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Future Of 4-engine Widebodies?  
User currently offlinePHX787 From Japan, joined Mar 2012, 6942 posts, RR: 18
Posted (2 years 1 week 18 hours ago) and read 8846 times:

I ran a search on this, couldn't find anything within the last few years.

If you put the 748 and 380 aside, it seems like the direction Boeing and Airbus are moving, with the 787, 777X (most likely), and A-350 being dual-engine aircraft, and the A340 line being shut down, do you think that the proposed "Y3" project by Boeing has any business being a 4-engine aircraft?

What stands as the future of widebodies with 4 engines, given the apparent sluggish sales as of late with the 748?

Do you think that the 777 replacement, which is supposed to bridge an apparent gap (according to wikipedia) between the 777 and 747, would have 4 engines?

What are the advantages and disadvantages of 4 engines as opposed to 2?

I ask this simply out of curiosity, as the 340 happens to be one of my favorite aircraft to spot.

Thanks, Zach  


One of the FB admins for PHX Spotters. "Zach the Expat!"
55 replies: All unread, showing first 25:
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (2 years 1 week 18 hours ago) and read 8720 times:

Quoting PHX787 (Thread starter):
do you think that the proposed "Y3" project by Boeing has any business being a 4-engine aircraft?

Yes, if the weight band that Y3 eventually ends up in is high enough.

Quoting PHX787 (Thread starter):
What stands as the future of widebodies with 4 engines, given the apparent sluggish sales as of late with the 748?

The 748 is probably the last of the 747 line, but if you want 900,000+ lbs MTOW aircraft, you need 3 or 4 engines. 3 has its own issues so, unless we switch to blended wing bodies, that weight class will probably be quads for the forseeable future.

Quoting PHX787 (Thread starter):
Do you think that the 777 replacement, which is supposed to bridge an apparent gap (according to wikipedia) between the 777 and 747, would have 4 engines?

If it's between the 777 and 747, I don't think you'd need 4 engines. Between the latest GE90-115B's and the bigger wing Boeing has proposed for the 777 upgrade, you can nicely fill in this area with a twin. However, if you want to actually replace the 747 mission you can't do with with twins with any engine that's currently supposed to be around.

Quoting PHX787 (Thread starter):
What are the advantages and disadvantages of 4 engines as opposed to 2?

4 engines requires considerably less installed thrust, so for a particular MTOW you need a lot less engine. It also used to have a significant advantage in flying far from diversion airports but the regulators have pretty much blown that distinction away and the twins have reached such high ETOPS ratings that it doesn't really matter.

Against that you've got double the systems, double the complexity, double the engine maintenance, etc., etc. You only really want a quad if you can't get engines big enough to make it a twin.

It's possible that other economic factors might bring a big trijet back (three GE90-115B's is enough thrust for well over 1,000,000 lbs MTOW) but I'm not going to hold my breath.

Tom.


User currently offlineplaneguy727 From United States of America, joined Mar 2007, 1210 posts, RR: 1
Reply 2, posted (2 years 1 week 10 hours ago) and read 8102 times:

There are still two areas for long haul fights where ETOPS rules prevent twins from being the norm - Australia/New Zealand to S. America and Australia to Africa. As long as non-stop flights are planned in these areas there will be need for 3 or 4 engine aircraft.


I want to live in an old and converted 727...
User currently offlinejfk777 From United States of America, joined Aug 2006, 8090 posts, RR: 7
Reply 3, posted (2 years 1 week 9 hours ago) and read 8019 times:
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Will engines get bigger then those on the 777 ? 747, A380 and future 500 passenger planes will probably be 4 engines. Can you imagine a 2 engine double decker A380. Hard to see.

User currently offlinetsnamm From United States of America, joined May 2005, 624 posts, RR: 0
Reply 4, posted (2 years 1 week 8 hours ago) and read 7844 times:

Quoting PHX787 (Thread starter):
What are the advantages and disadvantages of 4 engines as opposed to 2?



fuel burn... with the cost of fuel continually going up, efficiency will be a main driver...4 engines will only be used where fewer is impossible....with fuel costs being the largest expenditure for airlines now and going forward, getting by with fewer more efficient engines will be the norm.


User currently offlinePHX787 From Japan, joined Mar 2012, 6942 posts, RR: 18
Reply 5, posted (2 years 1 week 2 hours ago) and read 7384 times:

Ok so....

Quoting jfk777 (Reply 3):
Will engines get bigger then those on the 777 ? 747, A380 and future 500 passenger planes will probably be 4 engines. Can you imagine a 2 engine double decker A380. Hard to see.
Quoting tdscanuck (Reply 1):
Yes, if the weight band that Y3 eventually ends up in is high enough.

What you're saying here is that a certain weight requires more engines. I can see that. Like you all said, I too can't see a 747 or an A380 with 2 engines (even though IIRC the GE90 testbed was able to fly with just the GE90

Quoting tsnamm (Reply 4):
with fuel costs being the largest expenditure for airlines now and going forward, getting by with fewer more efficient engines will be the norm.

I see. So 4 engines aren't fuel efficient, then. What about (bear with me here) a larger aircraft with 4 GEnx engines?   

Quoting planeguy727 (Reply 2):
There are still two areas for long haul fights where ETOPS rules prevent twins from being the norm - Australia/New Zealand to S. America and Australia to Africa. As long as non-stop flights are planned in these areas there will be need for 3 or 4 engine aircraft.

Explains QF and LA's choice of aircraft.

Quoting tdscanuck (Reply 1):
The 748 is probably the last of the 747 line, but if you want 900,000+ lbs MTOW aircraft, you need 3 or 4 engines. 3 has its own issues so, unless we switch to blended wing bodies, that weight class will probably be quads for the forseeable future.

I thought the whole blended wing body idea was scrapped because it would never work at certain airports, like JFK or CDG or LHR, because of its sheer size?
Even though the A380 is large, the modifications required weren't that serious. That plane landed on 18L at CVG with no issue back in 2007, but a blended wing body would never be able to land at CVG (to give an example)



One of the FB admins for PHX Spotters. "Zach the Expat!"
User currently offlinesweair From Sweden, joined Nov 2011, 1806 posts, RR: 0
Reply 6, posted (2 years 1 week 2 hours ago) and read 7352 times:

Even Boeings BWB test aircraft went from 3 turbojets to 2  

User currently offlinedennys From France, joined May 2001, 824 posts, RR: 1
Reply 7, posted (2 years 11 hours ago) and read 6662 times:

Quoting PHX787 (Thread starter):

The last quads will be the 748 and the A340s left I guess ; I always fancied about a 777 four engined , but this deam will not come true
cheers


User currently offlineRWA380 From United States of America, joined Feb 2005, 2876 posts, RR: 5
Reply 8, posted (2 years 10 hours ago) and read 6520 times:

I think Air Force One and the other aircraft like Japan One and so forth are going to be 4 engined as far in the future as I can see. The 4 engines mean if something so tragic came up that (with mid-air refueling) was staying in the skies for extended period of times, the possibility of an engine failure would be higher, and 4 is better than two if you loose an engine.


Rule number One, NEVER underestimate the other guys greed
User currently offlinesweair From Sweden, joined Nov 2011, 1806 posts, RR: 0
Reply 9, posted (2 years 10 hours ago) and read 6497 times:

I cant see aircraft larger than the 77W-9X being a twin even in the future. One engine out at take off will set the limit.

The current record is 127,900 lbf not a normal thrust setting. Tubes with wings limit the size as well. Maybe if you put them above the fuselage like on the BWB..

The energy problem of mankind will make life interesting, how do we go on without cheap fuel?


User currently offlinejfk777 From United States of America, joined Aug 2006, 8090 posts, RR: 7
Reply 10, posted (2 years 9 hours ago) and read 6301 times:
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Quoting RWA380 (Reply 8):
I think Air Force One and the other aircraft like Japan One and so forth are going to be 4 engined as far in the future as I can see. The 4 engines mean if something so tragic came up that (with mid-air refueling) was staying in the skies for extended period of times, the possibility of an engine failure would be higher, and 4 is better than two if you loose an engine.

Its likely the next Air Force One, probably a 748, will be the last 4 engine Presidential plane. IF the one after that comes in 2035-2040 it will probably be a twin. But at some point Boeing could make a 747 & A380 replacement, so a 797, 808 or 818 could have four engines. Then who knows there may be an entirely new technology by then.


User currently offlineRWA380 From United States of America, joined Feb 2005, 2876 posts, RR: 5
Reply 11, posted (2 years 9 hours ago) and read 6268 times:

Quoting jfk777 (Reply 10):

Its likely the next Air Force One, probably a 748, will be the last 4 engine Presidential plane

I have to agree the next two planes will be 748's, but after that I'd expect twin technology will be far advanced.



Rule number One, NEVER underestimate the other guys greed
User currently offlineunityofsaints From Ireland, joined Nov 2011, 47 posts, RR: 0
Reply 12, posted (2 years 9 hours ago) and read 6230 times:

Quoting dennys (Reply 7):

The A380 will easily outlast the 748i.


User currently offlinebabybus From , joined Dec 1969, posts, RR:
Reply 13, posted (2 years 7 hours ago) and read 5985 times:

The long haul future will be exclusively A380. People will expect that amount of space and comfort. They won't want to be stuck in a seat with their knees round their ears for 22hrs as the twin jets force you to do.

The twin jets will be the low cost airline and charter airline type long haul aircraft. The long thin route expectation doesn't seem to have materialized.

That's my opinion anyway.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (2 years 7 hours ago) and read 5912 times:

Quoting PHX787 (Reply 5):
Like you all said, I too can't see a 747 or an A380 with 2 engines (even though IIRC the GE90 testbed was able to fly with just the GE90

One GE90 is plenty to move the mostly empty 747 test bed, absolutely. Just as one GE90 is plenty to move a completely full 777-300ER. But it's after one engine failure that things get interesting, and the 747-8i and A380 are too big to fly safely, fully loaded, on one current engine.

Quoting PHX787 (Reply 5):
So 4 engines aren't fuel efficient, then. What about (bear with me here) a larger aircraft with 4 GEnx engines?

4 engines are less fuel efficient than 2 for an equal sized airplane. But, with the current airplane sporting 4 GEnX engines, you'd need a ~180,000 lbs engine if you wanted to build it as a twin. And that doesn't exist today.

Quoting PHX787 (Reply 5):
I thought the whole blended wing body idea was scrapped because it would never work at certain airports, like JFK or CDG or LHR, because of its sheer size?

That depends on how big you make it. The BWB configuration has several issues (evacuation, airport infrastructure, load/unload connections, etc.) that aren't insurmountable but have to be worked out.

Quoting RWA380 (Reply 8):
The 4 engines mean if something so tragic came up that (with mid-air refueling) was staying in the skies for extended period of times, the possibility of an engine failure would be higher, and 4 is better than two if you loose an engine.

4 is just like 2 if you lose an engine (there is a subtle difference in the required climb gradient but they both "work"). It's only after two engine failures that things diverge. And two independent engine failures basically don't happen on the same flight (dependent failures do, but they impact quads just as much as twins).

Quoting babybus (Reply 13):
The long haul future will be exclusively A380. People will expect that amount of space and comfort. They won't want to be stuck in a seat with their knees round their ears for 22hrs as the twin jets force you to do.

What does comfort have to do with aircraft size? You can put 30" pitch in an A380 and you can put 60" pitch in a 737.

Tom.


User currently offlineStitch From United States of America, joined Jul 2005, 29680 posts, RR: 84
Reply 15, posted (2 years 7 hours ago) and read 5872 times:
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Quoting planeguy727 (Reply 2):
There are still two areas for long haul fights where ETOPS rules prevent twins from being the norm - Australia/New Zealand to S. America and Australia to Africa. As long as non-stop flights are planned in these areas there will be need for 3 or 4 engine aircraft.

VA flew SYD-JNB with a 777-300ER when they were V Australia.


User currently offlinecchan From New Zealand, joined May 2003, 1753 posts, RR: 2
Reply 16, posted (1 year 12 months 4 days 23 hours ago) and read 5465 times:

Quoting babybus (Reply 13):
The long haul future will be exclusively A380. People will expect that amount of space and comfort. They won't want to be stuck in a seat with their knees round their ears for 22hrs as the twin jets force you to do.

Comfort has very little to do with how many engines the plane has, it all depends on the airline's interior config. I can't see how the long haul future would be "exclusively" A380: for a lot of present long haul routes, demands and economics just don't justify an A380.

Quoting tdscanuck (Reply 14):
What does comfort have to do with aircraft size? You can put 30" pitch in an A380 and you can put 60" pitch in a 737.

I can think of a few examples here: BA's 318, HX's all J 332, NH low density 73G. These are probably more comfortable than an A380: at least you don't see a big crowd on board.


User currently offlinesteex From United States of America, joined Jun 2007, 1564 posts, RR: 9
Reply 17, posted (1 year 12 months 4 days 23 hours ago) and read 5402 times:

Quoting Stitch (Reply 15):
VA flew SYD-JNB with a 777-300ER when they were V Australia.

They flew it with a significant northern detour to stay within ETOPS limits, though.

Edit: Didn't pay close enough attention at first, but thought I'd also note that V Australia flew MEL-JNB, not SYD-JNB.

[Edited 2012-04-18 15:05:19]

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 18, posted (1 year 12 months 4 days 17 hours ago) and read 5022 times:

Quoting planeguy727 (Reply 2):
There are still two areas for long haul fights where ETOPS rules prevent twins from being the norm - Australia/New Zealand to S. America and Australia to Africa. As long as non-stop flights are planned in these areas there will be need for 3 or 4 engine aircraft.

That's why ETOPS-330 was invented. Once that's approved (and it's coming) there will no longer be any need for 3 or 4 engines on any currently viable route.

Tom.


User currently offlinegemuser From Australia, joined Nov 2003, 5552 posts, RR: 6
Reply 19, posted (1 year 12 months 4 days 16 hours ago) and read 4969 times:

Quoting tdscanuck (Reply 18):
That's why ETOPS-330 was invented. Once that's approved (and it's coming) there will no longer be any need for 3 or 4 engines on any currently viable route.

Unless there is a MAJOR political change in Australia there will be NO ETOPS > 180 operations into Australian airspace by any airline. No Australian PM or their political party will take that risk to their political future.

Gemuser



DC23468910;B72172273373G73873H74374475275376377L77W;A319 320321332333343;BAe146;C402;DHC6;F27;L188;MD80MD85
User currently offlinetullamarine From Australia, joined Aug 1999, 1427 posts, RR: 0
Reply 20, posted (1 year 12 months 4 days 16 hours ago) and read 4958 times:

Quoting Stitch (Reply 15):
VA flew SYD-JNB with a 777-300ER when they were V Australia.

The routing of the VA 77W ended up being 3 hours longer than if the route had been undertaken by a 747 or A340. I assume SA will probably codeshare with VA on these routes in future now the competition authroities have deemed the QF/SA JSA as monopolistic.

For the forseeable future VLA will remain 4 engined. This is because there is no engine available (or proposed) that would pass the requirement for a fully laden plane to take off in an engine-out scenario.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 21, posted (1 year 12 months 4 days 16 hours ago) and read 4916 times:

Quoting tullamarine (Reply 20):
For the forseeable future VLA will remain 4 engined. This is because there is no engine available (or proposed) that would pass the requirement for a fully laden plane to take off in an engine-out scenario.

I'm not following you here; all current airliners (2, 3, or 4 engines) can take off fully loaded with an engine out.

Tom.


User currently offlinegarpd From UK - Scotland, joined Aug 2005, 2579 posts, RR: 4
Reply 22, posted (1 year 12 months 4 days 14 hours ago) and read 4757 times:

Quoting unityofsaints (Reply 12):
he A380 will easily outlast the 748i.

How do you know this for sure?



arpdesign.wordpress.com
User currently offlineRWA380 From United States of America, joined Feb 2005, 2876 posts, RR: 5
Reply 23, posted (1 year 12 months 4 days 13 hours ago) and read 4699 times:

Quoting unityofsaints (Reply 12):
The A380 will easily outlast the 748i

As far as longevity? I seriously doubt that. The 747 has been a work in progress for Boeing since the late 60's and the 748i is all of that knowledge learned, plus all the new technology combined. The A-380 is new technology, and already having stress cracking issues. I doubt the last 748i flying many years from now (cargo or not), will be sharing the skies with the A-380.













.



Rule number One, NEVER underestimate the other guys greed
User currently offlineBurkhard From Germany, joined Nov 2006, 4360 posts, RR: 2
Reply 24, posted (1 year 12 months 4 days 12 hours ago) and read 4617 times:

Quoting PHX787 (Reply 5):
What about (bear with me here) a larger aircraft with 4 GEnx engines?

You can buy it, and I look forward to see it daily in a few days. This aircraft is called B748I, and expected to be at least 10% more fuel efficient than the most efficient twin, the 77W.

Quoting tdscanuck (Reply 14):
But, with the current airplane sporting 4 GEnX engines, you'd need a ~180,000 lbs engine if you wanted to build it as a twin. And that doesn't exist today.

We know that the market for VLA is not very big, maybe 1000 aircraft over 25 years. While a 180,000 lbs trust engine isn't impossible, it would be extremely expensive to design, certify and build the first - I doubt any of the companies wants to invest that money.


User currently offlinesweair From Sweden, joined Nov 2011, 1806 posts, RR: 0
Reply 25, posted (1 year 12 months 4 days 12 hours ago) and read 4816 times:

Does the BWB have any merit as an airliner? It´s a lot wider than a tube with wings but shorter, up to 30% more efficient than a tube with wings I read somewhere, is this at the same size or what?

Windows and exit limitations seems to be a big hurdle for a passenger model, windows is not that hard to replace I would imagine, as people in the middle row in a WB already fly without a window close to them. But the emergency exits might be a problem with say 6-8 aisles in width.

But as a freighter with no usual gate clearance issues it might shine, g-forces in turns wouldn't be a problem for most cargo either.

2-3 mega sized turbines above the fuselage and in the rear, shielding noise to the ground as well.

This would be a huge project designing a BWB, sort of like the 747 was in its day, however I think its even bigger challenge then the first WB. Maybe a project funded partly by the military is doable or a cooperation between Airbus and Boeing like the 380 started as.


User currently offlineqf002 From Australia, joined Jul 2011, 2886 posts, RR: 2
Reply 26, posted (1 year 12 months 4 days 10 hours ago) and read 4692 times:

Quoting Stitch (Reply 15):

VA's flights to JNB were canned because the necessary detours made the flight horribly uneconomical. Quads are absolutely necessary for flights across the bottom of the Indian and Pacific Oceans, but the A380 should sort these out until at least 2040 given QF is getting more in 2019-20.


User currently offlineFabo From Slovakia, joined Aug 2005, 1211 posts, RR: 1
Reply 27, posted (1 year 12 months 4 days 10 hours ago) and read 4789 times:

I was under impression a 4 engine is nominally more fuel efficient compared to a twin on longer sectors, since 4 less powerful engines work more efficienty than 2 comparable more powerful engines on a comparable airframe, due to simple fact that jets are most efficient at higher thrust setting.

eg. say 330/340, were it the same size, and weight (barring extra engines).
A 340 will need to take-off with 75% of take-off thrust, therefore less extra power is needed compared to an A330 with 50%.
Therefore each engine in A340 will have to produce of 33.3% of required thrust at TO power, while each engine in 330 will have to produce 100%. (this is of course only considering portion after V1). Lets say higher climb requirements for 4 holer are insignificant.

Now lets say take-off thrust required for TO would be 100K. That means each engine could be say 40K on A340 (compensating for extra drag) and 100K on A330.

If for cruise you need 100K of altitude-corrected thrust, each A330 engine in cruise will only deliver 50% power, while each A340 engine would produce about 85-90% of power (again, compensating for drag, from 83%)

Wouldnt the efficiency of engine producing 90% of power be better than that of engine producing 50% of power?
(of course, climb would be somewhat less efficient on 4holer, but since we are talking primarily long-haul, it should not be that much of a deterrent)


I have read, that, in effect, this was the reasoning of SQ for originally choosing A340 over B777, but since there was usually a bottleneck of traffic between Singapore and Bankok, it was forced to stay low, unable to climb due to traffic, while 777 would already be at the cruise level, therefore negating the positive effect of 4holer, and thereby in the end resulting in SQ going for 777 in the end.



The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlineStickShaker From Australia, joined Sep 2004, 722 posts, RR: 5
Reply 28, posted (1 year 12 months 4 days 10 hours ago) and read 4767 times:

Quoting planeguy727 (Reply 2):
There are still two areas for long haul fights where ETOPS rules prevent twins from being the norm - Australia/New Zealand to S. America and Australia to Africa. As long as non-stop flights are planned in these areas there will be need for 3 or 4 engine aircraft.

How many aircraft are required here - about a dozen or so ?
Not really enough to influence Boeing or Airbus to continue a line of quads if there is no other demand. It eventually will be a case of using whatever is available - 380/748i.


Regards,
StickShaker


User currently offlinejoost From Netherlands, joined Apr 2005, 3149 posts, RR: 4
Reply 29, posted (1 year 12 months 4 days 9 hours ago) and read 4686 times:

Quoting babybus (Reply 13):
The long thin route expectation doesn't seem to have materialized.

I certainly think it has. The 330-200 made airlines open up plenty of long, new routes (> 11 hours) that didn't see direct air service before. The 787 will continue this evolution.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 30, posted (1 year 12 months 4 days 7 hours ago) and read 4533 times:

Quoting RWA380 (Reply 23):
The 747 has been a work in progress for Boeing since the late 60's and the 748i is all of that knowledge learned, plus all the new technology combined. The A-380 is new technology, and already having stress cracking issues.

When the 747 was new technology, it had lots of issues too (including cracking). The A380, so far, is just going through normal teething of a new design. I don't see any particular reason the A380 isn't also destined for a good long run; that's certainly more likely Airbus ever designing a new VLA.

Quoting sweair (Reply 25):
Does the BWB have any merit as an airliner?

Yes, lots, primarily around efficiency/cost. In return, as you listed, there are a lot of obstacles to be overcome.

Tom.


User currently offlinesteex From United States of America, joined Jun 2007, 1564 posts, RR: 9
Reply 31, posted (1 year 12 months 4 days 6 hours ago) and read 4352 times:

Quoting tullamarine (Reply 20):
For the forseeable future VLA will remain 4 engined. This is because there is no engine available (or proposed) that would pass the requirement for a fully laden plane to take off in an engine-out scenario.
Quoting tdscanuck (Reply 21):
I'm not following you here; all current airliners (2, 3, or 4 engines) can take off fully loaded with an engine out.

I think his point is that none of the current 4-engine VLA airliners would be able to take off on a single engine if they were instead 2-engine airliners. The amount of thrust necessary from each engine to make something like the A380 a 2-engine machine isn't feasible at the moment, so a frame that size will likely have four engines moving forward.


User currently offlineStitch From United States of America, joined Jul 2005, 29680 posts, RR: 84
Reply 32, posted (1 year 12 months 4 days 6 hours ago) and read 4391 times:
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Quoting tullamarine (Reply 20):
The routing of the VA 77W ended up being 3 hours longer than if the route had been undertaken by a 747 or A340.
Quoting qf002 (Reply 26):
VA's flights to JNB were canned because the necessary detours made the flight horribly uneconomical.

A non-direct routing is required for ETOPS-180 and ETOPS-240, but if they flew ETOPS-330, they could do it non-stop per GCM:

http://www.socialwelfareagency.org/Public/Graphics/Aviation/MELJNB.png

Light Shading: ETOPS-180
Medium Shading: ETOPS-240
Heavy Shading: ETOPS-330


User currently offlineunityofsaints From Ireland, joined Nov 2011, 47 posts, RR: 0
Reply 33, posted (1 year 12 months 4 days 5 hours ago) and read 4204 times:

Quoting garpd (Reply 22):
How do you know this for sure?

I don't know it for sure but it's a solid prediction given that:

1. The A380 has 145 more outstanding orders from 15 more customers
2. The A380 is a base design which is roughly 30 years younger than that of the 748
3. The A380 is, imho, more likely to get new customers
4. The A380 is, imho, more likely to get new variants (e.g. a -900)

I could go on but those are the most obvious ones.


User currently offlinePHX787 From Japan, joined Mar 2012, 6942 posts, RR: 18
Reply 34, posted (1 year 12 months 4 days 3 hours ago) and read 4011 times:

Quoting Burkhard (Reply 24):
You can buy it, and I look forward to see it daily in a few days. This aircraft is called B748I, and expected to be at least 10% more fuel efficient than the most efficient twin, the 77W.

I completely forgot about that >



One of the FB admins for PHX Spotters. "Zach the Expat!"
User currently offlinegemuser From Australia, joined Nov 2003, 5552 posts, RR: 6
Reply 35, posted (1 year 12 months 3 days 23 hours ago) and read 3777 times:

Quoting Stitch (Reply 32):
but if they flew ETOPS-330, they could do it non-stop per GCM:

But they can't and it's unlikely they will be able to do so in our life time. That was the point replies 20 & 26 were making.

Gemuser



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User currently offlineDocLightning From United States of America, joined Nov 2005, 18683 posts, RR: 58
Reply 36, posted (1 year 12 months 3 days 22 hours ago) and read 3710 times:

Quoting tdscanuck (Reply 1):
If it's between the 777 and 747, I don't think you'd need 4 engines. Between the latest GE90-115B's and the bigger wing Boeing has proposed for the 777 upgrade, you can nicely fill in this area with a twin. However, if you want to actually replace the 747 mission you can't do with with twins with any engine that's currently supposed to be around.

What do you mean? The 77W can fly more cargo and only about 1/8 fewer passengers as far as the 747-400. It is almost a 1:1 replacement for the 747-400.

The 747-400's engine-out thrust is about 175-180,000 lbf. Part of the reason that it needs so much engine-out thrust is because it's got four big, heavy engines. The 77W's engine-out thrust is 115,000 lbf and yet it carries roughly the same payload.

With advances in aircraft design and materials, aerodynamics, and engine design, it would certainly be possible to upgrade the GE-90 successor to generate well over 130,000 lbf. By sheer extension, such an aircraft would already outperform the 747-400.

Quoting tdscanuck (Reply 14):
4 engines are less fuel efficient than 2 for an equal sized airplane. But, with the current airplane sporting 4 GEnX engines, you'd need a ~180,000 lbs engine if you wanted to build it as a twin. And that doesn't exist today.

Two engines are lighter than four, so wouldn't you need less than 180k lbf?

Quoting Burkhard (Reply 24):
You can buy it, and I look forward to see it daily in a few days. This aircraft is called B748I, and expected to be at least 10% more fuel efficient than the most efficient twin, the 77W.

Is it more fuel-efficient than the A350 or 787? comparing an engine that went into service in 2011 to an engine that went into service in 2003 is not quite fair.


User currently offlinedennys From France, joined May 2001, 824 posts, RR: 1
Reply 37, posted (1 year 12 months 3 days 18 hours ago) and read 3498 times:

Well , have a try from EZE to SYD , the flight is about 15 hours above the Antartic aeras , then you will probably feel safer on board a 4 holer !

User currently offlineDocLightning From United States of America, joined Nov 2005, 18683 posts, RR: 58
Reply 38, posted (1 year 12 months 3 days 18 hours ago) and read 3476 times:

Quoting dennys (Reply 37):

Well , have a try from EZE to SYD , the flight is about 15 hours above the Antartic aeras , then you will probably feel safer on board a 4 holer !

A 4-holer is twice as likely to suffer an uncontained failure than a twin. I wouldn't want an uncontained failure in the middle of nowhere.


User currently offlinethegeek From Australia, joined Nov 2007, 2638 posts, RR: 0
Reply 39, posted (1 year 12 months 3 days 17 hours ago) and read 3342 times:

Quoting DocLightning (Reply 36):
The 747-400's engine-out thrust is about 175-180,000 lbf. Part of the reason that it needs so much engine-out thrust is because it's got four big, heavy engines. The 77W's engine-out thrust is 115,000 lbf and yet it carries roughly the same payload.

I submit that the difference in the climb requirements is another part of the reason for this. The MTOW difference doesn't account for the 1 engine out thrust difference!

Seems to bias against quads, but perhaps that is a good thing for this reason:

Quoting DocLightning (Reply 38):
A 4-holer is twice as likely to suffer an uncontained failure than a twin. I wouldn't want an uncontained failure in the middle of nowhere.


User currently offlineqf002 From Australia, joined Jul 2011, 2886 posts, RR: 2
Reply 40, posted (1 year 12 months 3 days 17 hours ago) and read 3332 times:

Quoting Stitch (Reply 32):
A non-direct routing is required for ETOPS-180 and ETOPS-240, but if they flew ETOPS-330, they could do it non-stop per GCM:

As previously discussed on other threads, the Australian CASA is the most conservative in the world (perhaps with good reason), and is unlikely to ever allow any further ETOPS/EDTO allowances over what exists today. Flights to NZ would be possible with twins, but flights departing from or arriving in Australia on these routes will be quads for the long term future (ie until the post-A380/787/A350 generation).


User currently offlineStitch From United States of America, joined Jul 2005, 29680 posts, RR: 84
Reply 41, posted (1 year 12 months 3 days 16 hours ago) and read 3299 times:
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Quoting qf002 (Reply 40):
As previously discussed on other threads, the Australian CASA is the most conservative in the world (perhaps with good reason), and is unlikely to ever allow any further ETOPS/EDTO allowances over what exists today.


I suppose it will depend on how much traffic QF and VA end up losing to other carriers who have hubs that can connect passengers via twins (EK at DXB comes to mind) on those missions within ETOPS-180.

[Edited 2012-04-19 21:23:31]

User currently offlineSCL767 From Chile, joined Feb 2006, 8604 posts, RR: 5
Reply 42, posted (1 year 12 months 3 days 16 hours ago) and read 3260 times:
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Quoting qf002 (Reply 40):
As previously discussed on other threads, the Australian CASA is the most conservative in the world (perhaps with good reason), and is unlikely to ever allow any further ETOPS/EDTO allowances over what exists today. Flights to NZ would be possible with twins, but flights departing from or arriving in Australia on these routes will be quads for the long term future (ie until the post-A380/787/A350 generation).

Would the Australian CASA permit certain carriers to operate twins between South America and Australia via New Zealand since CASA's rules are vague in that area?


User currently offlineYULWinterSkies From United States of America, joined Jun 2005, 2169 posts, RR: 5
Reply 43, posted (1 year 12 months 3 days 16 hours ago) and read 3183 times:

Quoting babybus (Reply 13):
The long haul future will be exclusively A380. People will expect that amount of space and comfort.

Yes, in your dreams!

Quoting joost (Reply 29):
Quoting babybus (Reply 13):
The long thin route expectation doesn't seem to have materialized.

I certainly think it has. The 330-200 made airlines open up plenty of long, new routes (> 11 hours) that didn't see direct air service before. The 787 will continue this evolution.

I agree, but the 787 will almost certainly not be the Revolution some hoped. Just an evolution.

Back to the op question: future of 4-engine widebodies? A380 and 748. Period. Yes they will be there for a long time and will keep being built for a while, but I do not think any brand new clean sheet design will ever be a 4 engine again. A and B have the VLA market covered for many decades to come. (yes, I do expect the A380 to undergo many evolutions as the 747 has done and keeps doing)



When I doubt... go running!
User currently offlinegemuser From Australia, joined Nov 2003, 5552 posts, RR: 6
Reply 44, posted (1 year 12 months 3 days 13 hours ago) and read 3011 times:

Quoting SCL767 (Reply 42):
Would the Australian CASA permit certain carriers to operate twins between South America and Australia via New Zealand since CASA's rules are vague in that area?

In that case I don't think CASA has any say as the flight into Australian airspace is only from NZL which only requires 90 min ETOPS.

Gemuser



DC23468910;B72172273373G73873H74374475275376377L77W;A319 320321332333343;BAe146;C402;DHC6;F27;L188;MD80MD85
User currently offlineBurkhard From Germany, joined Nov 2006, 4360 posts, RR: 2
Reply 45, posted (1 year 12 months 3 days 11 hours ago) and read 2935 times:

Quoting DocLightning (Reply 36):
Is it more fuel-efficient than the A350 or 787? comparing an engine that went into service in 2011 to an engine that went into service in 2003 is not quite fair.

All numbers I know show the 787 to be near to the 77W in fuel per seat, which is a great achievement for a much smaller bird, so it is still about 10% below the 748I and 20% below the A380. Once the 787-1000 or the A350-1000 are in the air, things might look different, but currently these are still more dream planes than real paper planes...

Quoting DocLightning (Reply 38):
A 4-holer is twice as likely to suffer an uncontained failure than a twin. I wouldn't want an uncontained failure in the middle of nowhere.

... but then I prefer a failure ove a 70000lbs engine over a 140000lbs engine due to the far larger damage it makes to the wings structure....


User currently offlineqf002 From Australia, joined Jul 2011, 2886 posts, RR: 2
Reply 46, posted (1 year 12 months 3 days 9 hours ago) and read 2748 times:

Quoting Stitch (Reply 41):
I suppose it will depend on how much traffic QF and VA end up losing to other carriers who have hubs that can connect passengers via twins (EK at DXB comes to mind) on those missions within ETOPS-180.

QF is sorted until 2040, so won't be making a fuss any time soon. VA has shown very limited interest in flying internationally at all and would be far more likely to partner with SA and AR than go the route by themselves. VA would also stand to benefit from flying pax via AUH and EY, so I doubt they care much either way.

Quoting SCL767 (Reply 42):
Would the Australian CASA permit certain carriers to operate twins between South America and Australia via New Zealand since CASA's rules are vague in that area?

Very difficult question I think... On the one hand:

Quoting gemuser (Reply 44):
In that case I don't think CASA has any say as the flight into Australian airspace is only from NZL which only requires 90 min ETOPS.

but the flight is still departing from/arriving into Australia as a direct flight, and CASA is probably involved in the entire flight beyond the Tasman crossing... It could be argued that QF/LA are anticipating the day when this exact situation arises (ie LA using 787's on their flights to NZ/Australia), with QF gradually taking over those flights that involve Australia using 744ER's (and A380's down the road), with LA to cut back to just flying into AKL (connecting to QF to MEL, BNE etc) to utilise the 787.

But really, we won't know until this actually happens.


User currently offlinegemuser From Australia, joined Nov 2003, 5552 posts, RR: 6
Reply 47, posted (1 year 12 months 3 days 7 hours ago) and read 2622 times:

Quoting qf002 (Reply 46):
but the flight is still departing from/arriving into Australia as a direct flight, and CASA is probably involved in the entire flight beyond the Tasman crossing.

Not sure, but I don't think so. The flight to/from & within Australian air space is below ETOPS180. I could see both NZL & Chile getting involved saying a flight between NZL & Chile is none of Australia's business.

Quoting qf002 (Reply 46):
It could be argued that QF/LA are anticipating the day when this exact situation arises (ie LA using 787's on their flights to NZ/Australia), with QF gradually taking over those flights that involve Australia using 744ER's (and A380's down the road), with LA to cut back to just flying into AKL (connecting to QF to MEL, BNE etc) to utilise the 787

Except that EDTO requirements apply to quads from 2015 or 2017, depending on what source you read. I could maybe see CASA granting EDTO 240 to quads (which they currently have, in effect). Their requirements are so loosely written that that could happen.

Gemuser



DC23468910;B72172273373G73873H74374475275376377L77W;A319 320321332333343;BAe146;C402;DHC6;F27;L188;MD80MD85
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 48, posted (1 year 12 months 3 days 7 hours ago) and read 2553 times:

Quoting Burkhard (Reply 45):
... but then I prefer a failure ove a 70000lbs engine over a 140000lbs engine due to the far larger damage it makes to the wings structure....

It makes no meaningful difference to the amount of damage. For analysis purposes, rotor burst fragments are treated as having infinite kinetic energy. They're going to go through everything in their way whether the engine was 30k, 70k, or 115k. The only difference will be the size of the holes. I'm not sure that a slightly bigger hole should be considered "far larger damage.". With a 4 engine, not only are the odds of a failure twice as high, there's twice as much systems stuff for the fragments to hit.

Tom.


User currently offlineqf002 From Australia, joined Jul 2011, 2886 posts, RR: 2
Reply 49, posted (1 year 12 months 3 days 7 hours ago) and read 2552 times:

Quoting gemuser (Reply 47):
Not sure, but I don't think so. The flight to/from & within Australian air space is below ETOPS180. I could see both NZL & Chile getting involved saying a flight between NZL & Chile is none of Australia's business.

I'm really not sure either, it certainly seems to be a grey area that's unclear in terms of the jurisdiction of the various groups. I tend to agree that the Australian authorities would have a limited say over operations via another port, but that's not to say that they couldn't argue for a say if they seriously believed that there was a significant risk to a flight to/from Australia...

Quoting gemuser (Reply 47):
I could maybe see CASA granting EDTO 240 to quads

Agreed. They've made it clear in their current policies that they are fine with quads, so I'd expect them to allow the more extended operations for quads beyond their inclusion in EDTO.

Quoting gemuser (Reply 47):
Their requirements are so loosely written that that could happen.

I think that's the whole problem with all this -- there is no solid policy or literature outlining what CASA's position is, so we can't really hope to predict their future policy moves... They might make a total u-turn and say okay to EDTO 330 for all aircraft overnight...


User currently offlineRevo1059 From United States of America, joined Mar 2006, 129 posts, RR: 0
Reply 50, posted (1 year 12 months 3 days 6 hours ago) and read 2544 times:

What about building an A/C that could be either 2 or 4 engines. Build it so that when needed 2 more engines could be "hooked up" and when not needed they could be taken off. I would think it would add some flexibility.

I know it wouldn't be a quick turn type of thing, but if new engines could be taken on or off overnight or in a day it could prove useful.


User currently offlinewarreng24 From United States of America, joined Nov 2005, 705 posts, RR: 0
Reply 51, posted (1 year 12 months 3 days 2 hours ago) and read 2405 times:

I legitimately believe that we may see another large tri-jet in the future.

The cost of fuel of the 4th engine will outweigh the development and maintenance cost of a tri-jet tail-mounted engine design.

As previously posted, these tri-jets will be marketed primarily at flights which are not ETOPS compatible.

[Edited 2012-04-20 11:20:48]

User currently offlineDocLightning From United States of America, joined Nov 2005, 18683 posts, RR: 58
Reply 52, posted (1 year 12 months 2 days 16 hours ago) and read 2087 times:

Quoting thegeek (Reply 39):

I submit that the difference in the climb requirements is another part of the reason for this. The MTOW difference doesn't account for the 1 engine out thrust difference!

What do you mean? It has to.

Quoting warreng24 (Reply 51):
The cost of fuel of the 4th engine will outweigh the development and maintenance cost of a tri-jet tail-mounted engine design.

How so? Fuel is 30-40% of the cost of operating an airliner. Fuel use per ASM does not equal CASM. Engine maintenance is a huge cost and is one of the reasons why quads do not compete well with twins.

Trijets have an issue in that the tail-mounting adds weight, complexity, and most importantly, NON-COMMONALITY to the airframe. Engine #2 has different attachments, different structural environment, etc. Furthermore, having an engine mounted way up there involves cherry pickers, scissors lifts, etc. etc. etc.

Airbus has partially addressed this issue in a recent patent (that I am too lazy to look up) for an engine that could be lowered through the fuselage for maintenance. But when it's just a quick issue, it becomes a real problem to lower the engine through the airframe, and so getting a mech up there in a cherry picker is easier. And that leads to a bigger delay and problems with dispatch reliability.

Quoting warreng24 (Reply 51):
As previously posted, these tri-jets will be marketed primarily at flights which are not ETOPS compatible.

Of which there are maybe 12 routes. Not nearly enough to justify an entire new type with an engine mounted on the tail.

If a trijet is ever introduced again, it will be because of thrust requirements.

A 77W has 230 klbf of installed thrust. It requires 115 klbf to get off the ground and maintain minimum climb gradient after an engine-out at V1 or higher.

The same aircraft could be built with three engines, each of about 70 klbf for an engine-out thrust of 140klb (it would be higher because the third engine would add weight and drag. Or it could be built with four engines, each of about 40-45 klbf.

Now, given the choice between three 70 klbf engines with one mounted on the tail in an awkward place to service and with all the awkward additional requirements that involves and four wing-mounted, identical, smaller engines, the quad wins.

The A380 could have been a trijet with three 110-125 kblf engines but instead it's a quad with four 70+klbf engines, but it wasn't. Why do you suppose that is?


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 53, posted (1 year 12 months 2 days 16 hours ago) and read 2087 times:

Quoting Revo1059 (Reply 50):
What about building an A/C that could be either 2 or 4 engines. Build it so that when needed 2 more engines could be "hooked up" and when not needed they could be taken off. I would think it would add some flexibility.

The problem is it wouldn't be competitive against dedicated twins or dedicated quads.

As a quad, it would be packing way more vertical fin than needed and way more structure on the inboard wing to support the loads from the twin configuration. As a twin, it would be backing around two whole extra sets of tubing/wiring/systems to support the engines that aren't there.

This is one of those cases where the point-optimization of modern transports gets in your way. The A330/A340 is about as close to this concept as you can get and I don't think anyone has ever swapped between the two.

Tom.


User currently offlineDocLightning From United States of America, joined Nov 2005, 18683 posts, RR: 58
Reply 54, posted (1 year 12 months 2 days 15 hours ago) and read 2066 times:

Quoting tdscanuck (Reply 53):
The problem is it wouldn't be competitive against dedicated twins or dedicated quads.

As a quad, it would be packing way more vertical fin than needed and way more structure on the inboard wing to support the loads from the twin configuration. As a twin, it would be backing around two whole extra sets of tubing/wiring/systems to support the engines that aren't there.

That's almost exactly how the A330/340 were designed, though.

The quad sold horribly. The twin is a smashing success.


User currently offlineRWA380 From United States of America, joined Feb 2005, 2876 posts, RR: 5
Reply 55, posted (1 year 12 months 2 days 6 hours ago) and read 1794 times:

Quoting warreng24 (Reply 51):
I legitimately believe that we may see another large tri-jet in the future.

The cost of fuel of the 4th engine will outweigh the development and maintenance cost of a tri-jet tail-mounted engine design.

As previously posted, these tri-jets will be marketed primarily at flights which are not ETOPS compatible

I was thinking the same exact thing reading this thread, and then here was your reply. I think a tri-jet could be useful for not just getting around some ETOPS stuff, but also flying places and routes where extra take off power could be an advantage. I am skeptical it will ever happen for the aforementioned reasons in this thread, but I'd love to see a new tri-jet.



Rule number One, NEVER underestimate the other guys greed
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