Boeing's studies of a heavyweight, very-long-range "-200X" derivative of the standard-body 777 are now focusing on an even heavier maximum take-off-weight design which has a strengthened wing, increased fuel capacity and a new wingtip design.
"We're getting feedback from the airlines on these models", says 777 product development chief engineer Michael Burtle. "When the airlines figure out what they want to do [for their ultra-long range requirements], we will be ready to support them."
The -200X study follows initial evaluations of a shortened, 15,725km (8,500nm)-range -100X variant, and later studies of a strengthened long-range -200X version with improved direct-operating costs per seat. The latest -200X study projects a higher maximum take-off weight of 322,340kg, greater than that in previous studies. For the first time, additional fuel-tank space has been found. The study takes wing fuel-tank capacity beyond the break-line area of the outboard wing, which was reserved, for the wing-fold mechanism. Although the fold option is still offered by Boeing, no airline has requested the feature.
The wing would require no significant structural strengthening, being at least 4,500kg below the design weight limit of the basic -200 wing, but the upper and lower skin gauges would be increased. Boeing is also evaluating a new wingtip for the -200X, which would improve cruise performance and help distribution of span-wise loading. The new tip would increase span by 0.68m on each side and would increase the already significant "wash-out" of the current wing.
"By increasing the rake of the tip, we get a little more span out of the trailing edge, which would give better performance at high speed and low speed," says Burtle.
The heavier aircraft would require the higher-thrust engines earmarked for the high gross-take-off-weight versions of the stretched 777-300. The latter timetable of these engine developments suggests that the earliest possible service entry opportunity for the heavier -200X would be from the year 2000 onwards.
This supports the apparent slowdown in ultra-long-range studies, which appear to be in flux as airlines assess the growth of "fragmentation" on such routes, the impact of the long-range 747-500X and the emergence of new A340 offerings from Airbus.
Industrie
First 777-200 IGW flew in October, but other variants may be a long way off.
Source: Flight International
