Aircraft

^{By Max Kingsley-Jones in London}

Boeing has released preliminary details of proposed design changes to the wing of the largest 787 twinjet variants as the programme reaches its 25% design release milestone.

Boeing has recently decided to increase the wingspan of the stretched 787-9 model by “around 2m [6ft]” to improve the aircraft’s performance, says the programme’s general manager Mike Bair. Until now the aircraft, which is still being defined, was to have the same 60m span wing as the baseline 787-8 model.

Bair says the decision was driven primarily by aerodynamic considerations: “The increased span gives us better lift over drag and better low-speed performance.”

The 787-9 is due to enter service in December 2010 with launch operator Air New Zealand which has four Rolls-Royce Trent 1000-powered –9s on order (a Boeing artist's impression of which is pictured below)

Meanwhile Bair says that the –9’s improved wing design “will probably be” the configuration adopted for the proposed 787-10 double stretch, which the manufacturer looks increasingly likely to decide to launch. “We’re very active in the market place with the –10. It’s not a matter of ‘if’ but ‘when’,” he says, adding that he expects a decision to proceed with the 300-310 seater “within the next 12 months”.

Bair says that existing engines developed by General Electric and R-R for the 787-8/9 models, which offer a maximum thrust of 75,000lb (341kN), will be satisfactory for the –10, although Boeing would have scope to install an engine with a larger fan and greater thrust if required.

The news came as Boeing announced it has completed 25% of all the design releases for the 787. One-quarter of all documents for manufacturing have been finalised. The fuselage and wing skins are among the elements defined from a tooling perspective. "We have seen tremendous progress by our international partners and the Boeing team working on the detailed design of this aircraft," says Bair.