GRAHAM WARWICK / PARIS
Material chosen over advanced alloys as Boeing aims to finalise business plan by early 2004
Boeing's planned 7E7 will use composites for the majority of the airframe, including the wing and fuselage, in a clear sign that the manufacturer intends the 200- to 250-seat airliner to be as advanced as is feasible in view of the 2008 in-service date. The company made the decision after also studying advanced aluminium alloys.
A toughened carbonfibre-epoxy composite has been selected as the main material. The wing will also include TiGr, a titanium-carbonfibre laminate offering low weight and long fatigue life. New aluminium alloys may still be used for smaller structural pieces, says Mike Bair, senior vice-president for the 7E7 programme. Real-time airframe health monitoring using continuous data collection from sensors embedded in the structure is also planned for the 7E7.
Boeing aims to reduce the final-assembly time for the 7E7 to just three days, compared with 13-17 days for its current airliners, by making the aircraft from fewer, but larger parts. Machining large monolithic parts from aluminium results in substantial wastage, which offsets the material's cost advantage over composites.
Customer acceptance was a potential concern, but US airlines indicated they would be comfortable with a composite airframe, says John Feren, vice-president, marketing, sales and in-service support on the 7E7. Asian carriers were more concerned, he says, because they do more of their maintenance in-house. But Bair says: "There has never been a maintenance issue with the 777 tail, and it's the same [composite] material as in the 7E7."
The materials decision is a major milestone in the plan to seek approval to offer the 7E7 to airlines, with the business case and business model expected to be presented to the Boeing board by the end of this year or early next. "We are convinced we can close the business case...but we have a fair amount of work to do," says Bair.
Feren says "some recovery" in the airline market will be required if the 7E7 is to be launched. He believes the strict launch criteria used for previous programmes, requiring a certain number of firm orders from a certain mix of airlines, will not be applied to the 7E7.
Efforts are continuing to refine the new business model. Companies named for Boeing's structures and systems teams are all potential risk-sharing partners. "No target has been set for the percentage of risk sharing," says Bair. Boeing is also prepared to accept public funding up to the 30% allowed by the large commercial aircraft agreement between Europe and the USA.
Source: Flight International
