Originally Posted by
bocastephen
I don't see how it needs a clean sheet design - you have the same overall design, just new materials. Just slapping new engines on a 757-300 isn't going to do it - if they want the higher range and efficiency, something needs to change, and that is likely the materials.
What you're suggesting
is a clean-sheet design. It's not as simple as saying, "Let's make the same fuselage as the 757, except just replace all the aluminum with carbon reinforced plastics." That's not how it works. You're talking about designing an entirely new fuselage, new wings, new engines...it's a whole new plane.
Originally Posted by
entropy
IPTE configured 763's aren't much different in capacity than a 752. What they really "want" is a lighter MTOW 787 (e.g. the 787-3) with 4500nm range. Now that Boeing has the 787 line operating... looking at adding a lighter optimized cousin may be a better option than re-engining or trying to scratch more life out of the 1960's 737.
a 4500 nm, ~200 passenger range aircraft would be able to do all of the 757 range limited operations, with only a slight increase in pax capacity.
The 787-3 is
a dog that won't hunt. It's just too big (wings, fuselage diameter, etc.) to be economical at that capacity.