Moderators: richierich, ua900, PanAm_DC10, hOMSaR
JoergAtADN wrote:It doesn't require a new wing to reduce the drag percentage. If Airbus would stretch the A380, they could use a smaller empenage, which means less drag.
Matt6461 wrote:JoergAtADN wrote:It doesn't require a new wing to reduce the drag percentage. If Airbus would stretch the A380, they could use a smaller empenage, which means less drag.
Simply less drag per seat isn't the right question to ask.
Rather, you want to work backwards from the economics: what efficiency delta would justify the risk/capacity/efficiency tradeoff of a bigger A380?
IMJ you need to be at around 50% trip cost delta per capacity delta for a stretch to be widely popular (I base this off efficiency comparisons between bigger and smaller planes for ~equal range). That's 50% versus smaller competition (i.e. 777-9), not 50% versus A388. Pick your own efficiency target if you like.
Only once you've picked your efficiency target should you begin working backwards from there to investigate whether the technical/aero solution meets your target.
Can you achieve that kind of game-changing efficiency delta via a smaller empennage and slightly less fuselage drag per pax? Almost certainly not.
Matt6461 wrote:Bjorn/Ferpe also reiterates that the A380's drag composition is such that induced drag is 20% greater than parasitic. Last time I pointed this out I think SomebodyinTLS asked whether that could be True
SomebodyInTLS wrote:Matt6461 wrote:Bjorn/Ferpe also reiterates that the A380's drag composition is such that induced drag is 20% greater than parasitic. Last time I pointed this out I think SomebodyinTLS asked whether that could be True
Must have been someone else. Aerodynamics was literally my worst subject at uni - I'm left with a general understanding but I never pretend to know much about it.
VirginFlyer wrote:Matt6461 wrote:There's actually a similar thing happening with airliners. Most drag is related to size (parasitic) instead of weight (induced) for most airliners.
That's actually not true of the A380, however. The whale is quite efficient on size despite the big wing because its double-deck fuselage has only ~25% more wetted area than a 77W.
But the whale is quite heavy and compounds that problem with insufficient span - thus a lot of induced drag ( ~ lift ^ 2 / span ^ 2 )
I would find it incredibly surprising if in cruise parasite drag is not the greater source ofdrag. Induced drag reduces at a square of speed, while parasite drag increases at a square of speed. While you may be right (or you may not - I would want to see hard data here) that at a given speed in the cruising range an A380 would producd more induced drag when expressed as a percentage of parasite drag at that speed, compared to a 777, in both cases that percentage would be less than 100. Otherwise if what you are saying is correct, that in cruise induced drag is greater than parasite drag, then that means the aircraft is flying on theback (or left hand side) ofthedragcurve, and that would be rather surprising in itself.
mjoelnir wrote:I would say that Emirates has no hurry answering if they would order an A380 plus, they have still 47 A380 on order and we know that EK really wants a neo. Tom Enders mentioned a possible A380 order from China, perhaps the A380 + is aimed in that direction..
mjoelnir wrote:What else does matter than drag per seat? The only other thing that comes to mind are engines.
mjoelnir wrote:The point is, that most operators of the A380 did not go for a high seat density but rather comfort and prestige.
mjoelnir wrote:I agree that the A380 does not sell, but the problem is not CASM, but that it is to large for most airlines.
mjoelnir wrote:A situation I see coming for the 777-9 too.
VirginFlyer wrote:I think it may have been me
Revelation wrote:mjoelnir wrote:Revelation wrote:Indeed true, but after TXWB it seems on T7000 RR made a change that they had to back out late in the game, which meant a lot of costly re-testing, which also messed up the schedule. I raise this point not to denigrate RR (such things happen in development...), but to show that their spending has been greater than anticipated, which might explain why they decided against coming up with an engine for A380NEO. I don't know if it was known at the time, but we now know the last T900 PIP didn't go according to plan either, which presumably also meant more spending than intended.
I thought the T7000 followed corresponding changes and delays on the T1000ten, being a derivative of that engine, just with additional bleed and smaller power take off.
I can't remember where I read a more detailed story, but https://www.bloomberg.com/news/articles ... icing-snag says:Delays to the first flight of Airbus SE’s revamped A330neo jetliner stem from an unexpected requirement for extra testing of the model’s Rolls-Royce Holdings Plc engines, according to the planemaker.
... and my recollection is that this 'extra testing' came from a change they made late in the development cycle. Or I could be mixing things up. In any case, it's extra testing which adds extra costs and delays deliveries which delays revenues, which is the main point.
Rolls-Royce confirms that an upgraded version of the Trent 1000 engine for the Boeing 787 fleet will be delayed one year before entering service and reducing fuel burn levels to the originally promised standard.
Last year, R-R discovered that a new, cost-saving material used to make the banded stators in the compressor was not ready for operational service, so the company redesigned the component with a conventional metal, Moore says.
“That was a cost reduction opportunity and on the basis of the test results it didn’t work out as we thought it would,” he says. “We took time to fix that. Certification is an important milestone but what you want is a robust product and something the customer can use as an everyday, reliable machine.”
Moreover, fatigue testing on the Trent 1000-TEN revealed cracking in the intercase about one-third of the way through the 3,000h-cycle, Moore says. In that case, a pedestal attaching a solenoid to the intercase cracked under the pressure. After tearing down the engine, R-R discovered that the out-of-balance testing conditions had exceeded the design parameters, so the components were being shaken harder than the engine was expected to experience in service. R-R’s engineers have slightly lowered the pedestal to prevent cracking and the redesigned component should re-enter testing by July, Moore says.
KarelXWB wrote:This needs some explaining as well because it's pretty complicated.
mjoelnir wrote:But here usually the argument is different, the 777-9 is needed because of it´s size and the A380 is not needed because of it´s size.
dubaiamman243 wrote:Quote:
"Beyond the new tweaks, the health of the programme depends on getting costs low enough so that Airbus can keep output ticking over at 12 a year without losing money, while it waits for what it hopes will be a rise in demand as air travel grows."
Slug71 wrote:CFRP would lower cost.
It could use the diet too.
Might be a good time to work out the details for a freighter version again.
2175301 wrote:I think that the evidence is that the B777 is out competing the A380.
reidar76 wrote:
The EU should put some "light pressure" on the gulf carriers. If they don't order more A380s soon, they can expect a future where their access to EU airspace and airports will be severely limited. If they think that they can fly into EU with only 777s, think again.
Polot wrote:Slug71 wrote:CFRP would lower cost.
It could use the diet too.
Might be a good time to work out the details for a freighter version again.
CFRP would not lower costs for Airbus. CFRP is not cheap, and neither is redesigning parts to add it to the aircraft.
Slug71 wrote:Polot wrote:Slug71 wrote:CFRP would lower cost.
It could use the diet too.
Might be a good time to work out the details for a freighter version again.
CFRP would not lower costs for Airbus. CFRP is not cheap, and neither is redesigning parts to add it to the aircraft.
CFRP is cheaper to produce than GLARE. Besides the wing, there shouldn't be much redesign needed.
parapente wrote:The A380 was built too big.Not a little too big,way too big.Nothing you do to the aircraft alters that fact.
caoimhin wrote:reidar76 wrote:
The EU should put some "light pressure" on the gulf carriers. If they don't order more A380s soon, they can expect a future where their access to EU airspace and airports will be severely limited. If they think that they can fly into EU with only 777s, think again.
Surely this must be a joke.
IslandRob wrote:BTW, has ANY airline expressed interest in the A380 PLUS? -ir
Slug71 wrote:Disagree.
The size is fine. Many airports just spent billions to accommodate it.
par13del wrote:Slug71 wrote:Disagree.
The size is fine. Many airports just spent billions to accommodate it.
Hmmmm, Airbus is on record that airports that could accommodate the 747 could accept the A380 with minimal to no change, so for the billions you are talking about all airports combined that had to widen taxiways, right?
Egerton wrote:However, I do find it strange that the engine triumvirate have a business model involving initial heavy loss making over many years. This cannot continue.
Polot wrote:I don't think the fuselage size is the problem
Matt6461 wrote:Polot wrote:I don't think the fuselage size is the problem
The A380 has the most efficient fuselage ever built but it could be better for its capacity.
A few strategic decisions hampered fuselage efficiency:
- In selecting 650-seats as the optimal size, Airbus used a fuselage that was much taller than optimal - in order to provide sufficient stiffness for 80m+ stretch.
- Airbus optimized for identical-width 10ab and 8ab layouts for UD and MD. That created inefficiency whereby the broadest point is at eye-level on MD.
- Airbus designed room for pax amenities in the belly - completely unnecessary given the already reduced cargo capability.
- In general, fuselages are optimal at ~11 fineness, though maybe less for a 2-decker. A388 is <9 due to optimization for 650 seats. This means much larger fore and aft tapering sections, which are less efficient on weight and wetted area per pax.
- Related to the above, Airbus had to place the rear bulkhead ~47ft from fuselage tail end in order to accommodate the massive horizontal stabilizer and its activator. That figure is ~33 for the 777 and was shorter for the MD12. The Hstab is as big as the A310's wing so it needs a massive tailcone. Again, this suboptimal constraint derives from building a 650-seater at 2000 tech.
It isn't very difficult to imagine a 550-seat 2-deck fuselage with far less wetted area and weight than today's A388. Depending on your assumptions about side walls, an optimal 550-seat fuse should have 1350-1400m2 wetted area against the A388's 1564m2 (10-14% reduction).
For example, use a triple-bubble with the following main dimensions:
- MD bubble 269in (22'5")
- UD bubble of 231in (19'3")
- Belly bubble that cuts off the the MD bubble below the MD floor, limiting its size to LD3 depth.
- If we assume 7in sidewalls, the MD is wider 7in wider at armrests than A380, the UD has equal width
The perimeter of that design is equivalent to a 24.08ft circle - ~7% less than A380 (Estimated at 25.8 equivalent).
It is two feet shorter than A380 and one foot skinnier.
With perfect hindsight given A380's experience, we could design the UD and fuselage such that the UD is only expected to carry premium classes. That would reduce weight in UD floor beams and enable thinner/lighter MD sidewalls. Premium seats weigh ~100lbs more than economy but spaced at ~4x less dense the overall load is much lighter.
In addition, we'd want to shorten the empty tail cone and would be able to, given the much smaller empennage. If we pull equal to 777, that would add 14ft of cabin length for no wetted area cost (small cost in additional pressure structure). If we pull even to the MD12 it adds ~17ft of cabin length.
It would probably also be wise to center the nose cone higher to allow a longer upper deck with a smaller cockpit located up there a la 747. A380 likely didn't use this because it would have penalized cargo and nose landing gear - plus the marginal benefit for an 80m design would be quite low. It would be fairly significant for a shorter design, however.
All in, you could probably build such a fuselage for about the same wetted area as the 777-9 (1339m2) with at least 40% more capacity. Given CFRP construction and shorter bending moments, it would likely be significantly lighter. Extrapolate the rest of the plane from the thing you're lifting (fuselage+contents) and you could have lower trip fuel cost than the 777-9 given 2025 engine tech and an 80m wing.
That's the plane that seems possible with 2025 tech but we'll never see it as long as Airbus is shackled to the whale's bloated corpse.
350helmi wrote:To me this seams great on paper, but I fear that there would be too little cargo room left if it was a 'short' double decker
350helmi wrote:I would suggest making it a little slimmer than it is today so it has 10Y seating on MD, meaning only very slightly wider than the 777 fuse (and not almost 11Y) and also have the A330 fuse width on UD so all of the current wasted space would be eliminated.
350helmi wrote:all the extra stucture that is needed for the double decker design.
350helmi wrote:it would be getting close enough to the largest possible twins that it would be counterintuitive
PlanesNTrains wrote:Matt6461, I liked the discussion you were having here:
viewtopic.php?t=775819
The Ecoliner that Keesje proposed was a very attractive idea and I'd love to see something like that come down the pike.
Slug71 wrote:CFRP would lower cost.
It could use the diet too.
SomebodyInTLS wrote:Slug71 wrote:CFRP would lower cost.
It could use the diet too.
No it would not, and I doubt you would save much weight anyway.
Were you aware that two of the largest CFRP components flying are the A380 centre-wingbox and rear pressure bulkhead? There are composites all over the A380 already so these things have been considered. The current GLARE upper fuselage panels are an advanced composite so CFRP is unlikely to improve things much there.
Then add the massive redevelopment and manufacturing costs of changing over to CFRP and it's a totally dead duck.
Matt6461 wrote:The A380 has the most efficient fuselage ever built but it could be better for its capacity.
Matt6461 wrote:In selecting 650-seats as the optimal size, Airbus used a fuselage that was much taller than optimal - in order to provide sufficient stiffness for 80m+ stretch.
Matt6461 wrote:Airbus designed room for pax amenities in the belly - completely unnecessary given the already reduced cargo capability
Matt6461 wrote:In general, fuselages are optimal at ~11 fineness, though maybe less for a 2-decker. A388 is <9 due to optimization for 650 seats. This means much larger fore and aft tapering sections, which are less efficient on weight and wetted area per pax.
Matt6461 wrote:The Hstab is as big as the A310's wing so it needs a massive tailcone. Again, this suboptimal constraint derives from building a 650-seater at 2000 tech.
Matt6461 wrote:It isn't very difficult to imagine a 550-seat 2-deck fuselage with far less wetted area and weight than today's A388. Depending on your assumptions about side walls, an optimal 550-seat fuse should have 1350-1400m2 wetted area against the A388's 1564m2 (10-14% reduction).
Matt6461 wrote:With perfect hindsight given A380's experience, we could design the UD and fuselage such that the UD is only expected to carry premium classes. That would reduce weight in UD floor beams and enable thinner/lighter MD sidewalls. Premium seats weigh ~100lbs more than economy but spaced at ~4x less dense the overall load is much lighter.
Matt6461 wrote:It would probably also be wise to center the nose cone higher to allow a longer upper deck with a smaller cockpit located up there a la 747. A380 likely didn't use this because it would have penalized cargo and nose landing gear -
Matt6461 wrote:All in, you could probably build such a fuselage for about the same wetted area as the 777-9 (1339m2) with at least 40% more capacity. Given CFRP construction and shorter bending moments, it would likely be significantly lighter. Extrapolate the rest of the plane from the thing you're lifting (fuselage+contents) and you could have lower trip fuel cost than the 777-9 given 2025 engine tech and an 80m wing.
Matt6461 wrote:If that economic equation somehow changes, you just use some main deck space for cargo/bags. The fact that nobody (aside from a few KLM frames) uses combis should tell you that cargo isn't your first priority.
Matt6461 wrote:What extra structure? I already accounted for floor beams, furnishings/systems, and increased bending moments.
flipdewaf wrote:I'm going to apologise before I start typing this Matt, I promise that I'm not picking on you but you do generate some interesting points so I feel I should come and discuss them.
flipdewaf wrote:One of the driving factors for the belly depth was the wing root thickness, having a spar going right through the cabin a la jetstream 31 was probably frowned upon.
flipdewaf wrote:I'd go with airbus on this one, there probably isn't that much to save on the floor weight and to lose flexibility for the airlines and effectively telling them where they can put certain seats would be pushing it.
flipdewaf wrote:I think we need more details of how that was accounted for, have you accounted for the extra length of the nose and tail sections. There is a lot of " the weight would remain static when we add capability because CFRP" around a.net.
mjoelnir wrote:According to Leeham the proposed changes do bring the A380 level with the estimated CASM of the 777-9.
Matt6461 wrote:So here's a spreadsheet of my fuselage model:
Matt6461 wrote:It's not that its the details but that the level of detail is almost too great in a specific area whilst neglecting others. I know I might be repeating myself but the fact that the assumption of the floor being 8 inches vs 12 inches is as important than if people actually fit in it.... If you can it would be useful to drive the cabin width in your equations from width at shoulder level.If you get into the nitty-gritty, you'd probably quibble with a few details.
Matt6461 wrote:The drivers for getting a good fuselage weight estimation are height width and length. if it turns out that its a bending dominated fuselage (it probably isn't, this thing is taller than a T7 and less than 80m) then you need other parameters such as root chord length engine weight and a few others.Happy to help make things more clear if this isn't.
Matt6461 wrote:Agreed, the wing is far too big and creates issues even there.And for a clean sheet, this wouldn't be a problem. Wing will be much smaller and therefore thinner at equal t/c.
Matt6461 wrote:Nothing on that one sorryDo you have any particular insight, btw, on the effect of UD weight on the A380's very high sidewall thickness?
Matt6461 wrote:I like the "block coefficient" value but to do it properly we should understand what drives the block efficiency number (actual to useful floor area) if your model doesn't encompass this then we could easily have a scenario where we are out on useful cabin area by 10%.Take A380's cabin lengths * width and divide by floor area of 545m2 (per Ferpe). That gives me a ~93% "block coefficient" of actual cabin area compared to a simple LxW calc.
Matt6461 wrote:I would say the long tailcone is more to do with fuselage height than width, you should scale this with fuselage height.When I do this calculation, I assume that the shorter tailcone allows the cabin to reach within 33 of the tail,
flipdewaf wrote:Matt6461 wrote:Agreed, the wing is far too big and creates issues even there.And for a clean sheet, this wouldn't be a problem. Wing will be much smaller and therefore thinner at equal t/c.
flipdewaf wrote:Am I right in thinking you're overall width is 269inches and the height is 251inches?
flipdewaf wrote:If you can it would be useful to drive the cabin width in your equations from width at shoulder level.
flipdewaf wrote:I like the "block coefficient" value but to do it properly we should understand what drives the block efficiency number (actual to useful floor area) if your model doesn't encompass this then we could easily have a scenario where we are out on useful cabin area by 10%.
flipdewaf wrote:I would say the long tailcone is more to do with fuselage height than width, you should scale this with fuselage height.
Taxi645 wrote:flipdewaf wrote:Matt6461 wrote:Agreed, the wing is far too big and creates issues even there.And for a clean sheet, this wouldn't be a problem. Wing will be much smaller and therefore thinner at equal t/c.
When you guys say the wing is far too big, to what are you referring exactly? I am asking because the wingloading is not that low, so the wing area seems appropriate even for this (non-stretched) MTOW.