Guy Norris/Los Angeles

BOEING IS gearing up to attack the cost of manufacturing carbonfibre-composite structures as part of a new phase of NASA's Advanced Composites Technology (ACT) programme.

"The biggest thing we need to do is to reduce manufacturing costs," says Boeing director of aircraft-structures engineering Jack McGuire. "Now we have NASA adhering to the idea that they need to help us with these costs, and not just with the technology itself."

Under this new $24 million phase of the ACT programme, which began in 1989, Boeing will design, analyse, fabricate and verify large composite fuselage structures for a commercial transport aircraft.

Under the programme, NASA also selected McDonnell Douglas to build and test a full-scale composite air-transport wing under an eight-year, $160 million, contract (Flight International, 2-8 August).

"The main thing we're after is manufacturing productivity and cutting costs, as well as design concepts that produce advantages from a maintenance stand-point. They should also be lightweight, have increased fatigue resistance and better resistance to corrosion [where they are bonded to conventional metallic alloys]," says McGuire. "This is the only way of getting the use of graphite [carbonfibre composite] to be competitive, and has the potential to give operators a drop in direct operating costs of around 9%."

Boeing will gradually work up to larger composite fuselage panels, revising the design at each step. It will look at the effect of "cut-outs" (windows, hatches and doors), interfaces with wings and pressurisation. It is also likely to receive a supplementary contract within the 1995-2000 timeframe of the current ACT phase to construct a complete fuselage section from advanced composites.

The practical benefits of earlier composite research work are already becoming apparent, as illustrated with the 777 - the first Boeing transport to be built with a composite primary structure. The company plans to build on its earlier success by developing an all-composite empennage for the stretched 747-X, if launched, saving some 20% in all-up total aircraft weight, says McGuire.

This is the first of two main 747 derivatives, which Boeing is studying as part of its New Large Airplane initiative. The second, even larger, 747-X could potentially entail the use of up to 50% composites in its wing and fuselage structure, compared to under 10% for the 777.

For the longer term, the company estimates that the carbonfibre-based composite component of the high-speed commercial transport could be between 80-90%. "We'd be relying heavily on a weight reduction that's affordable," says McGuire.

Source: Flight International