Boeing is making final adjustments to the configuration of the 747-500X/600X as it prepares for an expected programme launch in early 1997.The changes are being made following analysis of more than 1,000h of wind-tunnel tests in Europe and the USA. Although Boeing warns that some changes can still be expected, the latest configuration is "pretty close" to the final design, says John Hayhurst, vice-president and general manager of the 747-500X/ 600X.

The gradual shift towards the wider use of 777 systems, rather than sticking to the original goal of higher commonality with the 747-400, "-has probably helped" reduce the expected development time, says Hayhurst. "That's because the 777 systems are state-of-the-art and the team is mostly still here - to take that architecture and put it in the 747 is probably an easier task than updating the -400," he claims.

The company still faces a tight schedule, however, and is aiming at a first delivery date of December 2000. "By and large, the discussion [with potential launch customers] are proceeding very well," says Hayhurst.

The main change to the latest configuration (Model 763-223) is an increase in wingspan to 77.7m (255ft), some 1.2m larger than the previously released design. The overall height of the tail has also been raised by around 0.3m, to 21.6m. Slight reductions, have been made to the span of the horizontal stabiliser (25.8m) and width of the inner wheel-base (3.9m). The outer wheel-base using two six-wheel units, based on the 777 design has been increased, by 0.7m, to 10.7m. Overall length has also been decreased slightly, to 84.5m, but the -600X will still be almost 14m longer than the -400, and around 8.5m longer than the -500X.

The wing's configuration has virtually been frozen. The trailing edge will be fitted with relatively simple, single-slotted, flaps and double ailerons outboard. The low-drag wing design is "-optimised for noise", says product-development and operational-infrastructure chief engineer Duane Jackson. "We've achieved the same cruise Mach number [0.85] with slightly less sweep. It's really a trade-off between sweep angle and the structural weight of the wing." Boeing declines to specify the -500X/600X sweep angle, but it is thought to be around 36í.

The leading edge of the 750m2 (8,100ft2)-area wing has been designed with rigid Krueger flaps inboard and variable camber Kruegers outboard. These will be based on the same design as that of the original 747 and they can be deformed to suit varying speed requirements.

Source: Flight International