patrickjp93
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Future VLA Market?

Sat Jan 11, 2020 8:27 pm

I'd like some more technical thought on the future of large planes as the A380 and 747 ride off into the sunset with the 777X coming online in the context of changing air travel demand.

With Asia and India rapidly growing their travel demand both domestic and international, quite a few of the world's big hubs are already slot-restricted or slot-poor at this point, so we have pressures for more direct hub and even direct P2P travel between smaller hubs and destinations alongside pressures to move lots of people from Hong Kong, Shanghai, Taipei, Tokyo, Singapore, Kuala Lumpur, Mumbai, Bangalore, and Dehli into London, Paris, Frankfurt, Amsterdam, New York, Atlanta, Toronto, Vancouver, etc. and vice versa.

Given the prospects of another 1 billion annual fliers in the air yearly by the mid 2030s, do we still have room for birds bigger than the 777-9 while the economics of direct lesser hub flight are also changing? What would it take to justify a tri-jet A380 redux? Will we ever see twin-engine full-length double-deckers given the massive thrust requirements?
 
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Starlionblue
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Re: Future VLA Market?

Sat Jan 11, 2020 11:31 pm

If we see more VLAs, they will most likely be quads. The development cost for really large engines is very high, but the market is relatively small.

Unless designs change dramatically, we won't see trijets. The design complications are far too big.

That being said, there's always that "just around the corner" flying wing. :)
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Rossiya747
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Re: Future VLA Market?

Sun Jan 12, 2020 3:46 am

patrickjp93 wrote:
I'd like some more technical thought on the future of large planes as the A380 and 747 ride off into the sunset with the 777X coming online in the context of changing air travel demand.

With Asia and India rapidly growing their travel demand both domestic and international, quite a few of the world's big hubs are already slot-restricted or slot-poor at this point, so we have pressures for more direct hub and even direct P2P travel between smaller hubs and destinations alongside pressures to move lots of people from Hong Kong, Shanghai, Taipei, Tokyo, Singapore, Kuala Lumpur, Mumbai, Bangalore, and Dehli into London, Paris, Frankfurt, Amsterdam, New York, Atlanta, Toronto, Vancouver, etc. and vice versa.

Given the prospects of another 1 billion annual fliers in the air yearly by the mid 2030s, do we still have room for birds bigger than the 777-9 while the economics of direct lesser hub flight are also changing? What would it take to justify a tri-jet A380 redux? Will we ever see twin-engine full-length double-deckers given the massive thrust requirements?


Trijet A380??? The entire wing position would have to be redesigned.
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patrickjp93
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Re: Future VLA Market?

Sun Jan 12, 2020 4:14 am

Rossiya747 wrote:
patrickjp93 wrote:
I'd like some more technical thought on the future of large planes as the A380 and 747 ride off into the sunset with the 777X coming online in the context of changing air travel demand.

With Asia and India rapidly growing their travel demand both domestic and international, quite a few of the world's big hubs are already slot-restricted or slot-poor at this point, so we have pressures for more direct hub and even direct P2P travel between smaller hubs and destinations alongside pressures to move lots of people from Hong Kong, Shanghai, Taipei, Tokyo, Singapore, Kuala Lumpur, Mumbai, Bangalore, and Dehli into London, Paris, Frankfurt, Amsterdam, New York, Atlanta, Toronto, Vancouver, etc. and vice versa.

Given the prospects of another 1 billion annual fliers in the air yearly by the mid 2030s, do we still have room for birds bigger than the 777-9 while the economics of direct lesser hub flight are also changing? What would it take to justify a tri-jet A380 redux? Will we ever see twin-engine full-length double-deckers given the massive thrust requirements?


Trijet A380??? The entire wing position would have to be redesigned.

Given it's a bit too much plane for most airlines these days, a shrink of the 800 would require the same too. Heck even a twinge version would most likely require that because of the different bending moments and lesser twist.

The age of quads is over, but the A380 is a heavy bird to say the least. A trijet fixes most of the fuel economy issues without requiring ludicrous amounts of thrust per engine. Three XWB 97s could pull it off.
 
JayinKitsap
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Re: Future VLA Market?

Sun Jan 12, 2020 10:05 am

Going to bigger planes is essential, but the key is the AVERAGE size, not the size of the largest available plane.

Up gauging from a 738 to an A321 improves capacity a good bit. If all planes were up gauged by 20% the average size is up by 20%.

The largest will be the 779 for a couple decades. Not enough VLA orders to support a new clean sheet.
 
LH707330
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Re: Future VLA Market?

Sun Jan 12, 2020 8:43 pm

JayinKitsap wrote:
Going to bigger planes is essential, but the key is the AVERAGE size, not the size of the largest available plane.

Up gauging from a 738 to an A321 improves capacity a good bit. If all planes were up gauged by 20% the average size is up by 20%.

The largest will be the 779 for a couple decades. Not enough VLA orders to support a new clean sheet.

Bingo. I look out my window and see a constant stream of E175s going into Sea-Tac. Upgauging all NBs is how to fix the constraint, not worrying about moving 2x A330 SEA-AMS to 1x VLA.

If another VLA gets built, it'll likely be a quad for reasons mentioned above: cheap engines to share with a twin, and better ground clearance, etc. A quad is a better layout than a trijet.
 
blacksoviet
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Re: Future VLA Market?

Sun Jan 12, 2020 11:08 pm

The technology exists for a trijet with the same capacity as the 747-8.

Take the engines from the 77W, make the fuselage 20 feet longer and a couple inches wider than the 779. This will allow comfortable ten-abreast seating. Add a third engine in the tail and you have a 748 trijet with even longer range. This could cover the very top of the market for 35 years. After that, the technology might exist for a 748 twinjet with 9000 miles nautical range.

A trijet could serve as a stopgap for the VLA market, offering even greater range than the 779.

One day after we are all gone, there may be a twinjet that can fly 500 passengers in four classes, against headwinds halfway around the world from a hot and high airport. The engine technology simply does not exist at this time.
 
GalaxyFlyer
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Re: Future VLA Market?

Mon Jan 13, 2020 4:08 pm

blacksoviet wrote:
The technology exists for a trijet with the same capacity as the 747-8.

Take the engines from the 77W, make the fuselage 20 feet longer and a couple inches wider than the 779. This will allow comfortable ten-abreast seating. Add a third engine in the tail and you have a 748 trijet with even longer range. This could cover the very top of the market for 35 years. After that, the technology might exist for a 748 twinjet with 9000 miles nautical range.

A trijet could serve as a stopgap for the VLA market, offering even greater range than the 779.

One day after we are all gone, there may be a twinjet that can fly 500 passengers in four classes, against headwinds halfway around the world from a hot and high airport. The engine technology simply does not exist at this time.


You have no concept of how difficult that design would be. Entirely different airframe, mounting any of the 777x engines, let alone keeping it in balance, would be, hopefully, impossible.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 5:03 pm

I posted ideas about an A380 successor a long time ago (when folks were still deluded that the A380 was a good airplane). viewtopic.php?t=776333#p19165661

The talk of tri-jets is unnecessary. From the fundamentals of drag you should be able to see that a twin VLA (>450 seats) is very doable at late 2020's tech levels. viewtopic.php?f=5&t=776333&start=50#p19187833

But there's arguably no point in seeking a twin. The advantages of a twin are less important at VLA scale; a quad layout with two big engines that would do most of the cruise and two smaller for the takeoff and climb constraints could be more advantageous:

-Shorter vertical stabilizer
-Optimization of the two engines for their respective roles (cruise vs. climb/TO)
-Lower overall thrust due to more thrust with OEI at V2
-Combining the shorter Vstab and lower overall thrust, you get less weight and drag, which means less OEW, which means less fuel lifted for a given range, which means less OEW/drag/engines/Vstab... Run that loop...

IMJ there is a market for a double-decker of what would be 500 seats in today's OEM capacity schemes. Problem is that for Boeing to build it would kill the 777X and for Airbus to build it so soon after the A380 would be pretty humiliating and would face a lot of resistance from investors initially. Hopefully those dynamics are eventually overcome, especially as the 777X may end being a real dud.
 
GalaxyFlyer
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Re: Future VLA Market?

Mon Jan 13, 2020 5:07 pm

You need to study Part 25 and AC 25-7 to realize a quad designed that way doesn’t work. Failure of one of the big engines at V1 needs to be accounted for and that probably won’t work.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 5:11 pm

GalaxyFlyer wrote:
You need to study Part 25 and AC 25-7 to realize a quad designed that way doesn’t work. Failure of one of the big engines at V1 needs to be accounted for and that probably won’t work.


You need to read the thread before assuming I didn't account for failure of one of the big engines. It's explicitly in there.

Plus the following is simply obvious: Failure of a "big" engine on a quad is less deleterious of thrust than failure of a "big" engine on a twin. That's true regardless of the ratio of thrust between big and small engines.

I know it feels good and smart to cite a specific regulatory provision but before doing so, maybe check your fundamentals and common sense.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 5:18 pm

LH707330 wrote:
If another VLA gets built, it'll likely be a quad for reasons mentioned above: cheap engines to share with a twin, and better ground clearance, etc. A quad is a better layout than a trijet.


This is definitely one possibility.
Depending on the size of the VLA, however, another possibility is sharing engines with both NB's and a twin-aisle widebody. RR has done (/is doing) working on putting Ultrafan on both NMA and A350, for example. The smaller engine will be more optimized for shorter cycles - i.e. for the stress of TO/climb - while the larger will be more optimized for cruise. The smaller engine could be "thrust bumped" for TO/Climb with lower impact on the plane's cruise efficiency. A quad with both engines could take the best of both those worlds.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 5:30 pm

patrickjp93 wrote:
Given the prospects of another 1 billion annual fliers in the air yearly by the mid 2030s, do we still have room for birds bigger than the 777-9 while the economics of direct lesser hub flight are also changing?


Under current trends, I doubt we'll have much room for birds as big as the 777-9, including the 777-9. Because the 777-9's economics aren't much better than smaller planes that have greater flexibility and higher RASM. That's why the 777-9 isn't exactly flying off the shelfs (or flying at all).

The long-range NB's are going to eat into twin-aisle market share to an increasing extent, even absent the NMA. A321XLR covers most of TATL, which is the world's largest long-haul market and will remain so even in 2035 per A/B market outlooks.

That's going to challenge the long-term trend of >10hr market fragmentation. Why? Because EVERY long haul route relies on transfer pax and the NB's are going to start drawing those away.

Given that dynamic, I could see the 2030's market being split between NB's (<10hr routes), VLA's (>10hrs and shorter, thick routes), and E-planes for short haul between more convenient airports.

For my predicted dynamic to work, however, A/B/China will have to produce a new VLA with outstanding economics. Is such a plane possible? Yes, the fundamentals of a double-deck airplane dictate far better efficiency than for a single deck (except for the A380, but that was a terrible plane terribly executed).
 
blacksoviet
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Re: Future VLA Market?

Mon Jan 13, 2020 5:42 pm

GalaxyFlyer wrote:
blacksoviet wrote:
The technology exists for a trijet with the same capacity as the 747-8.

Take the engines from the 77W, make the fuselage 20 feet longer and a couple inches wider than the 779. This will allow comfortable ten-abreast seating. Add a third engine in the tail and you have a 748 trijet with even longer range. This could cover the very top of the market for 35 years. After that, the technology might exist for a 748 twinjet with 9000 miles nautical range.

A trijet could serve as a stopgap for the VLA market, offering even greater range than the 779.

One day after we are all gone, there may be a twinjet that can fly 500 passengers in four classes, against headwinds halfway around the world from a hot and high airport. The engine technology simply does not exist at this time.


You have no concept of how difficult that design would be. Entirely different airframe, mounting any of the 777x engines, let alone keeping it in balance, would be, hopefully, impossible.

I am not talking about a twin 747. I am talking about a twinjet with an airframe that has the same capacity as the 748. It would probably be a wide single decker. I don’t know if a hump would affect tail engine performance.
 
patrickjp93
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Re: Future VLA Market?

Mon Jan 13, 2020 6:12 pm

Matt6461 wrote:
patrickjp93 wrote:
Given the prospects of another 1 billion annual fliers in the air yearly by the mid 2030s, do we still have room for birds bigger than the 777-9 while the economics of direct lesser hub flight are also changing?


Under current trends, I doubt we'll have much room for birds as big as the 777-9, including the 777-9. Because the 777-9's economics aren't much better than smaller planes that have greater flexibility and higher RASM. That's why the 777-9 isn't exactly flying off the shelfs (or flying at all).

The long-range NB's are going to eat into twin-aisle market share to an increasing extent, even absent the NMA. A321XLR covers most of TATL, which is the world's largest long-haul market and will remain so even in 2035 per A/B market outlooks.

That's going to challenge the long-term trend of >10hr market fragmentation. Why? Because EVERY long haul route relies on transfer pax and the NB's are going to start drawing those away.

Given that dynamic, I could see the 2030's market being split between NB's (<10hr routes), VLA's (>10hrs and shorter, thick routes), and E-planes for short haul between more convenient airports.

For my predicted dynamic to work, however, A/B/China will have to produce a new VLA with outstanding economics. Is such a plane possible? Yes, the fundamentals of a double-deck airplane dictate far better efficiency than for a single deck (except for the A380, but that was a terrible plane terribly executed).

I'd argue the 777X isn't selling like hot cakes yet for a few reasons besides the ones you mentioned.
  • 737 MAX brings to light culture problems at Boeing that may have tainted the 777X as well, so airlines will wait and see how it goes with Emirates and Singapore
  • The 777-300ERs around the world are still fairly young and not yet in need of replacement
  • The 747-8I still has another decade plus of service before any will be replaced outright (loss of load factor and use doesn't count)
  • Emirates and Singapore will sell off their young fleets when the 777X arrives, so other airlines can replace older with newer without introducing a new type
  • The A350-1000 is excellent competition if you don't need 400+ seats

Now, as for narrowbodies over the Atlantic between America and Europe, sure, but not over the Pacific, and certainly not America-Africa or America-Asia other than MAYBE Russia. And trunk routes like EWR-FRA are going to be A350s and 747s or larger forever. And again, slot restriction is a looming problem for more and more European airports. Amsterdam has no slots left. CDG only has 30 some left to sell. LHR won't have any for another 7 years. Gatwick has another 30. Luton has plenty, but no demand for the airport. Madrid and Lisbon are okay, but demand for those two isn't increasing as fast as the rest of Europe, and without 5th freedom rights, you're not going to get traffic from the US3 or Air Canada in there, meanwhile no one's particularly excited to fly TAP or Iberia.

As India and China continue to develop and travel increases from those markets, Europe's going to be in a big bind with no slots, so some of the TATL narrow bodies will have to quit their day job to make room, which will funnel more people to the hubs, which means very full A350, 747, and 777X flights. When the A380s retire from Lufthansa, Air France, and British, there'll be a pretty heavy squeeze at exactly the wrong time imho.
Last edited by patrickjp93 on Mon Jan 13, 2020 6:22 pm, edited 1 time in total.
 
patrickjp93
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Re: Future VLA Market?

Mon Jan 13, 2020 6:20 pm

Matt6461 wrote:
patrickjp93 wrote:
Given the prospects of another 1 billion annual fliers in the air yearly by the mid 2030s, do we still have room for birds bigger than the 777-9 while the economics of direct lesser hub flight are also changing?


Under current trends, I doubt we'll have much room for birds as big as the 777-9, including the 777-9. Because the 777-9's economics aren't much better than smaller planes that have greater flexibility and higher RASM. That's why the 777-9 isn't exactly flying off the shelfs (or flying at all).

The long-range NB's are going to eat into twin-aisle market share to an increasing extent, even absent the NMA. A321XLR covers most of TATL, which is the world's largest long-haul market and will remain so even in 2035 per A/B market outlooks.

That's going to challenge the long-term trend of >10hr market fragmentation. Why? Because EVERY long haul route relies on transfer pax and the NB's are going to start drawing those away.

Given that dynamic, I could see the 2030's market being split between NB's (<10hr routes), VLA's (>10hrs and shorter, thick routes), and E-planes for short haul between more convenient airports.

For my predicted dynamic to work, however, A/B/China will have to produce a new VLA with outstanding economics. Is such a plane possible? Yes, the fundamentals of a double-deck airplane dictate far better efficiency than for a single deck (except for the A380, but that was a terrible plane terribly executed).


I mean in terms of aerodynamics, the double-decker is less efficient at the same passenger load (you get higher drag/length and less lift/length). But in terms of OEW and MTOW, maybe it's worth it? The E-sized jets pretty much max out at the proposed 777-10 length, so unless there are a lot of F-sized gates out there waiting to be filled by a 777-12 or w/e, I think the 777-10 is probably going to be the largest single-decker ever made. I suppose you COULD do a whole new plane just to fit 11 abreast at 3-5-3 or even 12 at 3-6-3 seating, but would anyone want to fly in it? I guess the 10-abreast A350 proves people will, but for a decent experience on a flag carrier?...
1.2*450 = 540 in a 2-class config, so I guess you could even make a Size E twin-jet VLA with that high of a capacity, but I think that would require 120,000lb. thrust engines, much longer folding wingtips, and a MUCH more efficient engine than the GE9X to pull off.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 7:01 pm

Patrickjp93 wrote:
in terms of aerodynamics, the double-decker is less efficient at the same passenger load (you get higher drag/length and less lift/length)


No. I really honestly don't mean any offense by this, I mean this only in the spirit of information, but you're ignoring the basics of aerodynamics.
What causes drag? For airliners, ~70% of drag is determined by surface area.
A double-deck fuselage can give you ~twice the seats per unit of fuselage length for ~25% more surface area per unit of fuselage length.
You can easily see this is the A380 vs. 777. Despite the objective fact that the A380 is a terrible design, its fuselage surface area is only ~17% greater for 50% more cabin area. http://i298.photobucket.com/albums/mm26 ... 1fb33c.jpg

I suppose you COULD do a whole new plane just to fit 11 abreast at 3-5-3 or even 12 at 3-6-3 seating


This would be monumentally stupid even if people wanted to fly in it. A 12ab plane would be ~25ft wide, meaning you can already fit two decks in it. There's some relatively small weight penalties for double deckers (e.g. floor beams have greater cantilevered span on UD, therefore heavier) but they're outbalanced by other factors.
For a given capacity, e.g., a double decker will be shorter than a single deck, which means lower bending moments in your fuselage. Those bending moments, meanwhile, are taken by a fuselage profile of greater height. Because resistance to bending ("moment of inertia") is proportional to the square of height, the fuselage is much lighter.

The problem is, of course, that a double-decker is impractical until you get to ~450 seats. The opportunity to develop such a plane will be once in a generation or rarer. We just happened to screw up our shot at it with the A380.

but I think that would require 120,000lb. thrust engines, much longer folding wingtips, and a MUCH more efficient engine than the GE9X to pull off.


Based on what though? How are you confident that it would require ~20% more than 777X? No offense but that output seems to stem more from an intuition about plane and engine sizes than from the fundamentals of drag at takeoff/climb, which I examine in one of the posts I linked upthread.
 
WPvsMW
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Re: Future VLA Market?

Mon Jan 13, 2020 7:08 pm

LCCs and ULCCs would love the 3-6-3 density, but don't have the networks or financial clout to be a launch customer, and without a launch customer A or B won't design the frame.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 7:18 pm

Patrickjp93 wrote:
I'd argue the 777X isn't selling like hot cakes yet for a few reasons besides the ones you mentioned.
737 MAX brings to light culture problems at Boeing that may have tainted the 777X as well, so airlines will wait and see how it goes with Emirates and Singapore
The 777-300ERs around the world are still fairly young and not yet in need of replacement
The 747-8I still has another decade plus of service before any will be replaced outright (loss of load factor and use doesn't count)
Emirates and Singapore will sell off their young fleets when the 777X arrives, so other airlines can replace older with newer without introducing a new type
The A350-1000 is excellent competition if you don't need 400+ seats


We have completely different mental frames.
You appear to believe that airlines ask "what 350/400-seater should I buy to replace my 350-seater?"
I believe airlines ask "what plane should I buy to maximize profit, given the flows of my home market and reasonably foreseeable transfer flows through my home market?"
If you think as I do - as I believe airlines actually do - then there's no mental box for size categories into which you slot plane purchases.
The facts of the world, I believe, show me right: many 777's are being replaced by 787's and will be replaced by NB's. EK is replacing A380's with twin-aisles. The market as a whole is replacing airlines that run the largest planes with airlines that run NB's.

The 747-8i is, btw, a non-entity in this conversation.

One of the critical insights, IMO, is that size is ALWAYS* a drawback.
*except in cases of extreme slot congestion.
Size implies lower RASM because modern revenue management systems (heck even non-modern ones) board the most high-paying passengers, leaving the rest "outbid." If you want to increase capacity/size, you have take on lower-yielding pax.

Size can be a justified drawback if sufficient economies of scale attend it.
For the 777-9, that condition appears not to hold: it has ~5% CASM advantage over A359 or B789. For most routes, the yield curve is sufficiently steep that incremental cost of the 777-9 exceeds incremental revenue. Were the 777-9 more efficient, that might not be true.
Last edited by Matt6461 on Mon Jan 13, 2020 7:37 pm, edited 1 time in total.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 7:35 pm

patrickjp93 wrote:
When the A380s retire from Lufthansa, Air France, and British, there'll be a pretty heavy squeeze at exactly the wrong time imho.


You need to do a little - at least SOME - numerical analysis on this.

Take FRA:
  • Per Wikipedia, it has ~1,400 movements/day.
  • LH bases 8 A380's there, IIRC.
  • Assuming each A380 makes slightly less than 2 movements/day at FRA, A380's account for 1% of FRA's traffic.
  • If LH replaced A380's with 789's, say the total movements doubles for given pax load: +1% traffic delta.

Is 1% delta to traffic going to tank the airfield?
I'm not going to pretend it's nothing but, given the massive benefits to LH of doubling frequency or expanding longhaul destinations served, LH could easily and profitably use 789's instead of A380's.

A critical insight is that large-scale longhaul traffic is a tiny fraction of airport traffic. Congestion is largely a matter of shorthaul, which encompasses most of the miles traveled, an even larger portion of trips taken, and larger yet portion of flights.

Don't buy Airbus' congestion rationale for the A380. That was a transparently stupid argument when the plane was launched and, given how badly the plane failed, it shouldn't even be considered nowadays.
 
GalaxyFlyer
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Re: Future VLA Market?

Mon Jan 13, 2020 7:50 pm

Matt6461 wrote:
GalaxyFlyer wrote:
You need to study Part 25 and AC 25-7 to realize a quad designed that way doesn’t work. Failure of one of the big engines at V1 needs to be accounted for and that probably won’t work.


You need to read the thread before assuming I didn't account for failure of one of the big engines. It's explicitly in there.

Plus the following is simply obvious: Failure of a "big" engine on a quad is less deleterious of thrust than failure of a "big" engine on a twin. That's true regardless of the ratio of thrust between big and small engines.

I know it feels good and smart to cite a specific regulatory provision but before doing so, maybe check your fundamentals and common sense.


I don’t see anything explicitly addressing the OEI case where there exist two different engines on quad. Not saying it can’t be done, I’d just like to see the specifics. Hint: loss of an engine in a quad has a higher net climb gradient than a twin, so loss of one of the big engines will be an issue. Pray, an example of even a prototype of a design where their are two high thrust engines and two lower thrust ones. It’s never been done, so I’m guessing engineering at all the design centers have looked and passed.

Yes, I went thru the linked threads.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 8:43 pm

GalaxyFlyer wrote:
I don’t see anything explicitly addressing the OEI case where there exist two different engines on quad. Not saying it can’t be done, I’d just like to see the specifics. Hint: loss of an engine in a quad has a higher net climb gradient than a twin, so loss of one of the big engines will be an issue. Pray, an example of even a prototype of a design where their are two high thrust engines and two lower thrust ones. It’s never been done, so I’m guessing engineering at all the design centers have looked and passed.


You're right, it wasn't in that post.
The analytical framework is the same as discussed in that post. It's just a matter of losing ~35% of thrust from failure of one big engine rather than 50% of the thrust as on a twin. Except, of course, that the climb gradient has to be 3% (if you scroll through my posting history you'll see that I'm very familiar with the regulatory climb gradients for twins/quads, btw).

It's an error to assume that an engineering department could properly resolve this issue. It'd be an economic analysis of the aerostructural benefits versus the logistical issues arising from two engine types. You'd need the accounting department at the very least to resolve the question but you'd need the strategic thinkers in the C-suites to dream it up before either engineers or accounts got to work. I'm not certain that occurred in any of the recent programs - are you? It wasn't an option for A380, as the -F and -900 needed four big engines. Wasn't an option for 747, as its engines were already as big as possible.
 
patrickjp93
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Re: Future VLA Market?

Mon Jan 13, 2020 9:31 pm

Matt6461 wrote:
Patrickjp93 wrote:
in terms of aerodynamics, the double-decker is less efficient at the same passenger load (you get higher drag/length and less lift/length)


No. I really honestly don't mean any offense by this, I mean this only in the spirit of information, but you're ignoring the basics of aerodynamics.
What causes drag? For airliners, ~70% of drag is determined by surface area.
A double-deck fuselage can give you ~twice the seats per unit of fuselage length for ~25% more surface area per unit of fuselage length.
You can easily see this is the A380 vs. 777. Despite the objective fact that the A380 is a terrible design, its fuselage surface area is only ~17% greater for 50% more cabin area. http://i298.photobucket.com/albums/mm26 ... 1fb33c.jpg

I suppose you COULD do a whole new plane just to fit 11 abreast at 3-5-3 or even 12 at 3-6-3 seating


This would be monumentally stupid even if people wanted to fly in it. A 12ab plane would be ~25ft wide, meaning you can already fit two decks in it. There's some relatively small weight penalties for double deckers (e.g. floor beams have greater cantilevered span on UD, therefore heavier) but they're outbalanced by other factors.
For a given capacity, e.g., a double decker will be shorter than a single deck, which means lower bending moments in your fuselage. Those bending moments, meanwhile, are taken by a fuselage profile of greater height. Because resistance to bending ("moment of inertia") is proportional to the square of height, the fuselage is much lighter.

The problem is, of course, that a double-decker is impractical until you get to ~450 seats. The opportunity to develop such a plane will be once in a generation or rarer. We just happened to screw up our shot at it with the A380.

but I think that would require 120,000lb. thrust engines, much longer folding wingtips, and a MUCH more efficient engine than the GE9X to pull off.


Based on what though? How are you confident that it would require ~20% more than 777X? No offense but that output seems to stem more from an intuition about plane and engine sizes than from the fundamentals of drag at takeoff/climb, which I examine in one of the posts I linked upthread.

Uh, no, the part that produces (most of the) drag is the cross-section, not surface area, and the cross section is about 35% larger than the 777X, not to mention the wings' cross section also matters here. Also, the wider fuselage also produces more lift from below as well, especially if it's ovoid rather than round. So there's more going on here than just total surface area per passenger. Also, using the 777X as the base design with the wall sculpting, it seems to me you can fit 12ab at 17.4" per seat in just 22.5 feet.

Yes, bending moments would be the big problem and would have weight costs associated with any mitigation, for sure. That's partly why I think a shrunken A380 concept would perhaps show well. The A380-800 can fit 814 in all-economy configuration, and the A380 Plus could fit almost 900. Let's scale that back to 600 with 2 full-length decks. You can probably fit that into an E gate with the right wing design.

Now, as for the thrust requirements, it IS a fair amount of guess work, but...

Going down to 2 engines reduces total weight from engines and plumbing. Take every ounce saved out of MTOW. Going to all-composite construction should take out another 15% of the A380's weight. You may also reduce the fuel tank volume since you're already burning 25% less fuel on the same trips before the engine improvements (which was a quote from I believe Alan Joyce explaining the fuel economics of the 787-9 vs. the 747-8I as the replacement for the 747-400ER), and no one needs to fly 600 people all at once from Aukland to London. So all of that weight removed too. Given we've dropped close to 1/5 of the weight of the jet, we can remove 1/5 of the thrust, which is around 64,500lbs of thrust using the average of the Trent 900 variants and the Engine Alliance GP7000.

So 81,500 * 4 = 326,000

326,000-64,500 = 261,500. That's not quite 240,000, but the A380 doesn't take as much runway length as the 787-10. So we can potentially reduce thrust by 4% and eat the difference in runway length. So subtract another 16,300lbs of thrust and we're at 245,200, or 122,600 lbs of thrust per engine. The remaining difference can likely be compensated for with improvements to aerofoil design, such as the A350 wing twist, not to mention folding wingtips to expand the span. I think 2*120,000lbs of thrust could work for an A380 redux if every ounce of weight that can be saved is.
 
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 9:42 pm

patrickjp93 wrote:
Uh, no, the part that produces (most of the) drag is the cross-section, not surface area, and the cross section is about 35% larger than the 777X, not to mention the wings' cross section also matters here. Also, the wider fuselage also produces more lift from below as well, especially if it's ovoid rather than round.


You are completely mistaken. My experience has been that folks tend to dig in when told they don't know the first thing about aerodynamics, so I won't put much effort in. Consider whether you googled a drag approximation for automobiles - cross-sectional comparison works somewhat there.

Otherwise I recommend you buy an aerodynamics textbook and/or start with this helpful series:

https://leehamnews.com/2014/11/04/funda ... ce-part-1/

We start with the drag which is independent of lift as this is the major cause of drag at cruise. There is one dominant cause of this type of drag, the air’s friction against the aircraft’s surface. When the aircraft flies through the air at high speed, in this case M 0.78 or 450 knots, it creates friction between the aircrafts skin and the air molecules which surrounds the aircraft. The level of friction is decided by the aircraft’s size and the smoothness of its skin. In the case of our 737 MAX8, the friction forces are in the order of 3.700 lbf out of a total value for drag independent of lift of 5,000 lbf. The main contributing areas of the MAX is shown in Figure 3.


Image

As you can see, the relevant index is "wetted area" (=surface area), not cross-sectional area.

Please just learn the basics and don't make the mistake of digging in. There's no shame in not knowing aerodynamics. Most people who have been posting here for years are completely ignorant on the topic.

If you're willing to learn, I'll explain why fuselage lift is not something to seek either.
 
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Re: Future VLA Market?

Mon Jan 13, 2020 10:09 pm

Matt6461 wrote:
patrickjp93 wrote:
Uh, no, the part that produces (most of the) drag is the cross-section, not surface area, and the cross section is about 35% larger than the 777X, not to mention the wings' cross section also matters here. Also, the wider fuselage also produces more lift from below as well, especially if it's ovoid rather than round.


You are completely mistaken. My experience has been that folks tend to dig in when told they don't know the first thing about aerodynamics, so I won't put much effort in. Consider whether you googled a drag approximation for automobiles - cross-sectional comparison works somewhat there.

Otherwise I recommend you buy an aerodynamics textbook and/or start with this helpful series:

https://leehamnews.com/2014/11/04/funda ... ce-part-1/

We start with the drag which is independent of lift as this is the major cause of drag at cruise. There is one dominant cause of this type of drag, the air’s friction against the aircraft’s surface. When the aircraft flies through the air at high speed, in this case M 0.78 or 450 knots, it creates friction between the aircrafts skin and the air molecules which surrounds the aircraft. The level of friction is decided by the aircraft’s size and the smoothness of its skin. In the case of our 737 MAX8, the friction forces are in the order of 3.700 lbf out of a total value for drag independent of lift of 5,000 lbf. The main contributing areas of the MAX is shown in Figure 3.


Image

As you can see, the relevant index is "wetted area" (=surface area), not cross-sectional area.

Please just learn the basics and don't make the mistake of digging in. There's no shame in not knowing aerodynamics. Most people who have been posting here for years are completely ignorant on the topic.

If you're willing to learn, I'll explain why fuselage lift is not something to seek either.


I took university level physics, including basic aerodynamics and aced it. That article is largely old hat from the days before we actually perfected laminar coatings. Also, NASA themselves would disagree with Leeham here.
https://www.grc.nasa.gov/www/k-12/airplane/drageq.html

Now, I am perfectly happy to learn why you don't want to chase after fuselage lift, but bear in mind you'll have to square that with the 797 and Aurora D8 design proposals, because have partly flattened lower surfaces on the fuselage to increase lift.
 
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Starlionblue
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Re: Future VLA Market?

Mon Jan 13, 2020 10:23 pm

I don't understand why you would need two different types of engines optimised for take-off and cruise respectively. Are the regimes really that different when it comes to RPM? Turbofans are running at 80-85% N1 in the cruise. The big change is mass flow.

GalaxyFlyer wrote:
Matt6461 wrote:
GalaxyFlyer wrote:
You need to study Part 25 and AC 25-7 to realize a quad designed that way doesn’t work. Failure of one of the big engines at V1 needs to be accounted for and that probably won’t work.


You need to read the thread before assuming I didn't account for failure of one of the big engines. It's explicitly in there.

Plus the following is simply obvious: Failure of a "big" engine on a quad is less deleterious of thrust than failure of a "big" engine on a twin. That's true regardless of the ratio of thrust between big and small engines.

I know it feels good and smart to cite a specific regulatory provision but before doing so, maybe check your fundamentals and common sense.


I don’t see anything explicitly addressing the OEI case where there exist two different engines on quad. Not saying it can’t be done, I’d just like to see the specifics. Hint: loss of an engine in a quad has a higher net climb gradient than a twin, so loss of one of the big engines will be an issue. Pray, an example of even a prototype of a design where their are two high thrust engines and two lower thrust ones. It’s never been done, so I’m guessing engineering at all the design centers have looked and passed.

Yes, I went thru the linked threads.


The only civilian design I can think of offhand with different types of engines is the Trident 3B with its tail-mounted small fourth engine.
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Matt6461
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Re: Future VLA Market?

Mon Jan 13, 2020 10:26 pm

patrickjp93 wrote:
I took university level physics, including basic aerodynamics and aced it. That article is largely old hat from the days before we actually perfected laminar coatings. Also, NASA themselves would disagree with Leeham here.
https://www.grc.nasa.gov/www/k-12/airplane/drageq.html


Ok genius. I could spend time explaining how wetted area would influence Cd if you choose the frontal area version of your NASA equation, such that both my concept and "NASA's" would give the same result, but I have better things to do with my time. If you want to believe that a 777-9 and 777-200 have largely the same drag (same frontal area, right?) then you do you.
 
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Re: Future VLA Market?

Mon Jan 13, 2020 10:42 pm

Starlionblue wrote:
I don't understand why you would need two different types of engines optimised for take-off and cruise respectively. Are the regimes really that different when it comes to RPM? Turbofans are running at 80-85% N1 in the cruise. The big change is mass flow.


The issue isn't RPM, it's factors like clearance control devices and other highly-sensitive and expensive components that are more extensively used on widebody engines than on NB's. The components are life-limited. For shorthaulers where fuel burn is ~30% of DOC, spending millions to eke out another % of SFC savings isn't worth it, as you'd lose more money buying and maintaining a more expensive engine than you'd save on fuel. For longhaulers, it is worth it.

While my proposal would envision using an NB engine on longhaul missions, that engine would be throttled back to the bottom of the "cruise bucket" (say 30% of max thrust) and thus would be burning comparatively little fuel, just as would the same NB engine if used as a normal NB engine.
 
LH707330
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Re: Future VLA Market?

Mon Jan 13, 2020 11:43 pm

I'm not convinced that a quad with two engine types is the right move. Airbus had three chances to try this design, first the 340, then 340NG, and finally the 380. In all cases, there were more powerful engines out there that they could have paired with a smaller set, yet they didn't. My guess is that practical considerations like maintenance, etc. kill the business case, even if the math were to work out a few % better.
 
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Matt6461
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Re: Future VLA Market?

Tue Jan 14, 2020 12:01 am

LH707330 wrote:
My guess is that practical considerations like maintenance, etc. kill the business case, even if the math were to work out a few % better.


I can totally see that being the case; I'm not convinced either. To be convinced, I'd need a squad of engineers, accountants, and management analysts, as would any CEO reviewing this proposal. I'm just putting up an idea whose detailed analysis I haven't seen analyzed elsewhere. I'd love to read about it if you've seen it analyzed elsewhere...

I can see several factors changing the calculus from the the '90's, if in fact such a proposal was seriously considered back then:

1. Power by the Hour contracts in today's marketplace make the maintenance of different types more manageable. An OEM could write a PBH contract for just the smaller engine or, more likely, tie such a PBH agreement into a marketing pitch for an airline's broader fleet that would, presumably, include many of the smaller engines mounted on NB's.
2. Technology burden, especially the economic preponderance of LLP's, has increased since the 90's. Whereas most maintenance used to be spent on labor, it's now spent on LLP's. Because this proposal involves a positive delta to labor mx expense and negative delta to LLP mx expense, the landscape may be different.

To know whether "maintenance etc." would outweigh the couple % performance benefit, we'd need to know something about the maintenance delta. Any idea on how to estimate that? Frankly I don't have such an idea, but I can't see it how it'd be huge. For four identical engines you need, say 20 mx personnel, for two pair of different engines, do you 25 personnel? Even if (1) the disparate pair is 10% lower in total thrust than would be the quadruplets and (2) the smaller engines are universal types like PW1100 or LEAP? I would expect the PW1100/LEAP mx expense being significantly lower, per lb-T, than the quadruplets. You have the LLP factor plus the sheer scale of NB engine mx infrastructure. That would mean you'd need a significant management/other delta for the administrative complexity added.

It's not like the OEM's are incapable of missing things or of making huge mistakes (see, e.g., MAX and A380).
 
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dennypayne
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Re: Future VLA Market?

Tue Jan 14, 2020 2:05 am

Matt6461 wrote:
To know whether "maintenance etc." would outweigh the couple % performance benefit, we'd need to know something about the maintenance delta. Any idea on how to estimate that? Frankly I don't have such an idea, but I can't see it how it'd be huge...<snip>... That would mean you'd need a significant management/other delta for the administrative complexity added.


I suspect the business case might hinge heavily on whether both of the disparate engines also had commonality with a given airline's existing powerplant mix. Certainly it would for an airline that does a lot of in-house work, but even for those that don't, the added complexity would seem to reduce the prospective customer list right off the bat (and thus provide less incentive for a manufacturer to pursue this design in the first place).



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WPvsMW
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Re: Future VLA Market?

Tue Jan 14, 2020 3:48 am

The Super 27 variant of the B727 had pod-mounted engines that differed from the #2 engine.
https://en.wikipedia.org/wiki/Boeing_727

I don't recall any other tri-jets in commercial service with a mixture of engine types.
Last edited by WPvsMW on Tue Jan 14, 2020 3:53 am, edited 1 time in total.
 
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Starlionblue
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Re: Future VLA Market?

Tue Jan 14, 2020 3:51 am

WPvsMW wrote:
The Super 27 variant of the B727 had pod-mounted engines that differed from the #2 engine.
https://en.wikipedia.org/wiki/Boeing_727

I don't recall any other tri-jets in commercial service with a mixture of engines.


The Trident 3B, though I suppose it was a 3½ jet at that point... :)

You can see the fourth engine above the third. The intake was on top of the centre intake, with a flap to close it when the engine was done after takeoff.

Image
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WPvsMW
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Re: Future VLA Market?

Tue Jan 14, 2020 3:55 am

Sb, would that a JATO configuration? ;)
http://heroicrelics.org/info/b-47/b-47-jato.html
 
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Starlionblue
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Re: Future VLA Market?

Tue Jan 14, 2020 5:14 am

WPvsMW wrote:
Sb, would that a JATO configuration? ;)
http://heroicrelics.org/info/b-47/b-47-jato.html


Those are some thick chemtrails :D

Here's Mexicana rocking it...

Image
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WPvsMW
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Re: Future VLA Market?

Tue Jan 14, 2020 6:04 am

At MEX, I presume.
I thought JATO was only on military a/c. A revelation.
The only control on JATO was ON and OFF... correct?
 
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Starlionblue
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Re: Future VLA Market?

Tue Jan 14, 2020 6:29 am

WPvsMW wrote:
At MEX, I presume.
I thought JATO was only on military a/c. A revelation.
The only control on JATO was ON and OFF... correct?


I think more like only "ON". AFAIK you could not turn them off. Just wait until they ran out of fuel. :D

Also emergency use only in case you lost an engine at takeoff. Good info in this video. https://youtu.be/G7LErwBNobU
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SAAFNAV
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Re: Future VLA Market?

Tue Jan 14, 2020 7:02 am

Matt6461 wrote:
patrickjp93 wrote:
Uh, no, the part that produces (most of the) drag is the cross-section, not surface area, and the cross section is about 35% larger than the 777X, not to mention the wings' cross section also matters here. Also, the wider fuselage also produces more lift from below as well, especially if it's ovoid rather than round.


You are completely mistaken. My experience has been that folks tend to dig in when told they don't know the first thing about aerodynamics, so I won't put much effort in. Consider whether you googled a drag approximation for automobiles - cross-sectional comparison works somewhat there.

Otherwise I recommend you buy an aerodynamics textbook and/or start with this helpful series:

https://leehamnews.com/2014/11/04/funda ... ce-part-1/

We start with the drag which is independent of lift as this is the major cause of drag at cruise. There is one dominant cause of this type of drag, the air’s friction against the aircraft’s surface. When the aircraft flies through the air at high speed, in this case M 0.78 or 450 knots, it creates friction between the aircrafts skin and the air molecules which surrounds the aircraft. The level of friction is decided by the aircraft’s size and the smoothness of its skin. In the case of our 737 MAX8, the friction forces are in the order of 3.700 lbf out of a total value for drag independent of lift of 5,000 lbf. The main contributing areas of the MAX is shown in Figure 3.


Image

As you can see, the relevant index is "wetted area" (=surface area), not cross-sectional area.

Please just learn the basics and don't make the mistake of digging in. There's no shame in not knowing aerodynamics. Most people who have been posting here for years are completely ignorant on the topic.

If you're willing to learn, I'll explain why fuselage lift is not something to seek either.


Wow. could you be any more condescending?
It's interesting to see that airlines are buying Boeing and Airbus products, but your ideas are floating around on A.net without any takers.

Why are you not the lead engineer at NASA or Boeing? Maybe you could educate them too.
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WPvsMW
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Re: Future VLA Market?

Tue Jan 14, 2020 7:26 am

Thanks. I know some "internal" JATO (vs. RATO) burned Jet A, so I assumed either JATO had separate fuel tanks or there was a fuel valve upstream.
 
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Re: Future VLA Market?

Tue Jan 14, 2020 11:38 am

Oh What a lovely thread!!!!

Starlionblue wrote:
If we see more VLAs, they will most likely be quads. The development cost for really large engines is very high, but the market is relatively small.
That seems fair, either a T1000 based or TXWB based quad, issue I see there is that to get an aircraft that is optimized and requires those thrust levels will have a monster of a wingspan and then nowhere to land.

Starlionblue wrote:
That being said, there's always that "just around the corner" flying wing. :)


I often wonder what will come first, the PAX BWB or viable nuclear fusion.

patrickjp93 wrote:
A trijet fixes most of the fuel economy issues without requiring ludicrous amounts of thrust per engine. Three XWB 97s could pull it off.
What are the fuel economy issues with the A380? My understanding is that the main issue was with the span wise loading giving a suboptimal induced drag at cruise allied to ver conservative engines that were also optimised more for reduced noise than fuel economy than would be standard. Not sure where the enormous redesign effort to remove an engine from the wing and place one in the tail accounting for the thrust paths and inherent structure, weight, balance, control, safety, type rating, training, certification.... changes required.

JayinKitsap wrote:
Going to bigger planes is essential, but the key is the AVERAGE size, not the size of the largest available plane.
absolutely, Hello A321/737-10

blacksoviet wrote:
The technology exists for a trijet with the same capacity as the 747-8.

Take the engines from the 77W, make the fuselage 20 feet longer and a couple inches wider than the 779. This will allow comfortable ten-abreast seating. Add a third engine in the tail and you have a 748 trijet with even longer range. This could cover the very top of the market for 35 years. After that, the technology might exist for a 748 twinjet with 9000 miles nautical range.
Its not lego! What you appear to be saying is "design a new plane".

blacksoviet wrote:
One day after we are all gone, there may be a twinjet that can fly 500 passengers in four classes, against headwinds halfway around the world from a hot and high airport. The engine technology simply does not exist at this time.
The technology exists, the reason we haven't done it is because its not necessary or an effective and efficient use of available resources.

Matt6461 wrote:
But there's arguably no point in seeking a twin. The advantages of a twin are less important at VLA scale; a quad layout with two big engines that would do most of the cruise and two smaller for the takeoff and climb constraints could be more advantageous:
Surely you would be just better off tailoring an engine for the aircraft mission profile than tailoring two for different parts...

patrickjp93 wrote:
I mean in terms of aerodynamics, the double-decker is less efficient at the same passenger load
The fuselage weight and surface area per passenger are significantly lower for the A380 than for a 777.

Matt6461 wrote:
The problem is, of course, that a double-decker is impractical until you get to ~450 seats.
Not sure of what the regs say about proximity of the pax cabin to the bottom of the aircraft but for some reason I have the idea of a 3-3/3-3 short haul double-decker stuck in my head...

patrickjp93 wrote:
Uh, no, the part that produces (most of the) drag is the cross-section, not surface area,
No, its the Surface area and to some extent the length for when the flow turn from laminar to turbulent, for practical purposes the length of a transport jets fuselage one can just assume its turbulent.

patrickjp93 wrote:
not to mention the wings' cross section also matters here.
If by wing cross section you means the profile then yes your are right, the t/c has a significant impact in terms of CLmax in the incompressible regime as well as the compressible regime, normally at odds with one-another.

patrickjp93 wrote:
Also, the wider fuselage also produces more lift from below as well
Maybe, but if you are getting appreciable lift from your fuselage then id suggest you've mounted wrong as its typically a bad place to get it from.

patrickjp93 wrote:
especially if it's ovoid rather than round.
I'm not sure what you mean, can you explain. Of course even if it was the case that an "ovoid" had those benefits you would still have to counter the increased weight in the floor and the increased weight required in the fuselage and the more limited length through bending moments at a lower height.

patrickjp93 wrote:
So there's more going on here than just total surface area per passenger.
There is, cross-sectional area not really being one of them.

patrickjp93 wrote:
Going down to 2 engines reduces total weight from engines and plumbing.
Does it? Surely the engines are bigger? and so are the pipes? and so are the mounts?

Matt6461 wrote:
don't make the mistake of digging in. There's no shame in not knowing aerodynamics. Most people who have been posting here for years are completely ignorant on the topic.
Learning is fun!

Matt6461 wrote:
Consider whether you googled a drag approximation for automobiles - cross-sectional comparison works somewhat there.
I would guess that the drag approximation for an automobile uses frontal area as the reference area, which of course you can do on an aircraft but then you'd have a world of difficulty trying to find relevant lift curve slopes and working out drag polars. You could do it for the fuselage and then convert it by the relevant factors when driving at aircraft level performance. Your best best bet is to do this if you are assessing the components individually for the build up method.

patrickjp93 wrote:
I took university level physics, including basic aerodynamics and aced it.
Really? I'm an engineer and have a masters in aerospace engineering with a specialty in experimental design and did my dissertation on wind tunnel testing of various profiles, it isn't cross section....

patrickjp93 wrote:
That article is largely old hat from the days before we actually perfected laminar coatings.
Cool, didn't know we had perfected them.

patrickjp93 wrote:
Also, NASA themselves would disagree with Leeham here.
https://www.grc.nasa.gov/www/k-12/airplane/drageq.html
I don't see any fundamental disagreements with the articles. You will note in the NASA page you used that the only mention of cross sectional area is as a reference area for the local fuselage drag coefficient, you can use any reference are you choose as it is only relevant to act as a consistent method to nondimensionalise.

patrickjp93 wrote:
but bear in mind you'll have to square that with the 797 and Aurora D8 design proposals, because have partly flattened lower surfaces on the fuselage to increase lift.
Wasn't aware that the 797 had been formalised, do you have a link?

Fred
Image
 
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lightsaber
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Re: Future VLA Market?

Tue Jan 14, 2020 2:17 pm

JayinKitsap wrote:
Going to bigger planes is essential, but the key is the AVERAGE size, not the size of the largest available plane.

This sums it up. Upgauging will occur. To others:

There is no economical 50-seat replacement. That category will go to the MRJ/E2. I like the idea of electrical aircraft, but until the globe can get off coal power, there isn't much benefit.

Most will be smaller planes growing. ORD and ATL will have to rationalize slot allocation (although ATL will grow, as will PHX, CLT, PHL, DEN, and SLC, so small cities will be served).

With growing range narrowbody range and (possibly) to he NMA, large widebodies will have to be more efficient.

Ironically, the A388 wasn't large enough. The main deck should have been 11-across and it should have been longer. The weight/space of the two stairs, elevators (people and carts), and added wiring/plumbing requires more scale for efficiency. It didn't help that the A388 was the last beer canned winged widebody (adds so much weight). Some better (crown, tail, or wasted stair space) crew rest was also required.

I think there will be BWB (flying wing) VLAs, but not for 15 years.

There is incredible growth in Asian airport capacity (China, India, Vietnam, and Indonesia) Those cities cannot support many VLAs. At crowded airports, larger aircraft will displace smaller, but mostly it will be RJs replaced by small narriwbodies (A220), hub bypass (LCC P2P or smaller longhaul bypassing crowded airports), or progressive upgauging.

For example, I hope most of the new capacity at LAX (taxiways will add 300 flights/day once new terminal space us built) is for thin service. VLA is for trunk routes. I want new TPAC destinations, new TATL destinations, but mostly direct flights or more direct flights to all the little cities I fly too (twice per week isn't enough, in particular as that is only Summer).

BWBs will be 3 or 4 engines due to the engine out characteristics of a no tail design. The next VLA must be far more efficient than smaller aircraft, the A380 wasn't enough more efficient.

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johns624
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Re: Future VLA Market?

Tue Jan 14, 2020 2:50 pm

I find it interesting that people keep starting threads about the next VLA and their reason is always "Asia". Yet, nowhere near the majority of combined A380/B748 production went to Mainland Asian country airlines. With Thai and Malaysian, they shouldn't have even gotten them. Like others have said, the key to solving congestion is to upgauge the smaller planes.
 
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Matt6461
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Re: Future VLA Market?

Tue Jan 14, 2020 3:14 pm

flipdewaf wrote:
patrickjp93 wrote:
So there's more going on here than just total surface area per passenger.


There is, cross-sectional area not really being one of them.


Thank you.

flipdewaf wrote:
I would guess that the drag approximation for an automobile uses frontal area as the reference area


You'rd being generous. There is a very well-known poster here (hint: fly) with whom I had a long argument on precisely this topic and, believe me, reference area wasn't even dreamed of in his philosophy.

For cars/trucks, they're in a Length/(Width*Height) domain in which the tradeoff between wetted area and Cdp for length increases cancel each other out (very roughly). With box-like forms, and ~2-3 fineness ratios, it seems the pressure gradients are so large they're as big as the friction component (just imagine gradients you'd see on a winged Range Rover at .85M). Even so, it's a very crude and unreliable metric for automobiles.

flipdewaf wrote:
Really? I'm an engineer and have a masters in aerospace engineering


But the other poster took a class that, in America, a fairly unremarkable "gifted" student can take at age 14 in most good high schools.

flipdewaf wrote:
Maybe, but if you are getting appreciable lift from your fuselage then id suggest you've mounted wrong as its typically a bad place to get it from.


So few people get this. Like one pretty easy solution to get more fuselage lift from all airliners would be to extend the wing's root chord along the whole fuse length. That would enable a thicker root section, and would support the fuse in static-maneuver bending stress, possibly making this revision weight-neutral. Now your whole fuselage is part of the wing reference area and is generating lift.

Why not do it? Because you've suddenly cut your aspect ratio at least in half and at least doubled lift-induced drag.
Folks act as if more lift is always better, regardless of the drag cost.

flipdewaf wrote:
Cool, didn't know we had perfected them.


You didn't hear? Then you also didn't hear that the coating was magically retrofitted on the 737-800 that Bjorn was analyzing in his article.

SAAFNAV wrote:
It's interesting to see that airlines are buying Boeing and Airbus products, but your ideas are floating around on A.net without any takers.


Never have I predicted that A/B would actually do what I've recommended. And I've explained why, for commercial reasons, it's not wise for them. Duopolies don't make socially-optimal investments.

There have been "takers" within the industry for my ideas, btw. NDA bars me from saying more.

lightsaber wrote:
ORD and ATL will have to rationalize slot allocation (although ATL will grow, as will PHX, CLT, PHL, DEN, and SLC, so small cities will be served).


Economists have had, for years, well-developed schemes for auctioning slots. The Bush admin even tried to implement it but industry lobbyists nixed that quickly. I'm not confident that a free-market society like the U.S. will ever implement a free-market economy in this domain. I could see an authoritarian society like China doing much better at using market incentives to allocate slots rationally. Politicians and regulators are for sale in our free market society, meaning no free market economy.
 
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keesje
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Re: Future VLA Market?

Tue Jan 14, 2020 4:07 pm

Matt6461 wrote:

You'rd being generous. There is a very well-known poster here (hint: fly) with whom I had a long argument on precisely this topic and, believe me, reference area wasn't even dreamed of in his philosophy.
..
But the other poster took a class that, in America, a fairly unremarkable "gifted" student can take at age 14 in most good high schools.


You have absolutely no idea :rotfl: but that doesn't matter, this is social media :bigthumbsup:
"Never mistake motion for action." Ernest Hemingway
 
patrickjp93
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Re: Future VLA Market?

Tue Jan 14, 2020 4:10 pm

johns624 wrote:
I find it interesting that people keep starting threads about the next VLA and their reason is always "Asia". Yet, nowhere near the majority of combined A380/B748 production went to Mainland Asian country airlines. With Thai and Malaysian, they shouldn't have even gotten them. Like others have said, the key to solving congestion is to upgauge the smaller planes.

given those regions are expanding passenger loads on long haul far faster than Singapore or the Middle East 3, there is a trend toward larger jets than the A321XLR and B787 being needed. The ONLY reason CX doesn't fly the A380 is their management could see the writing on the wall with no prospects for an A380 NEO and the 777X coming down the pipes. The government-controlled carriers will probably wait for the C919, but if that becomes untennable, their A350s are already packed to the gills, so the 777X can easily be justified for trunk routes like Beijing-NYC or TPE-LAX/SFO.
 
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Matt6461
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Re: Future VLA Market?

Tue Jan 14, 2020 5:03 pm

keesje wrote:
Matt6461 wrote:

You'rd being generous. There is a very well-known poster here (hint: fly) with whom I had a long argument on precisely this topic and, believe me, reference area wasn't even dreamed of in his philosophy.
..
But the other poster took a class that, in America, a fairly unremarkable "gifted" student can take at age 14 in most good high schools.


You have absolutely no idea :rotfl: but that doesn't matter, this is social media :bigthumbsup:


Social media doesn't forget:

Keesje wrote:
For aircaft and many other objects, the reference area is the projected frontal area of the vehicle (A).

viewtopic.php?f=5&t=1388729#p20242839

I'm glad that you don't mind looking ridiculously ignorant, as it's just social media. Otherwise I'd feel bad.
 
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keesje
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Re: Future VLA Market?

Tue Jan 14, 2020 5:23 pm

How many windtunnels have you seen from the inside or aircraft have you calculated induced, paracit drag for ..
"Never mistake motion for action." Ernest Hemingway
 
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Matt6461
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Re: Future VLA Market?

Tue Jan 14, 2020 5:36 pm

keesje wrote:
How many windtunnels have you seen from the inside or aircraft have you calculated induced, paracit drag for ..


How much wood could a woodchuck chuck?
 
patrickjp93
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Re: Future VLA Market?

Tue Jan 14, 2020 5:46 pm

keesje wrote:
How many windtunnels have you seen from the inside or aircraft have you calculated induced, paracit drag for ..

Not sure if that question was meant for me, but 1 and zero. Now, relevance to the thread topic?
 
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Matt6461
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Re: Future VLA Market?

Tue Jan 14, 2020 5:47 pm

patrickjp93 wrote:
given those regions are expanding passenger loads on long haul far faster than Singapore or the Middle East 3, there is a trend toward larger jets than the A321XLR and B787 being needed. .


Again you need the barest amount of quantitative analysis. Take PVG: Per wikipedia, ~146 pax/movement. So the average aircraft at PVG is 737-800 or A320-sized. Traffic needs to roughly triple - absent any airfield improvement - until the average aircraft needs to be 777-9 sized.

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