition of the term. For that matter, most engine failure fatalities in light singles are not the result of collision with terrain (which is usually survivable) but of failure to maintain flying speed (which usually isn't). That's basically a stall/spin anyway. Two things: First, approximately 19 percent of stall/spin accidents are preceded by an engine failure. But the primary accident cause is still listed as "stall/spin." There is one school of thought that considers this proper. Just because engine power is lost is no excuse to stall and spin. Gliders don't even have engines. However, that doesn't change the fact that had the engine kept running, the stall-spin would likely not have happened. Second, the contention that "failure to maintain flying speed" is "basically a stall/spin anyway" is pure myth. Spins are the result of two ingredients that must coexist: yaw and stall. And neither yaw nor stall is a function of airspeed. Up to the point where the wings decide to bend or break, stalls and spins can and do occur at any airspeed, and in any attitude. That's all great, but the reality is that in normal flight (not involving aerobatics or other abrupt maneuvering) stall avoidance is all about keeping your airspeed up. Those 19% of stall-spins caused by engine failure are the result of trying to stretch the glide or maneuvering to make a landing area, and likely both. In my experience, and based on the research I've read, I'd postulate that the majority of stall/spin accidents occur with the airplane operating somewhere between 1.07 to 1.20 times Vso and 1.15 to 1.41-g. In other words, with pilots pulling into an uncoordinated, accelerated stall while turning at bank angles between 30 and 45 degrees. That's great, but had those pilots maintained at least 1.3 Vso for these maneuvers, they would not have stalled. Thus saying airspeed is irrelevant is technically correct but not particularly useful. Yes, you can stall at any airspeed in any attitude. I've stalled at 100+ kts (in a plane which normally stalled at 60 kts), full power, and the nose 80 degrees below the horizon - as an aerobatic instructor I'm sure you know exactly what I did wrong to make that happen. That doesn't change the reality - in an engine-out situation, the stall-spin is caused by a failure to maintain flying speed. No -- the stall/spin is caused by yaw and stall, period. Don't yaw and the airplane will not spin, regardless of speed. Be aware of the relationship between g-load and airspeed trend and accidental stalls are less likely. Continuing to tell pilots to fly faster, in order to "maintain flyng speed," unneccessarily makes a lot of perfectly good runways either inaccessible or dangerous to too many pilots. I've seen only two stall/spin accidents here at my 2500-foot home airport over the years, but I've seen many more airplanes broken because they over-ran the runway flying fast enough to "maintain flying speed." As educators, we can do better than that... Rich http://www.richstowell.com |
#86
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Geez Michael, settle down! So much stress in the cockpit cannot be
conducive to learning or safety... (Michael) wrote in message . com... (Rich Stowell) wrote Really? If that were true, then there would be hard data. Yes, really No, not really. No hard numbers on actual engine failures (or stall-spins for that matter) - only the ones that led to an NTSB reported accident. Interesting that I cited a specific source for my statement, which you summarily ignore as either irrelevant or incapable of leading to numbers that might be relevant to the concerns that started this post. Have you read the study I cited? Have you followed up on the references cited in that study to see where it might lead in the quest for hard numbers on this issue? Or is it easier to just tell everyone else that they're idiots rather than trying to make a serious contribution to the discussion? True, but that's stating the obvious since NTSB only gets involved in, and thus only reports on, those encounters that have led to actual accidents. But this hideously skews the picture. The only way the events are comparable is if the probability of an engine failure leading to an accident is approximately equivalent to the probability of a stall-spin leading to an accident. This is exactly what I am disputing. If it "hideously skews the picture" wouldn't that apply to all accident numbers from NTSB? Each stall/spin accident represent the tip of the stall/spin problem. Each engine failure accident represents the tip of the engine failure scenario. Accident stats are a poor measure of our overall stall/spin awareness, and of our ability to cope with engine failures precisely because accident numbers represent the relatively few pilots who have had an accident. But useful information can be gleaned. Insight into the broader problems might be found as well. And yes, some kind of logical extrapolation may then be possible to assess the overall magnitude of the issue. Define "rarely." From an industrial accident prevention standpoint, the theoretical ratio 1:30:300 is often applied wherein for every 331 hazardous encounters of a similar type, only one will progress as far as an actual accident (significant damage and/or injury). The rest fall under "incidents" and "hazards." That ratio is nothing more than an expression of ignorance. In reality, depnding on the hazard the numbers can be very different. You neglected to define "rarely." And which "numbers" can be very different -- total numbers, ratios, what? Granted, total raw numbers can be significantly different between different accident types, but--as the study of industrial accident prevention postulates--they may be linked by comparable ratios or some other normalizing parameter. Industrial safety types love to quote statistics like this to scare people, but in reality there is usually a reason why some hazardous encounters lead to accidents or incidents while most do not. It's not random. These reasons generally have to do with individual skill, knowledge, and experience as well as factors the industrial safety people are never told because they involve routine violations of safety rules. Often the same dynamic plays out in NTSB investigations. The intent was not to scare anyone, but to try to add some perspective tying the comparatively rare accident to the unknown (perhaps unknowable) number of hazardous situations that are dealt with without further incident. And yes, there are always reasons why aviation accidents happen, be it attributable to Software (checklists, SOP's, etc.), Hardware (airplane, systems, cockpit layout, etc.), Liveware (the pilot, pax, ATC, etc.), Environment, or the interaction of some or all of these. In other words, typically 1 out of 331 encounters of a similar type results in an accident, whether it's precipitated by an engine failure or an inadvertent stall/spin. No, this is total nonsense because stall-spins and engine failures are not similar. First of all, a mechanical failure generally occurs in a manner that is beyond the pilot's control. When the main seal blows out, or the engine swallows a valve, or a rod goes through a cylinder, or the fuel injectors clog with rust - that's almost always completely independent of pilot skill, knowledge, and judgment. On the other hand, an inadvertent stall-spin is caused by the pilot. Therefore, we're not even looking at the same population. OK, Michael knows best, everyone else is an idiot. The point of the pyramidal accident ratio is not to compare engine failures with stall/spins. Yes, they are two dissimilar accident types in terms of the driving mechanisms -- the engine in one case vs. the pilot in the other. But that does not preclude the mix of accidents, hazards, and incidents within each population from sharing a common relationship. From that standpoint, so what if a hole is blown through the crankcase and the windscreen gets covered with oil, obscuring the pilot's ability to see well enough to land under control. The airplane still gets busted and it's still labelled an engine failure accident. Likewise, so what if the pilot skids a turn and causes the airplane to spin into the ground. It's still a stall/spin accident. But for each one of those accidents, there are many more pilots who, with an oil-slicked windscreen, were able to land under control; there are many more pilots who recognized the developing skid, corrected it, and continued under control. The industrial accident maxim only attempts to quantify how many within each group were able to avert the accident. You can disagree with the theory or its application (in which case, it would be beneficial to put forth an alternative), but can't you do it without denigrating? This is supposed to be a forum for learning -- is this how you treat your students? Just by virtue of the fact that the pilot allowed the inadvertent stall-spin situation to develop, we can expect that he is less likely to handle it properly. The same is not true of engine failure. I would disagree thusly: the pilot who does not routinely ("routinely" meaning at least 50% of the time) simulate an engine failure followed by a glide to landing (even from abeam the numbers would be beneficial) is equally as likely not to be able to handle an engine failure to a successful landing (i.e.: no accident) as a pilot who allows the development of an inadvertent stall/spin. I would postulate that the majority of active pilots (except maybe for students) practice simulated engine outs far less than 50% of the time. In the case of NTSB data, one could extrapolate to get a feel for the order of magnitude of problems pilots deal with in a particular category by multiplying the number of accidents by 331. This is absolutely ridiculous. In addition to the issue of hazard exposure (mechanical engine failures don't discriminate but stall-spins do) there is also the issue of hazard magnitude. Off field landings in gliders, for example, are VERY rarely fatal. The ratio there is 5000:1. On the other hand, I would be amazed if the fatality ratio for midairs was much better than 3:1. 331 may be a good all-around average in aviation (or it may not - data are not available) but to apply it indiscriminately to all types of hazards makes no sense at all. Be gentle, you're dealing with an idiot after all Please explain how an engine failure does not discriminate, yet stall/spin accidents do. The typical stall/spin profile involves a typical pilot on a typical flight -- sounds pretty indiscriminate to me. Please cite your source for the 5000:1 ratio for gliders. Also, glider pilots are always performing engine-out landings, so it would seem to make sense that they'd be better at it than those of us who fly powered airplanes. As for mid-airs, during the period 1977-1986, 40 percent of the mid-airs ended without injury. As for fatality ratio -- yes, the fatality rates between accident types is not at all equal. But for the purposes of counting accidents, a situation in which the pilot walks away unhurt, but the airplane's wing is torn off, is still an "accident" and is therefore equivalent to a case where a pilot lands in a field with the only damage being a tree branch through the windscreen, which kills the pilot. They are both accidents per the definition of the term. For that matter, most engine failure fatalities in light singles are not the result of collision with terrain (which is usually survivable) but of failure to maintain flying speed (which usually isn't). That's basically a stall/spin anyway. Two things: First, approximately 19 percent of stall/spin accidents are preceded by an engine failure. But the primary accident cause is still listed as "stall/spin." There is one school of thought that considers this proper. Just because engine power is lost is no excuse to stall and spin. Gliders don't even have engines. However, that doesn't change the fact that had the engine kept running, the stall-spin would likely not have happened. Second, the contention that "failure to maintain flying speed" is "basically a stall/spin anyway" is pure myth. Spins are the result of two ingredients that must coexist: yaw and stall. And neither yaw nor stall is a function of airspeed. Up to the point where the wings decide to bend or break, stalls and spins can and do occur at any airspeed, and in any attitude. That's all great, but the reality is that in normal flight (not involving aerobatics or other abrupt maneuvering) stall avoidance is all about keeping your airspeed up. Those 19% of stall-spins caused by engine failure are the result of trying to stretch the glide or maneuvering to make a landing area, and likely both. In my experience, and based on the research I've read, I'd postulate that the majority of stall/spin accidents occur with the airplane operating somewhere between 1.07 to 1.20 times Vso and 1.15 to 1.41-g. In other words, with pilots pulling into an uncoordinated, accelerated stall while turning at bank angles between 30 and 45 degrees. That's great, but had those pilots maintained at least 1.3 Vso for these maneuvers, they would not have stalled. Thus saying airspeed is irrelevant is technically correct but not particularly useful. Yes, you can stall at any airspeed in any attitude. I've stalled at 100+ kts (in a plane which normally stalled at 60 kts), full power, and the nose 80 degrees below the horizon - as an aerobatic instructor I'm sure you know exactly what I did wrong to make that happen. That doesn't change the reality - in an engine-out situation, the stall-spin is caused by a failure to maintain flying speed. No -- the stall/spin is caused by yaw and stall, period. Don't yaw and the airplane will not spin, regardless of speed. Be aware of the relationship between g-load and airspeed trend and accidental stalls are less likely. Continuing to tell pilots to fly faster, in order to "maintain flyng speed," unneccessarily makes a lot of perfectly good runways either inaccessible or dangerous to too many pilots. I've seen only two stall/spin accidents here at my 2500-foot home airport over the years, but I've seen many more airplanes broken because they over-ran the runway flying fast enough to "maintain flying speed." As educators, we can do better than that... Rich http://www.richstowell.com |
#87
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"Peter Duniho" writes:
"Kyler Laird" wrote in message ... Correct, genius. Similarly, there are engine problems that are quite independent of the number of engines on a plane. Such as? Other than fuel exhaustion, I'm at a loss to think of any. Fuel exhaustion certainly accounts for a lot, but there's also misfueling, fuel contamination, and intake clogging by widespread particulates. All are as about likely to take out one as they are several. BTW, one of the things I like about a twin is the slight difference in when such a loss is likely to happen. If one engine runs out of fuel, runs into bad fuel, or gets socked with ice/ash/..., at least I usually have a few seconds/minutes of power on the other one before it experiences the same thing. It might not seem like much, but it can be quite an advantage in sticky situations. (Yes, yes...and if I decide to be stupid, it also makes flipping the airplane over even easier - just like stalling a single upon loss of power.) --kyler |
#88
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"Kyler Laird" wrote in message
... Fuel exhaustion certainly accounts for a lot, but there's also misfueling, fuel contamination, and intake clogging by widespread particulates. What's "misfueling"? Sounds like fuel exhaustion to me. As for the others, you're right to the extent that all engines are run from the same fuel supply. Many twins have separate tanks for each engine and may or may not suffer the same problems. In any case, the incidence of those failures is extremely low, compared to the total number of failures (not counting fuel exhaustion of course which, if I recall correctly, is the number one cause of engine failures). The fact remains, having a second engine *does* significantly increase your chances of an engine failure, just as having extra cylinders increases your chance of having a cylinder failure. In most cases, it's a worthwhile tradeoff, but one shouldn't pretend the tradeoff doesn't exist. Pete |
#89
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"Rich Stowell" wrote in message om... Thanks for that, Big John, I recall seeing similar stats -- I'll have to dig around in my files to find the context and the reason for that second spike at 1,000 hours ... so much to do! The overconfidence that comes from having "four digit experience"? Tom -- just hit the 2,000 hour milestone...so I'm watching my ass. |
#90
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Peter Duniho wrote: "Kyler Laird" wrote in message ... Fuel exhaustion certainly accounts for a lot, but there's also misfueling, fuel contamination, and intake clogging by widespread particulates. What's "misfueling"? Putting jet-A in a gasoline burner (or vice-versa). George Patterson Some people think they hear a call to the priesthood when what they really hear is a tiny voice whispering "It's indoor work with no heavy lifting". |
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