Go-around after engine failure in light twin
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Hi Bluskis,
I guess our experiences differ, but thats OK. What you and I think due to our individial experiences doesn't matter much.
Google is such a marvellous thing, I found this NASA GA Reliability Report which attempts to give some figures.
Most of this is over my head, but it looks good
and as long as the source looks authoritative I always go straight to the conclusions anyway.
Page 34 says:
System reliability estimates are based on the probability that a Complex GA Aircraft Airframe System will successfully complete a 700 nautical mile six-hour flight.
The system reliability estimates are determined to be:
Airframe 0.99940
Electrical 0.99997
Powerplant 0.99986
Flight Control 0.98476
Ground Control 0.99598
Cockpit Instrumentation 0.976
So my understanding - which may be wrong, I am no stats whizz kid - is that you have a 99.986% probability of completing the 6 hour flight without an engine failure. I call that reliable, you don't. No problemo! What I did find surprising is the engine is more reliable than the airframe, I would never have got that - see how my individual experience is not worth much.
For a 100 hour a year pilot, 0.99986 ^ 16 = 99.77% of completing a year without an engine failure. That's a risk I am prepared to take.
What chance have you of having a problem after 300 hours, your experience?
0.99986 ^ 50 = 99.35 chance of getting through your 300 hours unscathed. This is extremely unlikely, to have this "on average", which implies more than once, is getting into very small numbers indeed.
You can put the figures in for a 1000 hour a year instructor (98% and I would be prepared to take that risk because I know that only a small percentage of engine failures result in injury due to training). A very busy 20000 hours a year flight school has 63% chance of getting through the year unscathed.
And if my figures don't exactly work out because not all flights are 6 hours long I don't care! It's close enough for me! So now we are getting some real statistically based numbers, let the GA SEP pilot make their own decision.
Regards
I guess our experiences differ, but thats OK. What you and I think due to our individial experiences doesn't matter much.
Google is such a marvellous thing, I found this NASA GA Reliability Report which attempts to give some figures.
Most of this is over my head, but it looks good
and as long as the source looks authoritative I always go straight to the conclusions anyway.Page 34 says:
System reliability estimates are based on the probability that a Complex GA Aircraft Airframe System will successfully complete a 700 nautical mile six-hour flight.
The system reliability estimates are determined to be:
Airframe 0.99940
Electrical 0.99997
Powerplant 0.99986
Flight Control 0.98476
Ground Control 0.99598
Cockpit Instrumentation 0.976
For a 100 hour a year pilot, 0.99986 ^ 16 = 99.77% of completing a year without an engine failure. That's a risk I am prepared to take.
What chance have you of having a problem after 300 hours, your experience?
0.99986 ^ 50 = 99.35 chance of getting through your 300 hours unscathed. This is extremely unlikely, to have this "on average", which implies more than once, is getting into very small numbers indeed.
You can put the figures in for a 1000 hour a year instructor (98% and I would be prepared to take that risk because I know that only a small percentage of engine failures result in injury due to training). A very busy 20000 hours a year flight school has 63% chance of getting through the year unscathed.
And if my figures don't exactly work out because not all flights are 6 hours long I don't care! It's close enough for me! So now we are getting some real statistically based numbers, let the GA SEP pilot make their own decision.
Regards
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Slim
This is the key. I live next door to an 18,000 hour plus ATPL who has never had an engine failure.
Bluskis has had some hairy moments.
You are looking at numbers across a huge sample and all you are seeing is the result of a normal distribution - 98% of the variance will be contained in 2 standard deviations.
If the other 2% doesn't concern you, then you have established a persoanl risk tolerance that is usable.
But it doesn't alter the probability/severity relationship
The posters who have pointed out the necessity of relating small probability and severity of consequence have it right.
Bluskis has had some hairy moments.
You are looking at numbers across a huge sample and all you are seeing is the result of a normal distribution - 98% of the variance will be contained in 2 standard deviations.
If the other 2% doesn't concern you, then you have established a persoanl risk tolerance that is usable.
But it doesn't alter the probability/severity relationship
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F3G,
I think we all agree that at the end of the day life is all about risk/reward ratios, and it would be nice for these decisions to be based upon fact.
So given the "real" statistics from the NASA report, do you think piston engines are reliable?
I think we all agree that at the end of the day life is all about risk/reward ratios, and it would be nice for these decisions to be based upon fact.
So given the "real" statistics from the NASA report, do you think piston engines are reliable?
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SS
As I said in a previous post, if you want to make good use of statistics you have to be prepared to do some work.
The statisics you refer to from NASA do not include the following, but when you fly your aeroplane they are surely included:
Human induced failures
Failure due to mechanics poor skills/procedures
Failure due to improper parts.
There are many other exclusions in the data as specified on page 11 of the document.
I am quite happy for you to make your own risk appraisal, as you are for me. The problem is others may make a risk analysis of their own based on this thread.
As I said in a previous post, if you want to make good use of statistics you have to be prepared to do some work.
The statisics you refer to from NASA do not include the following, but when you fly your aeroplane they are surely included:
Human induced failures
Failure due to mechanics poor skills/procedures
Failure due to improper parts.
There are many other exclusions in the data as specified on page 11 of the document.
I am quite happy for you to make your own risk appraisal, as you are for me. The problem is others may make a risk analysis of their own based on this thread.
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The problem is others may make a risk analysis of their own based on this thread.
Well bluskis, I don't think I would take much notice of what you and I have said, but I'd certainly take notice of what NASA and NTSB say. I think the best thing to do in this situation is cite authoritative sources and let them make their own minds up.
Regards
Well bluskis, I don't think I would take much notice of what you and I have said, but I'd certainly take notice of what NASA and NTSB say. I think the best thing to do in this situation is cite authoritative sources and let them make their own minds up.
Regards
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Slim Slag
There are no 'definitive' facts about engine reliability as applying to an individual, just a set of stats that allow a post hoc analysis and some regression analysis. You will find that probability will work over a big sample, but to the individual the severity of impact will be as critical and the decision will revolve around one's view on that.
Bottom line, risk/reward decisions are made on perception of the upside/downside equations, e.g. look at the FTSE 100 everyday. As the disclaimers say, past performance is no guarantee of future performance.
That's as good as it gets and trying to fit the stats to this discussions is the equivalent of using Procrustes' bed in Greek antiquarian literature - you will get the answer you seek, but it doesn't mean that it's valid.
I think you're barking up the wrong tree here - there is not a definitive answer to your question, too may qualitative variables are involved.
If you think that piston engines are reliable and that singles are safer for twins, then for you they are.
There are no 'definitive' facts about engine reliability as applying to an individual, just a set of stats that allow a post hoc analysis and some regression analysis. You will find that probability will work over a big sample, but to the individual the severity of impact will be as critical and the decision will revolve around one's view on that.
Bottom line, risk/reward decisions are made on perception of the upside/downside equations, e.g. look at the FTSE 100 everyday. As the disclaimers say, past performance is no guarantee of future performance.
That's as good as it gets and trying to fit the stats to this discussions is the equivalent of using Procrustes' bed in Greek antiquarian literature - you will get the answer you seek, but it doesn't mean that it's valid.
I think you're barking up the wrong tree here - there is not a definitive answer to your question, too may qualitative variables are involved.
If you think that piston engines are reliable and that singles are safer for twins, then for you they are.
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F3G,
Unfortunately I have to sit inside and monitor some systems today, the bad side is I cannot fly, the good side is I get to monitor PPRune
I admit to being confused. Are you saying the statement "Flying in light aircraft is safer than flying in public transport wide bodied jets" is correct? I know it is if you get killed in a 737 crash, but lets talk in general terms that the general public (i.e. me) understands.
Edited
Hey you know what F3G, you don't need to answer that. I've got a lot out of this thread, I am glad to have found that NASA report, and am happy with the fact I now have numeric figures which quantify the risks involved in flying SEP. That's more that I knew yesterday.
So cheers
Slag
Unfortunately I have to sit inside and monitor some systems today, the bad side is I cannot fly, the good side is I get to monitor PPRune
I admit to being confused. Are you saying the statement "Flying in light aircraft is safer than flying in public transport wide bodied jets" is correct? I know it is if you get killed in a 737 crash, but lets talk in general terms that the general public (i.e. me) understands.
Edited
Hey you know what F3G, you don't need to answer that. I've got a lot out of this thread, I am glad to have found that NASA report, and am happy with the fact I now have numeric figures which quantify the risks involved in flying SEP. That's more that I knew yesterday.
So cheers
Slag
Last edited by slim_slag; 11th Jan 2003 at 21:03.
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bluskis
Not if they followed the thread to the end, and share this philosophy (thanks slim_slag ):
The problem is others may make a risk analysis of their own based on this thread.
):
"I've got a lot out of this thread,... That's more that I knew yesterday"
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Slim Slag
I will answer...
No it is not - flying in public transport wide bodied jets is statistically much safer than flying in GA aircraft.
The reasons for this include Airline SOPS, two crew ops, higher standards of crew performance attained through training and recurrent training, more capable aircraft, more systems redundancy, more % of the flight spent in the cruise (a phase statistically less likely to experience serious incidents), operating in and out of airports with better approach aids, very high standards of maintenance funded by mega budgets, scrutiny by regulatory authorities, etc.
However, comparing the sample known as "public transport wide bodied jets" which has highly defined and controlled parameters, with the sample known as "GA aircraft" is a skewed comparison that will favout the jets sample.
The GA sample has broader, less defined parameters since it incorporates a far wider range of activities - e.g. private flying of many different missions, air taxi, corporate aircraft, crop spraying, missionary work etc.
For this reason, the 'public transport wide bodied jet' sample will provide less volatile data and the probability will say that it is safer. (Smaller standard deviation being the indicator.)
The point I made earlier about the linkage between very low probability and serverity is more about one's personal (qualitative) view of risks, so let me explain it again as you seem to be confused.
If you fly on a public transport wide bodied jet, the probability of a serious incident is very, very, very (etc) low. If you do have a serious incident leading to a crash or forced landing, the potential severity is very high. (Even this is not a 100% certainty though, as the A330 that made a forced landing without power in the Azores with only minor consequences demonstrates.)
It is this linkage that determines whether you think that flying is safe. The general public seem to think that the risks are acceptable if you look at the numbers who take flights, you even get some nervious pax who are scared by the potential consequences, but think it is very unlikely to happen to them - so travel.
Risk versus reward must be a subjective view when you think about it, since risks are always in the future and can only be quantitatively analysed once they have developed into historical record.
If you would like to understand statistics better, I recommend my clients to read 'Statistics for the utterly confused', by Lloyd Jaisingh which can be found at Amazon. (Note to BRL, I'm not advertising, have no personal interest )
I will answer...
Flying in light aircraft is safer than flying in public transport wide bodied jets [Is this true]
The reasons for this include Airline SOPS, two crew ops, higher standards of crew performance attained through training and recurrent training, more capable aircraft, more systems redundancy, more % of the flight spent in the cruise (a phase statistically less likely to experience serious incidents), operating in and out of airports with better approach aids, very high standards of maintenance funded by mega budgets, scrutiny by regulatory authorities, etc.
However, comparing the sample known as "public transport wide bodied jets" which has highly defined and controlled parameters, with the sample known as "GA aircraft" is a skewed comparison that will favout the jets sample.
The GA sample has broader, less defined parameters since it incorporates a far wider range of activities - e.g. private flying of many different missions, air taxi, corporate aircraft, crop spraying, missionary work etc.
For this reason, the 'public transport wide bodied jet' sample will provide less volatile data and the probability will say that it is safer. (Smaller standard deviation being the indicator.)
The point I made earlier about the linkage between very low probability and serverity is more about one's personal (qualitative) view of risks, so let me explain it again as you seem to be confused.
If you fly on a public transport wide bodied jet, the probability of a serious incident is very, very, very (etc) low. If you do have a serious incident leading to a crash or forced landing, the potential severity is very high. (Even this is not a 100% certainty though, as the A330 that made a forced landing without power in the Azores with only minor consequences demonstrates.)
It is this linkage that determines whether you think that flying is safe. The general public seem to think that the risks are acceptable if you look at the numbers who take flights, you even get some nervious pax who are scared by the potential consequences, but think it is very unlikely to happen to them - so travel.
Risk versus reward must be a subjective view when you think about it, since risks are always in the future and can only be quantitatively analysed once they have developed into historical record.
If you would like to understand statistics better, I recommend my clients to read 'Statistics for the utterly confused', by Lloyd Jaisingh which can be found at Amazon. (Note to BRL, I'm not advertising, have no personal interest
)
Last edited by Final 3 Greens; 12th Jan 2003 at 08:23.
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i really shouldn't but.. F3G my intelligent friend, I admit to being confused. And seeing as I know how many standard deviations my IQ is from the mean, I suspect others are too (please don't tell me how IQ means nothing, but by all means tell me I am an arrogant git ).
Let me suggest that at the end of the day, when faced with a problem like this, all us general public want to know are simple numbers we can get our heads around. We don't care about regression and standard deviations and the like. If you can put a simple figure on a problem then you have got us cracked. I found a figure - I did not make it up myself, I got it from a NASA paper entitled "General Aviation Aircraft Reliability Study". Well, that sounds pretty much like what I am looking for and I trust that source. I am open mined though, and will accept the result even if I don't like it.
The NASA paper said you have a 0.9999 (rounded) chance of completing a 6 hour SEP flight with your engine intact. For the statisticians amongst you, there was even a statistical analysis with all sorts of long terms and Greek characters in it. This number was good enough for NASA to publish it.
I ignored the Greek characters and looked at the number in the summary. The number has a lot of nines in it, one hell of a lot of nines in it, and that's good enough for me. That many nines sounds really good, it gives me a warm and fuzzy feeling (something you are going to have trouble quantifying with your stats, but I know what it means) Sure, it doesn't take into account the fact you may be hit by a meteorite which will rip your engine off its mount, but for me as a simple member of the public that doesn't matter. I call that an act of God, it is so unlikely I exclude it. OK, so you don't and you argue against the whole result because of that - but for the sake of my argument lets take a nine off the end of the NASA figure. What do we have left? One hell of a lot of nines.
So let the user read the reports and decide for themselves. I was out talking with members of the public last night and gave them the number with a lot of nines in it. All were very impressed and surprised how reliable SEP engines are. I suspect (and that is a wooly term but I throw it in anyway, I just love to live on the edge ) that most others will be impressed too.
Regards
Slag
While I am on this rant, let me throw out another simple number which may help put things in perspective for non statisticians.
When you go see your GP for a medicine, or your cardiologist for a surgical intervention, the medicine or procedure SHOULD be better than sugar pills or doing nothing. How is this known? A question is asked, research is done and statistics applied to the data. To get a drug/procedure approved, you need to show it is effective, but the cut off point that it is due to chance is 5%. I.e only being 95% certain it works is good enough for medicine.
Therefore when you take your drug (with side effects, possibly fatal) or have a surgical procedure (with side effects, possibly fatal), this is done to you with only one nine!
NASA give you four nines, and remember these nines are harder to get the more you have. So those of you who are happy to have a surgeon hack at you, just HAVE to be happy with flying SEP.
And I await the incoming missiles for that!
).Let me suggest that at the end of the day, when faced with a problem like this, all us general public want to know are simple numbers we can get our heads around. We don't care about regression and standard deviations and the like. If you can put a simple figure on a problem then you have got us cracked. I found a figure - I did not make it up myself, I got it from a NASA paper entitled "General Aviation Aircraft Reliability Study". Well, that sounds pretty much like what I am looking for and I trust that source. I am open mined though, and will accept the result even if I don't like it.
The NASA paper said you have a 0.9999 (rounded) chance of completing a 6 hour SEP flight with your engine intact. For the statisticians amongst you, there was even a statistical analysis with all sorts of long terms and Greek characters in it. This number was good enough for NASA to publish it.
I ignored the Greek characters and looked at the number in the summary. The number has a lot of nines in it, one hell of a lot of nines in it, and that's good enough for me. That many nines sounds really good, it gives me a warm and fuzzy feeling (something you are going to have trouble quantifying with your stats, but I know what it means) Sure, it doesn't take into account the fact you may be hit by a meteorite which will rip your engine off its mount, but for me as a simple member of the public that doesn't matter. I call that an act of God, it is so unlikely I exclude it. OK, so you don't and you argue against the whole result because of that - but for the sake of my argument lets take a nine off the end of the NASA figure. What do we have left? One hell of a lot of nines.
So let the user read the reports and decide for themselves. I was out talking with members of the public last night and gave them the number with a lot of nines in it. All were very impressed and surprised how reliable SEP engines are. I suspect (and that is a wooly term but I throw it in anyway, I just love to live on the edge
) that most others will be impressed too.Regards
Slag
While I am on this rant, let me throw out another simple number which may help put things in perspective for non statisticians.
When you go see your GP for a medicine, or your cardiologist for a surgical intervention, the medicine or procedure SHOULD be better than sugar pills or doing nothing. How is this known? A question is asked, research is done and statistics applied to the data. To get a drug/procedure approved, you need to show it is effective, but the cut off point that it is due to chance is 5%. I.e only being 95% certain it works is good enough for medicine.
Therefore when you take your drug (with side effects, possibly fatal) or have a surgical procedure (with side effects, possibly fatal), this is done to you with only one nine!
NASA give you four nines, and remember these nines are harder to get the more you have. So those of you who are happy to have a surgeon hack at you, just HAVE to be happy with flying SEP.
And I await the incoming missiles for that!
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SS
I had not intended to add any more to this diverted thread, however I would ask you to look again at page 11 of the NASA report you are putting so much faith in, and there you will find what they actually measured, or rather did not measure.
I think you will find the report is somewhat more restricted than you apparently believe.
How these restrictions would change the figures of the report I am unable to guess, but change them they will.
I had not intended to add any more to this diverted thread, however I would ask you to look again at page 11 of the NASA report you are putting so much faith in, and there you will find what they actually measured, or rather did not measure.
I think you will find the report is somewhat more restricted than you apparently believe.
How these restrictions would change the figures of the report I am unable to guess, but change them they will.
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Bluskis,
You are repeating yourself! If you were to read what I said on this engine failure related thread you would see I have always talked about "mechanical" engine failures. Pilots are the sort of people who happily take responsibility for themselves, and through training can minimise human engine failures. It's the mechanical things, like crank shafts snapping, that we cannot directly control. When you talk to pilots that is what is perceived to be the risk.
There is something you have totally missed here. If you claim to see "engine problems on average every 300 hours" the NASA report should be ringing alarm bells in your head. The NASA report shows (to my satisfaction if not yours) that non human induced engine failures (which is what it is measuring as you like to point out) are infrequent. According to NASA figures, there is a 99.35% chance that you will routinely complete 300 hours of flying SEPs on 6 hour legs, yet you seem to see problems regularly.
What does that tell you? The only explantion I can come up with (apart from you are making it up) is that you are seeing a serious problem with human induced engine failures. Some people need training, in fact from what you are saying the whole system is falling apart.
Personally I doubt that is the case, there is another more obvious explanation.
Cheers
Slag
You are repeating yourself! If you were to read what I said on this engine failure related thread you would see I have always talked about "mechanical" engine failures. Pilots are the sort of people who happily take responsibility for themselves, and through training can minimise human engine failures. It's the mechanical things, like crank shafts snapping, that we cannot directly control. When you talk to pilots that is what is perceived to be the risk.
There is something you have totally missed here. If you claim to see "engine problems on average every 300 hours" the NASA report should be ringing alarm bells in your head. The NASA report shows (to my satisfaction if not yours) that non human induced engine failures (which is what it is measuring as you like to point out) are infrequent. According to NASA figures, there is a 99.35% chance that you will routinely complete 300 hours of flying SEPs on 6 hour legs, yet you seem to see problems regularly.
What does that tell you? The only explantion I can come up with (apart from you are making it up) is that you are seeing a serious problem with human induced engine failures. Some people need training, in fact from what you are saying the whole system is falling apart.
Personally I doubt that is the case, there is another more obvious explanation.
Cheers
Slag
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I have to add my name to he who who posted earlier that he had experienced shedloads of failures.
I have had eight or nine power failures (depending on what you count, the ninth was a fuel pump failure and was rectified by changing tank and switching on the electric)
These eight have included two on jets (both fracture failures of a turbine discs) one of oil being shed everywhere, one CSU failure, three mag/ignition failures and one fuel to engine failure (either carb or injection, I forget which it is on the TB10).
I have additionally had two instances where engine indications have led me to (1) abort take-off (2) shut down an engine and land, but both turned out to be indicator failures.
The irony is that the only two which entailed mechanical breaking of a moving part were both jets (my hours are roughly 30% on jets the rest on pistons.) The oil one turned out to be a ground engineer not replacing the oil filler cap on turnaround, the rest are all failures of ancilliaries; but the effect was the same: either total or near total loss of power.
So I wonder if this is the nub of the differences being expressed here. Maybe pots only break out from crankcases, or crankshafts fail, once in in a thousand lifetimes, but maybe engines stop for other, non-pilot-error, reasons far more often?
My planning for engine failure would cover all cases, hence my personal decision to fly only with a spare!
W
I have had eight or nine power failures (depending on what you count, the ninth was a fuel pump failure and was rectified by changing tank and switching on the electric)
These eight have included two on jets (both fracture failures of a turbine discs) one of oil being shed everywhere, one CSU failure, three mag/ignition failures and one fuel to engine failure (either carb or injection, I forget which it is on the TB10).
I have additionally had two instances where engine indications have led me to (1) abort take-off (2) shut down an engine and land, but both turned out to be indicator failures.
The irony is that the only two which entailed mechanical breaking of a moving part were both jets (my hours are roughly 30% on jets the rest on pistons.) The oil one turned out to be a ground engineer not replacing the oil filler cap on turnaround, the rest are all failures of ancilliaries; but the effect was the same: either total or near total loss of power.
So I wonder if this is the nub of the differences being expressed here. Maybe pots only break out from crankcases, or crankshafts fail, once in in a thousand lifetimes, but maybe engines stop for other, non-pilot-error, reasons far more often?
My planning for engine failure would cover all cases, hence my personal decision to fly only with a spare!
W
Last edited by Timothy; 13th Jan 2003 at 15:09.
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WCollins
A point well made.
I once had a couple of spark plugs fail in a light single climbing out of Southend on a night sortie.
Not even an engine 'failure' as such, but it altered the way I thought about night flying, due to the realisation that it could happen to me.
Slim Slag
A litte question for you to ponder about your NASA survey.
How many SEPs can manage 6 hour sectors with legal reserves?
A point well made.
I once had a couple of spark plugs fail in a light single climbing out of Southend on a night sortie.
Not even an engine 'failure' as such, but it altered the way I thought about night flying, due to the realisation that it could happen to me.
Slim Slag
A litte question for you to ponder about your NASA survey.
How many SEPs can manage 6 hour sectors with legal reserves?
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SS has finally seen the point.
The NASA report was concerned only with design and manufacture reliability.
The figures would be somewhat different now with the recent Lycombing related fatalities, and grounding fiasco.
Like WC, these three problems I had were 'mechanics skill/procedure' related.
Definitely not covered by the report.
The fourth was magneto related, so could have been in either the manufacture/ design camp or the mechanics camp.
W C
Could you post how many hours per failure your experiences would average.
The NASA report was concerned only with design and manufacture reliability.
The figures would be somewhat different now with the recent Lycombing related fatalities, and grounding fiasco.
Like WC, these three problems I had were 'mechanics skill/procedure' related.
Definitely not covered by the report.
The fourth was magneto related, so could have been in either the manufacture/ design camp or the mechanics camp.
W C
Could you post how many hours per failure your experiences would average.
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Bluskis
Two jet failures in approximately 1000 hours of jets
Six piston failures in approximately 2000 hours of piston, of which half SEP half MEP, so you could say in 3000 hours of piston engine operation.
But, as we keep saying, that's just one set of anecdotal experience; we have just heard of the 18,000 hour guy who's never had an engine failure. I imagine that both his and my experiences are in the tails of the normal distribution.
I used to think that people flew singles until they had their first engine failure, then they moved to twins, but I now know this to be rubbish. Keef still flies his Arrer despite his near-death experience (though I do acknowledge that near-death isn't so worrying for a deeply religious person ) and I recently was talking to someone who flies old stuff (Moths and Percivals) who considers engine failures normal operation to be dealt with as they arise.
Also one cannot say too often that the SEP failure is a different beastie from the MEP shutdown. Often the MEP pilot will shut down an engine that an SEP pilot will struggle along with.
W
Two jet failures in approximately 1000 hours of jets
Six piston failures in approximately 2000 hours of piston, of which half SEP half MEP, so you could say in 3000 hours of piston engine operation.
But, as we keep saying, that's just one set of anecdotal experience; we have just heard of the 18,000 hour guy who's never had an engine failure. I imagine that both his and my experiences are in the tails of the normal distribution.
I used to think that people flew singles until they had their first engine failure, then they moved to twins, but I now know this to be rubbish. Keef still flies his Arrer despite his near-death experience (though I do acknowledge that near-death isn't so worrying for a deeply religious person
) and I recently was talking to someone who flies old stuff (Moths and Percivals) who considers engine failures normal operation to be dealt with as they arise.Also one cannot say too often that the SEP failure is a different beastie from the MEP shutdown. Often the MEP pilot will shut down an engine that an SEP pilot will struggle along with.
W
Last edited by Timothy; 13th Jan 2003 at 16:11.
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WCollins
I imagine that you are right in your assertion.
Of course when evaluating the probability of severe risks on an individual basis the wisest assumption is that you will be at the downside tail, unless you feel very lucky.
In consequence I agree with your earlier comment about planning broadly and Bluskis earlier comment about the value of being trained and current.
Slim Slag
I have just re-read your last posting - you should train as a sophist mate - you have the potential to become a modern day Protagoras
I imagine that both his and my experiences are in the tails of the normal distribution
Of course when evaluating the probability of severe risks on an individual basis the wisest assumption is that you will be at the downside tail, unless you feel very lucky.
In consequence I agree with your earlier comment about planning broadly and Bluskis earlier comment about the value of being trained and current.
Slim Slag
I have just re-read your last posting - you should train as a sophist mate - you have the potential to become a modern day Protagoras
Last edited by Final 3 Greens; 13th Jan 2003 at 10:28.
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F3G
I have just read some of that famous report.
The whole thing is an exercise in sophistry and obfuscation.
It is a fine example of how to lie with statistics. The size of sample is pathetically small and the conditions which are excluded make the whole exercise a waste of time from the point of view of estimating flight safety.
I reckon that it is something to do with trying to reduce Product Liability cases.
At any rate I wouldn't base anything actuarial on it!
W
I have just read some of that famous report.
The whole thing is an exercise in sophistry and obfuscation.
It is a fine example of how to lie with statistics. The size of sample is pathetically small and the conditions which are excluded make the whole exercise a waste of time from the point of view of estimating flight safety.
I reckon that it is something to do with trying to reduce Product Liability cases.
At any rate I wouldn't base anything actuarial on it!
W
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WC
So you didn't like the report much
There seemed to be an itsy bitsy over representation of Mooneys (9 from a small sample of 33) and a desire (that I did not understand) to relate the numbers to a 6 hour mission, which strikes me as unusually long for an SEP, even in the States where some people do use them for business trips. In fact, I wonder how many of the types listed could legally file a 6 hour IFR (or even VFR) flight with a full pax load or even at gross weight with pax offloaded for fuel? I'd be very surprised if this list included the 152 and the 172 - some of the others might just do it with long range tanks, but not with me as P1! (not just for safety reasons either - how ling can the average middle aged bladder hold out for?)
I'd guess that the average sector for a single is about 1hr, maybe 90 mins. I haven't read the report methodology properly, but in the real world I'd expect less stress and strain on an engine flying 6 hour sectors (with a long cruise segment at stable air temperatures and power settings) - especially the turbo variety and this would impact on the reliability in itself, although to what degree I don't profess to have a view.
At the end of the day, I prepare for engine failure every time I fly and just hope I never have to demonstrate my 'superior' skills!
So you didn't like the report much
There seemed to be an itsy bitsy over representation of Mooneys (9 from a small sample of 33) and a desire (that I did not understand) to relate the numbers to a 6 hour mission, which strikes me as unusually long for an SEP, even in the States where some people do use them for business trips. In fact, I wonder how many of the types listed could legally file a 6 hour IFR (or even VFR) flight with a full pax load or even at gross weight with pax offloaded for fuel? I'd be very surprised if this list included the 152 and the 172 - some of the others might just do it with long range tanks, but not with me as P1! (not just for safety reasons either - how ling can the average middle aged bladder hold out for?
)I'd guess that the average sector for a single is about 1hr, maybe 90 mins. I haven't read the report methodology properly, but in the real world I'd expect less stress and strain on an engine flying 6 hour sectors (with a long cruise segment at stable air temperatures and power settings) - especially the turbo variety and this would impact on the reliability in itself, although to what degree I don't profess to have a view.
At the end of the day, I prepare for engine failure every time I fly and just hope I never have to demonstrate my 'superior' skills!
