Tue May 31, 2005 2:02 am

Let's approach the original question a little bit differently. Given B787 composite technologies, could a B747-400 sized plane be designed to use two GE90s?

The GE90 has been tested at 127,000 lbs. of thrust and certified to 115,100 lbs. For the sake of argument, let's assume at it can be certified to 120,000 lbs. at a reasonable cost.

The B777-300ER has an OEW of 370,000 lbs and a MTOW of 775,000 lbs. The B747-400 has an OEW of about 395,000 lbs and a MTOW of 875,000 lbs.

Could a new design twin with 120,000 lb engines perform all the missions of a B747-400? The assumed increase in thrust would mean that our twin could have a MTOW of 810,000 lbs. The switch to composite construction would probably yield an OEW of about 350,000 lbs. With a max structural payload of 154,000 lbs (same as B777-300ER and slightly higher than the B747-400), 400,000 lbs of fuel could be carried (more than either the B777-300ER or B747-400).

So, yes, an all-new twin the size of the B747-400 could almost certainly be built using GE-90s. Of course, it wouldn't be a B747.

[Edited 2005-05-30 19:24:46]