I think that Boeing's twin-engine concept, well, without it, Boeing probably would have been gone a long time ago. Two engines are more fuel efficient than four or three. I have to argue though that the twin engines being made today or more than good enough, especially on the 777-300ER, powered by two 115,000 lb. thrust GE-90s. However, has anybody ordered the 777-300ER yet? If so, who? When would we expect to see them flying for an airline?

However, has anybody ordered the 777-300ER yet?

To date, 773ERs have been ordered/leased by EVA Airways, Pakistan International Airlines, Air France, ILFC, GECAS, Japan Airlines, All Nippon Airways, Emirates.... and perhaps Korean (their order is still unconfirmed)


When would we expect to see them flying for an airline?

Air France takes first delivery in April, for service entry next summer season.

These kinds of post make me ask the question: can different types be compared given the variety of routes?

For example if a plane is successful on LHR-JFK will it necessarily be successful on other similar length journeys?

Or does it mean that an A330-200 will succeed on one route, a 777-300 on another and a B747-400 on another, so despite our arguments in here an airline is simply going to choose the one that fits the majority of its routes best rather than buying a different type for each route it flies? I suppose this is what all those analysts do whilst we just "chat" about them!

I think I'm talking about the "perfect route"; if so what is it and which aircraft performs best on it?

Hope you can see what I'm saying here, not convinced I'm making sense...............

As always disagreements are welcome.

Concordeboy,

It seams very unreal that Airbus came up with the slogan.
However if Airbus did indeed came up with the slogan, it's nice to see the confidence airlines have, all over the world, in Airbus' twinjet, flying longhaul.  

It seams very unreal that Airbus came up with the slogan

I too thought it incredibly foolish (both the slogan, and its creation by a company that also manufactures twinjet longhaulers), but alas, it's true

ConcordeBoy: ....what happens when a 4engine aircraft loses [nearly] all power and goes down far too from a diversion field. That's a scenario which also has yet to occur, but has come pretty-darn-close on a few occuasions as well.

Same for both kinds. Just less likely on a quad.

ConcordeBoy: Then there's also the possibility that modified ETOPS/LROPS specifications will eventually be placed on ALL aircraft.

So what? The Quad would still be safer on the same route. Especially in that case, as the twin would have no advantage at all any more. Same with those airlines which already today apply the same high standards to both their ETOPS twins and their quads.


Hamlet69: Klaus, you and I have had many ETOPS-related discussions before, and I'm not going to rehash them here. But what do you mean by 'cheaper ETOPS concept'?

There you go:

Hamlet69: while the engines may be smaller and burn less fuel, there are 4 of them, not 2. That means that unless the smaller engines only burn 1/2 the amount of fuel as the larger engines, the aircraft as a whole will not be as fuel efficient as the twin. Sometimes that's true, sometimes it isn't - again, it goes back to the airline and the airline's routes.
Also, we must remember that there are other costs besides fuel efficiency: there's maintenance, purchase costs, spares costs, etc. All these must be x2 for a twin, x4 for a quad.


Lower cost is the only conceivable reason for something like ETOPS: A little compromise in safety at one place to save money, hopefully offset by measures in another place which don´t raise the total cost above the previous level.

It´s something that´s done all the time; Not everyone buys the safest car all the time (which often is more expensive); Not every product is manufactured as safe as it could be.

The reasons? Almost always cost is the driving force.

ETOPS certainly is no reason to panic. It´s just an avoidable, deliberate compromise on safety. And I just happen to dislike that kind of thing when it´s about something as critical as aviation.

I heard recently that UAL is bringing their 747-400s out of the desert. I knew that for a while, but here is the real brain-twister: I heard that the reason for this was because UAL's Boeing 747-400s were even more economical to run nowadays than their Boeing 777s! Four engines more economical than two? I tell you, it's not possible! How can this be? Are the Pratt & Whitney engines for the Boeing 777 really that fuel-inefficient?

This is mainly because UAL renegotiated their 747 leases and got a huge reduction in rates, so the 747s have become cheaper to fly than the 777s. Also, the 747-400 seats 120 more people than the 777-200ER, so the 747's fixed costs are spread out over more seats. Fuel burn per seat may also be lower on the 744, which is a general trend with increasing aircraft size. Apparently the 777-300ER will have seat-mile costs comparable to the 747-400's, but currently the -400 remains the most efficient airliner ever built.

--B2707SST

This is mainly because UAL renegotiated their 747 leases and got a huge reduction in rates, so the 747s have become cheaper to fly than the 777s.
****************

This is also due to the fact that they could not get a much better deal on the 777 aircraft because 777 is a very in demand aircraft, therefore the aircraft would be taken off them and sold / leased to someone else before dropping the ratesa long way. There are too many 747-400's floating at the moment, therefore it was easy to renegotiate on these.

Same for both kinds. Just less likely on a quad.

And do you have any corroboration for this claim whatsoever? ...of course not, because of the documented cases of jet aircraft losing all thrust in flight, each would have (and 1 did) affected a quad in the same manner as a twin.


Especially in that case, as the twin would have no advantage at all any more

Wrong again, twins will still maintain their much higher reliability and statistically lower likelyhood of an IFSD than quads


Lower cost is the only conceivable reason for something like ETOPS

While the aggregate operational costs over time may be lower... the initial costs for ETOPS operations are actually greater. E.g.: 772ER vs A343; more expensive aquisition for the twin, ETOPS-certified MX needed, cost of a IFSD diversion, etc.


It´s just an avoidable, deliberate compromise on safety

Talk about making a [pointless] mountain out of molehill.  

Even if what you claim were accurate, which it isnt--- it'd hardly compare to the fact that aircraft aren't made out of titanium, coated with fire retardant, and lined with Kevlar/Viton throughout their airframe. These are all compromises in safety. They can be done, just that no one's going to pay for that.

No. All you have to do is look at ANA, they are phasing out the "4" engine aircraft in favor of the Boeing "2" Engine aircraft. Of course the other example is Southwest, over 20 years of flying a twin engine aircraft.

Klaus: Same for both kinds. Just less likely on a quad.

ConcordeBoy: And do you have any corroboration for this claim whatsoever? ...of course not,

Sorry to disappoint you, but it´s an automatic consequence of redundancy. Same reason why other essential systems are duplicated at all.


ConcordeBoy: Wrong again, twins will still maintain their much higher reliability and statistically lower likelyhood of an IFSD than quads

The at least one engine out case is not the essential one for safety; It´s the all engines out case that ultimately counts (even quads can usually survive on a single engine according to the quad drivers around here).

At least some basic knowledge of statistics is essential here.


Klaus: It´s just an avoidable, deliberate compromise on safety

ConcordeBoy: Talk about making a [pointless] mountain out of molehill.

That´s a matter of opinion. For me, safety is somewhat important.  
Especially when the cost is reasonable.

Sorry to disappoint you, but it´s an automatic consequence of redundancy

You're not disappointing me at all... because your conclusion is anecdotal (at best). The relationship in this case is linear... the more your have, the more chances to go wrong.




It´s the all engines out case that ultimately counts *** At least some basic knowledge of statistics is essential here.

Which dear Klaus, is exactly why you're incorrect here. Statistically, the probability of occurence of an event which shorts-out all engines on a twin bears with itself a virtually congruent probability of shutting down all engines on a quad as well.




That´s a matter of opinion. For me, safety is somewhat important.
Especially when the cost is reasonable.

And what, pray tell, qualifies you to conclude that the safety/cost ratio concerning ETOPS operations is a compromise to human life?

Particularly when Boeing, Airbus, every major CAA of the world, a few hundred airlines.... and every major CAA of the world (i.e., neutral parties)... completely disagree with you?  

I wonder just how many inflight shutdowns (just a single engine) have happend on an ETOPS flight DURING THE ETOPS PORTION OF THE FLIGHT not 20 minutes out.

I wonder how many dual inflight shutdowns have happened during the ETOPS PORTION OF THE FLIGHT.

I wonder how many dual engine failures that have happened during the ETOPS PORTION OF THE FLIGHT.

I wonder just how far a twin should be allowed to fly from an airport. Should they always be within gliding distance? Bring back the 727, get rid of all the twins.  

I wonder just how many inflight shutdowns (just a single engine) have happend on an ETOPS flight DURING THE ETOPS PORTION OF THE FLIGHT not 20 minutes out.
*******

We'll about 6 months ago or so, A United 777 shut down an engine 3 hours and 12 minutes from land. While I am sure it was a nervous situation for all concerned, the plane was fine and landed without incident. Did this actually violate the ETOPS rating in that they were more than the 180 minute max from an alternate. Interesting note is that United have had only 16 inflight shutdowns of engines for the 2.3 million hours of flights on the United 777's. Only three inflight shutdowns for all 777 aircraft of any airline have been recorded during etops portions of the flights. This doesn't even mean that the engine failed, just that warning lights indicated problems, and often the warning light is the problem. I would say that this supports Concordeboys theory that the 777 and it's etops ratings border on ridiculously reliable.

Story below:

Record Diversion

United 777 flies for 192 min. on a single

PW4077, longest ever ETOPS diversion

United Airlines' Boeing 777 carrying 255 passengers flew over the mid-Pacific Ocean against strong headwinds for 192 min. under single-engine power Mar. 17 to land without incident at Kona on the western coast of the big island of Hawaii. Boeing confirmed that it was the longest single-engine diversion during Extended Twin Operations (ETOPS) since the advent of transoceanic twin-engine flights 20 years ago by a Trans World Airlines Boeing 767-200.

United spokesman Joe Hopkins said the 777 crew shut down the No. 2 PW4077-90 power plant after the engine indication and crew alerting system (EICAS) displayed a high oil temperature and low oil quantity. The No. 1 engine powered the aircraft, operating as Flight 842, for the next 3+ hr. to the Kona landing.

THE 777 HAD DEPARTED Auckland, New Zealand, bound for Los Angeles. Hopkins said the 777 was likely well past the midway point to Hawaii when the engine was shut down. United was operating the 777 in ETOPS mode on a route that, for planning purposes, is 180 min. from a suitable airport in still air with one engine operating. A Boeing official said the crew expected a 180-min.-long diversion but the 777 encountered headwinds that extended the flight by another 12 min.

The diversion during the ETOPS portion of the flight was the third recorded for all 777s, which have completed more than 400,000 flights under the FAA rules for extended-range operations. A 767 held the previous record for diversion length, but it was "not close" to the Mar. 17 diversion time, the manufacturer's spokesman said.

A PRATT & WHITNEY OFFICIAL said a detector in the No. 2 engine showed evidence of chips. Pratt and United will investigate what caused the problem.

Hopkins said United's 777 fleet has recorded a total of 16 inflight shutdowns during all phases of flight since the carrier's first 777 flight in May 1995. The United 777s have flown 2.3 million hr. during the eight years, with an inflight engine shut down rate of 0.0021 per 1,000 engine hours. United operates 60 777s. The aircraft was expected to be out of service at Kona for at least two days, if not more. United shipped a replacement engine by air to Hawaii, but it had to be placed on an oceangoing barge to reach the Kona airport where it was to be installed. In addition to the crew on board Flight 842, 10 passengers occupied the first-class cabin, 47 were in business-class and 198 in economy. After the Kona landing, passengers were accommodated on United and other airline flights.

777 crew shut down the No. 2 PW4077-90 power plant

Great story, wrong engine: was a PW4090  

I have no problem with flying on ETOPS aircraft - I have made countless lounghaul flights on 777's, A330's, 767's etc. - I have even flown transatlantic on at least 4 seperate round trips on chartered 757's.

My only concern (and its not enough to even give me second thoughts about boarding a twin for a longhaul flight) is that the longer ETOPS ratings concern me - in the event of a single engine outage - the remaining engine obviously works at a much higher rate to maintain height and speed than it would do when both engines are working fine. Since most engine failures occur at times of peak stress (i.e. takeoff) then running the engine continuously for a number of hours at a high power setting increases the potential for engine failure.

If I ever experienced an IFSD on a twin - I would be concerned - I would also be looking at the remaining engine and would probably quickly discover religion  

RickB

If I ever experienced an IFSD on a twin - I would be concerned

The question is, "would you even be aware"? ... much less, "concerned".


It's not like the captain is going to hit up the P.A. with a technical walkthrough of the diversion.  

"Easy answer - nobody wants it."

"Oh by the way Gigneil you say that nobody wants it (747) well that's why it's the worlds most commercially recognised and successful widebody."

"People wanted it. Past tense.
The 747 line is dismally short. When they run out of orders, they will close it as well, unless they do something about it."

Gigneil, though you're correct about the current status of the 747 orderbook, I believe you oversimplified the reasons why nobody has thusfar ordered a proposed improved version. There was genuine interest in some of the proposals, even the 747X, even though it garnered no orders. The steep launch discounts on the A380 that Boeing was unwilling or unable to match steered potential 747X customers toward that model, instead, the attraction of its' newer technology clinching the deal. But airlines DID look at the 747X; Boeing simply didn't make it an attractive enough deal. Had Boeing been as aggressive as Airbus in trying to sell it, they would've gotten SOME orders, just not as many as Airbus. If the really large airplane market opens up in the next few years as Airbus predicts, there'll be opportunity for 747 Advanced (using 7E7 engines and other technology) sales, this 450 seater should be able to more than hold its' own with the likely much heavier 465 seat A380-700. I agree the 747-400 is about done, except for the freighter but it's too early to count out an improved 747, especially with an improving market. True, it's only a stopgap against the A380 until Boeing brings out something new (the BWB?) but in light of Lufthansa's urging of Boeing to study a 450 seater and a need to replace many 747-400s starting soon, I see continued opportunity, albeit somewhat modest. The Advanced freighter should certainly garner some customers, not all freight carriers want something as large as the A380-800F and some won't want to spring for the specialized loading equipment it requires. Though the 747's best days are almost certainly behind it, I believe it still has another 20-30 years of life IF Boeing makes the right improvements and prices it attractively (yes, that last stipulation could be a problem). It must be significantly cheaper than the A380 to remain saleable but if it is, I see no problem for it to hang onto a smaller share of the jumbo market. Sorry, just don't like to see someone burying the 747 before it's really dead.

Is there any empirical evidence to backup the arguments here? On how many occasions has a plane lost all its (2,3,4,etc) engines? The flights through volcanic dust spring to mind but weren't those engines re-started? How many times has a plane lost ALL its engines due to on-board failure?

If we worried about things like this how many times would any of us cross the road????????

The Boeing 747, simply the best, today and tomorrow. Boeing, if you are reading this PLEASE continue to develop this project.

Klaus: Sorry to disappoint you, but it´s an automatic consequence of redundancy

ConcordeBoy: You're not disappointing me at all... because your conclusion is anecdotal (at best). The relationship in this case is linear... the more your have, the more chances to go wrong.

And that´s exactly how redundancy works: Trade the nuisance of a somewhat increased frequency of non-fatal defects for a significantly reduced frequency of fatal defects. In a redundant or "failsafe" system, you need an increased number of simultaneous component failures in order to lose the system. This kind of thinking is applied all over the place - with the notable exception of the number of engines in some planes.


ConcordeBoy: Which dear Klaus, is exactly why you're incorrect here. Statistically, the probability of occurence of an event which shorts-out all engines on a twin bears with itself a virtually congruent probability of shutting down all engines on a quad as well.

Wrong. There would be no need to impose special additional restrictions to twins with ETOPS if that were the case. With modern quads progressively being manufactured and maintained to those same standards, the relative safety margins of quads vs. twins are going back to where they started a few decades ago.


ConcordeBoy: And what, pray tell, qualifies you to conclude that the safety/cost ratio concerning ETOPS operations is a compromise to human life?

The reasoning behind ETOPS is on public record.


ConcordeBoy: Particularly when Boeing, Airbus, every major CAA of the world, a few hundred airlines.... and every major CAA of the world (i.e., neutral parties)... completely disagree with you?

They don´t. They just accept the compromise as it is at this time. But public acceptance should not be taken for granted.

Well, one thing I know... the EIGHT engine design did hurt Hughes Aerospace!

:D

Seriously, if 2 engines can fail... why can't 4? If 4 can fail.. why can't 8?
I see this 2 vs 4 engine argument as hopeless. Why have 4 engines that has an inflight shutdown every 4 million hours per engine when you can have 2?

There more problems at stake... fire, decompression etc.
I'd rather take an ETOPS 180 flight than a quad flight that's more than 180 mins away from the nearest divert.

Single engine failures during cruise don't kill you immediately... decompression and fire can kill you immediately!

I'd be more worried on an JNB-PER on a standard quad than on an ETOPS certified Twin. (note the use of the word "Standard").

Mandala499

I wonder if the average passenger would notice an inflight engine shutdown? Maybe......maybe not. Any slight movement not fully intercepted by deft rudder control could be "turbulence". And everyone likes it when it gets quieter (to a point, lol). Probably would also depend on how close you were to the wing...in first class up in front...I doubt anyone would notice.

And that´s exactly how redundancy works:

What you dont seem to understand about redundancy is that its utility plateaus after a given threshold. Considering today's technology; nearly all airlines, manufactures, CAAs, analysts, etc firmly believe that threshold to be two engines.

As Mandala499 and others have continuously pointed out, if redundancy was the say-all-to-end-all in aviation safety; every airliner would that eight to ten engines. Cost not withstanding.



There would be no need to impose special additional restrictions to twins with ETOPS if that were the case

Actually, that argument can already (and to some extent, is) being made.



They don´t

hogwash... if they didnt, ETOPS would not exist. Simple as that.



They just accept the compromise as it is at this time. But public acceptance should not be taken for granted.

Again, the argument works both ways:
the day a quad spashes down 3hrs+ from shore, burns middair, or Mt. Erebus gets another group of inexpectant visitors; will be the day ETOPS/LROPS becomes mandatory for all aircraft. No compromise/exceptions for quads/tris allowed.

ConcordeBoy What you dont seem to understand about redundancy is that its utility plateaus after a given threshold. Considering today's technology; nearly all airlines, manufactures, CAAs, analysts, etc firmly believe that threshold to be two engines.

That´s got nothing to do with stagnating returns... It´s simply a matter of financial pressure and subjective acceptability at the time. And as we all know, such perceptions are subject to change.

Suggesting a single backup of an essential system was already approaching saturation is simply laughable (not just, but also mathematically). The first system goes - and you´re already back to your last line of defense. Sorry, but that´s not a minor thing, when you can have two or even three layers of redundancy for only marginally higher cost.

"Good enough" is a concept that should be considered very, very carefully when applied to aviation safety. And my impression is that the progressive stretching of the ETOPS limits is mainly driven by commercial interests with the implied assumption that "We´ve been lucky so far - why should it end tomorrow?"


ConcordeBoy Again, the argument works both ways:
the day a quad spashes down 3hrs+ from shore, burns middair, or Mt. Erebus gets another group of inexpectant visitors; will be the day ETOPS/LROPS becomes mandatory for all aircraft. No compromise/exceptions for quads/tris allowed.

"Spending" the higher safety margin of a quad on riskier routes is basically the same kind of thinking that brought us ETOPS for improved twins over unimproved quads... It depends on how much higher the risks are and how large the margin was to begin with.

"Good enough" is a concept that should be considered very, very carefully when applied to aviation safety. And my impression is that the progressive stretching of the ETOPS limits is mainly driven by commercial interests with the implied assumption that

Again, that goes back to the question of what on Earth do you think qualifies you to qualify that margin of safety; particularly when no significant industry nor non-industry authority agrees with you?


"riskier" routes? Please  

"We´ve been lucky so far - why should it end tomorrow?"

I think ETOPS operations goes a little bit further then a "hope and a prayer", each time a twin departs on a ETOPS flight. I believe that the engines are monitored quite closely, even during flight via data link.

Having four engines didn't help quite a few quads in the past. There is only one fuselage, one verticle stab, one horizontal stab, one wing, and one fuselage.

Just going back a few years shows that stabilizers are fairly important. Look at the American A300 and Alaskan MD80, no engine problems there. China Air didn't report any problems with engines when the fuselage came apart, neither did TWA. What about the MD11 that had a fire, or the Value Jet in Florida.

I could go on and on about accidents that ocurred over the past decade that had nothing to due with engines, yet I can't think of any that were the caused by an engine failure on a twin during the ETOPS portion of the flight. I can think of engine related accidents on Tri Engines (United) and quads (El Al).

And we should acknowldge that most in flight shut downs happen for an inidication fault or minor engine problem, and if need be, the engine could be restarted in case of an emergency.

ConcordeBoy: Again, that goes back to the question of what on Earth do you think qualifies you to qualify that margin of safety;

Several semesters of university statistics for theory; About 25 years of hardware and software design, implementation and debugging for a bit of practical experience with failure analysis and failsafe system design...

Just some basic knowledge about statistics would already suffice, however.

I don´t have a beef with your admiration for the 777 - it´s an impressive machine and a huge achievement for the teams who designed and build it. And compared to some earlier airliners it´s a marvel of reliability.

You just shouldn´t lose perspective about it. The laws of physics don´t make an exception for Boeing any more than they do for Airbus.

ConcordeBoy: particularly when no significant industry nor non-industry authority agrees with you?

Wrong. Boeing carefully tiptoes around the issue, while Airbus is happily poking the wound at every turn. And as silly as that game can get, there´s actual substance behind the issue.

With other safety factors comparable, the new ETOPS-quality quads (A345/A346, soon A388 - Boeing apparently gave up on the quads) again have a fundamental advantage over twins at the same level. It´s not necessarily absolute, and not even necessarily dominating other factors. That´s never been my point.

It´s "just" a factor that may one day have to stand up to the questions of grieving relatives and unhappy insurance providers. It may be that it still will be good enough. But then again, it may not.

"Should we have done more to improve safety?" has very often been the question in the aftermath of a disaster; And it can apply to insufficient (single!) engine redundancy just as much as to inadequate fire suppression or other factors.

It´s not the only point; Just the only one where a deliberate decision has been taken into what I see as a potentially dangerous direction.


ConcordeBoy: "riskier" routes? Please

It was your own argument.



Shenzhen: I think ETOPS operations goes a little bit further then a "hope and a prayer", each time a twin departs on a ETOPS flight. I believe that the engines are monitored quite closely, even during flight via data link.

The question is not about "unsafe". It´s about "could be safer".

Several semesters of university statistics for theory; About 25 years of hardware and software design, implementation and debugging for a bit of practical experience with failure analysis and failsafe system design...

In summary... nothing  



Just some basic knowledge about statistics would already suffice, however.

True, but as you're apparently lacking in that, I asked for further corroboration... should any exist



Boeing carefully tiptoes around the issue, while Airbus is happily poking the wound at every turn.

Both of these claims are utterly and completely false.

Boeing has all-but based its future survival on ETOPS... that hardly qualifies as "tiptoeing around the issue".

And if Airbus is so happy to poke the wound, pray tell: why do they continue to offer twinjets designed primarily for 8-12hr operations featuring lengthy ETOPS-governed segments?



It´s "just" a factor that may one day have to stand up to the questions of grieving relatives and unhappy insurance providers.

Seriously, do I need to create a continual soundbyte for the following phrase?
Say it with me now: "It works both ways"  



The question is not about "unsafe". It´s about "could be safer".

*refer to previous soundbyte*

ConcordeBoy: In summary... nothing

Of course not. What can math and experience do against a firmly embedded infatuation? Nothing!  

ConcordeBoy: True, but as you're apparently lacking in that, I asked for further corroboration... should any exist

I´ll refer you to this earlier thread for that. Please prove me wrong if you can. I´m always happy to learn.


Klaus: Boeing carefully tiptoes around the issue, while Airbus is happily poking the wound at every turn.

ConcordeBoy: Both of these claims are utterly and completely false.

Boeing has all-but based its future survival on ETOPS... that hardly qualifies as "tiptoeing around the issue".

That´s exactly why they won´t touch the inherently greater safety margin of a quad with a barge pole if they can avoid the issue.


ConcordeBoy: And if Airbus is so happy to poke the wound, pray tell: why do they continue to offer twinjets designed primarily for 8-12hr operations featuring lengthy ETOPS-governed segments?

They´re leaving it to the customer, while recommending their quad-engined models for the more demanding routes. Including the full story we´re discussing in here.



ConcordeBoy: Say it with me now: "It works both ways"

No such luck. Modern quads have all the safety of modern twins plus significantly higher engine redundancy. What´s so hard to understand about this simple fact?

He just doesn't get it Klaus, You've tried very hard but he's not having it.

Two points here,

Boeing has definitely been the watcher whilst Airbus has continuously stolen it's thunder with it's very pro-active marketing. It's rather interesting to note just how many US airlines are turning to Airbus now...hmm yes indeed. This would have been totally unthinkable 20 years ago.

ETOPS cannot provide an absolute guarantee, there are no absolutes with Aviation Physics.

ConcordeBoy, shouldn't you perhaps think of renaming your userID to ETOPS.

Yeah, seems like a lost cause... But I´ve always had a weakness for those...  

"With other safety factors comparable, the new ETOPS-quality quads (A345/A346, soon A388 - Boeing apparently gave up on the quads) again have a fundamental advantage over twins at the same level."

Klaus, being a firm believer in redundancy myself, I see the logic of your argument. However, do the new quads you mention NOW meet the same strict engine maintenance standards as twins, since until LROPS is adopted they don't have to? I'm aware Airbus is pushing for LROPS and has likely designed its newer quads for that standard but until the protocol is adopted, I doubt A345/6 operators are maintaining their A/C engines at ETOPS-level. I'd like to see LROPS adopted; all aircraft would be safer but for now, I think the A340NG airlines are probably not complying with this standard because they don't yet have to. I'd feel better myself being on a '4-holer' on an extreme LR flight though I'd still fly a twin (comtemplating Continental's EWR-HKG 777 run next year). No doubt, if one of the 777s failed and I knew it, I'd be sweating. However, as to whether it was mistake to only make a twin 777, that's still up in the air. Boeing didn't want to completely cannibalize 747 sales which a quad 777 would've done. It hasn't given up completely on quads as it's still pushing for 747 growth versions. If that fails, it may indeed have been folly not to do the quad 777 but that didn't seem likely in 1990 when the 777 was launched, as the 747-400 was then selling like hotcakes, the twin seemed right. It's still possible to do a quad 777 but only with an expensive redesign: wing, major systems, structure changes, etc. We'll have to see how the sales race plays out in the next few years to be sure who was right; remember the 777 vastly outsold the A340 in 1990, though Airbus has gained ground over it recently. I do see both sides of this argument so I can't take a firm position for either-though I prefer myself to be on a quad, I see the frequent economic advantage of twins as well. Good night, all.

With other safety factors comparable, the new ETOPS-quality quads (A345/A346, soon A388 - Boeing apparently gave up on the quads) again have a fundamental advantage over twins at the same level.

This is the key argument in what has become a difficult to follow thread.  

Given the same quality of design and level of technology in a quad as to a modern ETOPS twin, you cannot assemble any argumentation of statistics in which the twin will win within the framework of engine systems.

Do I feel safer on a 777 than a DC-10, L-1011, or 747-200 over the Pacific? You bet your ass I do.

Do I feel safer on an A340-600 over the Pacific than a 777? Statistically, yeah, I have to. No amount of rhetoric can change that all other things being equal a loss of 25% system integrity is vastly preferable to a 50% loss.

N

AMM744,
man whatsup with you having a problem with twin engine jets??? every one of your posts on this thread has something negative about crossing an ocean in a twin engine aircraft such as the 767 or 777!!! have you had a bad experience where the plane you flew on lost both engines? you wouldnt put your family on a 777 or 767 over the Atlantic? thats one of the funniest things I have ever heard. Do statistics not mean anything to you? does the fact that the 767 has more time and miles across all the oceans than all other aircraft combined if I read correctly not mean anything to you? the chances of one of those engines failing is sooo rare let alone both of them is unheard of. Sounds like your one of those suckers that sees the words "4 engines 4 long haul" on the side of airplanes and immediately think that 2 engine aircraft are unsafe.

It's time to move on from this topic, there simply is nothing else to discuss and by now it must be clear that there are two distinct camps on this subject.

Let's put this one to bed.

I hear you AMM744. Now that we all know who prefers 2 and who prefers 4, its time to end it. Its going nowhere.

Some numbers... not that is matters.

397,057,777 ETOPS flights (777)

Of the 618 ETOPS events that have been reported, only 16 were during the ETOPS portion of the flight. 13 diversions, 1 air turn back, and 2 continued to their destination.

Of the 618 ETOPS events, 98 were technical diversions.

12 of the technical diversions were due to Engines.

Of the 12 technical diversions related to Engines, 5 resulted in an IFSD (in flight shut down)

Data is from June 1995 through Mar 2003

There are over 25 thousand 757,767 and 777 ETOPS flights per month, and growing.

They´re leaving it to the customer, while recommending their quad-engined models for the more demanding routes.

They could recommend a horse in a hoopskirt, but airlines are going to fly the twin if it suits their economics better as there is no statistically significant margin of safety compromise whatsoever.


Modern quads have all the safety of modern twins plus significantly higher engine redundancy. What´s so hard to understand about this simple fact?


Quite simply because it said statement is not a fact... plain and simple.

Your (il)logic of quads (even if built to certain levels of ETOPS specifications) lacking a "compromise" in safety relative to twins, with the former continuing to be flown outside the parameters of ETOPS, is inherently flawed. Should said aircraft also adhere to ETOPS route restrictions, the "risk" decreases.



It's rather interesting to note just how many US airlines are turning to Airbus now...hmm yes indeed. This would have been totally unthinkable 20 years ago.

As would the current number of LoCo airlines; which constitute the overwhelming bulk of airlines you describe [that, and US's continual beef with Boeing over US427].




ETOPS cannot provide an absolute guarantee, there are no absolutes with Aviation Physics.

And the purpose of such a pointless statement is....?

Klaus, what other redundancy issues are you concerned about?

Don't get him started...perrrleease.

The 777 hasn't outsell the A340. You have to look at the A330/340 package and then compare all the orders to the 777-200/ER models. But the winner is definitely Airbus if you compare all the A330/A340 members against the B777-family.

The 777 hasn't outsell the A340

Not sure what dreamworld you're in, but here on Earth, the 777 has outsold the A340 by nearly double.  

>>>Boeing has definitely been the watcher whilst Airbus has continuously stolen it's thunder with it's very pro-active marketing. It's rather interesting to note just how many US airlines are turning to Airbus now...hmm yes indeed. This would have been totally unthinkable 20 years ago.<<<

In essence, the quad versus the twin is a marketing tool. Airbus has put a lot of resources into their quad aircraft and will naturally advocate this in a purely safety driven agenda, if I were them I'd do the same. Of course this is the purpose of marketing.

I just read an excellant article in November "Air and Space" magazine about Airbus. The article called "Airbus Pulls Ahead" tells the story of how Airbus came together during its formative years and progressed up till the present time. One of the founders tells of how they succeeded in competing against Boeing. And that is not to build the same product as your competitor. This I take as a primary reason they've concentrated so heavily on the quad.

I'd imagine if Boeing stayed with the quad for long distance routes that Airbus would be stealing the thunder with a revolutionary twin. And ironically, Klaus would be browbeating Boeing for not getting with the times and developing globe girdling twins like Airbus.

As far as U.S. carriers buying Airbus products, AFAIK they're all twins or at least until Fedex takes delivery of the A380.

>>>ETOPS cannot provide an absolute guarantee, there are no absolutes with Aviation Physics.<<<

Can a quad provide an absolute guarantee?

Sigh... The thread that wouldn´t die...  


FDXmech: In essence, the quad versus the twin is a marketing tool.

It is that, too. But marketing is always at its best when it has a foundation in reality... And Airbus does indeed have a leg to stand on when they´re claiming that there´s an inherent safety advantage for quads over twins. Just as much as Boing does when they´re arguing that the gap isn´t all that large.


FDXmech: I'd imagine if Boeing stayed with the quad for long distance routes that Airbus would be stealing the thunder with a revolutionary twin. And ironically, Klaus would be browbeating Boeing for not getting with the times and developing globe girdling twins like Airbus.

Nope. My beef is with ConcordeBoy´s fanatical and sometimes irreal fascination with ETOPS.
It´s okay as far as it actually goes. But ETOPS doesn´t do miracles. That´s where I see the need for a bit more realism and for a correction.


FDXmech: Can a quad provide an absolute guarantee?

No, but when I´m flying transpacific, for instance, I´ll take all the safety I can get.

Apart from not being able to provide an answer for A380

Isn't Boeing's answer to the A380 to not enter that market segment beyond the capacity of the 747-400, and instead concentrate on aircraft designed to better serve markets with by point to point service from airports that the A380 can not serve? In that respect, I would assume that their strategy, if proved successful, is embodied in the follow on versions of the 777 and the ground breaking design of the 7E7.

I agree the thread is going nowhere-neither camp will budge on their position. And I'm firmly on the fence in a non-partisan viewpoint myself. I must admit my personal quad preference is not based on hard statistics which have shown twins to be safe; it's largely because I psychologically need the security blanket of seeing 4 engines to reassure myself I'm safer. I do believe they inherently are but the facts so far don't appear to back up my assumption. I like many other passengers would prefer quads to predominate on the long-range flights but many airlines have sound economic reasons for using twins on these routes, a reality I can't deny. As long as the safety record of twins holds up on such long flights, as it has for 20-something years, they will continue to be used. I imagine if a twin loses both engines and does go down, ETOPS will be reviewed but likely continued because the stats have been so good. But airlines who don't want to deal with the possible ETOPS diversion headaches are choosing quads in large numbers. I guess it's nice that there is a choice available, choice is good. Anyway, we've seen some good spirited debate from both sides here and I have to say I'm in agreement with much of BOTH, as non-committal as that may sound.

Artsyman...I'll pray along with you.