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Twin Engine ETOPS...Pushing Their Evolution Limits  
User currently offlineManfredj From United States of America, joined Mar 2007, 1132 posts, RR: 0
Posted (6 years 6 months 2 weeks 1 day 17 hours ago) and read 12763 times:

Just a thought, are we pushing twin engine ETOPS aircraft to their limits of endurance? I agree that the media has indeed reported on these incidents more than in the past, but the amount of shut downs seem to have increased over the years.

I am a firm believer in the "right wall" of evolution. Basically, you can only make something so powerful and large until you have pushed the envelope to it's limits. Maybe in our ultra fuel conscious world (which I don't necessarily agree with), we have given up safety and practicality in exchange. Again, we leave the FAA to write these rules in blood, only after the fact do we learn our lessons.

Just compare the amount of twin VS quad and triple engine shut downs over the past few years to find out. The answer may be clearer than you thought. I'd hate to think we're flying around in airplanes equipped with engines we may think have stood the test of time, but in reality we are just human test-beds only to find out they don't compare favorably with our less fuel efficient engines of the past.


757: The last of the best
127 replies: All unread, showing first 25:
 
User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 42
Reply 1, posted (6 years 6 months 2 weeks 1 day 16 hours ago) and read 12694 times:



Quoting Manfredj (Thread starter):
Just compare the amount of twin VS quad and triple engine shut downs over the past few years to find out.

If you're talking about the inconvenience of having to divert when one engine fails on a twin, you may have a point. If you're talking about the chances of an accident due to a single engine failure, I'd need to see some numbers before I started worry.

Quoting Manfredj (Thread starter):
Maybe in our ultra fuel conscious world (which I don't necessarily agree with), we have given up safety and practicality in exchange

Flying will always involve a trade-off between safety and economics/convenience/practicality. The only way for flying to be 100% safe would be for us to stop flying.  Smile


User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 2, posted (6 years 6 months 2 weeks 1 day 15 hours ago) and read 12582 times:



Quoting David L (Reply 1):
Flying will always involve a trade-off between safety and economics/convenience/practicality. The only way for flying to be 100% safe would be for us to stop flying.

We try to reduce the risk as far as economically possible, or at least that is what we call it. It's easy to say the one remaining engine is acceptable when you are behind the keyboard.....but if you were on an aircraft depending on one remaining engine, your range of acceptability would be narrowed.

Seems to me that design is going in the wrong direction overall. Instead of trying to push the two engine envelope, we should use longer range thinking by engineering these engines so that 4 can be hung at the same cost and efficiency as two are now. We gain efficiency without losing redundancy.

All we hear now is "4 engines are dead"......4 engines should be a goal, not a hinderance.


User currently offlineDw747400 From United States of America, joined Aug 2001, 1258 posts, RR: 1
Reply 3, posted (6 years 6 months 2 weeks 1 day 14 hours ago) and read 12441 times:

To the best of my knowledge, no modern ETOPS twin has ever lost both engines due to independent failures in both engines. In other words, no ETOPS twin has ever been in a situation that wouldn't have resulted in complete engine failure on a quad.

Can there be two independent failures in modern engines? Of course. Anything can fail. But statistically speaking, you have a lot of other things to worry about first. I'd be more concerned an electrical fire in the cockpit could prevent the crew from performing their duties than about dual independent engine failure. We know there are thousands of other possible failure points on any large airliner Most critical ones have backups, but many are still less reliable than a modern turbine engine.

From an operational standpoint, twins can be an issue since an engine failure results in an immediate diversion--more engines doesn't guarantee you get where you want to go, but you do have more options.

Quoting MD80fanatic (Reply 2):
Instead of trying to push the two engine envelope, we should use longer range thinking by engineering these engines so that 4 can be hung at the same cost and efficiency as two are now.

Any technology developed like that would certainly be applicable to twins, for an even greater gain.



CFI--Certfied Freakin Idiot
User currently offlineStitch From United States of America, joined Jul 2005, 30883 posts, RR: 86
Reply 4, posted (6 years 6 months 2 weeks 1 day 14 hours ago) and read 12404 times:
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Twin engines have been in use on airplanes since shortly after the airplane was invented.

That they continue in use to this day should be proof-enough that the concept is safe.


User currently offlineFlyingClrs727 From United States of America, joined Apr 2007, 733 posts, RR: 0
Reply 5, posted (6 years 6 months 2 weeks 1 day 13 hours ago) and read 12353 times:



Quoting Stitch (Reply 4):
Twin engines have been in use on airplanes since shortly after the airplane was invented.

But should ETOPS be extended to 330 minutes? Such extensions would make routes like IAH-SYD possible with twin engined planes.


User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 6, posted (6 years 6 months 2 weeks 1 day 13 hours ago) and read 12319 times:

Transcons were conceived to use multiple (as in more than two) engines....the trend towards two only was spurred by supposedly higher fuel prices and a certain type of propulsion pissing contest driving the manufacturers to see how big a single engine can be made. Ohhhh, my fan is bigger than yours?

Quoting Dw747400 (Reply 3):
Any technology developed like that would certainly be applicable to twins, for an even greater gain.

See, there ya' go.

You can do it even cheaper with one engine.....so why not do that? Statistics "prove" that single engine flight is safe. Don't know about you.....but I prefer as much redundancy as is possible to cram on an airliner.

Simply put.....when cargo MUST get to it's destination, intact and alive, as many layers of redundancy are applied as is possible. When redundancy is disposed of, it is the same as reducing the value of your cargo (pax). Would an armoured car manufacturer use only 1/8" plate steel, since it would statistically stop 92% of the ammunition commonly available to the public? No, they go for whatever the vehicle frame can possibly carry and still be licensed to operate safely. Uhhhh, that's right.......$$$ is far more important than people. Never mind.

[Edited 2008-02-10 10:46:53]

User currently offlineStitch From United States of America, joined Jul 2005, 30883 posts, RR: 86
Reply 7, posted (6 years 6 months 2 weeks 1 day 13 hours ago) and read 12316 times:
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Quoting FlyingClrs727 (Reply 5):
But should ETOPS be extended to 330 minutes?

I don't see any reason why it shouldn't.

Frankly, I believe the decision by the FAA to effectively do away with ETOPS restrictions for US operators is a logical one. It sets a higher bar for maintenance and reliability and requires stronger on-board fire-suppression systems as well as additional oxygen supplies to support longer times at higher altitudes and on-board defibrillators. So the planes are actually safer.


User currently offlineTranspac787 From United States of America, joined Jul 2007, 3203 posts, RR: 13
Reply 8, posted (6 years 6 months 2 weeks 1 day 13 hours ago) and read 12313 times:



Quoting FlyingClrs727 (Reply 5):
But should ETOPS be extended to 330 minutes? Such extensions would make routes like IAH-SYD possible with twin engined planes.

I personally think that yes, ETOPS-330 should be given to new-generation twins. 772LR, 773ER, 787, A350. I think it should be limited to them though...which really isn't all that great of a problem, as there really aren't any other twins that have the range to make ETOPS-330 routes.

As a bit of a side-note.....IAH-SYD can be made under current ETOPS-207 rules, if you use a bit of a dog-legged route. It has been my understanding that the routes most needing ETOPS-330 would be those crossing over the south pole...SYD-EZE and others.



A340-500: 4 engines 4 long haul. 777-200LR: 2 engines 4 longer haul
User currently offlineSeaBosDca From United States of America, joined Sep 2007, 5387 posts, RR: 4
Reply 9, posted (6 years 6 months 2 weeks 1 day 13 hours ago) and read 12267 times:



Quoting MD80fanatic (Reply 6):
a certain type of propulsion pissing contest driving the manufacturers to see how big a single engine can be made.

Huh?  boggled  sarcastic 

The first engines physically bigger than those used on any quad were the 777 engines (GE90, Trent 800, 777 variants of PW4000). The 777 was not designed so the engine manufacturers could show off big fans. The 777 was designed to be what it is: a heavy, long-range airliner vastly more cost-effective than those that had come before. The size of the fans was simply what was necessary to bring the 777 into being.

Fans on both twins and quads have gotten bigger over the years for one reason: the high bypass ratio benefits efficiency.

Quoting MD80fanatic (Reply 6):
I prefer as much redundancy as is possible to cram on an airliner.

Thousands of twins operate all over the world every day. The total operational history of twins encompasses many millions of flights. Out of all those flights, there have been no situations, to my knowledge, where a twin commercial airliner lost both engines independently in such a way that a quad would have continued flying after losing two engines in the same manner.

Your redundancy would just be a waste of money that would result in more expensive tickets. Fortunately, airframe manufacturers and airlines understand this.


User currently offlineRJ111 From , joined Dec 1969, posts, RR:
Reply 10, posted (6 years 6 months 2 weeks 1 day 13 hours ago) and read 12263 times:

The only 2 routes i can think of off the top of my head which would benefit from Etops 330 would be JNB-PER/SYD

User currently offlinePlunaCRJ From Uruguay, joined Nov 2007, 574 posts, RR: 2
Reply 11, posted (6 years 6 months 2 weeks 1 day 12 hours ago) and read 12102 times:



Quoting RJ111 (Reply 10):
The only 2 routes i can think of off the top of my head which would benefit from Etops 330 would be JNB-PER/SYD

And SCL/EZE- AKL/SYD. In fact, both LAN and Air New Zealand plan to use their new 787 on the SCL-AKL route.


User currently offlinePlaneInsomniac From Canada, joined Nov 2007, 678 posts, RR: 0
Reply 12, posted (6 years 6 months 2 weeks 1 day 12 hours ago) and read 12067 times:



Quoting Dw747400 (Reply 3):
To the best of my knowledge, no modern ETOPS twin has ever lost both engines due to independent failures in both engines. In other words, no ETOPS twin has ever been in a situation that wouldn't have resulted in complete engine failure on a quad.

Can there be two independent failures in modern engines?

Once again, I cannot understand why people use this hypothetical situation of "two independent engine failures" as the litmus test for twin engine safety.

Honestly, what does that have to do with anything?

The fact of the matter is that even if only one engine fails on a twin, this reduces the margin of error - human, mechanical, or otherwise - to almost zero. Even if the second engine is still running.

If one engine fails in a quad, the situation is much less critical. Less relative loss of thrust, less reduced range, less asymmetrical thrust.

I would certainly much rather be in a quad with three running to perform an emergency landing in bad weather or with heavy crosswinds than in a twin with one running.

I would also certainly much rather be in a quad with three running over the middle of the Pacific, hundreds and thousands of miles away from the next airport, than in a twin with one running.

Honestly, who in their right mind wouldn't?

And now it's starting to look like we have in-flight shutdowns on large twins not only monthly, but rather weekly or daily.

What does "but nobody has died (yet) due to two independent engine failures on a twin" have to do with relative safety?

This is what can happen to a twin even if only one engine fails:

http://www.youtube.com/watch?v=TKZjlvagrPo

And this happened to the Boeing people! They barely managed to keep her on the runway. Of course, they made some software change now or something. Which is certainly going to work well until a truly unexpected situation comes along.



Am I cured? Slept 5 hours on last long-haul flight...
User currently offlineDfwRevolution From United States of America, joined Jan 2010, 968 posts, RR: 51
Reply 13, posted (6 years 6 months 2 weeks 1 day 11 hours ago) and read 11517 times:



Quoting Manfredj (Thread starter):
Just a thought, are we pushing twin engine ETOPS aircraft to their limits of endurance?

Yes, we will soon reach the maximum endurance of twin engined aircraft: when they can connect any two cities on Earth. Then we will have no more endurance to add.

It's 2008 people. I can't believe this is even an issue anymore.


User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 14, posted (6 years 6 months 2 weeks 1 day 11 hours ago) and read 11588 times:

The idea would be to have each engine consuming it's own fuel from it's own source for the most part (except in emergencies). Why would that be difficult? It wouldn't at all.....just a bit more expensive.

If failure is not an option.....then these are the things that must be done. That BA777 was in no man's land when the unthinkable happened, and if it weren't for a highy skilled human being..... Personally.....I would take a long hard look at ETOPS in light of this "impossible" twin failure. Maybe the media did not make enough out of this story?

I cannot see what the purpose is for the rabid resistance to the return of multi-engined long haul? You folks just want the biggest possible engines to hang from your wings? Are you sure you are not all from Texas?  scratchchin 


User currently offlineStitch From United States of America, joined Jul 2005, 30883 posts, RR: 86
Reply 15, posted (6 years 6 months 2 weeks 1 day 11 hours ago) and read 11486 times:
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Quoting MD80fanatic (Reply 26):
The idea would be to have each engine consuming it's own fuel from it's own source for the most part (except in emergencies). Why would that be difficult? It wouldn't at all.....just a bit more expensive.

First, a manufacturer would have to evenly split the fuel-load between both engines across the same number of tanks. So the tanks on the right wing would feed the right engine and the tank on the left wing would feed the left. Then you need two center tanks - one tank for each wing. So you need to dedicate more underfloor space to holding the tanks which eats into cargo.

Second, an airline has to calculate fuel burn not just for the entire flight, but also for each engine (since they can burn at different rates). If you need all 100,000 liters of fuel to fly a mission, it won't help that the engine on the right wing will burn 49,000 liters while the engine on the left wing will burn 51,000 liters since that means you're on one engine for the final approach.  eyepopping 



Quoting MD80fanatic (Reply 26):
If failure is not an option.....then these are the things that must be done. That BA777 was in no man's land when the unthinkable happened, and if it weren't for a highy skilled human being..... Personally.....I would take a long hard look at ETOPS in light of this "impossible" twin failure.

First, there is no such thing as truly "fail safe".

Second, that 777 flew almost it's entire flight with two perfectly functioning engines. And it flew a great deal of flights before it with two perfectly functioning engines.

The majority of car accidents happen within a few miles of one's domicile. Maybe those people who believe twins should be banned as unsafe because the engines failed at the last moment should also advocate to not let people drive to or from their home because it's unsafe?


User currently offlineTranspac787 From United States of America, joined Jul 2007, 3203 posts, RR: 13
Reply 16, posted (6 years 6 months 2 weeks 1 day 11 hours ago) and read 11446 times:

Quoting MD80fanatic (Reply 26):
The idea would be to have each engine consuming it's own fuel from it's own source for the most part (except in emergencies). Why would that be difficult? It wouldn't at all.....just a bit more expensive.

This is actually normal procedure....

Quoting MD80fanatic (Reply 26):
If failure is not an option.....then these are the things that must be done. That BA777 was in no man's land when the unthinkable happened, and if it weren't for a highy skilled human being..... Personally.....I would take a long hard look at ETOPS in light of this "impossible" twin failure. Maybe the media did not make enough out of this story?

You keep dodging the questions asked of you. Let's play devils advocate for a bit......

In the case of the BA 747 that lost all four engines due to volcanic ash ingestion, how would "highly skilled human beings" have made any difference if they didn't restart the engines?? 744's do not have a RAT or any emergency hydraulic systems. So, if you lose all four engines, the plane is essentially out of control. A 777 does have a RAT, as do the 767 and 757.....all ETOPS airplanes.

Or the case of the recent QF 744 quad generator failure. If that had happened over the Pacific, the battery would have powered the plane for 30 minutes. On a 777, in the event of a dual generator failure the APU can be started in-flight. A 744's APU *cannot* be started in-flight. Back to the 777 though... even if you have a dual generator failure and you can't start the APU, you still have the HMG which will provide emergency power to the aircraft until it can land. As long as the hydraulics are running, the HMG provides AC power. A 744 does *not* have an HMG.

You see......there are freak accidents for both twins and quads. Some planes are better equipped to deal with them than others. To put the 777 in good light, do you remember the engine failure of a UA 772ER on AKL-LAX?? The 777 lost an engine at almost the exact point at which it was furthest from a divert field......Murphy's Law. Anyhow, the 777 limped 192 minutes on a single engine to KOA....which, as far as I know, still holds the record for the longest divert on a single engine, as the flight was being operated under ETOPS-207.

Quoting MD80fanatic (Reply 26):
You folks just want the biggest possible engines to hang from your wings? Are you sure you are not all from Texas?

Damn, you got us.  

Edit~ spelling

[Edited 2008-02-10 13:13:39]


A340-500: 4 engines 4 long haul. 777-200LR: 2 engines 4 longer haul
User currently offlineManfredj From United States of America, joined Mar 2007, 1132 posts, RR: 0
Reply 17, posted (6 years 6 months 2 weeks 1 day 10 hours ago) and read 11273 times:



Quoting Stitch (Reply 7):
Frankly, I believe the decision by the FAA to effectively do away with ETOPS restrictions for US operators is a logical one. It sets a higher bar for maintenance and reliability and requires stronger on-board fire-suppression systems as well as additional oxygen supplies to support longer times at higher altitudes and on-board defibrillators.

Yes, that may be, but we're talking about the reliability of engines....not life support systems.

Quoting SeaBosDca (Reply 9):
777 was designed to be what it is: a heavy, long-range airliner vastly more cost-effective than those that had come before.

Thanks for proving my point. I'm not as interested in cost efficiency as I am safety of those on board. My point is...we are just beginning to learn about LONG RANGE twin aircraft safety. We all know they are more efficient, but at the cost of safety?

Quoting MD80fanatic (Reply 6):
but I prefer as much redundancy as is possible to cram on an airliner.

Thank you, as a pilot, my main concern is life preservation in the event of a problem in the air.



757: The last of the best
User currently offlineSeabosdca From United States of America, joined Sep 2007, 5387 posts, RR: 4
Reply 18, posted (6 years 6 months 2 weeks 1 day 10 hours ago) and read 11155 times:



Quoting MD80fanatic (Reply 26):
You folks just want the biggest possible engines to hang from your wings?

I think you're the one obsessed with monster engines. You're the only one who brought it up... and you did it again in spite of my original explanation of why fans are bigger than they used to be.

Quoting SEPilot (Reply 32):
Again, THERE IS AS OF YET NO EVIDENCE THAT IT WAS AN "IMPOSSIBLE" TWIN FAILURE.

 checkmark  And what evidence there is strongly suggests something else: a non-engine-related failure that would have robbed power from all engines on a quad. The engines both continued to run as expected given the amount of fuel they received. The issue is that, for as-yet undetermined reasons, the engines were not receiving fuel as commanded by the A/T and the pilots.

Quoting MD80fanatic (Reply 19):
Once again....more is always better.

Except when the existing redundancy has been sufficient to prevent a problem from ever happening in tens of millions of flights. In that case, I'd rather have the cheaper tickets than more unnecessary redundancy and the costs and weight associated with it.

You seem to be continuing to make the same arguments, ignoring a number of rather convincing responses to them further up the thread. I also wonder, if you feel so uncomfortable with twins, how you can be an "MD80Fanatic."  confused 


User currently offlineGearup From Canada, joined Dec 2000, 578 posts, RR: 1
Reply 19, posted (6 years 6 months 2 weeks 1 day 10 hours ago) and read 10974 times:



Quoting DfwRevolution (Reply 25):
t's 2008 people. I can't believe this is even an issue anymore.

It will always be an issue. We can throw statistics around like confetti but many people will always doubt that it proves anything is safe. For instance, we know as someone has said earlier, that you are safer in a commercial aircraft than you are in your own car on the freeway and we know that this can easily be proven but there are many people terrified of flying. The only reason why a person is terrified is because they fear they will die because the aircraft may crash. To such a person the statistical safety of air travel is meaningless. I have been involved in the maintenance and overhaul of aircraft engines for a number of years and I know how well designed and engineered they are. The MRO processes and procedures are extremely stringent especially for engines from an ETOPS aircraft. Do I feel safe on a long over water flight on a twin? Yes I do, but for all of that I am one of those who as a Boeing engineer said on the documentary '21st Century jet', "The only reason I put 4 engines on an aircraft is because I don't have room for 5". I think the original poster asks a very valid question all the more so because of the number of IFSD's of late. I still feel better when I look out the window and I see 2 engines under the wing because if it is statistically unlikely (in the extreme) to lose both engines on a twin for unrelated causes, it's darn near impossible on a quad. In many ways it's more a philosophical thing - whether you are a 'the glass is half full' type of person or a 'the glass is half empty' person. As such the debate will continue forever.



I have no memory of this place.
User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 20, posted (6 years 6 months 2 weeks 1 day 10 hours ago) and read 10947 times:



Quoting Seabosdca (Reply 35):
And what evidence there is strongly suggests something else: a non-engine-related failure that would have robbed power from all engines on a quad.

Assuming one would be ignorant enough to design a four engined bird where ALL powerplants and fuel systems get signals to/from/through a common component....that when it fails, all fail. Am I the only one that sees this? The BA incident puts on display the -fact- that both those engines are not fully independent (as they obviously should be, and ETOPS should require them to be).


User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 21, posted (6 years 6 months 2 weeks 1 day 10 hours ago) and read 10911 times:



Quoting Seabosdca (Reply 35):
I also wonder, if you feel so uncomfortable with twins, how you can be an "MD80Fanatic."

The >MD< gives me an added level of confidence, despite it's twin configuration......"Douglas' hard-earned reputation for a thorough time-tested design. I feel much more vulnerable on a 737.


User currently offlineTranspac787 From United States of America, joined Jul 2007, 3203 posts, RR: 13
Reply 22, posted (6 years 6 months 2 weeks 1 day 10 hours ago) and read 10892 times:



Quoting MD80fanatic (Reply 37):
Assuming one would be ignorant enough to design a four engined bird where ALL powerplants and fuel systems get signals to/from/through a common component....that when it fails, all fail. Am I the only one that sees this? The BA incident puts on display the -fact- that both those engines are not fully independent (as they obviously should be, and ETOPS should require them to be).

And you are still assuming that you know the failure to be the direct cause of a failed component that has control over both engines. As people have said, no official findings have been released. Until then, you really should stop making wild speculations.



A340-500: 4 engines 4 long haul. 777-200LR: 2 engines 4 longer haul
User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 23, posted (6 years 6 months 2 weeks 1 day 9 hours ago) and read 10709 times:

Quoting Transpac787 (Reply 40):
And you are still assuming that you know the failure to be the direct cause of a failed component that has control over both engines. As people have said, no official findings have been released. Until then, you really should stop making wild speculations.

Whoa now......it was you folks telling me that two engines failing for different reasons on each, at the same time, was next to impossible (and I fully agree with you). Now then the most likely cause is that both failed from the same prime mover.

I'll be more general to avoid flareups.

The engines did not fail, but both failed to provide thrust. In other word's they failed to function in parallel. To assume that two different uncontrollable issues occurred under the same wings, at the same time, is the wild speculation. If it were ice or contaminants in the fuel.....that was engineering undersight (bigtime).

[Edited 2008-02-10 14:27:19]

User currently offlineStitch From United States of America, joined Jul 2005, 30883 posts, RR: 86
Reply 24, posted (6 years 6 months 2 weeks 1 day 9 hours ago) and read 10646 times:
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Quoting Manfredj (Reply 33):
Yes, that may be, but we're talking about the reliability of engines....not life support systems.

Actually, we seem to be ranging all over the place. But any current generation engine, be it employed in a single, twin, tri or quad configuration is more reliable now then it's predecessors and it's successors are likely to be even more reliable.

Quoting Manfredj (Reply 33):
My point is...we are just beginning to learn about LONG RANGE twin aircraft safety.

A300s and A310s have been flying missions over 4000nm since the 1970s. 767s have been doing missions between 4000nm and 6000nm since the 1980s and A330s and 777s have been doing missions over 6000nm since the 1990s.


25 ACdreamliner : while i agree heartiedly, i don't see why trijets are not the norm at the minute. i.e. I imagine a 3 engines upgraded CFM-56 A332 size plane would be
26 SEPilot : Trijets require a very complex, expensive, and heavy structure for the third engine. And the larger diameter the engine the larger the problem. Plus
27 Planemaker : I agree, but we are approaching virtual "fail safe" technology. No, comprehensive (it is only partial now) real-time engine monitoring and bench mark
28 Manfredj : I thought engine monitoring was already in play as we speak. I know that if you fly for continental, for example, if you over-rotate (27 degrees) pas
29 Frontierflyer : I say bring back the md11, nah! As much as I love the 11 SEPilot is right, trijets are expensive, that third engine is a pain. I've read that maintanc
30 Planemaker : The example that you give (exemption reporting) is very different than the one that I brought up... comprehensive real-time engine monitoring and ben
31 Post contains images Osiris30 : Douglas don't (or didn't) make the engines on the MD80 my friend.. they have nothing to do with the odds of the engines failing at all... but hey why
32 Post contains images FlyDeltaJets87 :    Well stated. I wouldn't be surprised if it's because more twins are operating now a days too, which therefore, is going to increase the number o
33 Manfredj : An accident in a 737 doesn't impact it's safety record nearly as much as an A380 because of the amount of 737's in the sky. Does that mean we should
34 Planemaker : Your initial question still dosen't make sense. Just how is it that we are approaching the "performance threshold" by tacking on a bit more steady-st
35 FlyDeltaJets87 : It will also come down to the number of people killed. An A380 crashing will kill 500 to 800 people, which will surely make the news. The real shocke
36 Alfa75 : Shouldn't this be in Tech/Ops?
37 Seabosdca : Nope. The biggest and most powerful turbofan ever (the GE90-11xB) is also one of the most reliable ever, 3 recent and unrelated IFSDs (which are the
38 FlyingClrs727 : If a trijet Such an engine would be fantastic for a very large C-5 class three engined BWB freighter. The USAF might actually need the extra reliablil
39 Thegeek : The Kegworth air disaster!! Of course, counterring that you have the C-5 with one idling engine and one stopped engine, El Al 1862, and Concorde. I d
40 Cchan : It will probably cost more in maintenance of 4 engines instead of 2. Which comes first? Twin, tri, or quad? I think the 763 ER has comparable engine
41 FlyingClrs727 : Some airlines have the same engines on their 767's and 744's. United actually services its 747's to ETOPS standards, and their 744 engines are interc
42 MD80fanatic : Not exactly. Multiple smaller engines need not work as hard as two large ones pushing the same load. Say a certain large engine from a twin is good f
43 NYC2theworld : Umm....the Concorde has four engines...And the Concorde crashed due to the fact FOD was on the runway which punctured a tire.
44 Planemaker : Not exactly? It is the exact opposite of what you speculate... or more precisely, conjure up.
45 NCB : 747's don't have a RAT because the windmilling of the engines produces enough power for hydraulic powered controls to work. So if you loose all engin
46 Planemaker : Real-time, comprehensive monitoring and bench marking (RR and Boeing both have limited real-time monitoring available) that will be available in next
47 Thegeek : Hence it was part of the counter point. If Concorde were a twin it wouldn't have crashed as quickly, but may have crashed anyway. Drunk? Wouldn't tha
48 Plairbus : personally i feel much more comfortable con a four than on a twin jet, i know and read a hundred of times the possibility and all this about but i pre
49 Hirnie : Real- time monitoring will show in real time that the engine shuts down, of what ever reason. As the name of the system says: it's a monitoring syste
50 Planemaker : No it does not. What you are referring to is basically what EICAS displays. What I am referring to is far more detailed monitoring and benchmarking t
51 ThirtyEcho : There are no ETOPS requirements for four engine airplanes. I rest my case.
52 Cchan : The difference is that on a twin if one engine fails, they tell you that they have to land at an airport nearby, but on a quad, even when 2 engine fa
53 ThirtyEcho : There are no ETOPS requirements for four engine airplanes. I rest my case.
54 Dragon6172 : I would venture to say that if a quad lost two engines, they would not continue to their destination. A lot of things dependant of course. For exampl
55 David L : That's what some people "learned". Others learned (as if they hadn't already known) that you don't deliberately put an aircraft, with however much or
56 NCB : The problem with such a system is that one can't put a sensor on every single part of the system because it is economically not possible. Such a syst
57 MD80fanatic : We could argue this quite well, but not here. (tired of having posts deleted) In short.....the official reason for Concorde crash is bollocks. Well t
58 MD80fanatic : Rather than use -more- engines, you folks would cover the two engines we use now with a spider web of sensors attempting to predict what may never hav
59 2175301 : Please explain to me why it is that people must get to a designated destination.... I also point out that your do not make sense. Auto Manufactures f
60 SEPilot : I can show you 2 quads that crashed where a twin almost certainly would not have; the two 747's that crashed because 2 engines fell off. On the other
61 NCB : Hum a quad has more chances to go down in the event of an uncontained engine failure...hum hum hum. This is new to me, explain please
62 Seabosdca : Because optimizing two engines rather than insisting on four makes travel more affordable for more people, while (as demonstrated by the safety recor
63 MD80fanatic : Are you sure about that? I was just riding in my friend's new Toyota Tundra and it had airbags all over the place. Side, top, front.....I think there
64 Manfredj : We'll if this is true, than this whole thread is useless. I'm skeptical about your conclusion. The more I think about it, the safety of 2 vs. 4 or 3
65 Seabosdca : Enjoy your $10,000 ticket from AUS to DFW. *Everything* in transportation is a question of what's economically possible.
66 Trex8 : could you give us more details please on these incidents, are you talking about the 742F pylon problems?
67 Post contains images FlyDeltaJets87 : Mono. The Wright Flyer was a single engine plane with two propellers. Thanks, but I'll see what I can do about getting a ride on a KC-10 here in the
68 Bwohlgemuth : If ETOPS-180 or ETOPS-207 had caused massive problems/inconvenience/death, I don't think we would be looking at approving ETOPS-330. Sort of a simple
69 Killjoy : Even if we completely ignore the fact that quads are more likely to have other types of failures (such as dual bird strike), and assume that they're i
70 FlyDeltaJets87 : The same reason you won't see ESOPS is the same reason we probably won't ever see just one pilot in the cockpit. There is no safety net with a single
71 David L : And, even then, the design was altered (instrumentation improvement and reverser lock-out in flight, as I recall). Slapping another two engines on wo
72 Post contains images FlyDeltaJets87 : That was a joke at the BA flight that had an engine shut down on a 747 in-flight and yet still continued to its destination, and a lot people raised
73 Post contains images David L : Ah, whoops.
74 SEPilot : With twice as many engines you have twice the chance of an uncontained failure. Certification requirements are that an airliner be able to take off a
75 MD80fanatic : Philosophical differences prevents me from further discussion of this topic (without being censored). I don't believe a value can be placed on a human
76 MD80fanatic : Leaving that airliner one bird strike or compressor stall away from certain mass death. Yep, that's covering all the safety bases. Oops, sorry.......
77 SEPilot : And yet what you consider one bird strike or compressor stall away from certain mass death has yielded the absolute safest way to get from point A to
78 FriendlySkies : MD80fanatic: Having skimmed through your posts, I'm failing to see the logic in your argument. Are you suggesting that we design a 4 engine aircraft w
79 David L : I have to agree. Then it has to be asked again: how much would you be prepared to pay for a flight in an aircraft that has zero chance of having an a
80 Robsawatsky : This kind of thread comes up again, and again, and has almost nothing to do with engineering, probability, statistics or cost and everything to do wi
81 Seabosdca : We have good reason for our sanguinity. The rate of accidents caused by systems or mechanical failure is vanishingly small in all current-generation
82 Manfredj : How far back do they go? Are they [statistics] skewed for the amount of twins VS. quad and three holers?
83 SEPilot : From what I can determine since the beginning of the jet age there have been four twins that have crashed because of engine problems and two trijets
84 Hirnie : People in this discussion seem to think that operating a quad on longhaul missions is that expensive that poeple can not afford to travell on them any
85 David L : You know, that's discussed so often here that I'm surprised it hasn't come up in this thread before now - good spot! Those pilots who post in Tech/OP
86 Post contains images Planemaker : Please compare the sensor package on the A380 vs the A300 to see how far we have come. And we will be able to put a sensor on virtually every compone
87 SEPilot : And the airlines are all scrambling to replace their 744's with 77W's and A340's are selling like week-old flapjacks. Virgin tried the "4-engines for
88 NCB : No the problem with the EL-AL is that it was way above MTOW at take-off and that the number 3 engine when separated took all the flaps that were depl
89 Viscount724 : I suggest you check with the FAA re your statement. Revised ETOPS rules effective a year ago now affect all aircraft, not just those with 2-engines.
90 SEPilot : But the simple fact is that if it had been a twin the engine would have separated cleanly and not damaged the flaps or leading edge. Two other 747's
91 PlaneInsomniac : Really, it's the same method again. You take an incident which can most likely be ascribed to design deficiencies of one particular plane type (747)
92 Transpac787 : This effects an A340, A380, 747, etc....just as much as it would effect A330, 777, 787. A 744 a MGTOW will *not* be able to fly on two engines. So, i
93 PlaneInsomniac : It also should be noted that there were at least two jet crashes where the number of engines played a role: - The BMI crash: shutdown of wrong engine
94 Post contains images Transpac787 : Which, of course, is a direct quote from the Simpsons
95 Planemaker : I do get a chuckle how people use "old" incidents that have no bearing on the latest generation of twins that will be EIS... and much less so on the
96 Viscount724 : Have there been any accidents caused by all engines failing on a multi-engine jet airliner (for any reason including fuel exhaustion) where all aboard
97 Post contains images PlaneInsomniac : You got me And yet the same methodology is used here over and over again in the case of quads. Incidents on 747 Classics and even trijet models which
98 Post contains images Seabosdca : The truth of what you argued is irrelevant to the (self-evident) truth of this statement. (Except as applied to A380s ) An actual determination of wh
99 SEPilot : I have never said that it was a "typical quad problem." Aviation has gotten so safe that almost all accidents are unique events. It is only when a de
100 MD80fanatic : You base your entire argument on today and before. What about tomorrow and beyond? Just because it hasn't happened yet, does not mean it never will.
101 MD80fanatic : It is more than likely less for quads. Please don't mistake the added safety factor afforded by quantum leaps forward in navigation and communication
102 Planemaker : This has nothing to do with this thread about "pushing twin-engine ops too much." The facts are that the Trent 1000 and the GEnx will be a step chang
103 NCB : A 777 doesn't crash with one failed engine nor does an A340 experiencing an unrelated double engine failure on take off after V1. Can't tell for sure
104 Killjoy : Faced with comments like these, it seems pointless to try to write well thought out replies. Stay on the ground. Seriously. (the BA incident was prob
105 LTBEWR : Perhaps the issue is more psychological as to passengers than to the airlines and professionals in the business. No longer does the '4 engines for lon
106 SEPilot : Aviation has so many possibilities of disaster that it is impossible to guard against all of them. That is why safety regulations have been developed
107 Planemaker : Yes, your memory has utterly failed you!! Forget about 3.5 years ago... I have always believed in the eventual EIS of pilot-less airliners and have i
108 Post contains images FlyDeltaJets87 : I don't think so. The only planes that can be controlled from the ground are UAVs right now, which don't carry passengers for obvious reasons. I see
109 SEPilot : Excellent point. In GA most requirements are dictated by insurance companies, not the FAA. If the insurance companies were nervous about ETOPS operat
110 Post contains images Planemaker : I know so. No one can keep up a single-engine aircraft after an engine failure... no one! Commercial aircraft could be controlled from the ground...
111 R2rho : Well, despite the recent reports of IFSDs, I still think that current twins are extremely safe. However, there is one issue that I think needs to be a
112 Transpac787 : Quite right you are. However, I wasn't talking about a single engine failure, I was talking about a dual-engine failure, in which a 777 most certainl
113 SEPilot : This is one of Zeke's pet peeves about ETOPS. I don't know what the airlines consider in selecting alternate landing sites, but I'm sure they must ta
114 Planemaker : Absolutely no chance in that happening!!!!
115 Tdscanuck : The number of shutdowns is going up because the number of airliners is going up. The shutdown *rate* has been dropping for years. That was true of pi
116 Post contains images Seabosdca : Who woulda ever thunk a Canuck would be the voice of reason? Thanks for the best post in this thread.
117 Thegeek : Not sure about the second 747 which had 2 engines fall off. I'm only aware of El Al 1862. I did a search and couldn't find anything. Can you give som
118 MD80fanatic : I changed my mind, deal with it. :p No engine related crashes prior to 1975. Several since. Now tell me again how modern designs provide plenty of re
119 SEPilot : The simple fact is that prior to 1975 there were a small fraction of the number of jetliners flying as there have been since. Even so, I only count e
120 AAN777AN : Accepting for the moment that this hypothesis as true, how do you argue that all four engines of a quad would not have been similarly affected? Taken
121 Post contains images FlyDeltaJets87 : The plane is fine at 35,000 feet in similar temperatures, and the passengers can stay in the plane unless there's a safety reason to get them off. Ye
122 Post contains links SEPilot : Here's the Wikipedia article, which is the most detailed I could find quickly. http://en.wikipedia.org/wiki/China_Airlines_Flight_358 According to an
123 Post contains links and images David L : " target=_blank>http://en.wikipedia.org/wiki/China_A...t_358 In that case... http://aviation-safety.net/database/record.php?id=19911229-0 There you g
124 Post contains links Planemaker : But the singling out of fuel flow for investigation suggests investigators are zeroing in either on fuel contamination — perhaps from an external f
125 Thegeek : Alright thanks. Wonder why I've never heard of this one before.
126 David L : Neither had I. I was only aware of the Amsterdam accident and a JAL 747 dropping an engine on departure from ANC, with more favourable results.
127 Post contains images Osiris30 : Ok Kegworth... ok.. I'll give you that.. hard to blame the airframe for pilot error though (regardless of number of power plants). The Lauda cases is
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