Size of 18 t GTF?

[chornedsnorkack]

The current Pratt and Whitney GTF projects are the launched Mitsubishi Regional Jet, with engines from 6,7 to 7,5 t, and the launched but orderless Cseries, with engines from 9,3 to 10,4 t.

However, see
http://www.flightglobal.com/articles/20 ... ebody.html

PW says that they will not offer GTF over 18 t in near term. But this does imply that they do offer a GTF up to 18 t - much more than the 10,4 t of C130 - in near term.

What would a 18 t GTF be like?

It turns out that the fan diametre of the 10,4 t Cseries GTF is 188 cm.

Too big to fit A321 - the biggest, CFM56-5B3 has just 174 cm diametre fan - and too feeble to lift it, as A321 needs 15 t engine thrust.

The MRJ GTF fan diametre is 142 cm.

So - what would be the fan diametre of an 18 t GTF?

Also, just why shouldn