BA747 3 engine LAX-LHR article
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Originally Posted by Jumbo Driver
An interesting article, Rugerdog- thanks for the link.
In this article, Captain Meryl talks specifically about the BA 747-400 LAX-LHR event and says:
It is my opinion that had a U.S.-based airline pilot taken off from LAX and lost an engine, the logical airport to land at was, in fact, LAX. Why? Because, the Federal Aviation Regulations (FAR's) state that in the event of an engine failure, the airplane will land at the "nearest suitable airport."
In this article, Captain Meryl talks specifically about the BA 747-400 LAX-LHR event and says:
It is my opinion that had a U.S.-based airline pilot taken off from LAX and lost an engine, the logical airport to land at was, in fact, LAX. Why? Because, the Federal Aviation Regulations (FAR's) state that in the event of an engine failure, the airplane will land at the "nearest suitable airport."
What she would need to address is a 744 departing NRT or LHR OEI to the USA, what would a FAR Part 121 crews do ? We all know the answer, its been done before in three and four engine aircraft.
For the FAA to be consistent, will QF now be receiving a fine ....
http://www.atsb.gov.au/publications/...200404214.aspx
Last edited by Zeke; 26th Apr 2006 at 05:57.
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B747-400 two engine performance
Getline's article did bring up an interesting point though. At or near gross takeoff weights, the BA747 in question would have had dismal performance on only two engines, should another have also failed in flight. Due to the 747's lower thrust to weight ratio than that of ETOP twins, at higher weights with the loss of two engines, does the 747 actually match the performance of a far less heavy twin operating on one engine?
Would the BA747 have been able to have cleared the Rocky Mountains on only two engines should the worse case scenario have developed? What about if another engine had failed over the mid-atlantic? Would the aircraft have been able to descend to max E/O altitude and still have the range to divert? What if weather at lower altitudes mitigated the divert to the nearest suitable landing airport as well?
One can certainly argue the remoteness of a double-engine failure ever have occuring at all of course, but sometimes the impossible and improbable become the possible and inevitable. Stuff happens.
Would the BA747 have been able to have cleared the Rocky Mountains on only two engines should the worse case scenario have developed? What about if another engine had failed over the mid-atlantic? Would the aircraft have been able to descend to max E/O altitude and still have the range to divert? What if weather at lower altitudes mitigated the divert to the nearest suitable landing airport as well?
One can certainly argue the remoteness of a double-engine failure ever have occuring at all of course, but sometimes the impossible and improbable become the possible and inevitable. Stuff happens.
Last edited by Rugerdog; 26th Apr 2006 at 06:32.
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"IF" is a mighty big word Mr Dog!!! So let me get this straight, the Captain was in compliance with FARs and the flight turned out just fine!
The reason quads have 4 engines is to improve safety if one stops. 747ER weighs 910k and has 252k thrust, a 330 weighs 510k and has 160k thrust.
He was in a slightly worse position thrustwise but in a much better position in terms of redundancy than the average twin embarking on a 180 minute ETOPS sector at high AUW. If you lose another, your Thrust to Weight on 2 differs from the twin on 1 by <10% at MUW.
Maybe all twins shoul be converted to Tris or maybe we should get all the B52s out of Davis so that we can debate 5 engines failing on an 8 engined aircraft. Following the so called experts logic above, reversion to 7 engines would require an immediate diversion
The reason quads have 4 engines is to improve safety if one stops. 747ER weighs 910k and has 252k thrust, a 330 weighs 510k and has 160k thrust.
He was in a slightly worse position thrustwise but in a much better position in terms of redundancy than the average twin embarking on a 180 minute ETOPS sector at high AUW. If you lose another, your Thrust to Weight on 2 differs from the twin on 1 by <10% at MUW.
Maybe all twins shoul be converted to Tris or maybe we should get all the B52s out of Davis so that we can debate 5 engines failing on an 8 engined aircraft. Following the so called experts logic above, reversion to 7 engines would require an immediate diversion
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but sometimes the impossible and improbable become the possible and inevitable. Stuff happens.
What Rugerdog says above is absolutely correct (and I am only using his words to make my point, not attack him as an individual). These words make the argument for caution - but it is a generic argument, more like a safety admonition than an absolute. It really does not help, because, if you apply the argument in the following context, the get to a logical outcome that even our B777 experts would not like :
Situation: B777 on one engine over pacific has to fly for three hours to get to an airport.
Safety rule: "but sometimes the impossible and improbable become the possible and inevitable. Stuff happens."
Conclusion: twin-engined operations are unacceptable because to end up on one engine is too risky (in case improbable "stuff might happen" and the remaining one engine might fail - then you don't need to come up with mountain scenarios ... ).
On this basis the exchange of opinion and the ensuing nonsense in postings here can continue forever.
What is involved in this matter is quantifiable in terms of risk, redundancy, etc. However, it seems preferable to some to just use the matter to throw back unsupported opinions and contrived scenarios to try to "prove" their point. The threads on this matter are mainly a testimony to a "dialogue of the deaf" in which prejudices and unsupported opinion can continue for ever (and a day).
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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.
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Originally Posted by Cerberus
Maybe all twins shoul be converted to Tris or maybe we should get all the B52s out of Davis so that we can debate 5 engines failing on an 8 engined aircraft. Following the so called experts logic above, reversion to 7 engines would require an immediate diversion
I am not so sure if the twins have that much less backup then the B 747.
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I don't know exactly why they decided to land at Manchester or what ever airport but from what I have been able to pick up they had an issue getting fuel out of one tank so did it as a precaution. Someone said they had 16,000 pounds on landing. I have made decisions in my career I am sure others would find fault with but I still would do the same again. One situation usually has about three solutions, all of which would work just fine. I just don't like second guessing another pilot's actions when they were there and had over 12 hours to talk with their people and come out with a solution that worked just fine. By the time they left Gander airspace they should have been at a weight that another engine loss would not be that critical. We obviously don't worry about losing the second engine on our two engine aircraft or we wouldn't have 180 minute ETOPS
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I am not so sure if the twins have that much less backup then the B 747.
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The rules are what they are, but I can not believe that they were written with the intention to be used this way.
If one sets the number of engines aside, I do believe the redundancy is very similar given the fact of the APU and RAT etc....it has to be, because the probability of a failure within any of the subsystems is not very different.
If one sets the number of engines aside, I do believe the redundancy is very similar given the fact of the APU and RAT etc....it has to be, because the probability of a failure within any of the subsystems is not very different.
Last edited by AIMS by IBM; 26th Apr 2006 at 14:03.
Regarding the comparison between a 747 on 3 engines and an ETOPS aircraft being made by Rugerdog and Cerberus.
An additional factor to consider is that, all else being equal, a 747 on 3 engines is 50% more likely to have an engine failure than an twin (since it has 50% more engines operating - 3 vs 2).
Consequently while the performance of a 747 on 2 may not be a lot worse than an twin on 1 - the 747 is 50% more likely to end up on 2 (when it is starting with 3) than the twin aircraft is to end up on 1.
An additional factor to consider is that, all else being equal, a 747 on 3 engines is 50% more likely to have an engine failure than an twin (since it has 50% more engines operating - 3 vs 2).
Consequently while the performance of a 747 on 2 may not be a lot worse than an twin on 1 - the 747 is 50% more likely to end up on 2 (when it is starting with 3) than the twin aircraft is to end up on 1.
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If it is unsafe to continue flight on three engines because of the likelyhood of another engine failing,then,by the same logic a twin should never be allowed to get airborn.It will in no time be a glider.So lets go back to where we should be.Twins should not be allowed to fly beyond the glide distance to a suitable airport and maybe then quads should land ASAP when one engine fails
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Stagger, using your logic then, a single engine jet is subjected to half the risk of an engine failure of a twin and 25 % the risk of an engine failure of a 747 so we should go back to the barnstorming era?
Please note that nowhere in my post did I advocate a safe number of engines.
I simply pointed out that a factor to consider is that the more engines you have the more likely you are to experience an IFSD. It is, of course, not the only factor to consider. In addition to the probability of an IFSD, you obviously need to consider the consequences of an IFSD.
The fact is, that all else being equal, a quad (that's flying on 3) is 50% more likely to experience an engine failure than a twin (on 2).
But if a quad can divert on 2 as safely as a twin on 1, then this increased probability of diversion may not be a significant issue.
The probability of an IFSD is factored into the calculations behind ETOPS. The probability of an IFSD should similarly be factored into the calculations behind a quad (that's flying on 3) continuing its flight. The fact that a tri-jet might routinely travel the route is not necessarily relevant since the consequences of an IFSD are different for a tri-jet on 3 than for a quad that's flying on 3.
I simply pointed out that a factor to consider is that the more engines you have the more likely you are to experience an IFSD. It is, of course, not the only factor to consider. In addition to the probability of an IFSD, you obviously need to consider the consequences of an IFSD.
The fact is, that all else being equal, a quad (that's flying on 3) is 50% more likely to experience an engine failure than a twin (on 2).
But if a quad can divert on 2 as safely as a twin on 1, then this increased probability of diversion may not be a significant issue.
The probability of an IFSD is factored into the calculations behind ETOPS. The probability of an IFSD should similarly be factored into the calculations behind a quad (that's flying on 3) continuing its flight. The fact that a tri-jet might routinely travel the route is not necessarily relevant since the consequences of an IFSD are different for a tri-jet on 3 than for a quad that's flying on 3.
Last edited by stagger; 26th Apr 2006 at 16:41.
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Stagger
Is this not just a red herring? You will no doubt claim it misleading to suggest that this means the safest aircraft will necessarily have one engine. However, when you work out why such a deduction is wrong will that not also suggest why your claim, as quoted above, is completely misleading and a distraction from the issues at hand?
a factor to consider is that the more engines you have the more likely you are to experience an IFSD.
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Originally Posted by stagger
An additional factor to consider is that, all else being equal, a 747 on 3 engines is 50% more likely to have an engine failure than an twin (since it has 50% more engines operating - 3 vs 2).
Consequently while the performance of a 747 on 2 may not be a lot worse than an twin on 1 - the 747 is 50% more likely to end up on 2 (when it is starting with 3) than the twin aircraft is to end up on 1.
Consequently while the performance of a 747 on 2 may not be a lot worse than an twin on 1 - the 747 is 50% more likely to end up on 2 (when it is starting with 3) than the twin aircraft is to end up on 1.
Firstly, Stagger, a 747 does not start with 3 engines.
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?
In other words, statistics would need to show more double-engine failures on 4-engined aircraft than single-engine failures on twins.
Not so, I think !
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Stagger, more of the same:
Do you really mean this? Think about it.
the 747 is 50% more likely to end up on 2 (when it is starting with 3) than the twin aircraft is to end up on 1.
No a 747 does not start on 3 engines. But we are comparing a 747 starting on 3 with a twin. The fact that the quad originally had 4 is not really relevant when it comes to calculating the probability of a future failure.
Even though the thread title is "BA747 3 engine LAX-LHR" some of you seem to have missed that I was considering a 747 on 3, not a 747 on 4, and this has led to some misunderstandings.
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).
It's quite straightforward - but whether this difference is important depends entirely on the consequences of an engine failure in each case.
GGV - I suggest you think about it.
3 engines vs 2 engines
3 engines that can fail vs 2 engines that can fail
An analogy...
3 lottery tickets vs 2 lottery tickets = 50% more lottery tickets
This an extremely basic probability issue - I don't see why people have such trouble grasping it.
All I am suggesting is that before embarking on an extended flight over the North Atlantic it needs to be considered that the quad (on 3 engines) is 50% more likely to experience an IFSD than a twin on 2. This is just one factor to be considered - there are of course many others.
Even though the thread title is "BA747 3 engine LAX-LHR" some of you seem to have missed that I was considering a 747 on 3, not a 747 on 4, and this has led to some misunderstandings.
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?
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).
It's quite straightforward - but whether this difference is important depends entirely on the consequences of an engine failure in each case.
GGV - I suggest you think about it.
3 engines vs 2 engines
3 engines that can fail vs 2 engines that can fail
An analogy...
3 lottery tickets vs 2 lottery tickets = 50% more lottery tickets
This an extremely basic probability issue - I don't see why people have such trouble grasping it.
All I am suggesting is that before embarking on an extended flight over the North Atlantic it needs to be considered that the quad (on 3 engines) is 50% more likely to experience an IFSD than a twin on 2. This is just one factor to be considered - there are of course many others.
Last edited by stagger; 26th Apr 2006 at 17:39.
Controversial, moi?
stagger, you are not perchance an accountant working on the BA team trying to steal our pensions are you?
Your mathematics seems very similar to those used in the BA spreadsheets.
Your mathematics seems very similar to those used in the BA spreadsheets.