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WesternDC6B
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 7:34 pm

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.

One never knows. The Dornier X was a "VLA" for its time, and the world likely thought they'd never see her like again. It certainly didn't in propellor-driven craft, but the jet age changed everything.

If some new propulsion technique comes along - and I have no idea what that could be - things could change again.

About the only propulsion system I can think of that is feasible now is politicians facing to the rear of the aircraft, making speeches. All that hot air could move considerable mass!   
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WesternDC6B
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 7:36 pm

Quoting astuteman (Reply 24):
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 haven't a clue what you mean. Please explain. Thanks very much.
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LH707330
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 7:49 pm

Quoting Revelation (Reply 27):
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...

It is now, but some of the proposals like PW2000s or GTFs have been quads: http://aviationweek.com/defense/b-52...ne-resurfaces-usaf-reviews-studies

Quoting SEPilot (Reply 30):
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.

The other issue with that is that the engine thrust needed to build an ETOPS twin didn't exist before then either.

Quoting speedbored (Reply 33):
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+?

No, not necessary. If you scale a 115B up to 150k, you get a 3.71m fan. With newer tech you might get ~4m, but not 5m+

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. Sure, electricity seems to be sufficient for cars, but would something electrically powered be sufficient for something as massive as an airliner?

Barring any crazy new invention, it'll have to be some hydrocarbon, as other energy sources do not have the same energy content/weight/volume parameters to be competitive.

Quoting wingman (Reply 47):
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.

I think the "quads suck" sentiment is overstated. As Matt points out, the problems with the existing batch of quads is not due to a fundamental flaw in the configuration:

Quoting Matt6461 (Reply 20):
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)
 
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speedbored
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 8:00 pm

Quoting LH707330 (Reply 52):
No, not necessary. If you scale a 115B up to 150k, you get a 3.71m fan. With newer tech you might get ~4m, but not 5m+

But I was talking about GTF technology, not scaling up a non-GTF, previous generation GE115B.

If you look at the GTF on the NEO, it has about 24K thrust with a 2.06m fan. Scale that up to 150K and you have a fan requirement of just over 5m. Then factor in that PW are talking about increasing the bypass ratio from 12 to 15 in the next generation and you are well on your way towards 6m.
 
AYVN
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 8:29 pm

I think optimal number of engines is not as simple as it seems.
On a plane 2 engines is minimum for safety, that is something that can be agreed?
2 engines should be cheaper to aquire and maintain than 4 or 6 or 8.
But when it is question of really big engines it might not be the case. How many engines does a big ship need:
http://en.wikipedia.org/wiki/MS_Oasis_of_the_Seas ,6 engines with 7 propulsion points. And this ship is not in danger of faling out of the sky even if it only would have 1 engine with one propulsion. So there must be a size after what it is more economical to increase number of engines?
 
CaptCosslett
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 8:35 pm

I would like to know will we ever see a Large single engine plane, something the size of a 737/320 with one large jet engine in the tail ala DC-10. Just my 2 cents  Wow!
 
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NYPECO
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 8:48 pm

I wouldn't say that it's completely impossible that we will ever have another 4 engined aircraft.

Quoting CaptCosslett (Reply 55):
I would like to know will we ever see a Large single engine plane, something the size of a 737/320 with one large jet engine in the tail ala DC-10. Just my 2 cents Wow!

Don't give them ideas!  
 
CaptCosslett
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 8:52 pm

Also, I meant add the large single engine A320/737 size plane, would also be single piloted. Ryanair will order them in the hundreds!!!
 
LH707330
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 9:34 pm

Quoting speedbored (Reply 53):
But I was talking about GTF technology, not scaling up a non-GTF, previous generation GE115B.

If you look at the GTF on the NEO, it has about 24K thrust with a 2.06m fan. Scale that up to 150K and you have a fan requirement of just over 5m. Then factor in that PW are talking about increasing the bypass ratio from 12 to 15 in the next generation and you are well on your way towards 6m.

The 5.13m fan is if you figure 2.06m fan and 24k thrust, which is A319 territory. I think the engine is designed for 33k with the lighter-thrust variants as derates, so going by 33k and 2.06m would scale to 4.38m in a GTF. Keeping thrust static and improving the core will get you more area, but not >5m.
 
planemaker
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 9:42 pm

Quoting 4holer (Reply 6):
"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.

Or will see an MD-11 style jet... without the wing mounted engines....  
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a380787
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 10:07 pm

Not in the next 10 years, but airport constraints dictate that eventually we have to go to more VLAs. Unless RR and GE can create 150k lbs or 200k lbs engines down the road, there will still be a need for VLAs.

Airports like LHR aren't expanding physically (we can assume most NIMBYs are too powerful), thus upgauging is the only real option.

Airbus A380 may be slightly ahead of its time, but the need for VLAs are very real. You can't build a 600-pax twin if there aren't any suitable engines to go with it.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 10:13 pm

I am still holding hope that Boeing will revive the 757 production line, but replace the two P&W or RR engines with four small units. The only problem is that it won't give us venerable A-nutters a thread for this forum on twin-engine narrowbody trans-Atlantic flights. Can't win 'em all!

  

  

  


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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 10:19 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...

Why assume that? The 747 line could be entirely shut down in 5-10 years with a much smaller production run of 747-8's than there were of 747-400's and 747 classics (100, 200, 300, and SP) There will be much smaller numbers of spare parts built for the -8's than for previous generations of 747's. There will also be a fewer planes available to part out for spares than the previous generations. Unless the Pentagon intends to also replace the fleet of E4-B's, I think the USAF should just buy up some retired late production 747-300's for spare parts and keep the VC-25 fleet running for another 25 years+. They could even make some upgrades like winglets and GENx engines. If they can keep the B-52 flying for 90-100 years, why not a late production 747-200 for half that?
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 10:44 pm

Quoting a380787 (Reply 60):
Airports like LHR aren't expanding physically (we can assume most NIMBYs are too powerful), thus upgauging is the only real option.

Why assume that airlines will just up-gauge their metal flying to LHR? If NIMBY's kill off LHR expansion/replacement, perhaps some of the connecting traffic will just bypass LHR and go to hubs that have more capacity and political support for future expansion. If a future 737/757 narrow body replacement had higher gross weight versions with heavier duty landing gear and bigger wings for longer range, perhaps United could target thin markets they currently reach from EWR from IAH, or ORD. Perhaps American could use the same versions of planes to fly thin routes from ORD, DFW, or MIA.
 
a380787
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 10:54 pm

Quoting flyingclrs727 (Reply 63):

Why assume that airlines will just up-gauge their metal flying to LHR? If NIMBY's kill off LHR expansion/replacement, perhaps some of the connecting traffic will just bypass LHR and go to hubs that have more capacity and political support for future expansion. If a future 737/757 narrow body replacement had higher gross weight versions with heavier duty landing gear and bigger wings for longer range, perhaps United could target thin markets they currently reach from EWR from IAH, or ORD. Perhaps American could use the same versions of planes to fly thin routes from ORD, DFW, or MIA.

The hub bypass can only occur to a certain degree. O&D demand to major global cities will only grow over time.

US/Canadian carriers have the flexibility of routing through multiple hubs. Many airlines globally are very singular oriented, say AF, KL, SQ, CX etc.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Tue Mar 03, 2015 11:20 pm

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

Ever is such a big word. Somewhere between now and a million years from now, who knows. LHR will probably still have only two runways and the AirBoeing Alliance will be racing COMAC to launch the first 4,000-seat aircraft with 8 propellers powered by a nuclear reactor.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 1:39 am

My guess is that the only 4 engine jets you'll see built anymore will be designed for military airlift. That being said, if one were efficient enough, it might get a commercial variant, but likely for cargo only IMO.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 3:28 am

Quoting Matt6461 (Reply 32):

The technology can probably do it now; I just think a quad is more efficient

Why do you think that? I see no break point where a quad is more efficient than a twin. If you can make an engine large enough, the advantages of a twin still win out.

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

They will buy a twin. The next AF1 after the 748 will almost certainly be a twin.

Quoting astuteman (Reply 45):

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

That is a very real possibility. Liquid fuel, specifically kerosene, is probably the best (in terms of calories/kg and calories/l known, and so far nothing better is on the horizon. Hydrogen is better in calories/kg when you ignore the problems of containing it and the dangers it poses, but I do not see an easy solution to those problems, especially for a large aircraft.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 4:16 am

Quoting SEPilot (Reply 67):
Why do you think that? I see no break point where a quad is more efficient than a twin. If you can make an engine large enough, the advantages of a twin still win out.

I am 100% open to convinced otherwise. But I listed the advantages of a quads and twins in my earlier post and think those are broadly right. What do you think are the twin's advantages for VLA's if feasible? If you're going to say maintenance cost then how do you quantify that benefit versus the quads lower overall thrust, which also reduces maintenance cost?

One factor I'm trying to quantify is whether and what extent twins have a production and capital cost advantage. Seems intuitively right that 200k Thrust is cheaper to build in two engines than four but maybe not?
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 6:59 am

Quoting md80fanatic (Reply 13):
Thus a commercial transport utilizing such engines will likely start with 4, then 3 ... and back again to the absolute minimum of 2.

Why is 2 the minimum? Just get single engine reliability to the point that twin engine is now and you can save half your costs.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 10:06 am

Quoting Matt6461 (Reply 68):
I am 100% open to convinced otherwise. But I listed the advantages of a quads and twins in my earlier post and think those are broadly right. What do you think are the twin's advantages for VLA's if feasible? If you're going to say maintenance cost then how do you quantify that benefit versus the quads lower overall thrust, which also reduces maintenance cost?

The primary reasons twins have the advantage over quads are first, it is cheaper to build and maintain one large engine than two smaller ones, and the physics of jet engines dictates that the larger an engine is, the more efficient it is. There are several reasons for this; the most often mentioned is that losses at the blade tips are a smaller portion of the total airflow the larger the engine is. But there are other factors at work, such as lower heat loss and the ability of the flame to stay hotter. These all have to do with area being related to the square of the radius while volume is related to the cube. And these relationships only improve the larger you go. And they outweigh the advantages you cite for quads (which are correct, by the way.) These relationships apply specifically to jet engines; other types of engines may have very different scaling effects.

Quoting KD5MDK (Reply 69):
Why is 2 the minimum? Just get single engine reliability to the point that twin engine is now and you can save half your costs.

You will never get reliability good enough that people will trust a single engine. Bear in mind that ANY failure can bring the plane down; a 10 cent O-ring could kill 300 people. Jet engine reliability has made astounding progress, but it is not perfect and never will be.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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speedbored
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 11:49 am

Quoting SEPilot (Reply 70):
These all have to do with area being related to the square of the radius

Correct.

Quoting SEPilot (Reply 70):
while volume is related to the cube.

The volume of a sphere, maybe. But what does that have to do with a turbine engine? The volume of air moved is dictated by the fan area and the speed of the airflow that the fan can generate. Totally unrelated to the cube of the radius.

Quoting SEPilot (Reply 70):
You will never get reliability good enough that people will trust a single engine. Bear in mind that ANY failure can bring the plane down; a 10 cent O-ring could kill 300 people. Jet engine reliability has made astounding progress, but it is not perfect and never will be.

Totally agree - I can't see any of the certification authorities ever certifying a single engine aircraft for more than 10-20 passengers. Of course, some clever engineer may, one day, come up with a multipurpose APU that could be used to generate enough thrust in the even of an engine failure to safely get an aircraft back to an airport.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 12:27 pm

Quoting SEPilot (Reply 70):
it is cheaper to build and maintain one large engine than two smaller ones, and the physics of jet engines dictates that the larger an engine is, the more efficient it is.


You're likely right about the production cost of two versus one engine. Given the quad's lower overall thrust requirement, however, how can we know which effect dominates - total thrust or cost per lb-T?

Same with maintenance - which effect dominates? There's a recent thread in tech ops that contains a link showing the A340-300's mx cost per lb-T being only 3% higher than for a 77E. That's the only data point I've seen on the ckmparison. Going from twin to quad on a large (V2-limited) plane will save more than 3% of total thrust requirement easily.

You're definitely right about tip clearance and I cited that in my quad v twin reply. Tip clearance loss is proportional to (1-T^2), where T is tip clearance as a proportion of fan radius. T is so small for tightly-engineered modern turbofans, however, that I'd be surprised if going from 55k to 110k lbs-thrust made even a 1% difference. VLA engines will be big whether quad or twin so tip clearance is already a smaller issue than for e.g. a narrowbody. Meanwhile, a quad engine optimized to cruise at 85% max thrust versus 70% max thrust has a roughly proportional 20% increase in cruise OPR. That's probably worth 3-5% SFC. The numbers I've seen show the GP7200 and Trent 900 having slightly better cruise SFC than the GE-90-115B. I'd send a link but I'm on my phone... Also Lee ham News has a good "deep analysis" of the A380 showing its fuel efficiency to slightly beat the 77W per seat despite being a terribly over built plane with a stubby wing.

Re heat loss - engine cores have to be cooled anyway so isn't this a non issue or even a slight advantage for the quad?

My exercise "designing" the A380X in tech ops has convinced me that the bending relief effect of four engines is very important for big planes. Recall that Airbus was able to use the same spar structure for A330 and 340 solely due to bending relief.

One other quad VLA advantage is that the smaller engines should reduce landing gear height - a 2-decker's rotation angle is less critical to MLG design because of the stubbier fuselage.

Twins definitely would have less complicated and lighter support systems (Pylons, fuel pumps, pneumatics for bleed).

I used to think twins were always better for exactly the reasons you cite. My first A380X post in tech ops last year was basically a twin for those reasons. The more I've researched the more I think a quad is best.for a big plane. I can't provide a lot of hard numbers on my side, just a judgment call that the countervailing trends intersect somewhere around VLA size. If you have more insights or better numbers I'd much appreciate your sharing.
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 1:49 pm

Almost every unimaginable device and system from Star Trek (except for the Enterprise itself) came true and beyond, right down to Lt Uhura's (Bluetooth) ear piece piece. Even the "Cone of Silence" from Get Smart, was recreated by the CIA. About 20 years ago some construction workers found a "Time Capsule" buried by Nuns in the early 19th century and one of the first things written in the letter inside was "are there flying machines?"...I believe mankind will invent something that will replace a fossil fueled flying machine. Anti-Gravity technology? I believe that will be invented, potentially propelled by some sort of thrust and that could include 4 "thrusters"...making a 787 look like a lawnmower. So if we are talking the FUTURE then IMHO...sure. Although, probably not in my lifetime.
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 2:04 pm

Quoting SEPilot (Reply 67):
Quoting Matt6461 (Reply 32):

The technology can probably do it now; I just think a quad is more efficient

Why do you think that? I see no break point where a quad is more efficient than a twin. If you can make an engine large enough, the advantages of a twin still win out.

When reading about future propulsion technologies and the leaders at the forefront, one cannot ignore the buzzwords "distributed thrust" littered everywhere. That IS the future, apparently, the use of multiple smaller power plants as opposed to two huge wonkers. If the atmosphere were consistant at all altitudes, and temperatures, then one propulsion scheme could be optimized for it. As it is though, a turbofan is most efficient in only regime and a compromise in all the others.

I think the notion of bringing online extra power when needed, and retracting it when it's not has some promise. A 777 really only needs it's massive thrust on takeoff, and on a go around ... otherwise those huge gaping maws are a detriment to overall efficiency.

There are a lot of cool things on the immediate horizon, and when it's all said and done I think what will be occupying the conversations here will be anything but "2 engines forever!". I think it will be fun.  
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 2:19 pm

Quoting blueflyer (Reply 65):
Ever is such a big word. Somewhere between now and a million years from now

If Boeing even exists 100 years from now, likely they will be focused on interplanetary manned spacecraft. 300 years building the starship Enterprise.

Oh I just can't wait!!!!   

[Edited 2015-03-04 06:21:03]
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neutrino
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 5:57 pm

Quoting KD5MDK (Reply 69):
Why is 2 the minimum? Just get single engine reliability to the point that twin engine is now and you can save half your costs.

Assuming the reliability has gotten to the point of close to perfect, where are you going to put that big single jet engine? Certainly not fighter-style which takes up a huge portion of fuselage real estate. Nor anything like the second holer ala L-1011 or DC-10/MD-10. As for on one wing, don't even think about it.
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planemaker
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 6:06 pm

Quoting speedbored (Reply 71):
Totally agree - I can't see any of the certification authorities ever certifying a single engine aircraft for more than 10-20 passengers. Of course, some clever engineer may, one day, come up with a multipurpose APU that could be used to generate enough thrust in the even of an engine failure to safely get an aircraft back to an airport.

I certainly see the day for SE RJs.   Two things can make it a reality:

1) Improved designs and materials (already being done).

2) Comprehensive real-time monitoring (even down to the individual bearing level, which is starting to be done already, for example).

Quoting neutrino (Reply 76):
Nor anything like the second holer ala L-1011 or DC-10/MD-10.

A variant of that approach... twin vertical fins with the engine mounted between.

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cageyjames
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 6:11 pm

Just put a propeller on the front and be done with it.
 
LH707330
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RE: Will Boeing Ever Build Another 4 Engine Jet

Wed Mar 04, 2015 9:48 pm

Quoting SEPilot (Reply 70):
You will never get reliability good enough that people will trust a single engine. Bear in mind that ANY failure can bring the plane down; a 10 cent O-ring could kill 300 people. Jet engine reliability has made astounding progress, but it is not perfect and never will be.

No it won't, where would you find a 10-cent O-ring on a plane? 
Quoting planemaker (Reply 77):
A variant of that approach... twin vertical fins with the engine mounted between.

Just when you thought they couldn't get uglier than an A380....
 
rwessel
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RE: Will Boeing Ever Build Another 4 Engine Jet

Thu Mar 05, 2015 2:10 am

Quoting md80fanatic (Reply 74):
I think the notion of bringing online extra power when needed, and retracting it when it's not has some promise. A 777 really only needs it's massive thrust on takeoff, and on a go around ... otherwise those huge gaping maws are a detriment to overall efficiency.

Not quite true - at altitude you largely need those gaping maws to generate the much reduced cruise thrust because of the thinner air. Assuming an L/D of 20:1, a 750,000lb 777 would need some 37,500lbs of thrust, or 18,750lbs per engine, for level flight. At 35kft, where the air is about 23% the density at sea level, you'd need about the same fan as you would for an engine that produces 80,000lbs of thrust at sea level. So about 30% smaller (in area) than the fan for 115klbs, but that's not taking into account single engine performance either.

But a twin's maws will still be a bit bigger (net) than a quads.
 
JoeCanuck
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RE: Will Boeing Ever Build Another 4 Engine Jet

Thu Mar 05, 2015 3:19 am

I think the next evolution of aircraft will dictate the number of engines. As some have pointed out, a BWB, (or some other exotic design), might be more efficient with a bunch of small engines, rather than a couple of big ones.

I think the tube with wings design will be with us for a very long time for single aisle aircraft, but the next VLA's will at least be a hybrid.

They won't come around for a few decades, but I think we will see them.
What the...?
 
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RE: Will Boeing Ever Build Another 4 Engine Jet

Thu Mar 05, 2015 4:39 am

Quoting rwessel (Reply 80):
But a twin's maws will still be a bit bigger (net) than a quads.

Nice job describing what is going on.

The question about maintenance of two big engines vs four smaller ones to me is answered intuitively. The costly bit comes from having to replace compressor and turbine blades at rebuild time as they get worn down. You can make the argument that the twin has to have a lot of excess capacity due to the engine out case, but the reality is that the excess capacity just doesn't get used in normal operation. All those blades are in essence over-built so they wear down slower. Now consider that the quad has twice as many engines to take off the wing and send to the shop and rebuild and then twice as many blades that get more severe usage than in a twin and one can imagine that the rebuild cost is going to be higher.

To me this all supports the basic observation that these days only the VLAs have four engines, and both B747 and A380 are struggling to survive.
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RE: Will Boeing Ever Build Another 4 Engine Jet

Thu Mar 05, 2015 5:02 am

Quoting SEPilot (Reply 70):
You will never get reliability good enough that people will trust a single engine. Bear in mind that ANY failure can bring the plane down; a 10 cent O-ring could kill 300 people. Jet engine reliability has made astounding progress, but it is not perfect and never will be.

I did specify current levels of safety.

It's possible air travel is too safe today and it would be more efficient making air travel cheaper and spending the money on reducing driving to the airport.
 
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kanban
Posts: 4021
Joined: Sun Jan 06, 2008 1:00 am

RE: Will Boeing Ever Build Another 4 Engine Jet

Thu Mar 05, 2015 5:41 am

Quoting LH707330 (Reply 79):
No it won't, where would you find a 10-cent O-ring on a plane?

Oh yes you can find them.. (at OEM cost).. and an o-ring in a flap retract actuator got pinched yielding a pin head sized piece of debris which clogged a metering port causing an asymmetrical condition which almost crashed a 737 back in the 1990s. not an engine item but an issue none the less.. and I'll bet some engine o-rings have a cost to the OEMs of under 25 cents
 
planemaker
Posts: 5411
Joined: Mon Aug 25, 2003 12:53 pm

RE: Will Boeing Ever Build Another 4 Engine Jet

Thu Mar 05, 2015 10:21 pm

Quoting LH707330 (Reply 79):
Just when you thought they couldn't get uglier than an A380....

They'll hand out really dark eyeglasses to passengers and spotters. 
Quoting KD5MDK (Reply 83):
It's possible air travel is too safe today and it would be more efficient making air travel cheaper and spending the money on reducing driving to the airport.

From an purely economic perspective you are absolutely correct.
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