# 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:** 3
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [March 30, 2007, 5:52pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/41 "2007-03-30T17:52:38Z")
Yeah, we’ve got to remember that an engineering success can still be a hideous financial disaster. Airlines don’t buy airplanes because they’re cool, they buy them because they hope to make money by hauling cargo and passengers. ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [March 30, 2007, 6:28pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/42 "2007-03-30T18:28:46Z")
[QUOTE=Xema] There are, but they aren’t principally realted to fuel economy (which is really quite good for giant aircraft, and indeed is one of the reasons for their existence). . [/QUOTE] Somewhere on the net I read that the fuel consumption/100 passenger km (on a presumably fully loaded aircraft), for the A380 would be under 4 liters, which does sound impressive. As an aside, why’d they decide to name their planes ‘airbuses’? We know the thrill and glamor of air travel has long sinced leached away, but must they remind us by calling them ‘buses’? 😃 ---
**Author:** ![Autolycus](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Autolycus](https://boards.straightdope.com/u/Autolycus)\ **Post date:** [March 30, 2007, 6:35pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/43 "2007-03-30T18:35:44Z")
As long as the plane is not on a treadmill, I think the sky is the limit. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [March 30, 2007, 6:59pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/44 "2007-03-30T18:59:26Z")
[QUOTE=Autolycus] As long as the plane is not on a treadmill, I think the sky is the limit. [/QUOTE] That’ll never get off the ground… ---
**Author:** ![Autolycus](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Autolycus](https://boards.straightdope.com/u/Autolycus)\ **Post date:** [March 30, 2007, 7:00pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/45 "2007-03-30T19:00:33Z")
[QUOTE=Sunspace] That’ll never get off the ground… [/QUOTE] Sorry for the hijack, but is that what The Doper Collective finally decided in that famous thread? I lost track by the end :smack: ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [March 30, 2007, 7:34pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/46 "2007-03-30T19:34:47Z")
[QUOTE=fiddlesticks] Another limiting factor is the FAA’s requirement that in an emergency a plane at maximum capacity must be capable of being completely evacuated in 90 seconds. 33 people were injured when Airbus ran their test on the A380, but they made the time limit and thus the test was still a success. Story here: [What makes the airplane evacuation test so dangerous?](http://www.slate.com/id/2138847/) [/QUOTE] Interesting. The article says 32 of the 33 injuries were from “slide burns,” but doesn’t say what the single other injury was. Guess it wasn’t _too_ serious, whatever it was. The A380 already has plenty o’ problems and Airbus is bending over backwards (and laying off staff and closing some factories) to hang onto its current customers. I think the “superbig passenger airplane” trend may have ended with this very aircraft. Anything much bigger probably isn’t going to be cost- and fuel-effective, barring remarkable engineering advances. And if the A380 isn’t the last of its kind, an accident involving one of these monsters (and we all know that, sooner or later, there will be such an accident, unfortunately) will quite possibly be its death knell. Imagine another Tenerife, but with two A380s… :eek: ---
**Author:** ![kellner](https://avatars.discourse-cdn.com/v4/letter/k/c2a13f/32.png) [@kellner](https://boards.straightdope.com/u/kellner)\ **Post date:** [March 30, 2007, 8:11pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/47 "2007-03-30T20:11:56Z")
[QUOTE=Elendil’s Heir] Interesting. The article says 32 of the 33 injuries were from “slide burns,” but doesn’t say what the single other injury was. Guess it wasn’t _too_ serious, whatever it was. [/QUOTE] One participant broke his thigh when he collided with others at the bottom of a slide. Apparently that’s to be expected. I wonder whether they told the participants. (Apropos of nothing, the company that organized the test for Airbus belongs to friends of my parents) ---
**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, 9:44pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/48 "2007-03-30T21:44:20Z")
[QUOTE=Elendil’s Heir] Anything much bigger probably isn’t going to be cost- and fuel-effective [/QUOTE] As noted above, one of the most important justifications for large aircraft is fuel efficiency, measured in terms of passenger-miles per gallon. The A-380, on paper at least, will do quite well in this - it’s probably capable of over 100 pmpg. But the real issue is overall cost effectiveness, and this gets very complex, with hundreds of issues contributing. The jury is certainly still out on the A-380. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [March 30, 2007, 10:28pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/49 "2007-03-30T22:28:21Z")
[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. [/QUOTE] **Stranger** also mentioned “off-axis seating” in an earlier post. Even in current wide-bodies, the passengers sit pretty close to the roll axis. But whenever a flying wing banked into a turn, the passengers nearest the wingtips would be pressed down into their seats or feel the floor drop out beneath them. ---
**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, 11:13pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/50 "2007-03-30T23:13:24Z")
[QUOTE=Robot Arm] **Stranger** also mentioned “off-axis seating” in an earlier post. Even in current wide-bodies, the passengers sit pretty close to the roll axis. But whenever a flying wing banked into a turn, the passengers nearest the wingtips would be pressed down into their seats or feel the floor drop out beneath them. [/QUOTE] Presumably in a flying wing, you’d still place the passengers–who have the annoying tendency to get up and move around, throwing off weight balance–near the center axis, and place fuel and cargo out at the extremities. And flying wings don’t tend to cope with extremes in banking very well; they either start to want to boomerang or pitch forward (depending on the sweep angle of the wing) so you probably wouldn’t be doing any crazy maneuvering with them (which also limits their ability to resist and land in crosswinds). The concerns about emergency egress are real, but rather than posing an absolute limitation on the shape of the aircraft they dictate using different methods for evacuation. One notable problem is fuel tankage; on modern conventional jets most if not all of the fuel is stored in “wet wings”; should the aircraft have an catastrophic locational conflict with intervening ground structure, the wings, with their deadly load of combustables and manically spinning parts are likely to separate and be left in the wake, whereas on a flying wing or blended wing body the fuel is probably going to be located adjacent to passenger accomodations. Again, this isn’t a showstopper, but it does require additional methods for ignition retardation and fire suppression. Stranger ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 31, 2007, 2:42am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/51 "2007-03-31T02:42:55Z")
[QUOTE=Stranger On A Train] Presumably in a flying wing, you’d still place the passengers–who have the annoying tendency to get up and move around, throwing off weight balance–near the center axis, and place fuel and cargo out at the extremities. [/QUOTE] I doubt that normal passenger movement would be much of an issue. It would take the concerted movement of a bunch of passengers to have any real effect. FWIW: High-performance sailplanes with empty weights around 600lbs can carry as much as 400 lbs of waterballast - 200 in each wing. Obviously, they aim to dump this prior to landing. You’d think the case where one dump valve fails would be a disaster - one wing is now 200lbs heavier than the other. But it’s actually no big deal. After touching down, when the glider slows below about 25mph the heavy wing will go down despite full aileron deflection. This usually results in nothing but a minor groundloop. ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [March 31, 2007, 3:01am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/52 "2007-03-31T03:01:55Z")
With regards to flying wing designs, wouldn’t they be unpleasant for the passengers further out from the centre? Somebody upthread has mentioned increased air-sickness due to potentially being seated oriented away from the exact direction of travel, but I’m more interested in what happens during turbulence, or when a plane has to bank or turn. When you are in the fuselage of a plane which banks suddenly, you are merely tilted to one side, but surely further out along a wing, you could be suddenly dropped or raised ten or twenty vertical feet _as well as_ the usual mildly unpleasant effects felt by tube-fuselage passengers. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [March 31, 2007, 5:44am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/53 "2007-03-31T05:44:01Z")
[QUOTE=Xema] FWIW: High-performance sailplanes with empty weights around 600lbs can carry as much as 400 lbs of waterballast - 200 in each wing. Obviously, they aim to dump this prior to landing. You’d think the case where one dump valve fails would be a disaster - one wing is now 200lbs heavier than the other. But it’s actually no big deal. After touching down, when the glider slows below about 25mph the heavy wing will go down despite full aileron deflection. This usually results in nothing but a minor groundloop. [/QUOTE] On the other hand, a Dash 8 has a maximum imbalance of 600 lbs between main fuel tanks. If people were seated out on the wing, that’d be like having two people get up and move from one wing to the other. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 31, 2007, 10:23am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/54 "2007-03-31T10:23:19Z")
[QUOTE=1920s Style “Death Ray”] On the other hand, a Dash 8 has a maximum imbalance of 600 lbs between main fuel tanks. If people were seated out on the wing, that’d be like having two people get up and move from one wing to the other. [/QUOTE] Some big folks on that Dash 8! (I’d always heard that the standard passenger is reckoned at 170 lbs). With a max weight around 34,000lbs, a Dash 8 is around 3 percent of the weight of a superjumbo. So the big plane should be insensitive to the normal movements of passengers - it would take something like 100 people all moving a substantial distance together to produce the equivalent imbalance. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [March 31, 2007, 11:29am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/55 "2007-03-31T11:29:37Z")
[QUOTE=Xema] Some big folks on that Dash 8! (I’d always heard that the standard passenger is reckoned at 170 lbs). [/quote] Say you have 10 people seated on each wing. Take two off the left wing and put them on the right wing and you have a difference of four people, 4 x 185 (standard weight in our company) = 740 lbs. > [@](#): > > With a max weight around 34,000lbs, a Dash 8 is around 3 percent of the weight of a superjumbo. So the big plane should be insensitive to the normal movements of passengers - it would take something like 100 people all moving a substantial distance together to produce the equivalent imbalance. It was more of a response to your bit about the glider which implied that a large imbalance is not a problem. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [March 31, 2007, 11:44am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/56 "2007-03-31T11:44:56Z")
On a B747 a fuel imbalance advisory comes on with a difference of 3000 lbs between the outboard tanks, that’s 16 people (or 8 moving from one wing to the other.) Now it’s only an advisory which means it’s not a serious issue. But I think it’s safe to say that the lateral loading and subsequent movement of passengers in a flying wing type design would need to be considered. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [April 1, 2007, 3:08pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/57 "2007-04-01T15:08:14Z")
[QUOTE=1920s Style “Death Ray”] On a B747 a fuel imbalance advisory comes on with a difference of 3000 lbs between the outboard tanks [/QUOTE] I’d presume those outboard tanks are a lot further from the centerline than passengers ever would be. > [@](#): > > I think it’s safe to say that the lateral loading and subsequent movement of passengers in a flying wing type design would need to be considered. They would, though I expect this will be overwhelmed by the issue of maneuvering discomfort associated with seating passengers far from the centerline. IOW, before you have potential imbalance problems from passengers moving around, you have passengers puking when the plane banks for a turn. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [April 4, 2007, 5:33am UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/58 "2007-04-04T05:33:56Z")
What if a poisonous snake was let into the airplane and everyone rushed from one side of the plane to the other in order to avoid it? It could happen! ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [April 4, 2007, 4:52pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/59 "2007-04-04T16:52:55Z")
In late August or early September of 1961, I was in a DC-8 at 33,000 feet over the Gulf Of Mexico Coming from Merida to New Orleans just a bit after dark and the pilot told us there was an eclipse of the moon taking place and we could see it out the left side and to please move slowly. We all rushed to the left side and the plane tipped probably 15 degrees before he could get it back level. Over the intercom he said, “Folks, I said slowly…” It was funny at the time and the clear view from that altitude was beautiful. We were not full but there were a lot of people that moved that small amount in a DC-8 and it did cause a big reaction from the aircraft. YMMV ---
**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:** [April 4, 2007, 6:56pm UTC](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838/60 "2007-04-04T18:56:01Z")
[QUOTE=Stranger On A Train] This doesn’t really make any sense…however, is outside the experienece of commercial aircraft designers, and thus represents a risky…risk to manufacturers…utter failure from a financial perspective. Stranger [/QUOTE] We may be arguing the same point. It isn’t technical feasability that is the problem for manufacturers, but market forces and public perception. The SST and Concorde, for example, didn’t fail because of any lack of understanding or implementation of technology, they were a failure of marketing and industry perception. Manufacturers banked on the gamble that airlines desired speed \> efficiency as their prime market value, and lost. This is also today’s limiter for manufacturers to build _commercially_ marketable next-generation aircraft. The technology is proven and well-understood. You could mount a rocket motor to a football helmet and fly it just fine today with the right software. Public perception and market appeal are the drivers today, and airlines (but not manufacturers) traditionally desire to babystep into new technologies. Manufacturers desire just the opposite, and are frustratingly slowed with new design by market perception, especially with aircraft where safety is of such high concern. [Previous page](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838.md?page=2) [Next page](https://boards.straightdope.com/t/big-airplanes-where-does-it-end/397838.md?page=4)