Originally Posted by
JSlo
Perhaps in terms of capacity to cost or something? Otherwise, isn't the whole point of the 787 and 380 a race to efficiency? Boeing has posted that the 787 will be 20% more efficient than other aircraft of similiar size. Help me out on this one I am kinda curious.
I am no engineering expert- just from what I have read in various journals that this is part of the whole 787 effort using composites and lighter weight materials and the new engines etc to maximize efficiency?
The important part of Boeing's stat is "than other aircraft of similar size." Larger aircraft have a distinct advantage (or "economy of scale") when it comes to efficiency. The "race to efficiency" is mostly about improving engine performance, as well as constantly working to lighten the airframe and reduce the drag coefficient.
United flies ORD-HKG (~7,800 mi) on a 747-400 and burns about 375,000 lbs of fuel. CO flies EWR-HGK (~8,050 mi) on a 777-200ER and burns about 300,000 lbs of fuel. A UA 744 (new config) carries 374 pax. The CO 772 carries 285 pax.
UA burns 1,002 lbs per passenger
CO burns 1,052 lbs per passenger
In this crude example, the United 744 is "more efficient" per passenger, even though it burns more fuel (assuming that they fill every seat).
Of course, on many routes cargo plays a major role in both revenue and weight, therefore changing the factors of efficiency.
Despite the above example, efficiency of a given aircraft on a given route can be dictated by many factors beyond strict fuel flow. Cruising altitudes, runway lengths (at departure), winds aloft and other performance characteristics of a specific aircraft may make it better or worse suited for a given route.