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doulasc
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Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 3:51 am

After the Boeing 747 ceases production will Boeing ever build another 4 engine jetliner? will there ever be another
tri jet like the 727?
 
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TheRedBaron
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 3:57 am

I would take a few Mh370 or accidents on twins and media frenzy to make a quad feasible ...

I bet the A380 will be the last Airliner with more than 2 engines to be designed...

TRB
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rotating14
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:01 am

I say no chance. We're in a different era of aviation. A lot of what a 4 engine aircraft can accomplish can be accomplished by the up and coming twins, ie 777-9, A35J I'm almost sure that after the A380 has made her last touch down on the piano keys, there won't be another quad built. The only person who needs quads is the President of the United States.
 
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kanban
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:02 am

not as a standard winged tube or sub sonic commercial plane
 
tmiw
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:06 am

Quoting rotating14 (Reply 2):
I say no chance. We're in a different era of aviation. A lot of what a 4 engine aircraft can accomplish can be accomplished by the up and coming twins, ie 777-9, A35J I'm almost sure that after the A380 has made her last touch down on the piano keys, there won't be another quad built. The only person who needs quads is the President of the United States.

I wonder what will happen 30 years from now when the US government needs to choose another replacement for Air Force One. Will they let up on the quad requirement or will Boeing build a custom quad just for it?
 
joffie
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:06 am

Quoting doulasc (Thread starter):
will there ever be another
tri jet like the 727?

No, the technology of 2 engines today is obviously much better than the 60's and 70's. There are no need for the extra engines. The three-engine configuration is one of the worst possible due to the added structural and mechanical complexity of a tail engine. A quad configuration is more desireable than a trijet, and it's likely that twins will continue to be pervasive as larger and larger engines become viable. (https://www.airliners.net/aviation-forums/general_aviation/read.main/2286194/)

Quoting doulasc (Thread starter):
will Boeing ever build another 4 engine jetliner

I think the 747-8 signals the end of the 4 engine Boeing. On another topic, whats happening now the C-17 production has wound up?

Quoting TheRedBaron (Reply 1):
I bet the A380 will be the last Airliner with more than 2 engines to be designed...

Agreed. Boeing is now focused on the future of the 777, and maybe future introduction of the 797 (which I have no idea what it is meant to look like).
 
4holer
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:08 am

"Ever" is a tough word to use. And while there may never be another tri-jet "like the 727", there may be one someday with 3 buried in or above a BWB or something like a Sonic Cruiser.
Ghosts appear and fade away.....................
 
steeler83
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:12 am

Quoting joffie (Reply 5):
Boeing is now focused on the future of the 777, and maybe future introduction of the 797 (which I have no idea what it is meant to look like).

A double decker twin jet perhaps?  

In all seriousness, I must concur that as much as I like the trijets, quads, and the T-tails the era of such technology is over...
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2175301
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:52 am

I would also be careful of the word "Ever."

Also, Boeing builds more than just passenger aircraft...

So, I do think it will happen; although it may be a very limited production run (perhaps only a few copies of a specialized test plane). The engines may also be fairly small.

I do not believe the configuration will be anything like the modern 4 engine passenger aircraft. Think flying wing, or perhaps even flying saucer....

For specialized military vehicles there are several applications where this could occur.

For conventional passenger aircraft. I think it would be unlikely.


Have a great day,
 
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BlueSky1976
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:57 am

Short answer: no.
Long answer: not a chance.

Twins are the future. The only Boeing's all-new quad jet would be a military transport, a successor to C-5 and C-17 most likely.
Proudly avoiding 737 MAX since 18.11.2020.
 
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Boeing778X
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 5:06 am

For an airliner, I wouldn't count on it. The days of tri and quad jets will end, and quite soon. Powerful, Next Generation VLAs like the Boeing 777-9 really take away the need for jets like the 747, and they do the job better. The A380 will almost certainly go quickly in the years ahead as well.

The A330, A350-900, -1000, the 787-8, -9,-10 and the 777-300ER, -8 and -9 are pretty much everything the world will want out of a jet.

You want a long range product? Look at the A350-900, 787-9 or 777-8.
Want a good regional or medium haul product? Try the A330 or 787-8.
Want an efficient, high density long hauler? 787-10.
Want a Flagship that makes your company look as good as the money you'll save? A350-1000, 777-300ER or 777-9.

Not only that, but I think a few of these types will make it as freighters too, especially the 777-8.
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A332DTW
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 5:11 am

Two words... engine reliability. Turbofan engines have come a long way, and they will continue to develop. Based on that, I think manufacturers will not see much reason to develop new trijets or quadjets for the airline industry.
 
pa747sp
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 5:37 am

If there is no regulatory requirement for more than two engines, airlines are going to want twins. 2 engines means half the engine maintenance of 4. Stuff like that is really important to airlines.

However, the argument over high capacity dense routes via hubs vs lower capacity non stops is always evolving. It could be for the foreseeable future that twins will be able to replace VLAs in many situations, but eventually capacity constraints within the air traffic system may see airlines with no choice but to move on to even larger aircraft, and there may be a need for a VLA 4 engine aircraft. Engine size is one thing that could be a problem. Engines at the moment hang under aircraft wings, and most airports are equipped to handle aircraft of a certain height. It could turn out that its not possible to build an engine with enough thrust to fit under the wing of a VLA with only two engines, and still allow it to operate from most airports. Moving a wing up to the top of the fuselage is a possible answer, but aircraft manufacturers like being able to 'sit' the airframe on a wing box, and considering that all modern medium-large passenger aircraft use this model, clearly it is the most efficient. Some large military jets use high-wing design. I'm assuming thats to allow them to operate from poorly paved airfields.
Hence we might yet see 4-holers again.
Nothing seems as good since the VC10.
 
md80fanatic
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 5:58 am

Assuming the future -only- includes kerosene-driven turbines, 2-engines are it. Major jumps in turbofan technology happened in the 20th century and significant efficiency increases now are approaching the point where the costs to develop no longer outweigh the savings expected.

Cue the "next" propulsion type ...

Naturally, a totally new type operating on new fuels will necessarily require multiple redundancies, the same process turbofans required early in their development. Thus a commercial transport utilizing such engines will likely start with 4, then 3 ... and back again to the absolute minimum of 2.

Have no fear ... 3-holers WILL be back someday.  
 
LH707330
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:38 am

Quoting tmiw (Reply 4):
I wonder what will happen 30 years from now when the US government needs to choose another replacement for Air Force One. Will they let up on the quad requirement or will Boeing build a custom quad just for it?

They'll adapt somehow....

You all are forgetiing the most legendary Boeing quad we'll ever have, that will remain in service until the 2050s: the B-52MAX with four engines.
 
rugger
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:45 am

Quoting 2175301 (Reply 8):
I would also be careful of the word "Ever."

Because there are a lot of people out there that will tell you it means the same as "all" !! And generalization is never viewed as being politically correct.
 
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LAX772LR
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 7:15 am

Quoting TheRedBaron (Reply 1):
I would take a few Mh370

...what evidence is there that anything involving the loss of MH370 was engine/ETOPS related??



Quoting TheRedBaron (Reply 1):
or accidents on twins

In the history of transoceanic twin operations, we've never once seen a dual independent failure in a twinjet that wouldn't have crippled any quadjet to an equal degree. And that's millions of flights and billions of seat/miles. Not once.

No amount of media frenzy is going to overcome that.

Sure they may bitch and screech for a few weeks (or a few months, if they're CNN), but then the public will quickly remember that they care more about what Paris is wearing or who Kim is screwing, and it'll be a non issue.

Certainly not something that will affect OEM design philosophy in any way, form, or fashion.
I myself, suspect a more prosaic motive... ~Thranduil
 
aviationaware
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 9:23 am

Quoting kanban (Reply 3):
not as a standard winged tube or sub sonic commercial plane

This. Short or mid term, there is absolutely zero chance for a new four holer from Boeing. However, in the far future, who knows. Hopefully, in the decades to come there will be engine technologies we don't even dream of yet and maybe those can even mean octopods or whatever.
But as a conventional 20th century gas turbine airliner - no.
 
chiad
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 9:32 am

Quoting doulasc (Thread starter):
will there ever be another
tri jet like the 727?
Quoting 4holer (Reply 6):
And while there may never be another tri-jet

"Never" is a really long time!
I would have to go With Yes on this one.
 
parapente
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 9:50 am

There are some BWB designs where a series of small engines suck air in across the top boundary layer thus creating greater efficiency. But other than this I see no reason what so ever.Why would they?
 
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Matt6461
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 10:59 am

Don't just accept the MSM hype against 4-engine jets. There are numerous engineering and economic advantages for quads over twins. Twins have advantages too, but for large jets the quad is best.

Quad advantages:
-lower installed takeoff thrust requirement means (1) lower maintenance, (2) lower engine size, weight, and drag
-because quad has less excess thrust it cruises closer to max OPR, meaning better thermodynamic efficiency and lower SFC
-the placement of the four engines farther along span gives greater bending relief, meaning a lighter wing
-lower thrust and lower engine-out yaw moment enable a shorter vertical stabilizer

Most of these factors increase in importance as a plane gets larger:
-cruise is generally a bigger part of mission fuel burn for large planes
-wing spar weight is bigger fraction of MOEW, meaning bending relief is more useful
-planes taking off from longer runways (large planes) are limited by V2 engine out conditions instead of V1 field length conditions, meaning the quad advantage of lower SLS takeoff thrust is most useful for large planes

Twins have advantages too:
-bigger engines have lower tip turbulence loss. But tip clearance factor decreases with engine size so that smaller planes benefit from this twin factor more larger ones
-at equal total system thrust, two engines are cheaper to build and maintain than four. So a smaller, V1-constrained plane will have better maintenance cost most likely. But not by a ton - most mx cost is proportional to thrust

All of the recent large quads are comparatively inefficient designs.
-747 is old
-A340, especially -500 and -600, were stretches too far and suffered higher empty weights than competitors
-A380 is suboptimal design - a 550 seater carrying a wing built for a 650 seater, then shoved into the 80m box (too much weight and both parasitic and induced drag)

If Boeing ever does a clean sheet VLA it will probably be a quad. Fat chance of another VLA happening though.
 
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Matt6461
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 11:06 am

A clean sheet Boeing VLA quad would be a pretty amazing plane btw. I've described an A380 with an optimized wing and other changes in tech ops. A380X Part 3: Business Case (by Matt6461 Mar 2 2015 in Tech Ops) That plane would have 30% lower cash operating costs per seat than a 777-9 and/or A388CEO. A clean sheet CFRP competitor would be 5-10% better. But that's just not gonna happen.
 
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moo
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 11:49 am

Quoting BlueSky1976 (Reply 9):

Short answer: no.
Long answer: not a chance.

Never say never.

At some point we are going to get a larger aircraft (yes, I don't believe the A380 is the last of its breed, in the next 100 years I expect to see something twice its size) where the logistics of hanging a single engine with a thrust rating of 500,000lb on a wing becomes problematic on the airframe.

It may also be that we see a step change in engine architecture where we can achieve an improvement in efficiency of 95% over current engines, but with a reliability reduction of 10% (yeah, numbers pulled out of the proverbial) - would such a situation not make 4 or 6 engines a better prospect than staying with more reliable, significantly less efficient engines?

I'm sure an airline would be fine with a 30 minute engine swap out at each end of a journey if it mean reducing trip costs by 95%, especially if the engine being swapped out is easily refurbished and goes on to the next aircraft.

There are all manner of reasons why we may see quads again.
 
tailskid
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 11:55 am

Will Ford ever build another flathead V8?

That question remains unanswered for 60 years now. I suspect this Boeing question will suffer the same fate.
 
astuteman
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 12:21 pm

Quoting Boeing778X (Reply 10):
The A380 will almost certainly go quickly in the years ahead as well.

About Mach 0.855 for the decades to come when it will continue in production  
Quoting Matt6461 (Reply 20):
If Boeing ever does a clean sheet VLA it will probably be a quad. Fat chance of another VLA happening though

My thoughts are the opposite way.
I think there's every chance that Boeing will do a "clean-sheet VLA" sometime in the future (they are doing a "brownfield" one as we speak). I'm pretty sure that future technology will allow a genuine 500 seater on 2 engines, though

(etided for crap spelyng)

Rgds

[Edited 2015-03-03 04:22:50]
 
hz747300
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 12:27 pm

Oh man, I think Boeing should build a civilian C-17 / C-5 with three levels of passengers. I'm sure there is some way to add a ten car garage sized fuel tank to give it sufficient range as well as using the lightweight technologies learned from the 787/748 programs. I could seek EK offering a top level first class only, second level business class, and third level, economy. They can keep the ramp in the back for faster loading / unloading coach passengers.

It'll NEVER happen... dare to DREAM!
Keep on truckin'...
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 12:50 pm

Quoting A332DTW (Reply 11):
Two words... engine reliability. Turbofan engines have come a long way, and they will continue to develop. Based on that, I think manufacturers will not see much reason to develop new trijets or quadjets for the airline industry.

People always talk about efficiency when it comes to twins, but they forget that the real reason for quads was power. It took more than two engines to get some of the larger planes off the ground and to their destinations.
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Revelation
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 12:55 pm

Quoting A332DTW (Reply 11):
Two words... engine reliability.

Personally, I'd go with the two words "engine cost". Four engines cost a lot more to acquire and maintain versus two.

Quoting LH707330 (Reply 14):
You all are forgetiing the most legendary Boeing quad we'll ever have, that will remain in service until the 2050s: the B-52MAX with four engines.

Surely it's eight engines, hung in four pods...

http://www.madracki.com/usarmyhawk/jpg/b52.jpg
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B8887
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:02 pm

Quoting doulasc (Thread starter):
After the Boeing 747 ceases production will Boeing ever build another 4 engine jetliner?

I think the short answer answer is no...

But, on the other hand, do you think technology will mature enough for a single engine, short to medium haul passenger airliner in the near future, from another manufacturer, perhaps?...

B8887
 
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moo
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:07 pm

Quoting hz747300 (Reply 25):
It'll NEVER happen... dare to DREAM!

Years ago people sold their entire lives worth in order to buy a one way ticket on an ocean liner. Travelling across the ocean on a ship was something you only did if you could seriously afford it, and even then for most it was a single time event as you sought out a new life. Yet today I can book a two week cruise for less than a months wages, all for nothing more than personal amusement.

Years ago taking a long distance flight on an aircraft was something only the rich did - intercontinental was out of the question for most people. Yet today we take 8, 9 hour flights to go on holiday.

Think about the future, when flights to Australia from the UK are no longer arduous, insane slogs and instead are much more like going on a cruise than a cattle hauler.

The move to twins today is nothing more than an economic decision - two engines burn less fuel than the equivalent four engine thrust, maintenance etc. However theres no reason that might not change - with power by the hour support contracts, maintenance is much less of an issue, so efficiency becomes the primary consideration.

Will we see advancements in the future which don't scale to 115", 105,000lb size engines? Perhaps, its not out of the scope of possibility. Would this see a switch back to 3, 4, 6, 10 engines? Maybe.
 
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SEPilot
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:13 pm

Quoting redflyer (Reply 26):

People always talk about efficiency when it comes to twins, but they forget that the real reason for quads was power. It took more than two engines to get some of the larger planes off the ground and to their destinations.

That is very true, but it is also true that until turbofans proved their reliability that regulations forbade an airliner from flying a route that carried it more than one hour from an emergency landing field. ETOPS was not even considered until the 80's.

I am also of the opinion that there will never again be a new airliner with more than two turbofan engines. But as md80fanatic correctly stated if a completely new engine technology emerges it is a different story. As for a new, larger airliner, we are pushing the limits of what the airport infrastructure can accommodate. The A380 should have a longer wingspan; it is severely hampered by a very poor aspect ratio, which is one of the big reasons why the 779 and A3510 will be more fuel efficient, probably even if the A380 gets new engines. So the idea of a twin engined double decker is feasible given that current technology can produce an engine with 150K lbs thrust, if it must be limited to an 80m wingspan it will also be hampered. I think the 777X is just about the limit of what folding wingtips will allow-I do not think anyone will accept control surfaces in the folding part, and there still will be the problem of the wingspan on the runway. And there is absolutely no chance that the airports in major cities will be redesigned and rebuilt to accommodate 90 or 100m wingspans.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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Revelation
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:19 pm

Quoting moo (Reply 29):
Think about the future, when flights to Australia from the UK are no longer arduous, insane slogs and instead are much more like going on a cruise than a cattle hauler.

The move to twins today is nothing more than an economic decision - two engines burn less fuel than the equivalent four engine thrust, maintenance etc. However theres no reason that might not change - with power by the hour support contracts, maintenance is much less of an issue, so efficiency becomes the primary consideration.

I don't think it will change much, because the ones making the ultimate economic decisions are the pax who decide they'll put up with 12 hour flight durations in a 10-abreast 777 so they can spend more money once they get on to the ground.
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
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Matt6461
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:23 pm

Quoting astuteman (Reply 24):
I'm pretty sure that future technology will allow a genuine 500 seater on 2 engines, though

The technology can probably do it now; I just think a quad is more efficient. Or do you see a future 500-seater being around the 779's MTOW and wingspan? That's possible, twin might be better at that size.
 
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speedbored
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:47 pm

I would never claim to understand all of the technology that goes into today's engines, let alone the likely next generation ones, but I can't help thinking that perhaps the next generation of geared fan engines (like the RR Ultrafan) may prove to have constraints imposed by:
1) fan size
2) gearbox size/weight
3) gearbox cooling
4) gearbox reliability
which will mean that for large aircraft, it might make it more sensible to have 4 engines instead of 2 on the next VLA. Just imagine how huge the fan would need to be, even for just a 150,000lbf+ geared engine. 5m+?

I have a feeling that we might have to wait 20 years to find out, though. Unfortunately, I can't see any manufacturer making an all new VLA anytime soon.
 
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moo
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:50 pm

Quoting Revelation (Reply 31):
I don't think it will change much, because the ones making the ultimate economic decisions are the pax who decide they'll put up with 12 hour flight durations in a 10-abreast 777 so they can spend more money once they get on to the ground.

I think over the next 100, 200, 500 years that will change significantly as we make technology breakthroughs.

The reason we go on cruises is because the profit in providing the holiday environment vastly over took the profit involved in just carrying passengers from point A to point B. I see something similar happening for aircraft in the future.
 
rta
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 1:52 pm

For commercial airliners (as we currently know it), I don't think so.
Twins are just as reliable and more efficient than quads.

I wonder what will happen to AF1, when it comes to retire the 747-8s. Thankfully, that won't be for a long, long time  
 
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moo
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 2:01 pm

Quoting rta (Reply 35):
I wonder what will happen to AF1, when it comes to retire the 747-8s. Thankfully, that won't be for a long, long time  

Is 25 years a long, long time?   Thats how long the current 747s have been around, so thats how long we can assume the -8s will be around...

Another replacement will certainly be within my natural life time, and I'm 35.
 
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Revelation
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 2:12 pm

Quoting moo (Reply 34):
The reason we go on cruises is because the profit in providing the holiday environment vastly over took the profit involved in just carrying passengers from point A to point B.

Yet the cruise ship reduces the holiday expense by providing lodging so there's a great incentive to stay on the ship and spend money there. Not sure we'd see that with an aircraft. The furthest we've come is EK's first class suites with showers. There's a long way to go from there to something akin to a cruise ship. Granted if you give it 100, 200 or 500 years things could change but the trend line seems to be that the rich are getting richer and the poor are getting poorer. Seems the nearer term thing to do is keep selling customized 747s to the ultra rich so we can have more four holers out there! 
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
The heart has its seasons, its evenings and songs of its own
 
S75752
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 2:26 pm

Above all, this question makes me curious if/when we will see the GE90/9X/10X-150/155.

The last applications for 4 engines at least in commercial aviation have been the 748 and 380 - and we see how the Airlines have voted with their money regarding those. I think the VLA's might have a chance to stay when/if the next mega-engines come around, as above. But quads are unlikely.
 
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moo
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 3:01 pm

Quoting Revelation (Reply 37):
Not sure we'd see that with an aircraft.

Unless there is a breakthrough in speed, Australia is still 24 hours away from LHR - but imagine a round the world tour on an aircraft, 20 destinations in 2 weeks? Alaska to Hong Kong and everything in between? Cover much more distance than a cruise ship but the same basic reasons for doing it  
Quoting Revelation (Reply 37):
he trend line seems to be that the rich are getting richer and the poor are getting poorer

Meh, standard rhetoric from the usual people imho.

I started out with just GCSEs, didn't go to University or get any further education, and I'm now earning more than most of my peers from school, and well above the average for my age. I'm most certainly not one of the "rich" getting "richer" as I started out with no money...
 
Slcpilot
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 3:27 pm

Allow me to think outside the box for a moment. Imagine a future technogy that gives us a very large amount of electrical power, at very little cost. Super cheap, super efficient solar, fusion, space based solar collection mirrors, dark energy harvesting....whatever...it doesn't matter.

Well, electrical energy storage still isn't practical on a large scale, but hydrogen would prusumably become cheap as a result. What if it turned out large bulbous airliners were powered by multiple engines were close to an optimum design trade off given relatively free fuel.

I guess several planes have flown with hydrogen power (Tu-154?), but I'd imagine little effort has been put forth so far into power plants optimized for hydrogen burning, given a multitude of factors that make it in no way practical at the moment.


SLCPilot

[Edited 2015-03-03 08:07:18]
I don't like to be fueled by anger, I don't like to be fooled by lust...
 
rta
Posts: 1414
Joined: Mon Jan 26, 2015 2:01 am

RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 3:56 pm

Quoting moo (Reply 36):
Is 25 years a long, long time?   Thats how long the current 747s have been around, so thats how long we can assume the -8s will be around...

Another replacement will certainly be within my natural life time, and I'm 35.

I could be wrong, but I heard they expect about 30 years from these planes. So, I think we're looking at 35 years before the -8s will be tired.

Either way, 25 or 35 years, is still pretty long for me (in a good way).  
 
GRRECPGRR
Posts: 65
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 4:27 pm

This issue has two sides...history and the future.

As we historically understand it, we had quad and tri jets simply because of the limitations of technology in creating reliable engines with thrust. Remember those early jets were giants compared the engines on the regional jets, yet their thrust ratings are similar, 8-15,000. As tech advanced, we got bigger engines with more thrust, but the reliability wasn't there. Err on the side of caution with redundancy, thus quads. As the L1011, DC10 and such were coming around, engines were better, but still the need for redundancy was called for. Some progress with twins were made, the DC9 and 737 are evidence of that.

Today, we have much more capable engines, both in what they produce in power such as the beast on the 777 at 115K+ of thrust, to the reliability of years of service on wing without removal.

Tech has made the need for the quad and tri jet obsolete. There may still be a want factor, the need factor has been overcome.

This takes us to the future. Who knows what will happen with design in the future. As pointed out, a blended wing may very well use 3 or 4 engines, we don't know yet. But we now have some VLJs that are designed with only a single jet engine as its entire planned engine compliment. Who would have thought that possible 40 years ago?

Therefore, to say that there will never be another tri or quad jet design is strictly speaking from an historical perspective and understanding. Who knows what the future will bring to us in another 50-100 years. A 787 and A350/A380 are a far cry from what Wilbur and Orville conceived and flew that day on the sand dunes of Kitty Hawk, NC. Just as the change has been dramatic in that time frame, so will the leap forward be for the next.
 
S75752
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 5:45 pm

Quoting SLCPilot (Reply 40):

The question that comes to my mind is what will power commercial aviation after oil, considering they use a massive amount of it. Sure, electricity seems to be sufficient for cars, but would something electrically powered be sufficient for something as massive as an airliner?
 
richierich
Moderator
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:04 pm

Quoting chiad (Reply 18):
"Never" is a really long time!
I would have to go With Yes on this one.

Never is a long time. But I feel comfortable saying that Boeing will NEVER build another subsonic four-engined jet (for passenger/commercial usage.) They have a better chance of disappearing and dissolving as a corporation than building a contemporary megajet.

With that said, who knows about supersonic transportation. Concorde has come and gone, and although there are no new supersonic airliners beyond the sketch and initial design phase, it is not a stretch to imagine four jets on these aircraft, should they ever materialize. But I'm not expecting this to happen in my lifetime (and I hope I have several decades left!)
None shall pass!!!!
 
astuteman
Posts: 7184
Joined: Mon Jan 24, 2005 7:50 pm

RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:07 pm

Quoting S75752 (Reply 43):
The question that comes to my mind is what will power commercial aviation after oil, considering they use a massive amount of it

Synthetically produced petroleum, created using an abundance of clean Nuclear fusion power ?  

Rgds
 
bmacleod
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:07 pm

With A380 sales stalling and looking bleak; my    is on Boeing sticking with 2 engines....
"What good are wings without the courage to fly?" - Atticus
 
wingman
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:38 pm

Quoting bmacleod (Reply 46):
With A380 sales stalling and looking bleak; my    is on Boeing sticking with 2 engines....

Right now the 380 is arguably in a halfway decent spot, depends on who's talking and what day it is. The real issue is when you look at it combined with the other three 4 engined aircraft in the past 20 years, namely the 747-8, the 345 and the 346. All three of those got their lunch eaten by the 777 and now the 380 has to contend with a new 777 in addition to the 350 and the 787. In my mind I just don't see another 4 engined Boeing..ever. Maybe a triple BWB as per the many renditions.

Anyway, Airbus at least has the field all to themselves for a long time. That gives them a sporting chance to produce the 380 for another 20-30 years. But the problem is that virtually all R&D at Boeing, Airbus, PW, RR and GE is going to go into optimizing twins. So every 10-15 years Airbus will be forced into another upgrade project to keep that plane competitive.

Think of all the threads we'll have here on A.net.
 
A332DTW
Posts: 921
Joined: Tue Jan 06, 2015 3:54 am

RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 6:51 pm

Quoting redflyer (Reply 26):
People always talk about efficiency when it comes to twins, but they forget that the real reason for quads was power. It took more than two engines to get some of the larger planes off the ground and to their destinations.

  

Quoting Revelation (Reply 27):
Personally, I'd go with the two words "engine cost". Four engines cost a lot more to acquire and maintain versus two.

I agree, cost is a major factor, but does cost supersede performance... depends on who you ask.

As redflyer mentioned above, widebody aircraft needed tons of power to get off the ground and to maintain endurance. 3 or more engines was the solution until ETOPS in the 80s began to take precedent.
 
slinky09
Posts: 661
Joined: Sat Jun 06, 2009 5:03 pm

RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 7:19 pm

Quoting md80fanatic (Reply 13):
Naturally, a totally new type operating on new fuels will necessarily require multiple redundancies, the same process turbofans required early in their development. Thus a commercial transport utilizing such engines will likely start with 4, then 3 ... and back again to the absolute minimum of 2.

That was my thought - should supersonic or hypersonic travel become economically feasible with a new type of propulsion, who's to say a four engined aircraft would not be designed? I wouldn't say ever in that context for either Boeing or Airbus or a new entrant. 'Never' implies a view of the future solely based on what we know now, things will change ...

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