# Big airplanes--where does it end? **URL:** \ **Category:** Factual Questions\ **Created:** [March 28, 2007, 3:17pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838 "2007-03-28T15:17:34Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 29, 2007, 3:53am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/21 "2007-03-29T03:53:53Z")
[QUOTE=David Simmons] My concern about composite structures is that they are all individually made and repeatability is suspect, at least to me. With metal sturctues, the elements are out in the open and visible. With laminates the quality of the lamination is hidden and can’t be detected without fairly sophisticated methods. [/QUOTE] Production sailplanes of composite construction began appearing nearly 50 years ago, and seem to have had little problem with variable quality in their structure, despite manufacturing techniques that have mostly been a good deal less sohisticated than those now used on airliners. > [@](#): > > I think the[breaking off of that Airbus’ tail in Jamaica, Queens](http://www.iasa.com.au/folders/Safety_Issues/RiskManagement/A300previous.html) is a good example of what I see as the problem. My understanding is that the problem was inherent in the design - the rudder could not cope with full deflection of the type the copilot used. It was not a quality control problem. > [@](#): > > I don’t think a metal vertical stabilizer and rudder have ever broken off because of excessive rudder pedal movement. It probably wouldn’t be tough to design one that would do so, nor should it be formidable to design a composite empennage that isn’t subject to this failure. (For the record, I certainly feel that this crash indicates substandard design. The notion that the problem should be avoided by telling pilots to refrain from stomping on the rudder pedals is dubious.) ---
**Author:** ![The\_Controvert](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)\ **Post date:** [March 29, 2007, 4:00am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/22 "2007-03-29T04:00:09Z")
Where does it end, you say? IMHO, it ends with total, irreversible environmental devastation and the end of humanity as we know it. In the push for ever greater profits and with no costs for pumping out extra carbon, companies will compete to lower prices. Lower prices, in turn, cause everybody to consume our limited natural resources at ever increasing rates and pump out more pollution, too. Once everybody in China can afford air travel, the planet is pretty much doomed. Nobody wants to enact the legislation to save us all and once the non-linear effects of climate change kick in, it will be too late and Earth will be on the fast track to a Venusian atmosphere and the extinction of humanity. One day in the distant future, Alien historians will study the relics left on Earth and piece together the story. Their scholars will agree that the A380 was the landmark event that doomed the human race. Aren’t you glad you asked? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 29, 2007, 4:12am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/23 "2007-03-29T04:12:18Z")
[QUOTE=Xema] Production sailplanes of composite construction began appearing nearly 50 years ago, and seem to have had little problem with variable quality in their structure, despite manufacturing techniques that have mostly been a good deal less sohisticated than those now used on airliners. [/quote] Sailplanes move much slower and see dramatically lower aerodynamic loads than jet aircraft. I doubt many–if any–have seen the kind of operational hours that a typical commerical jet sees. Stranger ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 29, 2007, 4:25am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/24 "2007-03-29T04:25:17Z")
[QUOTE=Xema] Production sailplanes of composite construction began appearing nearly 50 years ago, and seem to have had little problem with variable quality in their structure, despite manufacturing techniques that have mostly been a good deal less sohisticated than those now used on airliners. [/quote] Yes, I know it can be done. I took basic flight training in[Vultee BT-13s](http://www.warbirdalley.com/bt13.htm). After WWII had been going a while, the construction was changed to use laminated plywood for most of the fuselage and wings. The structure was aluminum in the fuselage from the nose to just aft of the rear seat and in the wings out to just past where the landing gear was located. Everything else was plywood. As far as I know there was no trouble with them although they were restricted from spins > [@](#): > > My understanding is that the problem was inherent in the design - the rudder could not cope with full deflection of the type the copilot used. It was not a quality control problem. I vaguely recall reports of delamination in the vicinity of the point of vertical stabilizer attachment. I must admit I don’t know whether or not that was a result of the rupture or contributed to the failure. The report in my cite don’t mention it. > [@](#): > > > [@](#): > > > > I don’t think a metal vertical stabilizer and rudder have ever broken off because of excessive rudder pedal movement. > > It probably wouldn’t be tough to design one that would do so, nor should it be formidable to design a composite empennage that isn’t subject to this failure. Now that I think back, the[North American AT-6](http://www.aviation-history.com/north-american/at6.html) was restricted from spins because of possible tail failure on recovery. > [@](#): > > (For the record, I certainly feel that this crash indicates substandard design. The notion that the problem should be avoided by telling pilots to refrain from stomping on the rudder pedals is dubious.) It’s quite possible that composits are even better than aluminum today. However, everyone is entitled to an unreasonable fear or two. 🙂 ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 29, 2007, 11:30pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/25 "2007-03-29T23:30:11Z")
[QUOTE=Stranger On A Train] Sailplanes move much slower and see dramatically lower aerodynamic loads than jet aircraft. [/QUOTE] I fully agree that sailplane parts would not be suitable for use on a jet. Presumably, parts for a jet would be designed with different loads in mind. > [@](#): > > I doubt many–if any–have seen the kind of operational hours that a typical commerical jet sees. Certainly true. A few training sailplanes have reached 12,000 hours; it wouldn’t be strange for a high-time airliner to see four times that. ---
**Author:** ![R.P.McMurphy](https://avatars.discourse-cdn.com/v4/letter/r/7993a0/32.png) [@R.P.McMurphy](https://boards.straightdope.com/u/R.P.McMurphy)\ **Post date:** [March 29, 2007, 11:50pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/26 "2007-03-29T23:50:36Z")
[QUOTE=CookingWithGas] There is a new [world’s largest passenger airplane](http://en.wikipedia.org/wiki/Airbus_380). Is there an engineering limit to how big you can make an airplane? How big can it get before there is no way to attach the wings so they won’t fall off from their own weight? [/QUOTE] Just to talk in very pedestrian terms. . . When trying to understand airplane construction keep in mind that the wings support the fusilage. The wings are actually one structure that lifts the rest of the plane. They are not two structures that can break off like chicken wings. A wing is not something that is attached with bolts and welds and spit and glue. In a sense, there is really only one wing, its just that the stuff we like to ride in sits balanced in the middle. Is that pedestrian enough? ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [March 30, 2007, 12:24am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/27 "2007-03-30T00:24:48Z")
**Crescend** has a point. It’s been just over 50 years since the first nuclear reactor to operate in flight, on the [NB-36H](http://www.brook.edu/FP/projects/nucwcost/anp.htm). (The reactor was operational during some flights but was never used to power the plane; the experiment was to determine if a plane bearing a nuclear reactor could in fact fly stably.) A question of the aeronautical-engineer contingent: I gather the issue with a flying wing or equivalent is stability and/or maneuverability, particularly at takeoff/landing, and that the traditional fuselage plane is a tradeoff between the advantages of a flying-wing design and the needed stability and maneuverability. In that case, what would be wrong with a “Flying Arrowhead”? The majority of the plane is airfoil – the “barbs” of the arrowhead – with a small tail – the “stub” of the arrowhead – added to improve stability and maneuverability, appropriate stabilizers being added where needed. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 30, 2007, 1:46am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/28 "2007-03-30T01:46:59Z")
[QUOTE=Polycarp] In that case, what would be wrong with a “Flying Arrowhead”? The majority of the plane is airfoil – the “barbs” of the arrowhead – with a small tail – the “stub” of the arrowhead – added to improve stability and maneuverability, appropriate stabilizers being added where needed. [/QUOTE] I’m not an aeronautical, but [F-14 with folded wings](http://www.fas.org/man/dod-101/sys/ac/f14j.jpg) looks sort of like an arrowhead to me. ---
**Author:** ![cerberus](https://avatars.discourse-cdn.com/v4/letter/c/71e660/32.png) [@cerberus](https://boards.straightdope.com/u/cerberus)\ **Post date:** [March 30, 2007, 2:13am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/29 "2007-03-30T02:13:51Z")
The F-117 looks like an arrowhead, as did its’ ancestor, Have Blue. The F-111 also resembles an arrowhead when its’ wings are fully folded. If you really want to get big in terms of cost-effective, large-scale capacity, you’re going to have to return to dirigibles. You should be able to out-size an A-380 by fitting a Globe-master with seats. At a certain point, the exercise becomes ridiculous. Then again, we haven’t had a triple-decker airliner yet, at least not a modern production version. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 30, 2007, 2:22am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/30 "2007-03-30T02:22:29Z")
[QUOTE=Polycarp] what would be wrong with a “Flying Arrowhead”? [/QUOTE] An important indicator of aerodynamic efficiency (at least for subsonic flight) is aspect ratio: efficient wings should be relatively long and narrow. This would seem to be a problem for an “arrowhead” design. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 30, 2007, 2:32am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/31 "2007-03-30T02:32:21Z")
[QUOTE=cerberus] If you really want to get big in terms of cost-effective, large-scale capacity, you’re going to have to return to dirigibles. [/QUOTE] This has been much discussed on SDMB. Views vary. But a dirigible that would carry anything like the load of a large airliner would be so large as to be highly vulnerable to bad weather (i.e. winds). Its inherently slow speed and high fuel costs (substantially higher per passenger-mile than an airliner) would mean it would have a poor chance of being economically viable. ---
**Author:** ![BobPi](https://avatars.discourse-cdn.com/v4/letter/b/3da27b/32.png) [@BobPi](https://boards.straightdope.com/u/BobPi)\ **Post date:** [March 30, 2007, 2:37am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/32 "2007-03-30T02:37:50Z")
Another consideration, at least for the moment, is the size of the airport. Many of today’s airports can’t handle planes of this size, let alone larger, and that will make them less economically viable. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 30, 2007, 2:48am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/33 "2007-03-30T02:48:02Z")
[QUOTE=cerberus] You should be able to out-size an A-380 by fitting a Globe-master with seats. [/QUOTE] Doesn’t look as if it would work. [This site](http://www.fas.org/man/dod-101/sys/ac/c-17.htm) gives data for the Globemaster: Span: 170 ft Length: 174 ft Max takeoff weight: 585,000 lbs [This site](http://www.airbus.com/en/aircraftfamilies/a380/a380/specifications.html) gives the following for the A-380: Span: 261 ft Length: 239 ft Max takeoff weight: 1.235 million lbs ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 30, 2007, 3:01am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/34 "2007-03-30T03:01:48Z")
[QUOTE=Polycarp] A question of the aeronautical-engineer contingent: I gather the issue with a flying wing or equivalent is stability and/or maneuverability, particularly at takeoff/landing, and that the traditional fuselage plane is a tradeoff between the advantages of a flying-wing design and the needed stability and maneuverability. In that case, what would be wrong with a “Flying Arrowhead”? The majority of the plane is airfoil – the “barbs” of the arrowhead – with a small tail – the “stub” of the arrowhead – added to improve stability and maneuverability, appropriate stabilizers being added where needed. [/QUOTE] Flying wings are statically stable (if designed correctly) but tend toward dynamic instability; that is, when you start to go into a turn (yaw), instead of tending back toward the original orientation, they’ll accelerate into the turn, or worse yet exhibit some kind of rolling or pitching behavior. (I’m using yaw as an example here but the same could be true for manuevers in other directions.) So it’s not so much takeoff and landing manevers–though certain aspects can make those tricky, too–but maneuvers in non-level flight that cause problems. The arrowhead shape you describe _is_ a blended wing body, like the F-117. It has essentially the same problem as a flying wing (though more places to mount control surfaces and verticle or diagonal stabiliizers). Aside from that, the main advantage of a BWB is that you have more latitude over the internal envelope, and the mass stays more centered; whereas a flying wing is all aerofoil, a BWB is a thickish fuselage which provides some continuity of lift (although its own L/D is usually pretty unimpressived, so it shouldn’t be considered a “lifting body” per se) and somewhat smaller, typically swept back (or variable geometry, like the F-14 and B1-B) wings that don’t provide a lot of lift at low speeds, making them difficult to handle during takeoff and landing. Stranger ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 30, 2007, 3:03am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/35 "2007-03-30T03:03:12Z")
[QUOTE=cerberus] The F-117 looks like an arrowhead, as did its’ ancestor, Have Blue. The F-111 also resembles an arrowhead when its’ wings are fully folded. [/QUOTE] And in commercial aircraft, so does the [Concorde](http://www.concordesst.com/) ---
**Author:** ![FRDE](https://avatars.discourse-cdn.com/v4/letter/f/e68b1a/32.png) [@FRDE](https://boards.straightdope.com/u/FRDE)\ **Post date:** [March 30, 2007, 10:57am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/36 "2007-03-30T10:57:29Z")
[QUOTE=N9IWP] Well, we know for a fact that heavier than an A-380 plane can work: the An-225 > **[Antonov An-225 Mriya](https://en.wikipedia.org/wiki/Antonov_An-225)** > > The Antonov An-225 Mriya (Ukrainian: Антонов Ан-225 Мрія meaning dream; NATO reporting name: Cossack) was a large strategic airlift cargo aircraft designed and produced by the Antonov Design Bureau in the Soviet Union. It was originally developed during the 1980s as an enlarged derivative of the Antonov An-124 airlifter for transporting the Buran spacecraft. On 21 December 1988, the An-225 performed its maiden flight; only one aircraft was ever completed, although a second airframe with a slight... Though that is cargo plane (wonder how many people could you cram into one?) There are also large volume aircraft like the [Boeing Dreamlifter - Wikipedia](http://en.wikipedia.org/wiki/Boeing_747_Large_Cargo_Freighter) and the [Airbus Beluga - Wikipedia](http://en.wikipedia.org/wiki/Airbus_Beluga) But again those are cargo planes, not sure if they could handle all the people you could cram in them. Brian [/QUOTE] When the 1991 Gulf War broke out a friend of mine saw the Russians evacuating their locals in one of those in Bahrain - they just had loads of bubble wrap, no seats. An interesting variation of tourist class 🙂 ---
**Author:** ![MMI](https://avatars.discourse-cdn.com/v4/letter/m/53a042/32.png) [@MMI](https://boards.straightdope.com/u/MMI)\ **Post date:** [March 30, 2007, 1:39pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/37 "2007-03-30T13:39:58Z")
IIRC one of the issues with blended wing bodies for passenger use has to do with evacuating the cabin in case of emergencies (on the ground, obviously). There is a great deal of experience in getting lots of folks out of narrow metal tubes within the time frame required by the FAA. A blended wing body passenger plane is generally envisioned as having larger, wider, room-shaped rooms, probably on more than one level, not all of which are adjacent to an external wall of the aircraft. Obviously this is not a structural or aerospace engineering issue, nor a limit that affects a non-airliner ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [March 30, 2007, 2:25pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/38 "2007-03-30T14:25:42Z")
[QUOTE=Crescend] If you consider Ekranoplans (ground effect craft), the answer may be [“very big indeed”](http://en.wikipedia.org/wiki/Beriev_Be-2500). [/QUOTE] Holy crap! Five times the all-up weight of a Caspian Sea Monster! :eek: ---
**Author:** ![GargoyleWB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gargoylewb/32/199_2.png) [@GargoyleWB](https://boards.straightdope.com/u/GargoyleWB)\ **Post date:** [March 30, 2007, 3:59pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/39 "2007-03-30T15:59:33Z")
[QUOTE=Stranger On A Train] … but lacked complex automatic control systems required to actively stabilize such aircraft in flight. We have this capability now, but only on expensive military aircraft; developing this for commercial use will require substantial investment and an even higher degree of confidence in the reliability of electronic systems and software. Stranger [/QUOTE] I disagree a tad with this. Dynamic flight control has been a proven technology for decades and has been the _enabler_, not the retardant, of modern military aircraft. It is reliable advanced airframes and materials that have had to play catch up with the flight systems. Adapting it to commercial aircraft would be trivial, and current commercial aircraft already rely on a lot of dynamic software control (to detect and control rudder flutter for example). I think it is again the reliability and ‘public faith’ in new structural materials that will be the hurdle. This is reflected perfectly in a previous poster’s comment about not trusting the 787’s larger windows because of the composites. No mention was made of the crazy amount of computing software required to keep the plane airborne, and I think the public associates advanced computing technology with greater safety, instead of unreliability. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 30, 2007, 4:39pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/40 "2007-03-30T16:39:35Z")
[QUOTE=GargoyleWB] I disagree a tad with this. Dynamic flight control has been a proven technology for decades and has been the _enabler_, not the retardant, of modern military aircraft. It is reliable advanced airframes and materials that have had to play catch up with the flight systems. Adapting it to commercial aircraft would be trivial, and current commercial aircraft already rely on a lot of dynamic software control (to detect and control rudder flutter for example). I think it is again the reliability and ‘public faith’ in new structural materials that will be the hurdle. [/QUOTE] This doesn’t really make any sense. BWB require less in the way of component structural stiffness; you don’t have to have long, think aerofoils cantilevered out further and further to get increasing lift. You have plenty of internal volume to add structure and shift weight around. You don’t need any kind of advanced materials or construction techniquest to build a BWB or flying wing; this can be done with aluminum alloys and other very conventional materials and construction methods. What you do need, though, is active, fly-by-wire automated control systems to deal with the positive feedback of the flight dynamics of such bodies. A tube & swept wing body is inherently dynamically stable, and the controls are correspondingly less complex than that of an unstable body, in the same way that a gyroscope is easier to balance than a straw. It’s also the case that, in the commercial aircraft industry, the behavior of standard aerofoils is well understood, and extrapolating the effect of making dimensional changes doesn’t get anyone out of their comfort zone. The behavior of non-standard aerofoils and load distributions, however, is outside the experienece of commercial aircraft designers, and thus represents a risky and costly development program with the possibility of cost and schedule overruns and design restarts. I’m not saying that we don’t have automatic controls to deal with positive feedback, but such systems are currently the domain of military and experiemental aircraft; the understanding of these systems and their application in commercial aviation is a substantial learning curve for engineers, and a risk to manufacturers. The last real “out-on-a-limb” commercial aircraft development were supersonic transports, and they were an utter failure from a financial perspective. Developing control software for an aircraft–any aircraft–essentially reverts to first principles and is almost unique for every class of airframe; but at least with a standard configuration the same principles and basic models apply. Going to a new type of aircraft shape, and especially one that is not aerodynamically failsafe, requiring vastly more confidence in reliability and/or greater redundancy, is a huge hurdle, especially when you then have to convince airlines–for whom the failure or removal from service of a single model of aircraft which may make up a substantial portion of their fleet may cause severe financial hardship–to buy into your design and place orders when a single component has yet to fly. Stranger [Previous page](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838.md?page=1) [Next page](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838.md?page=3)