Slow down on “797” launch

The news agencies are buzzing with stories that Boeing CEO gave the go-ahead for a new replacement for the 737.

This isn’t what we said and what he did say is not new. Do a Google News search to check out all the stories.

McNerney said Boeing prefers a new airplane, and it does; this isn’t new.

He said evaluation continues. This is true; R&D on a re-engine has not, repeat not, been discontinued. This is because no definitive decision has been made.

So slow down, everybody. This isn’t the launch of a new airplane at Boeing.

45 Comments on “Slow down on “797” launch

  1. I believe Boeing will be far better off, in the long run, with launching a new airliner to replace the B-737NG series. At best, any incremential improvements the the B-737NG, up to but not including reengining it, will only make it about the same as the A-32X-NEO. Reengineing the B-737NG is a huge engineering task, not insurmountable, but an expensive one. A B-737RE will only be good for about 10 years, or so, when Airbus gets ready to launch their A-32X replacement airliner.

    Just go with the new Boeing NB design now and take full advantage of it, over the A-320NEO.

    • 10 years with 400 or 500 airplanes per year, that means roughly 5000 airplanes. With an investment of only 1 billion, a short life on the market is not a big issue. It could be a much bigger issue to spend 10 or 15 billions in a brand new airplane which is obsoleted 4 or 5 years later by an airplane with even better technology.
      Anyways, nobody knows if Boeing will be able to sell its 737 at the same rate until 2020. They could have very tough years between 2016 and 2020, exactly at the time they will need some cash for the R&D of the 797.

      • I doubt Airbus, or Boeing can count on 400-500 NB orders per year for 10 years.

  2. Another advantage may be that McNearney would no longer be running things by the time 7X7 replacement for 737** gets serious on the drawing boards, AND a few lessons learned re 787 may also help.

  3. What will be the 797 ? A single-aisle airplane (which is lighter) or a twin-aisle ? For some airlines or some routes, one is the best, for other airlines or other routes, this is the opposite.
    The problem is not only in technology. The problem is marketing. One airplane is maybe not the right answer, they could have to design TWO airplanes, a small one (the single-aisle) to compete with the Bombardier C-series and to replace the 737-700, and a bigger one (the twin-aisle) to compete with the A321NEO or to replace the 757 and the 737-900ER.
    Airbus has a better opportunity to re-engine its single-aisle. The price (1 billion euros) is not so big, so the risk is limited. That gives them time to see what the market really wants and that forces Boeing to take a big risk. Sometimes it’s good not to be the first to fire.

  4. Just one more thing : the A320 and the 737 are the cash-cows for their respective manufacturers. A brand new airplane of this size is a much bigger risk than to lose the tanker contract.

  5. On the tanker contest, Boeing turned in their FPR today.

    All we know about the next Boeing NB family is it is entended to replace every model of the B-737NG and the B-757. It is also aimed at getting a good portion of A-32X sales. Time will tell on that, since some airlines are dedicated Airbus customers and others are dedicated Boeing customer. I think Boeing is aiming for those airlines that switch back and forth.

    • Nuts to it. My post hasn’t shown up on Flightblogger yet, so here is what I have to say:

      This reminds me of the situation almost exactly 10 years ago. Airbus was in the middle of the A380 developement and Boeing was working on the 777-200LR & 777-300ER. In the spring of 2001, Boeing cancelled both the 747x and 767-400ER programs which brought alot of unwelcome and negative attention from Boeing emlployees, the markets and the press. The stockholders were probably the only ones happy with this decision.
      Eager for a distraction, Mr. Mulally trotted out the new saviour for Boeing, the Sonic Cruiser. Unfortunately Mr. Mulally’s ploy succeeded way beyond his wildest dreams and he was quite disgruntled to find out that instead of this announcement reducing the pressure, it got almost worse as everybody wanted to know more and more about this wonderful new aircraft.
      It very quickly became quite obvious to some that the Sonic Cruiser was a mere red herring whose effectiveness had mixed results. Nobody was unhappy with Boeing an longer but now the expectations had grown that much more.
      (for some backgrounder info, see: http://members.forbes.com/global/2001/0528/056.html)
      Over time, most Boeing employees came to realize what the Sonic Cruiser really was but they had also heard whispers of something that would satisfy their desire for a new aircraft program, the Yellowstone Project. While not as sexy as the Sonic Cruiser, it would be a brand new aircraft and not another variant of a previously developed aircraft.

      Which brings us to the 787. Nothing more need be said about that project.

      My point being that Boeing (and most of the rest of the world) knows that due to the low clearance to the ground, it cannot do a re-engine as cheaply as Airbus can.
      That explains why Boeing has had low customer interest in a re-engine option, while Airbus had pretty well the opposite reaction. Now that Airbus has announced the go ahead for the NEO, Boeing feels it has to respond and not let Airbus seem to be taking the initiative. Hence all of this talk of a new narrow body by Boeing.
      But look at the estimated dates, near the end of the decade. Is that for program launch, first flight, entry into service? Based on what most aircraft programs are going through, they will need to launch that program within the next 2 to 3 years if they want an EIS of 2020. That means they should be well into their preliminary developement work stage. I personally do not get the impression that such is the case.
      If 2020 is program launch, then they really don’t have that big a jump on Airbus, do they?
      Another factor that is being overlooked by all is the fact that the 737 is a 50 year old design that has had a free pass on many (certainly not all) certification items that have been introduced since the sixties due to grandfathering. ThBoeing might find themselves having to make a few more compromises in design than they are used to for a replacement narrow body.
      So the really big question I am asking is, What is Boeing really saying and what is Boeing really doing?
      To me, the 2 actions are mutually exclusive.

      For an interesting look back at what Boeing itself was saying back then, look at the interview with Walt Gillette back in 2002. Items like publicity stunt, lack of developement (where he openly admits that the Sonic Cruiser was announced very early in the development cycle) and the open denial of lack of airline interest are all covered. See (at bottom of page): http://www.boeing.com/news/frontiers/archive/2002/july/i_ca2.html

  6. First of all of course Leeham is right, and their analysis shows what distinguishes professionals from aviation geeks with a blog chasing headlines.

    As for the announcement, I place that in the same line as the ‘1,000 more 767s’. In other words, if that’s what Boeing management truly believe, then I would like to have something of what they are smoking.

    But let’s parse the statement. Sometime at the end of this, or early next decade. So, with the by now customary delays we are looking at 2023 – 2025 for EIS. Which is, surprise surprise, what everybody is saying could be a realistic window for an all-new narrowbody with a 20-25% ops cost improvement. Which is, in reality, just saying ‘honestly, we ain’t got no clue, but by kicking the announcement into the long grass people may at least think that we do, and it doesn’t matter either way.’

    But even if this is all correct, I really don’t see how leaving Airbus with a 10-15 year sales window on the NEO (remember, they start delivering in 2016, but they are selling it today) is going to be a desaster for Airbus and successful one-upping by Boeing. Maybe someone can explain?

    Finally, let’s keep in mind that on these timelines, nobody can stop Airbus from launching their own all-new narrowbody in, say, 2016, for EIS in 2025 (delays included). So that would give Boeing a sales advantage of 0-5 years on the outside.

    Anyone who thinks that this constant muttering by Boeing shows that they somehow have a secret master-plan that will allow them to wipe the floor with Airbus should really have a closer look at calendars.

    • probable EIS 2025:

      That imho won’t wash the way Boeing thinks.
      My guess is newly emerging tech will hugg the later part of the decade
      or go into even the next decade. that would open a developement window
      in the same timeframe. But expectable delays will be inserted after
      this window and not before. See the Dreamliner with for 2008 adequate
      tech going to customers in 2012 that is 4 years late. Same will happen
      with a new NB. Thus EIS will be nearer 2030 than early/mid decade.

    • I just don’t see Airbus being able to begin developement of a new NB in 2016. That year is the current expected EIS of the A-320NEO, followed by the A-321NEO in 2017 and the A-319NEO in 2018.

      If Boeing can get its B-797, or whatever designation they eventually give it in service around 2018, the A-32X-NEO project could become wasted time and money.

      Has Boeing screwed up the management of the B-787 and KC-X programs? Yes, they have. Has Airbus screwed up the management of the A-380, A-400, and A-330MRTT programs? Yes, without a doubt.

      Now the question becomes who has learned from those management FUBARs? For each OEM that question remains unanswered, for now.

      • Hmpf.
        There is fubar and FUBAR and FUABARsquared.
        Could you be so kind and quantify the amount of Fubar associated with each project ( in units of F if you please 😉

        IMnsHO and going by Boeings foot dippings there will be no announced as planned EIS for this new plane before 2022.

      • KC135TopBoom :I just don’t see Airbus being able to begin developement of a new NB in 2016. That year is the current expected EIS of the A-320NEO, followed by the A-321NEO in 2017 and the A-319NEO in 2018.
        If Boeing can get its B-797, or whatever designation they eventually give it in service around 2018, the A-32X-NEO project could become wasted time and money.

        If in 2018… If pigs had wings… If I were pretty and cool.. How is this supposed to work? We have 02-11 now. They have not even decided what they want to do, they have not offered anyone anything but spin, and they have not finished studying the matter. They have less than seven years to EIS 2018. It will take them 9 years to go from announcing the 787 to a proper production run, so they would need to shorten the circle by 2 years. I think not.

        2020 if they can decide this year is the absolute earliest. Which gives the NEO eight years of sales. Hard to see how that would amount to a waste of money.

      • I personally don’t see a 319NEO happening but I agree with the gist of your point and will go you one better.
        A350-800 and, if it happens, A350-1000.
        We are looking at companies who used to do great programs and then take a few years to recover for the next big effort. Du´ring these recovery periods, many people were laid off (especially in North America). Now we are looking at these companies as if they can time programs . Yet this is something they have actually seem to gone out of their way to prove they cannot do and even worse, aside form platitudes of lessons learned, have not really demonstrated that they will improve on said performance by any significant factor.
        So I don’t see Airbus’ “planning” to be any more realistic than Boeing’s. Unless they truly mean to launch in 2025?!

  7. I’m a glass half full guy, some of the time, and presume that the airframe manufacturers will move to more realistic schedules after the trainwrecks they have recently experienced.

    Having said that, if you think that a proof of concept on wing happens for something really good by 2018, then yes, you’d be looking at 2027-2030 for EIS.

    That’s the issue I have with Leeham’s earlier view on an end-of-this-decade EIS for a new NB with 20% operating cost savings. What are the technologies behind it? I can’t see them.

    • ” What are the technologies behind it? I can’t see them.”
      I am in full agreement with you, I can’t see them either. Boeing itself said that a technology breakthrough is required for the launch of the new programme. I am not sure it happened…

    • Didn’t the B-787 program begin in 2003 or 2004? Then that is 7-8 years, to date. I agree the B-787 is very late, but Boeing has brought airplane programs in less time in the past. The B-777 program took about 6 years from launch to the first delivery. The B-787 is light years more advanced that anything flying as an airliner today, yes, even more advanced that the A-380. No one has ever built an airliner like the B-787 before. Boeing’s biggest screw-ups on this program is the out-sourcing and the Marketing Dept. driving its public debut on 07-08-07, a PR stunt the engineers and builders could not meet.

      Can Boeing bring the B-797 to EIS by 2018? It is very possible if management bean counters keeps their fingers out of the program. So the real question is can Boeing’s management do that?

      • Announced in 2003. Who cares about first delivery? The programme won’t ramp up production in any meaningful way until 2012, so that makes nine years, and I am being generous.

        The supposed technological superiority over anything flying now is just a weak excuse. But even if you accept it, then the supposed technological superiority of the new NB over everything else implies it’ll also be late.

        If Boeing has an all-new NB EIS by 2018 I’ll by every commentator in this discussion a beer. How about that?

      • In relation to “marketing stunt” the Dreamliner ( what a fitting name ) is a very homogenous product. i.e. product and process was marketing think driven, with success one sight say going by the ordering book. But that was never followed by a competent and reality based realisation cycle. It _has_ some disctinctly differeing marketing driven details. It is not “lightyears” ahead.
        More like lightyears off into a narrow dead end valley that makes turning difficult.
        My tentative guess is you won’t see another nonderived design using barrels from Boeing.Beyond being “duh obvious” it is not the way to go to gain what the basic building material promises. I see similar limitations with the other marketing obvious design decissions.

      • A few papers from DLR may help understand why retaining the current tube and wing configuration is not optimal when switching from aluminium to CFRP as primary structure, and even less optimal for NBs than WBs due to the problem of scaling. Reducing the weight of the fuselage by up to 30 percent in combination with another step-change in propulsion technologies is what will likely be required if a new NB will be a game changer.

        I don’t think Boeing is anywhere ready to go for a double shell full composite NB in the foreseeable future. I therefore expect them to go for an aluminium fuselage, which will look like a scaled up C-Series.

        http://www.dlr.de/fa/en/Portaldata/17/Resources/dokumente/institut/2003/2003_03.pdf

        http://www.dlr.de/fa/Desktopdefault.aspx/tabid-1481/2087_read-3588/

  8. As in the past Big B has an opportunity to put their shoulder to the wheel and come up with something new and spectacular from a clean sheet of paper for a replacement aircraft, question is will they? If they play it safe and go for just a redo of the 737 with carbon-fibers and other light weight materials I think they will become their own worst enemy. Engine technologies and aeronautical research from NASA and private developers are progressing quickly and working closely with suppliers is always a good idea too. With other airframes entering into the single aisle world you past performance and name will not carry you very far. You will need to capture the imagination of the public and the airlines or find something else to do.

  9. If Boeing feel good about technologies available now to put into their bird for a 2018-2020 EIS, then great, hope it works out for them. I think Airbus went the right way by re engining. Out of the $1.3 billion development cost, Airbus is paying a fraction and is extending the production run by another 10+ years. It’s an excellent investment for them. Boeing need to be careful about the existing 737 order book crumbling and with slow production and ramp up there will be a not insignificant revenue loss that they need to correct around 2020. What is a little annoying is that Boeing keeps spinning this line that NEO only just brings the A320 to the 737NG level… yeah right, why feel the need to launch the new aircraft then?

  10. For both airframers, it’s not a question of if, but when, they come out with a brand new design. It’s also not a question of whether they upgrade their current product – they will – but of how much.

  11. A Boeing 737 Re-do makes sense if they adhere to the KISS Principle..(KEEP IT SIMPLE, STUPID), but the new engines must be lighter and/or create less drag to relieve strain on those wing bolts… This could be a worthy project to replace their plans for the KC-X which are “dead as disco”….

    Daniel Sterling Sample
    SPACE DESIGNS
    Los Angeles

    sample.daniel@gmail.com

  12. There was a little gem in Flight the other day, which unfortunately I cannot find about a Rolls Royce claim to have an interim series of engines that will be available around 2018 prior to open rotors in 2025.
    At the lower end was a two shaft conventional turbine to suit 737/320 sized airframes with a 20% reduction in fuel burn and low emission and noise levels.
    Maybe this is the technology Boeing are looking at?
    As an aside, I seriously wonder if the Leap X business plan has fallen over?
    Its hard to believe launching that engine could have occurred if there was not a serious expectation that Boeing would be a launch customer.
    With the expected performance IMHO it cannot justify anything other than a re-engining programme.

    • I think a new engine from Rolls Royce will struggle against the Pratt PurePower engine on the next generation of planes. It will be an untested concept put up against a mature engine that will already be in its refinement stage. The Rolls Royce engine would need to offer a step change in efficiency – I doubt it will manage this. Its best bet is if LeapX fails to make the transition to the next generation and GE is looking for a partner for its new engine. A long shot, though.

  13. Look at Flightblogger (Jon Ostrower). It was covered as part of the PNAA coverage.

    • I would be very surprised if Airbus is “tonedeaf” to those projects.
      ( and all seem to have EU research grants attached )

      But is the timeframe realistic?

  14. Tell that to the fanboys on A.net who are already congratulation Boeing on their new aircraft. Thank heavens there are still people left with reasoning and comprehending skills to know that this just means Boeing is still evaluating what to do next, but a re-enginging looks less likely.

  15. 797 will be a MiniMe version of the 787. NEO concept is a good idea for the near future. But not the best long-term strategic move entering the veiled-land-of-things-to-come. What comes next after NEO a Mini-Me of the A350? Airbus is just postponing the inevitable ALL composite future.
    Boeing sees the future and long term I’m betting they will go with a 797. Airbus is a worthy competitor. Good luck to them.

    P.S. Split the procurement on you-know-what. It way beyond cost-benefit analysis now. Time for the often dismissed, lost art and greatly misunderstood logic that germinates in a smoke filled room of politicians.

    • While you may be right on the B-797, A-320NEO and A-360/-370 (what I am currently calling the A-32X follow-on). I disagree with splitting the KC-X buy.

      I still would like to see Congress cancel the KC-X, and reengine and upgrade the KC-135Es.

  16. OV-099 :
    A few papers from DLR may help understand . ….
    I don’t think Boeing is anywhere ready to go for a double shell full composite NB in the foreseeable future. I therefore expect them to go for an aluminium fuselage, which will look like a scaled up C-Series.
    http://www.dlr.de/fa/en/Portaldata/17/Resources/dokumente/institut/2003/2003_03.pdf
    http://www.dlr.de/fa/Desktopdefault.aspx/tabid-1481/2087_read-3588/

    ++++
    basic problem with double hull/shell concept whre cargo is not pressurized. A major profit for airlines is the cargo. A lot of cargo simply cannot tolerate 30 to 40 k altitude. Most liquids, live animals as dogs, etc and various sealed devices not built for 8 to 10 psi delta pressures.

    so to use that cargo hold, ALL cargo would have to sorted, labeled, etc.

    Ever since the DC-10 disaster over france in the late 60’s early 70, s special provisions have been made to rapidly equalize the pressures between passenger and cargo holds in the event of a door failure – which as I recall resulted in floor beams bending, and essentially taking or binding the control cables to stabilizer and rudder, and the resultant loss of control.

    However. given the inherent strength to weight of composites, it may not be as difficult to design say an elliptical or similar shape to give max headroom, max witdth in passenger area, and a ‘ semi ‘ slab sided lower hull or other shape to gain max volumetric efficiency for cargo AND passengers with significantly less ‘ circulairity ‘ than has been most common to date.

    • Please do note the Gondola Concept is a proof of concept design using the Cargo compartment as a secondary structure and as the primary “crash element”. If pressurization to 5000-6000ft, or a different level of pressurization than the passenger cabin (i.e. 8000-9000ft) is required, you would need to dimension for that and add additional structure, tightness of cargo doors etc.

      Clearly, “full barrel”787 type know-how will be of little use in these new designs. What you want is a few large full length integrated panels (co-cured stringers, frames etc) with an outer layer (mold-line) serving as both the outer skin and detection layer (for impacts). Doing that, you can reduce the thickness of the “stressed” skin, and consequently, serious weight reduction will be able to be implemented. A baby-jet version of the 787 is IMO a non-starter. Sorry!

      • OV-099, you are assuming Boeing is going to build a mini-B-787 composet structured airplane. I don’t know if they will or will not, none of us know, we can only guess at this point. But, the B-787 has other features that could be incorproated into a new design NB B-797. Features like all electric and no pneumatic systems for deicing, lower cabin altitude with higher humidy levels for more comfort, bleedless engines similar to the RR Trent-1000 and GEnx-1B, but on a smaller scale and lower thrust level, larger main cabin windows, etc.

      • No, I’m not assuming that they re going to build a baby 787. In fact, I thought I made my self clear when I stated it’s IMO a non-starter and that I believe that Boeing will not build a “797” with a 787-type fuselage. As for the electric architecture, true they can incorporate modified 787 systems. I’m of the opinion though that a truly “electric” architecture will start to make more sense if fuel cell powered electric propellers will be used on NG/NNG vehicles during the cruise phase (internal combustion engines for take-off and landing).

        As for the cabin pressurization, please do note that the A380 cabin can be pressurized to less than 6000ft equivalent altitude and has higher humidity levels as well, and that consequently, a an aluminium fuselage is not that “handicapped” in this area. However, these features are not as important on short flights as they are on long intercontinental ones, making it a trade-off on future NBs.

  17. OV99- you are still missing the point regarding a double barrel lower pressure cargo hold.

    In simple terms – to make such a complex structure in 737 size out of any material based on the ONE in a million or more flights that MIGHT be a crash advantage is NOT likely to sell well for a variety of reasons.

    In fact, a smaller diameter barrel or ogive structure has overall less stress for a given internal pressure than a larger diameter, even out of aluminum, glass, steel, composite, etc.

    AS to the efficiency of a ‘ flying wing ” structure for short haul, while better than a wing – tube, it is unlikely that passengers will be very happy- the ability to see out is VERY important, which is why larger windows excite everyone. Passenger psycholgy is VERY important. For a differnt example, it is MUCH safer to have rearward facing seats in almost any crash, etc. But just try to sell the kids/adults in the back seat of your van on that concept, let along hundreds/thousands of passengers in an airplane.

    • No, I’m not. As I said we’re talking about a proof of concept design, so don’t be too hung up about the “crash requirements”. What you don’t want is LARGE CUT-OUTS as is presently being done on conventional fuselages. Separating the passenger cabin from the cargo compartment structurally as outlined in the Gondola concept, shows how you can avoid the large structurally complicated cut-outs in the primary load-bearing structure. That’s what’s important, not the level of pressurization you optimise the lower hold for (i.e. 6000-4000 ft). As for a BWB type of NB; I’ve not mentioned that concept at all. I’m not sure why you bring it into the discussion.

      • Addendum:

        That’s what’s important, not the level of pressurization you optimise the lower hold for (i.e. 6000-40000 ft).

      • The capable of bearing pressurizing loads cabin floor weights in as extra. This is in the research example alleviated by lighter construction in the underfloor cargo space. The research target was a black fuselage with acceptable/good crash worthiness.

        But notice ( page 2003_03.pdf:page4:fig2 ) the layered skin in the design that has
        been trotted out into the publication world recently by Boeing and Cessna 😉

      • The capable of bearing pressurizing loads cabin floor weights in as extra.

        Sure, but if you manage to achieve fuselage weight reductions in the order of 30 percent that extra structure is not a show-stopper. Also, it makes sense to reinforce the cabin floor shell (one-piece, full passenger cabin length), as composite materials tend to have significantly higher tensile strengths than compressive strengths; with the cabin bottom floor shell in the Gondola concept being in compression.

        For a CFRP-based next generation NB, it’s equally important that the design incorporates impact protection for the load-bearing “stressed” skin since the operating environment is very different from that of the WBs (i.e. much greater probability of ramp-rash and impact). Seemingly, one of the best way to protect composite fuselage load-bearing structure is with the double shell concept.

  18. What is it you are trying to prove re 737x or whatever? Large cutouts eq cargodoors have been around for decades. VERY few have come undone in flight or seriously compromised single barrel integrity. While the ‘ concept’ may be reasonable or valid, of what practical commercial purpose or use is it ? And why is is part of a 737x discussion whether of composites or aluminum or cardbord ?

    NUff….

    • A new NB aircraft will have to conform to all the newer certification requirements.

      Grandfathering from a fifties design and the elegant preemption done on the 737NG will not be possible ( or the FAA will stoop even lower than before ).

      CFRP has “energy release” type failure in contrast to (light) metals that tend to have deformative/absorptive failure properties.

    • Don, please do read the following paper. You seem to be somewhat confused with the meaning of the term “cut-outs”. BTW, I’m not trying to prove anything. I’m just saying that you won’t have a considerable reduction in fuselage empty weight, or in the weight reduction needed in order to make a “797” game-changing, if the fuselage design for your “797” is of the conventional wing-and-tube configuration and if CFRP is the chosen material. As I’ve said, I dont’t believe Boeing is anywhere ready to go for such a revolutionary type of a design, partly because the composite fuselage know-how gained from the 787 will not be directly transferable to a “797”.

      http://www.dlr.de/fa/en/Portaldata/17/Resources/dokumente/publikationen/2004/11_kolesnikov.pdf

      2.4 Specific Properties of Standard Metal Fuselage Construction (page 3).

      Standard aluminum fuselage of a big passenger airplane is a semimonocoque construction with shell, stringers and frames. The fuselage contains a cockpit and passenger compartment, both sections experiencing surplus internal pressure i.e. hermetic. The lower bearing panel of this fuselage experiences loads caused by global impact of bending moment, torque, intersecting forceas well as the surplus internal pressure. It contains rather big cutouts (fig. 4): front pit, pits for primary landing gears and wing/fuselage juncture, as well as the baggage and cargo hatches. The biggest cut-out for landing gear pit and wing/fuselage juncture is located in the area of largest bending moments.

      These cutouts weaken the lower panel construction, which operates mainly in constriction and experiences the danger of losing steadiness, and generate strain concentration. Flat panels limiting landing gear pits, and cockpit floor in the area of primary landing gears and wing juncture are loaded with surplus internal pressure and experience bend impact. Hence the standard fuselage in the lower panel area is not an optimal ‘light’ construction from the point of view of structural mechanics, and arrangement of pits and cutouts in load carrying structure requires the increased material consumption. Practically all big passenger airplanes of leading aircraft world companies such as Airbus, Boeing, Tupolev and Ilyushin have similar fuselage constructions.

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