FWIW I think the "market analysis" used to justify the A380 launch was largely a case of the tail wagging the dog. Around 2000, the Airbus market forecast was for 2000 VLAs to be sold over the subsequent 20 years. Boeing's contemporaneous prediction was for 500 sales, and even their numbe...
Jump to postAlso, 4 engine would require strengthening of the wings thus made the wings larger and heavier. Which would add weight penalty to the overall weight of the aircraft. Thus reducing efficiency. Don’t the engines provide bending relief to the wings though? Exactly. A quad's wing will be lighter than a...
Jump to postYou asked me to determine at what point "upgauging" would be popular". This popularity is amongst real airlines and these real airlines have business models, which are fundamental to the decisions they make regarding aircraft acquisitions. I don't want to beat a dead horse, and I thi...
Jump to postI can't just say 10% lower costs treat that as a general rule and apply it across different airlines with different business models operating in very different market environments. First, I didn't say 10% lower costs; I said MCC rather than average cost of CASM is more relevant metric. 10% lower co...
Jump to postBlended wing concepts are coming... and could alter the concept of the cabin and the need for an upper deck for high capacity. Why exactly? I'll try not to sound too annoyed here but it does irk me that, on a site of supposed airliner enthusiasts, people can't be bothered to learn and/or to integra...
Jump to postThis example does not adequately reflect the reality of operating and purchasing an aircraft. CASM is an metric of the cost per seat. It does not adequately convey they value, nor revenue potential of that seat. A F seat is larger and heavier than a Y seat and it take up more space, yet it is sold ...
Jump to postI assume we DO remember that fragmentation is a real thing, and supposedly the ace in the hole for the 787? To speak of fragmentation as merely a thing, one that seems to operate for inscrutable reasons akin to the The Nothing , lets the A380 off the hook for its failure not to suck. Fragmentation ...
Jump to postDidn't Emirates reject the A380plus because it did not allow them to install the onboard product they wanted? EK didn’t like the A380plus because other than the winglets (which were honestly kind of slapped on and not fully tested/validated) there wasn’t any benefit for them. A majority of the A380...
Jump to postIs there technical description of EK's VLA proposal? Maybe something leaked somewhere online? IMJ 20-25% DOC improvement (vs. A380) for a mid-2030's VLA is very conservative. Clark and EK may lack insight into how suboptimal the A380 design was, given their enthusiasm for the plane. I imagine it &q...
Jump to postIs there technical description of EK's VLA proposal? Maybe something leaked somewhere online?
IMJ 20-25% DOC improvement (vs. A380) for a mid-2030's VLA is very conservative. Clark and EK may lack insight into how suboptimal the A380 design was, given their enthusiasm for the plane.
The A380-800 wasn't bad per se. It suffered from the 80x80m box limitation leading to less span and more chord than optimal, and an economic downturn which led to the cancellation of the -900. Bad timing overall. I spent a long time arguing about this a while back but yeah, the A380 was bad. I don'...
Jump to postWhen launching the 320neo, John Leahy said something to the effect of "you can get 20% spending 10B on a new frame, or you can get 15% on new engines spending 1B on a re-engine, so that's what we'll do and B will eventually follow." That's almost exactly what happened. These days it might...
Jump to postNote that the gravitational effect is quadratic while the "longer arc" effect is linear. So there remains a very small fuel savings effect.
Jump to postSkin friction drag is responsible for about 50% of the drag in cruise, it is a function of wetted area and characteristic lengths. Wetted area alone is not the perfect measure, as the major manufacturers are working on ways to increase wetted area while reducing skin friction drag through using lam...
Jump to postOver the years here I've had several discussions with folks obsessed with and/or involved in the aviation industry who seem not to understand the basics of what makes planes fly and create drag. One of the most vexing issues has been whether airliner drag is primarily a matter of frontal area (what ...
Jump to postHow long to get GE on the A350? GE9x's dry weight is ~2t greater than TXWB-97's. With nacelle and pylon weight it's probably a 6t OEW delta. Add in the delta to parasitic drag from the 9x's bigger nacelle and the A35K burns more fuel with the 9x than with the TXWB-97. GE could probably build a scal...
Jump to postOn the 779 another thing to consider on why it sells better than the a350-1000 is the engine maintenance cost of the XWB-97 and on-wing time, it’s not as good as carriers want it to be. That’s something QR has complained about, also another reason emirates does not want the -1000. What GE is offeri...
Jump to postGoogle 'Roll royce derated climb performance'. The pdf you find will answer all your questions. Thanks, the pdf is here: https://www.theairlinepilots.com/forumarchive/quickref/deratedclimbperformance.pdf. It definitively answers the question regarding ToC thrust - the derates wash out by then. The ...
Jump to postWhat are actual derate parameters? Something internal to engine like N1, fuel flow, temperature? Or engine actually gets altitude information and thrust is limited according to preprogrammed formula? On all Boeing non-737 models climb derates are a fixed percentage of full climb there. There are tw...
Jump to postI'm pretty sure that only applies to the dense air conditions where it gets the most strain. Higher up you want to allow higher settings because the engine is more thermodynamically efficient. That's what I'd have guessed but this... EG would a GE90-77 actually produce the same cruise thrust as a G...
Jump to postI'm wondering whether an engine derated for regional power - A330 Regional for instance - also has lower power at the top of its climb. Or does the derate only apply to absolute thrust values, which would only be relevant in denser air and lower speeds such as at takeoff. I would guess derate doesn'...
Jump to postI remember distinctly when I was doing my degree that the best first order guess for engine cost was to take the weight of the engine and if it was made of gold that's how much it cost. When someone quizzed him on more accurate methods the reply from a guy at RR was "People have tried, but gol...
Jump to postthe only things outside of the weeds of noise to estimate build cost is 1. Build rate, 2 Weight. Engine size relative to capacity can be a factor too as engines are much expensive, per pound, than airframes. Weight also has a non-linear relationship to cost - things like avionics and sensor/data sy...
Jump to postthe cabin areas are taken from this thread: viewtopic.php?t=769733 Ah ok, thanks. Ferpe (aka Bjorn Fehrm at Leeham) is a good source. That version of his floor areas, btw, applies rectangular arithmetic and doesn't adjust for nose/tail taper. This somewhat favors more stubby planes (eg 788) but the...
Jump to postCargo is taken account of by applying a fixed amount per ton/nm that is able to be taken. I hope you don't take these multiple replies in anything but the most constructive spirit. I appreciate what you're trying to do here, know it's not easy, am grateful you're doing. One other nitpick is your ca...
Jump to postI'm a bit suspicious of the extent of A321XLR's advantage here... Will wait for further explication. What's the A321NEO's cruise L/D? This seems very relevant to getting accurate figures from a Breguet equation. Per this article from Leeham , Max-8's cruise L/D is 17.9. From that figure, we can ext...
Jump to postdo you have an idea why anyone would order the 779X over the 350-1000? Either airlines are dumb or there's something about the model that makes the 779X appear unfavorably. Leeham's paywalled analysis, for example, shows a ~3% CASM advantage for 779 over A35K. One plausible source of discrepancy is...
Jump to postCan we at least see these parameters per plane?: ⋅ Trip cost ⋅ Cabin m2 (therefore assumed seat count) Cargo is taken account of by applying a fixed amount per ton/nm that is able to be taken. How is cargo taken into account? Do you apply the cargo revenue to offset trip cost and...
Jump to postTherefore, even if there was a monster plane that was ~20% more efficient per seat for trunk hub-2-hub routes (which won't ever exist), I highly doubt the overall trip journey was more fuel efficient if it introduced an extra stop. You'd need a magical invention - something that, for instance, cuts...
Jump to postBut I think most of the growth will come from secondary to secondary market and that’s where the A321LR is in a league of its own. Remember that direct flights have lowest total passenger cost. It’s almost always more expensive for an airline to fly a connection than direct. "Secondary to Seco...
Jump to post2 A321 disadvantages vs A330: * 4 engines less efficient than 2 * 4 cockpit crew flying is less efficient than 2 * 2 gates is less efficient than 1 * 2 landing fees is less efficient than 1 Isn't that all included in the CASM? CASM should have all flight costs, including crew, gate & landing co...
Jump to postIf you make it much wider than an A320 then tight 2 aisles become possible in the back with 737 Seating in 2-3-2 Y and then you can make a really nice 2x2x2 Y+, Y+ seems to be gaining a lot of traction. So left field question - what about a dual aisle design, 2-2-2 for premium but 3-3 in the back w...
Jump to postFor comparisons sake lets say the express cargo revenue is billed out at half that of a passenger. That 12t of extra payload is then equivalent to 60 additional paying passengers. Rates for FRA to USA are usually <$3/kg (higher right now but declining back to fundamentals). So your 12t is worth ~$3...
Jump to postGuys... Trip Cost Per-Seat Cost Two concepts whose assimilation would remove 99% of the confusion in this thread. Don't forget cargo volume cost. Wide-bodies have the edge in that arena but it's not black and white. Not sure what you mean exactly. Dividing trip cost by #seats gives you per-seat cos...
Jump to postIt's funny and fitting that this happened after the A380's demise. 747-8i was a bad idea but Long Live the Queen!
Jump to postThe small wing will be able to carry approximately 85t of cargo while the big wing will only be able to carry 75t of cargo. That's a big assumption. You've moved 10t from bending-relieving weight to bending-causing weight. You'd need to calculate the bending moment net of lower span. It could well ...
Jump to postThere are plenty of ways to reduce weight. I remember you mentioned in the tech ops working out the current 787-8 could operate without flaps. So a flap delete to save weight. I doubt Boeing has to optimise it that far. That was in context of keeping a "too large" wing though. With a Code...
Jump to postYou assume that airlines will buy the big wing 787-8 if the small wing 787-8 is not available but that is a false assumption. They will simply buy no aircraft at all for another decade and the older aircraft soldier on. That is lost revenue for Boeing. I was assuming they'd buy A321NEO or MAX-10 in...
Jump to postTechnically, the GE9x has the thrust record but its rated thrust is lower 110K vs 115K. It had to do with three of the big criteria test levels - one was RPM over speed, the second was fan diameter, can't remember the 3rd. https://www.geaviation.com/press-release/ge9x-engine-family/ge9x-breaks-guin...
Jump to postI can only surmise that Rolls-Royce seems to think that (very) large aircraft will have a market. They've started ground testing their gargantuan UltraFan, and the figures are mind-boggling. Compared to the next largest engine, the GE9x: GE9x fan Diameter: 136"... UltraFan Diameter: 140" ...
Jump to postI think the gate space and landing fee benefit fully justifies it. Also gate slots during peak periods airlines wouod be more likely to go from a narrowbody to a short haul optimised widebody. Think of a 500nm domestic flight the lightweight 787-8 would have nearly 10% lower total trip costs than a...
Jump to postSo intrigued with this idea I made a mathematical model of the 788 and shrunk the MTOW down to 200t and the wingspan down to 51.8m. I scaled the wing area with MTOW and did likewise with the engines and HTP. The OWE went down to 105t with an assumed max payload of 44t (440 max pax exit limit) and s...
Jump to postYour plane of reference is the aircraft interior Plain of reference... Nope - it's definitely "plane of reference". Yeah I'm an idiot. Only excuse is I think I got concussed playing rugby yesterday. Re gradual rotation into banks - maybe? Doesn't it seem likely, though, that in certain wi...
Jump to postYour plane of reference is the aircraft interior Plain of reference... As for Matt6461 and others - why is it so hard to imagine that a large BWB would just execute turns more gradually? When you need to turn you need to turn. Gradual turning could be mandated in some, but not all, situations. Fina...
Jump to postYou're missing the point... you don't notice height differences in metres when you're a couple of kilometres up! Yes you can, because you can see the height difference relative to passengers seated elsewhere in the cabin. The fact that you are a couple of kilometers up doesn’t matter, it depends on...
Jump to postYou're missing the point... you don't notice height differences in metres when you're a couple of kilometres up! Yes you can, because you can see the height difference relative to passengers seated elsewhere in the cabin. The fact that you are a couple of kilometers up doesn’t matter, it depends on...
Jump to postI think there's a good argument that A388 is far suboptimal but IMJ that mostly relates to the chosen cross section and capacity. Had Airbus chosen a smaller cross section (e.g. 8-6), it could have designed a much better plane at A388 capacity. Just curious, I remember you disclosing not having dov...
Jump to postany fanciful tech that can be applied to a VLA will find itself on the Gen2 re-engined/stretched/heavyweight variants of the A35x and the 78x families as well.. That's the crux of the issue for the article's argument based on new engines. But if there's something intrinsic to a VLA that makes them ...
Jump to postAlthough it makes no sense and probably wont ever happen, but I wish EK to be successful in convincing Airbus to create the longer bigger A380! Would be amazing! It makes tons tons of sense and should have happened already! I made that argument here: https://www.airliners.net/forum/viewtopic.php?t=...
Jump to postEngine math does not work this way. Feel free to provide your own math. Feel free to provide any quantitative analysis/argument - anything - backing up your point. Significant part of engine life cycle cost is overhaul cost. Retiring trent 900 right before overhaul interval means saving at least a ...
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