Originally Posted by
liteswap
I'm still intrigued as to why a wide body should be economical enough to stop a/c makers building longer aircraft with less frontal area. I suppose there must be limitations on the ground that effectively mandate a/c length. What are the other constraints?
There are a range of aerodynamic considerations. Foremost is that as the aircraft rotates for takeoff on the runway, that you do not bang the tail. This applies to the landing flare as well. To overcome this you would need to make the landing gear taller to increase the distance between fuselage underside and the ground, and that in turn makes it both more of a handful to control, and more difficult for ground equipment to service it.
Stretched versions of aircraft, such as the 757-300, or the 737-900, are regarded as being at the limit of tailstrike liability, and also for overlong ground unloading/loading times. Notably, both have been poor sellers compared to their standard-bodied conterparts.
Originally Posted by Seat62K
I seem to remember DC10s had 5-across in the central section. Yuk!
The DC-10, also the MD11 and the current Boeing 777, have fuselages that are sized for 9 seats across (the 747 is a bit wider, and is 10-across). With 9 seats you can either do 2-5-2 or 3-3-3. There are supporters of both layouts. Everey DC-10 I saw had 2-5-2, whereas I have seen both in the MD11 and the 777. The middle seat of 2-5-2 requires two people to move out of your way if in the middle of the row, but you can go in either direction, whereas there are two window seats in the 3-3-3 that require the "double excuse me". If the flight is 90% full then 2-5-2 allows four pairs in each row with the middle seat free, this is more difficult with 3-3-3. If we start a discussion of which is better, you go on for ever. I was once given a reprimand by a pax seated alongside for having the temerity to get up from my inside seat twice in a TWELVE HOUR flight from LAX to London; it's experiences like this that lead people to dislike seats not on the aisle.
Originally Posted by xeque
How about seats facing each-other with common leg room like the old style railway carriages?
The problem with this one is that there is then wasted space behind and underneath the backs of the two passengers in adjacent sections, which the "bus style" of conventional aircraft overcomes by having your legs go under the seat in front. So you would not get as many seats in. Also, pax are generally unhapy with rearward-facing seats, configurations with a few of these find them unpopular, and there are also safety issues as rear-facing pax are not protected from debris and loose items flying forward in a major incident (a Boeing study found loose items thrown forward were the No 1 cause of injuries in such incidents).