Pontifications: Advancing EIS for 777X

Special Edition of Pontifications

Advancing EIS of the 777X

Hamilton KING5_2

By Scott Hamilton

I’m somewhat bemused by all the fuss over the prospect of Boeing advancing the delivery of the 777X from early 2020 to late 2019. This has been the plan for more than a year. That’s what my sources have been telling me all this time.

It’s been the desire longer that that.

EIS in late 2019 was the original plan. When the Boeing Board of Directors gave the authority to offer the 777X for sale, the EIS was acknowledged to be late 2019. See our story from May 2, 2013.

Going to 2020 became the fall-back position. Take a look at this article on LNC from October 25, 2012. Even after early 2020 was firmed up as EIS, I continued to hear that Boeing would like to advance the EIS to late 2019. It was, like the 737 MAX, an effort to under-promise and over-deliver after years of delays on the 787 and 747-8 programs. (The MAX originally was announced as a late 2017 delivery date, later emerging as October. This was subsequently advanced to July, and market talk has been that a March EIS might be a new target.)

While some think these advanced dates are desired due to difficulties in bridging the production gap between the current generation airplanes and the new ones–which is probably true enough–the fact is, in both instances the earlier EIS dates were early desires in the program, not a response to gap concerns.


74 Comments on “Pontifications: Advancing EIS for 777X

  1. Slightly off topic: If the A350-8000 will indeed be designed to carry 40 more passengers than the 777-9, I’m coming around to the possibility of a one-and-a-half-deck design – instead of a super stretch (i.e. 82 – 85 m).

    A partial upper deck — with a single aisle cabin mounted on top of the current A350-1000 forward main deck cabin, should lead to a total fuselage height some 0.5 to 0.6 metres shorter than the fuselage height of the A380 (e.g. 8.41 m for the A380) — or about the same fuselage height as the forward fuselage of the 747.

    Thus, the nose section of a partial upper deck A350-8000 could look very similar in contour to the A380 nose section.

    I would put the staircase at doors 2 – just like on the 747 – but with 4 doors on the upper deck – instead of the 2 emergency exits that are available on the 747 upper deck. The aft upper deck doors would be at the top of the staircase, while the front doors would be in front of the cabin. The left forward door could be used for boarding.

    Incidentally, 0.6 metres is about how much the A380 flight deck is raised from the main deck. Hence, putting a partial single aisle upper deck on the A350, would mean that the relative position of the flight deck of a partial upper deck A350-8000 would remain the same — with respect to the lower fuselage — as the flight deck of the A350-900/-1000.

    If a partial upper deck A350-8000 would have about the same length forward fuselage as the A350-1000 — NB; slightly longer aft fuselage needed on the former due to balancing issues — then you’d have about 20 windows on each side of the upper deck’s single-aisle cabin. That would translate into about 90 extra economy class seats over that of the A350-1000 — i.e. with a seat pitch of 32″ — or about 40-45 more seats than the 777-9.

    The distinctive double-deck fuselage presented its own unique aerodynamic challenges, not least because no-one had ever to attempted to develop such a wide, blunt-nosed and ovoid cross-section of this scale before. “One of the design objectives was to maximise the width of the cabin, but minimise any ‘bad’ flow over the fuselage. There was a lot of work done in terms of optimising the flow around the doors and windows, and we have done well,” says Ogilvie, who adds: “There is virtually no supersonic flow over speeds up to Mach 0.89, and no shockwaves, which is really important.

    “Some of our customers want to belt along at M0.89, so we’ve deliberately gone out to make sure we’re shock free. We ended up playing tricks with the ovoid cross-section to get the flow to ‘go bad’ at M0.93. You have more ‘fatness’ up and down than you do in width, and the acceleration of the air from the nose is dependent on the curvature of the front fuselage. So we had to tailor the distribution of the curvature of the fuselage to maintain this acceleration,” he says. “We tried to make sure the velocity near the doors is as low as possible because the door areas can be susceptible to leaking and noise.”

    The nose shape was critical to not only helping achieve the correct aerodynamic flow lines, but also to helping obtain increased nose-up pitching moment. “After the mid-deck [cockpit location] was finalised in January 1998, we ended up with a shape that was flattened in planform with a more rounded look and less sharp curvature on the profile,” Ogilvie says. The mid-position also gave greater flexibility for the widest first-class cabin.


    • Engineer resources and money are the only impediment (well other than the fact the aircraft was not deigned for it in the first place and you would need an entirely new fuselage and wing.


    • It would have the same fuselage lower lobe throughout the entire aircraft, same single deck aft fuselage, same wing, same MLG, same cockpit and same empennage — as the A350-1000 — except, perhaps for a slightly taller vertical tail plane.

      I’d guess, though, that such an aircraft could be very well be named the A360-600…. 😉

      The bottom line, though, is that an A350-8000 carrying 40 more seats than the 777-9, would require either a super stretch exceeding 82 m in overall length, or a partial upper deck.

        • A generous 9 abreast I see. I’m suspicious, if this would work why didn’t Airbus do it? In particular, why the very thick sidewalls and upper floor?Probably for structural reasons, maybe this could be reduced with an all carbon tube. I also wonder if carbon might be a better material for very long tubes for aircraft such as the A350 8000 as it is supposedly underworked at the moment and more of the fibres can be orientated longitudinally.

          • @grubbie

            Yes, for structural reasons the A380 has thicker/deeper fuselage frames from just below the main deck to just above the upper deck – as is illustrated in one picture of the A380 fuselage in the link below.

            In order to minimise the depth of the fuselage frames in the forward fuselage of a partial upper deck A350-8000, you could increase the gauge (thickness) of the composite skin and use contoured frames that are less deep in the area of maximum fuselage diameter (i.e. at armerest level of the main cabin). That could be done in order not to decrease the width of the forward main cabin.


          • OV99:

            As stated previously by myself in allusion and one other poster in blunt terms, what you are doing is designing and all new aircraft requiring either all new engines or 4 engines costing at least 10 billion.

            Frankly with all the kludging you have going, it would cast vastly more than an all new aircraft.

            To use some US Southern vernacular, That Dog Don’t Hunt.

        • @Keesje

          Yes, very similar in concept, but your Ecoliner is, of course, a full double-decker. —

          One design challenge with a partial upper deck aircraft, is how you’d blend the upper deck hump onto the main fuselage, aft of the wing. On the 747, the upper deck “hump” is really part of a double bubble structure. It has a “flattened” structure in order to even out the contours of the circular main body and the upper deck. Hence, the side walls with the window belts are identical on the 747 constant diameter forward fuselage section and on the constant diameter aft cicrular fuslelage section, as well. On an A350-8000 with a forward partial upper deck – and even a partial upper deck dericvative of your 777-derived Ecoliner — the maximum diameter of the fuselage is at about the arm rest height of the main deck seats. Hence, the window belt on the main deck walls would be slighly different (i.e. more vertical) on the forward double deck section than on the aft fuselage section. However, a complex fuselage shape — such as the blending of an egg-shaped double decker forward fuselage with a single deck aft fuselage — should work out well for composite components with complex contours, as composites offer greater part-for-part consistency, compared to aluminium components that are subject to contour variations.

          In short, the blending of a non doubl- bubble, partial upper deck with the constant fuselage section of an A350-type fuselage, could perhaps partly be considered similar in scope to how you’d design a supersonic airliner with a variable cross-section.


          • @ov-099
            Great picture, how do they persuade us to cram ourselves into a flimsy aluminium tube like that?!

          • @grubbie

            The single aisle upper deck on a partial upper deck A350-8000 would have a constant diameter. In fact, it should have the same (constant) cabin width as the A320.

            What you’re seeing in the picture above is vaiable cross section. That’s not really what I’m talking about. What I am talking about is how you’d blend the egg-shaped forward double deck section with the current aft fusleage of the A350. The side walls (i.e. above armrest height on the main deck) and crown of the double deck section would be different in shape to that of the A350 fuselage. Hence, you you’d want to blend that section to the aft section similar to how you’d deal with a variable shaped cross section. However, you’d do it only “once”, and not “continuously” as is illustrated for a supersonic airliner fuselage having a variable cross-section.

  2. Beoing has issued a patent once for a B767 with an upper deck. That was a study to check the maximum potential of that aircraft. Let’s say so much: I didn’t go nowhere.
    The “cost” in terms of added weight for each passenger seat in such hump would be so prohibitive that any cost advantage over the “shorter” -1000 is gone, hence the entire idea pointless.

  3. All those Airbus stuff looks really nice and fancy, but it is too far-fetched from the real world in this case. A further stretch of the A350, if done at all, will be very similiar to the Boeing B787-1000 Model, close to the 80 meter mark, with a slightly increased MTOW of 10 to 15 tonnes(more fuel capacity?) and maybe some cargo hold galleys, lifts and lavatories like in the A340-600, to create more space for more seats on the maindeck.

    The real question is, how many additional sales will we see for the B777X in the future. It is a very capable but heavy plane. If you fly around with a daily loadfactor of 90 percent, you can buy a 35 tonnes lighter Airbus for almost the same purpose.

    • If they can get the rotation angle, going near 80m with galleys and lavatories downstairs is the most likely bet.
      As for the A380, looks like they went for 10-11, which like the 777 and 787 may be a bad compromise in width. What’s the ideal double decker cross section? Maybe about 9″ less wide, 243″ at armrest, with the vertical tangent at window height. Second deck, business at 1-2-1, or coach 2-2-2.

  4. Psst. EIS isn’t going to be 2019. And it isn’t going to be 2020 either. The seepage of experience, brains and skills is becoming a flood, morale is poor, and cost cutting cries a constant annoyance. Think 787 light.

    • Raoul – I think that you may be correct about the original 2021 date becoming real – however I have not seen any evidence to support either point of view.
      What I do feel however, is that GE may find it tough to get the required 15% saving quickly.
      The elephant in the room remains the shocking sudden drop in current 777 orders – Boeing must have been surprised by that development. The lack of 777 production in 2018 and 2019 will mean that workers may either be let go or be asked to work half-day. It will be too difficult to assist in 737 production due to the vast differences in location, work methods and materials.(Think Mustang workers assisting the Model T guys)
      Over at Airbus, CEO 330’s have seen a steep drop in orders, but not the total dry-up as seen for the 777-300.

  5. @Schorsch

    I’d guess that your’re thinking about the 767-X?


    As for increase in weight, how much would we be talking about?

    First; one should note that the 777-9, apparently, will have an OEW some 30 tonnes higher than the A350-1000, while carrying some 40 more passengers. FWIW, that’s just a few tonnes short of the OEW of the CS-100 (i.e. including empty weight of fuselage + empennage + wings + MLG etc.) – and the CS-100 has 130 economy class seats.

    2nd; for sure, a forward partial upper deck on an A350-8000 would have a significantly higher OEW than the A350-1000 — but 30-plus tonnes? One should also keep in mind that for a stretched fuselage, the increase in structural weight due to increased bending loads, increase by the square of fuselage length. Thus, an 82-m-plus, super stretched A350-8000 would obviously have a relatively large increase in fuselage structural weight, as well.

    3rd, if a partial upper deck A350-8000 would have the same overall length as the A350-1000, then you’d have no increase in fuselage bending loads. In fact, the forward and most of the centre fuselage would be taller than the aft fuselage. As the maximum running loads are acting in the centre of the aircraft -i.e. in the centre wing box area – the top part of the forward and aft fuselage experience tension. A perfectly contoured composite upper shell, therefore, especially in this highly tension-loaded environment of the fuselage, should be perfect for a forward partial upper deck.

    4th, I would be surprised, therefore, if a partial upper deck A350-8000 — having about the same overall length as the A350-1000, would have an increase in OEW of more than 15 tonnes – or about half the OEW of a CS-100. IMJ, that would be a conservative estimate.

    5th — and finally; 170 tonnes OEW for a partial upper deck A350-8000 (i.e. 155 tonnes for the A350-1000) — and capable of carrying 40 more passengers than the 15 tonnes heavier 777-9, would IMJ be a very capable airframe. MTOW would increase by, say, some 30 tonnes — for an overall MTOW of around 340 (metric) tonnes. The take-off engine thrust requirment, however, would probably have to be increased to over 105,000 lbs (e.g. TXWB-97 core + larger fan — a TXWB-105+?).

    • Addendum

      If someone asks about the logistics of transporting the tall forward fuselage sections of a partial upper deck A350-8000, then I’d say: Look to the A380. 🙂

      • Why bother with mundane concerns like building and assembling sections when its all fantasy football anyway. ( or that only matters when Boeing builds it?)

        But then those games only allow real players or coaches, they dont allow you to build a new player from existing parts and ones that dont exist.
        A tall forward fuselage A350…?

          • A ‘sim aircraft’ would be wasted as they just play with existing ideas and concepts rather than completely new ones.
            The first passenger double aisle, the 747, came about almost by accident, as up to that time it was believed bigger planes would be double deck but still single aisles top and bottom. It took some convincing at Pan Am that a double aisle was the way to go and even then that only worked for Boeing as they thought of the 747 as a ‘wide freighter’ with a few hundred for passenger travel.

  6. It is a bit early to suggest better than promised, lets wait a few years.

    • Trouble is Boeing will stick to its timetable until the very last minute to announce a delay, and then some will say no problem, could see that coming 6 months ago.
      Even now there is the belief that manufacturing a carbon fibre wing for 777X is easy since Boeing have done it for the 787- memories have faded since Boeing doesnt make the carbon fibre wing for 787, Mitsubishi does.

  7. I am surprised (not really) that a post relating to Boeing EIS updates has been hijacked by an in-depth discussion of a larger A350. It is to be applauded that Boeing senior management are being more realistic in their announced project schedules.

    Airbus seems to be going in the opposite direction with the ramping of A320neo and A350 production. The MAX and the X both are derivatives (albeit heavily modified) and as such should benefit in terms of the certification process but still have a long way to go.

    The fundamental question remains as to whether the products derived will have an enduring market appeal. There are clear question marks relating to the ‘future proofness’ of both these programmes and the quite substantial development costs will need to be recouped.

    The MAX development costs are of a different order to the A320neo but it appears the end product is at best on a par and at worst second best. The B777-x again is substantially new but again will struggle weight wise in relation to the A350 and there must be a question mark regarding further development potential.

    Airbus appears to be gaining better ‘bang per buck’ in terms of the modest NEO investments and are possibly better positioned to take on new projects going forward.

  8. If the 777x is a 10 billion dollar program, the cost of borrowed or invested money is 4%, that’s 400 million a year, or 100 million per quarter, so advancing ahead a quarter is worth 100 million.

  9. Well, that’s certainly quite a number of negative feedbacks that’s been posted in response to my opening comment. Let me address some the issues that have been raised.

    First, I’d no intention whatsoever to “hijack” Scott’s post. My (slightly) 😉 off-topic opening comment was — 1), partly a response/follow-up comment to Scott’s March 9th Post, where John Plueger, president of Air Lease Corp., was quoted as saying that “the whole idea of the A350-1100 is to cast about 40 more seats that the 777-9.” — 2), to elaborate on what exactly “40 seats more than the 777-9” actually would entail (i.e. around 80 more seats than the A350-1000) — and 3), the possibility that moving up the EIS of the 777-9, could be related to a “larger A350”. In fact, one journalist –Steve Wilhelm of the Puget Sound Business Journal — seems to believe that one reason for Boeing to speed up delivery of the 777-9, would be to help to “ward off” competition from an A350-8000.

    IMHO, therefore, I do not think it was entirely inappropriate on my part to look at some of the conceivable options for an A350-derived airframe capable of carrying some 80 more passengers than the A350-1000 and some 40 more passengers than the 777-9, since the latter aircraft is a direct competitor to the A350-1000 and a larger A350-based derivative, as well.

    Another reason for Boeing to speed up first delivery, if it can, would be to ward off possible competition from a super-stretch version of the Airbus A350-1000. Some observers have dubbed Airbus’ proposed 400-passenger jet, the size of the Boeing 777-9, the A350-8000.

    “It would have similar capacity and range (as the 777-9) and substantially lower seat-mile costs,” Airbus sales chief John Leahy said of the idea in a March 3 Reuters interview, during the Istat Americas air finance conference in Phoenix. “We are showing it to airlines right now.”


    2nd, as for fuselages having a different cross-section ahead and aft of the wing, we don’t have to look further than the 757. It’s surprising how many people don’t seem to realise that the 757 fuselage had a difference in cross sectional height fore and aft of the wing box (i.e. the difference is in the lower lobe). As for an aircraft having a different upper lobe structure than the baseline aircraft, we don’t have to look further than the A300-600ST Beluga and where even the standard A300 cockpit was moved down below the main deck level. For sure, the cargo deck on the -600ST is unpressurised, but still, it was a major undertaking.

    Just because the partial upper deck 747 has no commonality with any other Boeing aircraft doesn’t mean that a derivative of a current in-production wide-body could have a unique forward partial upper deck, while sharing a common fuselage and empennage structure, wing and MLG with that of the standard in-production WB.

    3rd, there’s been no talk about the landing-gear-footprint/wheelbase issues for a larger “super-stretched” A350. Interestingly, the A350-1000 has a slightly longer wheelbase than the 777-9. Why? Because the nose landing gear on the A350 (and A380) is positioned as far forward in the fuselage as possible, because the designers wanted to save weight and maximise the pressurised volume in the lower forward fuselage (i.e. electronics bay moved further forward, leading to a larger fwd. lower cargo deck). It’s interesting to compare the relative location of the nose gears for the DC-10, 777 and A350, respectively:

    DC-10: https://goo.gl/8uKpU0
    777: https://goo.gl/4d2Z5j
    A350: https://goo.gl/VZiXWJ


    A350-900: 28.66 m
    A350-1000: 32.48 m
    777-200ER: 25.88 m
    777-300ER: 31.22 m
    777-9: 32.3 m

    A 79.5 metre long, 9 frame stretched A350-8000 — 5 frames forward of the wing and 4 frames aft of the wing — would have a wheelbase of 35.66 m. However, such an aircraft would only roughly match the 777-9 in seating capacity; even if the former would be outfitted with a lower deck galley/toilet layout. An A350 derivative capable of carrying 40 more passengers would IMJ have to be stretched by at least 15 frames – 8 frames forward of the wing and 7 frames aft of the wing. It would be 83.3 metres long and have a wheelbase of 37.56 m; or 16.3 percent longer than the 779’s wheelbase.

    Whereas the 777-9 will be, more or less, compatible with todays infrastructure, IMJ a significantly stretched A350-1000 would have several “issues” — especially with respect to the significant increase in its wheelbase. The turn width, for example, would increase significantly.

    A350-1000 Airport Compatibility Brochure

    777X Airport Compatibility Brochure

    4th, the notion that I’m supposedly designing an all new aircraft that even would need 4 engines, seems to nothing but made out of thin air.

    Both the 777-300ER and 777X have MTOWs of about 352 metric tonnes. In comparison, the A350-1000 has a MTOW of 308 tonnes and the quad-powered 747-400 has a MTOW of around 400 tonnes. In fact, Boeing could conceivably put a 777X-type wing and a GE9X-type engine a 747-400 — leading to a significantly reduction in both OEW and MTOW (i.e. with the same payload/range performance as the 744).

    Again, as for the increase in OEW of a partial upper deck A350-8000, it would IMJ be no more than half of the entire OEW of a C-Series CS-100 aircraft — or around a 15 tonnes increase.

    By sharing the same lower lobe of the forward fuselage with the current A350-1000 and the same aft fuselage and empennage, wing and MLG, I can’t see how this would cost more than an all new aircraft.

    5th — and finally — instead of a conventional stretch where several operational constraints might have to be imposed on a super-stretched A350-8000, the equivalent capacity increase could IMJ be obtained by stretching the cross sectional height fore of the wing (i.e. in the +Z vertical axis) and balanced by a conventional stretch aft of the wing (i.e. in the -X longitudinal axis), while keeping the wheelbase unchanged.

  10. With all this advancement in large wide bodies, I see the A380 as a dead duck. Apart from EK, the interest is waning along with cancellations as airlines seem to have much more interest in large twins. The twins can fly more routes, serve more airports,and be shifted easily to match demand.

    • And you can fly more of them on a route with better frequency.

      AK Airlines that would seem to be a prime candidate for a 767 size aircraft but they stick with the 737s.

      The reasons is they are not stuck on one route, they can fly any route (not always the best but not a complete waste)

      In times of delays, they shift the 737-900s to that route and clear it up.

      Its the average that counts not any given run.

    • Thats what Boeing thought back in the sixties when designing the 747, they ended up making 1500 or so. And if the big quads time had come by 2010, why did Boeing put a new wing and engines on the 747.
      Low fuel prices are making a big quad more profitable for long range carriers

        • AF seem to be struggling with cash flow, there large numbers of 10 wide 777s don´t seem to be generating it. They have only just just stopped bleeding money at the cost of violent revolt by staff.

          • Hmm, seems more than a double stretch to put the onus on profibility on 777s when in fact its the staff that is not competitive .

            BA is not having that problem.

            Probably those old A340s they are flying that are at fault I you want to blame aircraft, BA didn’t buy any.

          • It´s not the aircraft, it is the freight market. These planes were bought to carry loads of freight, and without the freight non ME carriers have loads of unsold lift. So lots of seats jammed in and no margin.

    • 600 Passenger 4 class + cargo over 7000NM is no option for a twin in the foreseeable future. So aircraft will have more than 2 engines.

      For those that think capacity really isn’t that important, you’re off. 😉

      Boeing being kicked out of the(ir) VLA segment doesn’t mean the segment / market is gone.





      Later on Turkish and Garuda might be on. United keeps telling they are in talks but don’t see the business case. Again and again.

      • a BWB or HWB design would easily support that kind of mission on a pair of GE9x engines.

        taking a lesson from Lockheed’s HWB ideas and having containerized cargo outboard and passengers inboard would also enable a thinner, and therefore more efficient section, while not subjecting passengers to too much motion.

        cover the walls with “virtual windows” connected to passenger selectable outside cameras/video and you can save >50% of the weight of window structure, while providing the passengers a compelling experience.

        all this with a >30% reduction in CASM vs an A380.

        • The BWB studies point of the last 60 years didn’t take-off. Probably disadvantages beat the advantages. High empty weights aren’t measured in wind tunnels.

          • the 3 frequently cited difficulties with BWBs are building a non-cylindrical pressure vessel (increasing weight), emergency evacuation without long exposed sidewalls for doors, and passenger acceptance of a no-windows experience. the other big stated issue is how do you do a “stretch”

            modern materials technology can mitigate the weight penalty, especially if you consider decoupling the pressure vessel load structure from the flight load structure.

            no windows is not as big a deal as some would have you believe, people would get used to the idea of virtual windows (which can easily be much larger than real ones and positioned appropriately for every seat in the plane) in one flight and prefer it by the second.

            emergency evac is a sticky wicket, but I have no doubt it is solvable, although certain current certification rules may need to be changed.

            finally, in a BWB you wouldn’t stretch lengthwise by rows, you would stretch width wise by columns, which would have the additional benefit of adding wing area and fuel volume for the larger model without having to touch existing structure.

            with a HWB like Lockheed proposes, you solve the pressure vessel, evac and stretch issues and the windows are only an issue in the front half of the plane.

      • There may be a small market for VLAs. The 747-8 could hold its value, similar to the 764 and 753, and not be retired after half its life like the A345.

  11. Haha ? 7000 nm 600 pax in 4 class configuration plus cargo? Try again. The EK A380 with 615 passenger capacity is the only of its kind right now and it’s only in 2 classes. The cargo disability on the A380 is known by everyone so, … yeah. You’re not going to put 600 pax in 4 class configuration/7k nm/decent cargo in a twin but you are only getting 600 pax in the A380 and maybe 7k nm depending where you’re flying it.

    CX gets chastised for flying 5 frequencies of the 77W because the A380 could easily absorb the pax loads, ie what BA did with the 744 to the A380. Yet CX just posted net yearly profits of close to $775 million USD ($6 Billion HKD) These frequencies are working for them because it allows the flyer options during the day, not just one or two windows during the whole 24 hour day to choose a flight. TK themselves said that they prefer frequencies over the one or two jumbos flying daily. The notion of Guarda as a buyer is slim. This is not to disparage the A380, just to provide clarity as a viable people mover.

    • An A380 can move 80t payload (600pass + 20t) over that distance with sporty runway performance.

      A twin to match that with apple to apple cabin specs would be 120m long and have two 240k lbs engines.

      For your comparison that CX 777-300ER does 340 passengers and has ~14t left for cargo on a 7000NM flight. Lots of empty space left below deck.


      • why would each engine of a twin engine A380 equivalent have to have more thrust than all 4 engines of a current A380 (which has a maximum of 240k installed thrust and usually 232k)?

        The A330 doesn’t have double the installed thrust of an A340, it actually has exactly the same installed thrust (2X 70K vs 4X 34K)

        • @bilbo

          The A340-300 was designed to have a substantially higher MTOW than the A330-300.

          Although the A340 wing has virtually the same span as that of the 747-200, it has only 65% of the area, a high-aspect ratio having been chosen to cut both take-off and cruise drag. Span over the winglets is 60.2m and wing area is 362m2 (compared to the A300-600’s 260m2).

          The multi-role wing’s secret lies in the neat balance of bending moments (exerted on the fuselage by the wing) between the twin and four-engined versions. The A330 and A340 wing bending moments are within 1.5% of each other, allowing the two structures to be assembled in the same jigs.

          Because of bending relief from the weight of its outboard engines, the bending moment of a four engined aircraft is substantially lower than it is for a twin at the same maximum take-off weight. For the same fuselage weight, therefore, a twin needs a stronger, heavier wing than a quad.

          It follows that, for the same wing, the payload carried in the fuselage must be less for a twin than a four, which is exactly what has happened with the A330/A340: the latter carries about 20% more payload. This translates to about 30t of extra fuel, giving the A340 its long-range capability and requiring the addition of a centre-fuselage undercarriage leg. Design strength required was “only 1% higher than the A330”, says Jeff Jupp, BAe chief engineer, Airbus.


          • and yet, the A340-300 at 276k MTOW has the same range and passenger capacity as the A330 HGW at 242K MTOW.

            they have very similar installed thrust (136K vs 140k)

            a Twin does not require double the installed thrust of a quad. and the trade off is because of efficiencies of scale in turbines, those two ginormous engines loafing along at cruise get much better SFC than the smaller, harder working engines in the quad.

        • the reason why twins have higher total thrust than a quad with the same takeoff weight is the engine out at takeoff scenario. A plane has to be able to continue the takeoff if it loses one engine at the climb. That only leaves one engine for a twin, while the same engine out for a quad leaves 3.
          Of course that total installed thrust difference is only noticeable when the twin and quad are the same takeoff weight, later A340s were much heavier than their cousin the A330

          • yes, that is true, but they do not have double the installed thrust, more like 1.5x, which would make a twin A380 viable with dual 160k engines, not dual 240ks.

          • Bilbo, in that case, plot those numbers into the graph and tell yourself it’s ok. 🙂

        • Bilbo, if an A380 has 4x80k lbs installed, in a one engine off at MTOW in the worst conditions it has 240k lbs left. If it had 1 engine left (twin) that engine would have to compensate the significant induced drag created by control surfaces compensating asymetric thrust too. 240k lbs is on the low side.

          • an A380 has 4*68-70k installed, not 4×80. on a Twin you need enough thrust to continue gaining altitude and greater rudder authority, for that you do not need double the installed thrust of a 4 engine aircraft, more like 1.3-1.5 (although the A330 gives that the lie)

            the a340 had an MTOW of 276k with total max installed thrust of 136 (4x34k)

            the HGW a33o at 242k MTOW had max installed thrust of 140k (2x70k)

            these aircraft have identical fuselages and identical 7300 mile ranges.

            presumably if Boeing were to make a Twin to challenge the A380 directly with 20+ years of technology differentiation, they would be able to shave more than the 4% OEW/14% MTOW weight difference between the a330/a340 in the process, the engines alone would allow 15-20% less fuel to fly the same mission on an equally efficient airframe, and if boeing couldn’t shave 15% off the empty weight and beat the aero efficiency by at least 5% of an A380 which is hugely overbuilt for the never gonna happen stretch, they ought to just quit now.

          • your graph shows what they have, not what they actually need.

            clearly a 777-9 with an MTOW of 387 tons will get by with one engine out with 108K of thrust.

            an A380 is 634 tons. Assuming Boeing built an A380 competitor with 2020 materials and engine technology and with a structure optimized for the size rather than a structure optimized for the stretch, they would come in at approximately an MTOW of 525-550 tons for the same mission (15% less fuel just on engines alone, 15% structural weight by optimizing for the mission, virtuous cycle of less fuel = less structure)

            given those parameters, a new tech twin A380 equivalent would need 147-153K engines to provide similar 1 engine out performance to 777-9, not 240k.

      • And yet you left out the 275 seat version. On those models, there is no issue of “empty space”. And the Boeing link has expired.

        A twin to compete with the A380 doesn’t need to be small space shuttle. The 779 is already that with less than 80 meters in length and with less than 115k pounds of thrust. With the probable intro of the -8k, that applies more pressure on the A380 and the 779.

  12. There is a need for some VLAs both as freighters and as passenger jets. However, it does not appear to be a hugely profitable niche for the manufacturers. Therefore, Boeing is slowing production and Airbus faces probable rate cuts between 2018-2025 (or whenever or if ever they decide to do a 380neo or -900). What will happen as they are retired? Will they impact new builds? Can Airbus drop production and still make at least break-even in hopes the demand picks up in the future? There must not be a business case for the neo right now or they would have committed to it…

    The business case does not add up for the airlines, so orders are in dribs and drabs and nowhere near projections. But Airbus is stuck with it and it is not losing money anymore, so they have time to see if demand picks up. They just don’t seem willing to put more money into it right now…

    On the other hand, the new twins get bigger and are more flexible… by 2025 could a new twin be launched with 500 passengers and decent cargo capacity? It seems that expanding capacity from below (twins 300 to 350 to 400) may be better than quantum jumping capacity too high (quads 800 to 600 to 450-500) and then being forced to decrease seating to fill seats…

    • @TransWorld: Watch for our Pontifications Monday to explain why the 787-8 is dying.

    • I think the 787-8 / A330-200/800 area represents the upper area of the ” MoM / NMA Gap” both Boeing and Airbus are facing.

      But both the A330 and 787 are long haul machines. They have the wing / wingbox to carry 300+ people, a sea of fuel and a pile of containers over 12 hours. You can shorten the wings (787-3), lower MTOW, cram in more seats (A330R) but they remain beasty machines for short flights. Taking the kids to school with a Hummer 😉

      On the plus side, it enabled Airbus to keep increasing A330 MTOW / capacity-range for years.

      In the past I considered Airbus might use the paid for, stable A330 production line / supply chain to create a competitive medium aircraft for up to 5000NM. A 767 like aircraft, but standard LD3 capable. The enormous A330/340 wing & wingbox would have to go. A kind of A300NG, maybe assembled in Tianjin.


      It would fit in between the A321 and A350-900 and would continue to milk the A330 paid-for / commonality competitiveness.


  13. If the 779 really has a 30 tonnes (66,000 lb.) heavier empty weight than 3510 this would seem to be a real issue given that the gross weight of the 779 is only +/- 95,000 lb greater than 3510. Stated another way, the useful load of the 779 is only +/- 30,000 lb greater than 3510 with a gross weight +/- 95,000 lb. greater.

    Empty weight numbers are subject to a lot of variation based on exactly what is included.

    Does anyone (Bjorn, Scott, others) have a “best current real facts” apples to apples comparison of these likely (neither aircraft is in serial production) weights (masses). Just curious. –

  14. “bilbo”

    Where do you get the A380 weight of 634 tons. According to Airbus it is 575 tons?

    • Rudolph,

      Probably a metric/”English” confusion. One tonne = 1000 kg = 2205 lbs. One ton = 2000 lbs.

    • real tons, none of those silly made up “metric” tons…

      all my calculations were in english units, because thrust is generally discussed in english units

  15. Apparently not for the 777-9. If Bilbo’s big twin would have a MTOW of 525 t / 1150k lbs, thrust required on one engine would be 210-220k lbs in line with all existing passenger aircraft. The 150k lbs suggested for such an aircraft would be truly revolutionary and out of line with e.g. 787, 777X and A350.

    • 525T is 1050, not 1150 Klbs. 777 is 775 klbs with 2, 108klb engines and (should do) just fine one engine out for 330 minutes and at takeoff.

      increasing weight by 275klbs is a 35% increase in MTOW, so the one engine out thrust requirement should also increase 35% which equals 145.6 Klbs.

      there is nothing out of line with anything other than your math.

    • further: current big twins thrust to weight ratio for total installed thrust averages to .269 lbs thrust for every lb of MTOW. at that ratio a 525 ton super twin would need a total installed thrust of 282.5 Klbs, aka each engine at about 141 Klbs thrust.

      every single way you look at it, your assertion that each engine would need to be 210-240 klbs is just completely off base.

    • model MTOW totalThrust Thrust/weight
      777-9 775 216 0.278709677
      787-9 557 142 0.254937163
      A330-300 534 144 0.269662921
      a350-900 617 168.4 0.272933549
      0.269060828 avg
      notional twin A380 competitor
      1050 282.5138693

  16. The A380-800’s cabin with 478 m² (5,145.1 ft²) of floor space. For an apples to apples comparison a big twin needs the same amount of floor space.

    It seems a double decker is relative efficient cross section to create that amount of floor space. A single deck tube would waste a lot of space and could become very long (adding weight to keep stiffness).

    So the OEW of a twin would be about the same (specially considering 2 large engines require a heavier wing then 4 small ones).

    Comparing same size A333 and 789 it becomes clear CRFP isn’t the holy grail for weight savings. Breakthroughs in weight saving weren’t achieved.

    Having to take about the same fuel, OEW and payload, a similar total thrust required, with a single engines failure, to continue the takeoff seems likely.

    I once looked at a ~500 seater, that needed 150k lbs. But it was not really a twin, based on 2x 115 klbs engines and a 35k lbs tail APTU. Significant lower capacity then a A380.


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