Is this really a 787's peak performance. And why don't they make it?

[wumpus]

19 hours ago, mikegarrison said:

The main reason not to put the engines under the wings is because then you need taller landing gear. This is why many small jets (especially bizjets) put the engines elsewhere. The like to have very short (and light) landing gear so that they can also use the door as stairs.

You only get the full benefit of "the wings are holding up everything attached to the wings" when the landing gear completely supports the wings.  And that only happens in extreme cases like the U2 and B-52 where they have those funky little wheels at the end of the wings.  Certainly most planes get most of the benefits of that, but sometimes things get a little too hairy...  But think about how much structure was saved thanks to those little wheels on the end of the wing.

[mikegarrison]

5 hours ago, Dragon01 said:

Actually, it's not that passenger want windows, it's that they want emergency exits. Flying wings have trouble with that, FAA requires that emergency exits do not require climbing to get to them, and that they're a certain distance from all passengers, which is pretty much impossible to realize in a flying wing. The only exits possible are to the front, back and upwards, the latter don't count according to FAA definition, and the former will leave most passengers too far away from them.

It's not a problem with bombers, since the crew has ejection seats, anyway.

I don't think there is actually a rule about how far the exits are from the passengers, but I could be wrong.

The key rule is that for any plane with more than 19 occupants, the entire plane must be able to evacuated in 90 seconds -- with half the exists blocked. The effectively places limits on how far away seats can be from the nearest exit, even if there is no actual rule on that.

For airplanes with 19 or fewer occupants it is allowed to have a single exit.

Edited October 14, 2019 by mikegarrison

[kerbiloid]

Spoiler

15 hours ago, mikegarrison said:

The key rule is that for any plane with more than 19 occupants, the entire plane must be able to evacuated in 90 seconds -- with half the exists blocked.

Large KSP planes violate the rule. They are inappropriate.

 

[Guest]

16 hours ago, mikegarrison said:

The key rule is that for any plane with more than 19 occupants, the entire plane must be able to evacuated in 90 seconds -- with half the exists blocked. The effectively places limits on how far away seats can be from the nearest exit, even if there is no actual rule on that.

Same thing, really. The point is, exits on the nose and tail aren't going to cut it. Especially since aircraft tend to crash nose first, which would disable exits located in the wing's leading edge. A flying wing needs to be fairly large to make sense (small flying wings are not thick enough to comfortably carry passengers), so evacuating people becomes a real problem. A plane that would be possible to evacuate in 90 seconds through one end would probably waste a lot of space on having a wide aisle and very large exits.