BA747 3 engine LAX-LHR article
No - I'm a scientist.
But you don't need to be a scientist to grasp the very simple point I'm trying to make. It's not fancy mathematics and I'm a bit embarassed that my posting has led to thread getting diverted onto a tangent.
I was just trying to point out one factor that needs to be considered.
Perhaps we should just forget about it and go back to relying on our intuitions instead of maths
But you don't need to be a scientist to grasp the very simple point I'm trying to make. It's not fancy mathematics and I'm a bit embarassed that my posting has led to thread getting diverted onto a tangent.
I was just trying to point out one factor that needs to be considered.
Perhaps we should just forget about it and go back to relying on our intuitions instead of maths
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Originally Posted by Jumbo Driver
Secondly, if what you seem to be trying to argue were to be correct, then a 747 would be more likely to experience two engine failures on a flight than a twin jet would be to experience one. Are you really saying that?
Originally Posted by stagger
No I did not argue that.
I wrote that, all else being equal, a quad (that's flying on 3) is 50% more likely to experience 1 engine failure than a twin (on 2).
I wrote that, all else being equal, a quad (that's flying on 3) is 50% more likely to experience 1 engine failure than a twin (on 2).
The 747 will have started the sector on 4-engines (as around 99.99% of 747s do!).
So, if you are suggesting that, having already had one engine failure (i.e. flying on 3 engines) it is then still more likely to have a second failure than a twin on 2 engines (i.e. no failures - yet), then my suggestion above is indeed correct.
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Stagger ...
So a tri-jet compared with a twin ..... ?
So a twin compared with a single-engine ..... ?
This logic suggests that a gilder would be best (statistically speaking) at avoiding having an engine failure, even against the most reliable engine available. And so it would. But where does that get us?
Of course it is all in how you composed your argument: but you are doing statistics here, not flight safety - which uses statistics to assess flight safety outcomes. By setting it up to "compare a 747 on 3 with a twin" you neatly manage to avoid dealing with the probability of having two such failures on one flight. In fact your approach ensures that like is not being compared with like. This may be fun, but it is misleading for an operational audience.
When you say “This is just one factor to be considered....” you imply to the unwary that the risk of a second event increases as a result of the first failure. But of course you are not claiming that, are you? (What then of ETOPs?).
Whatever this is doing, it adds nothing to assessing the decisions made by the crew of this particular flight who, correctly, would not have taken such an argument into account.
But we are comparing a 747 starting on 3 with a twin.
So a twin compared with a single-engine ..... ?
This logic suggests that a gilder would be best (statistically speaking) at avoiding having an engine failure, even against the most reliable engine available. And so it would. But where does that get us?
Of course it is all in how you composed your argument: but you are doing statistics here, not flight safety - which uses statistics to assess flight safety outcomes. By setting it up to "compare a 747 on 3 with a twin" you neatly manage to avoid dealing with the probability of having two such failures on one flight. In fact your approach ensures that like is not being compared with like. This may be fun, but it is misleading for an operational audience.
When you say “This is just one factor to be considered....” you imply to the unwary that the risk of a second event increases as a result of the first failure. But of course you are not claiming that, are you? (What then of ETOPs?).
Whatever this is doing, it adds nothing to assessing the decisions made by the crew of this particular flight who, correctly, would not have taken such an argument into account.
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I think it is time to close this thread as there are far too many 'opinions' based on complete and utter ignorance of the aircraft, the rules, the type of flying involved etc. etc.
It is fairly obvious that once we get into the 'logic' being bandied about on here in relation to the odds of having a second or third engine failure together with the ramblings of armchair experts, the time has come to put this one to bed. As and when the case goes to court we can reopen it.
In the meantime, those of us who do actually fly the B744 can sleep well at night knowing that we have plenty of redundancy and don't have to "land at the nearest suitable airport" unless the QRH sais so or we decide we have to.
It is fairly obvious that once we get into the 'logic' being bandied about on here in relation to the odds of having a second or third engine failure together with the ramblings of armchair experts, the time has come to put this one to bed. As and when the case goes to court we can reopen it.
In the meantime, those of us who do actually fly the B744 can sleep well at night knowing that we have plenty of redundancy and don't have to "land at the nearest suitable airport" unless the QRH sais so or we decide we have to.
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Good move Danny
Perhaps now we can have a thread on BA's ridiculous fuel policy, fuel league tables, and pressure on Captain's to take minimum fuel.........and the affect it has when you divert, as a recent example showed.
Perhaps now we can have a thread on BA's ridiculous fuel policy, fuel league tables, and pressure on Captain's to take minimum fuel.........and the affect it has when you divert, as a recent example showed.
Sorry for sending the thread off on a tangent - I just wanted to point out an issue that I thought should be considered. Not the only, or most important issue.
I honestly didn't think my comments would cause such a fuss. I thought people would just say "sure - there might be an increased risk of an IFSD relative to a twin but this isn't important because diversion on 2 engines isn't a big deal in a 747".
Anyway, if anyone wants to discuss the IFSD probability issue further please send me a PM.
I honestly didn't think my comments would cause such a fuss. I thought people would just say "sure - there might be an increased risk of an IFSD relative to a twin but this isn't important because diversion on 2 engines isn't a big deal in a 747".
Anyway, if anyone wants to discuss the IFSD probability issue further please send me a PM.
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Originally Posted by bubbers44
Reminds me of the poor Navy fighter pilot with an ailing engine on his single engine fighter being told that he had to delay his landing because a B 52 was going to have to land first because he had an engine out. He said, Oh the dreaded seven engine approach.
What are the odds
Stagger raises a very valid point, one which intuitively most people miss.
If an engine failure is a random event, i.e has no connection to the plane itself or the crew operating than he is correct. With 3 engines you have 50% more opportunity of an engine failure than with two.
Think of the coin toss problem. You toss a coin 49 times and it comes up heads every time. What are the odds of heads on the 50th toss? Actually they remain 1 out 2. The coin does not "know" what happened before.
Likewise Donk 3 has no clue Donk 1 has packed it in. If Donk 3 figures it is time, it is time, Donk 1 does not enter the equation.
What the real issue is what is the probablity of two engines going at once. Very remote and considerably less than your getting murdered in a LA hotel room. People get murdered in LA hotels every year but multiple engine failures seem to be pretty scarce.
On the previous thread I asked if anyone could give a case of two or more modern jet engines failing on a single flight and the only ones offered were from bad fuel or bad maintenance. In either case 2 engines or 10 it makes no difference, bad fuel and you are going down. I understand that is why different mechanics work on different engines on the same ship. Makes perfect sense.
20driver
If an engine failure is a random event, i.e has no connection to the plane itself or the crew operating than he is correct. With 3 engines you have 50% more opportunity of an engine failure than with two.
Think of the coin toss problem. You toss a coin 49 times and it comes up heads every time. What are the odds of heads on the 50th toss? Actually they remain 1 out 2. The coin does not "know" what happened before.
Likewise Donk 3 has no clue Donk 1 has packed it in. If Donk 3 figures it is time, it is time, Donk 1 does not enter the equation.
What the real issue is what is the probablity of two engines going at once. Very remote and considerably less than your getting murdered in a LA hotel room. People get murdered in LA hotels every year but multiple engine failures seem to be pretty scarce.
On the previous thread I asked if anyone could give a case of two or more modern jet engines failing on a single flight and the only ones offered were from bad fuel or bad maintenance. In either case 2 engines or 10 it makes no difference, bad fuel and you are going down. I understand that is why different mechanics work on different engines on the same ship. Makes perfect sense.
20driver
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So let me get this straight. Your B52 is in higher peril of suffering another engine failure if it loses one engine out of its eight than say a 747 which has lost one out of its four, and far, far more risk of losing another one than your 777 that has already lost one out of its two? I see. Have you considered the additional degree of danger a further engine failure poses? I think not.
I think Danny, who owns this website, will be mightily peeved when he reads these shenannigans. I think logic has departed this place. We are stuck in a First World War type stalemate, neither side willing to give way or leave the other side to have the last word. Why don't we just leave it to the legislators to sort out? What is incontrovertible is that the crew did nothing wrong according to the rules of the FAA or CAA! Like it or not, that is it, PERIOD!
I think Danny, who owns this website, will be mightily peeved when he reads these shenannigans. I think logic has departed this place. We are stuck in a First World War type stalemate, neither side willing to give way or leave the other side to have the last word. Why don't we just leave it to the legislators to sort out? What is incontrovertible is that the crew did nothing wrong according to the rules of the FAA or CAA! Like it or not, that is it, PERIOD!
There are two different questions here (that I think people have been trying to address - not that I'm suggesting people should address)
1) Did the crew in this particular case make the correct decision according to current regulations and policies?
2) What should the regulations and policies be?
The "stalemate" that Rainboe alludes to is partly due to the fact that people are trying to answer different questions.
The issue I raised is not really relevant to question 1 - and it appears that question 1 is what is most important to people in this thread. So I'm sorry for raising the probabilities issue - and I don't think it needs to be discussed further here.
1) Did the crew in this particular case make the correct decision according to current regulations and policies?
2) What should the regulations and policies be?
The "stalemate" that Rainboe alludes to is partly due to the fact that people are trying to answer different questions.
The issue I raised is not really relevant to question 1 - and it appears that question 1 is what is most important to people in this thread. So I'm sorry for raising the probabilities issue - and I don't think it needs to be discussed further here.
Last edited by stagger; 27th Apr 2006 at 23:29.
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Originally Posted by stagger
So I'm sorry for raising the probabilities issue - and I don't think it needs to be discussed further here.
IMHO, those who wish to pursue the theory of probabilities as it applies (or doesn't) to engine failures, need to do so in another thread.
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There are two different questions here....
1) Did the crew in this particular case make the correct decision according to current regulations and policies?
2) What should the regulations and policies be?
1) Did the crew in this particular case make the correct decision according to current regulations and policies?
2) What should the regulations and policies be?
Where on Earth has question 2 come from now? We are not discussing what the regulations should be, for goodness sake, shall we stick to the question in hand- it appears hard enough for some of you to understand that let alone going hypothetical! You are some sort of scientist who has chosen to apply his non-aviation scientific principles to a subject you know nothing about, other than the feeling that the little you do actually know offends your sensibilities. It would be far better if this discussion was limited to those that know something about aviation and balancing risks, because quite frankly, some of you do not know what you are talking about. The glib 'they should have landed back at LAX' ignores a lot of additional dangers and risks they didn't need. Landing en-route would not have solved any problems and created more. They did the right thing, exactly as I would have done and almost all 4 engine long range pilots would have. You are achieving nothing with your daft theories of failure probabilities. Why don't you just give it a rest?
Rainboe
I wasn't really trying to pose those questions! I was simply trying to describe the questions that people have been trying to answer in this thread. I've edited my last post to make this clear. I believe, that perhaps without stating it explicitly, some people have been addressing the second issue.
And I apologised for previously trying to discuss question 2 myself. Moreover, with respect to the issue I raised I specifically asked people "to give it a rest" myself.
Please give me some credit for what I actually wrote!
Also I never made any suggestions about where anybody should have landed in any of my posts - glib or otherwise. None!
Nowhere did I claim the crew in this case contravened any rules. You must be thinking of another poster.
Does anyone here ever read what people have actually written?
I wasn't really trying to pose those questions! I was simply trying to describe the questions that people have been trying to answer in this thread. I've edited my last post to make this clear. I believe, that perhaps without stating it explicitly, some people have been addressing the second issue.
And I apologised for previously trying to discuss question 2 myself. Moreover, with respect to the issue I raised I specifically asked people "to give it a rest" myself.
Please give me some credit for what I actually wrote!
Also I never made any suggestions about where anybody should have landed in any of my posts - glib or otherwise. None!
Nowhere did I claim the crew in this case contravened any rules. You must be thinking of another poster.
Does anyone here ever read what people have actually written?
Last edited by stagger; 27th Apr 2006 at 23:53.
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The crew did not contravene the regulations of the FAA or the CAA! Can you read English? They did exactly as 4 engine long haul crews, American, British, Australian and worldwide have been doing for years
Actually Rainboe, what the FAA for years did allow is no longer the case. The interpretation, not the rule, has changed. On five occasions I've shut down one out of four and happily, paying due deference to proper contingency enroute planning, continued to destination.
Six years ago when I last played the game nobody wearing a suit with the matching management mask accessory said 'thank you'; instead a finger of admonishment was waggled in front of my face. I was told not to do it again and the reasoning given actually made sense having to do with compliance with the spirit of the regs rather than safety - a new FAA interpretation for a brave new world of improved safety. It was made perfectly clear that I would be placing my certificate in jeopardy with possible action to be taken against me should subsequent events additionally go awry (such as landing at MAN rather than LHR due to a flap over the FOB) if I was to press on after shutting down an engine.
The case that the feds are going to bring is one based upon prudence and judgment rather than safety. For what it's worth, in my book, 3 out of 4 always beats 2 out of 2, but my book counts for little as I'm not the one interpreting and enforcing the rules. Nothing theoretical about this, operating in US airspace (under the FARs) with one out of four shut down no longer means carry on regardless.
Stagger - right argument - wrong place
Stagger, every thing you said is true and makes perfect sense. Problem is you are talking to the back of the class so to speak. This discussion belongs on another thread where they don't tread.
However, to those in the front of the house, I put it another way.
Where would you rather be, a long way from the nearest strip in a ETOPS twin with one turning or same spot in a 4 burner with two out. Don't worry about the legalities, you are there and how you got there really does not matter, just which pickle would you rather be in?
20driver
PS - Don't worry about Rainboe, someone is trying to poison his food.
However, to those in the front of the house, I put it another way.
Where would you rather be, a long way from the nearest strip in a ETOPS twin with one turning or same spot in a 4 burner with two out. Don't worry about the legalities, you are there and how you got there really does not matter, just which pickle would you rather be in?
20driver
PS - Don't worry about Rainboe, someone is trying to poison his food.
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XL5
So on the basis of a full and detailed risk analysis they will be withdrawing ETOPS certification for twin engined aircraft and certainly not allowing single engined aircraft to operate at night. I think not.
The case that the feds are going to bring is one based upon prudence and judgment rather than safety.
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a new FAA interpretation for a brave new world of improved safety............
The case that the feds are going to bring is one based upon prudence and judgment rather than safety. For what it's worth, in my book, 3 out of 4 always beats 2 out of 2, but my book counts for little as I'm not the one interpreting and enforcing the rules.
The case that the feds are going to bring is one based upon prudence and judgment rather than safety. For what it's worth, in my book, 3 out of 4 always beats 2 out of 2, but my book counts for little as I'm not the one interpreting and enforcing the rules.
Sky9 puts it nicely. Is the FAA going to ban ETOPs operations, or is that mysteriously 'acceptable' these days when Boeing wants to sell 777s that are not disadvantaged against the rest of the world's 747s? **Incorrect information on number of US 747s edited out**
The FAA can make what regulations it likes. The US must learn to accept that the US is no longer the centre of the world's aviation. Wake up and smell the roses- the rest of the world has grown hugely. It no longer sets the rules of the game. It can wag its finger all it likes at American pilots, the rest will laugh in its face.
Last edited by Rainboe; 29th Apr 2006 at 06:32.
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Originally Posted by M.Mouse
XL5
That is a very illuminating post.
It does rather explain the current hullabaloo.
That is a very illuminating post.
It does rather explain the current hullabaloo.
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The FAA is not considering restricting two engine ETOPS. I don't know why it is even being brought up here. They may question a specific flight that shuts down one engine of a three or four engine plane and continues on to destination as to if it was as save as diverting.