WASHINGTON -- The U.S. government wants Boeing to demonstrate that composite fuel tanks and wings on its 787 Dreamliner resist fire long enough to let passengers escape in an emergency.
The Federal Aviation Administration (FAA) proposal this week is no different than what it expects from traditional designs when considering safety certification. But the request represents the first time the agency has weighed in publicly on its performance expectations for the use of carbon composites in major aircraft construction.
Traditional airliners are predominantly made of aluminum with some composite components. But Boeing is blazing a trail with the mostly composite Dreamliner, promoting the material's strength and lightweight properties to airlines seeking fuel efficiency.
Added FAA scrutiny of composites in a certification review for the first generation 787-8 was anticipated by Boeing.
"This is very much expected and the timing is expected as well. This is something we've been very intentional about in working with the FAA on the 787 program to identify all applicable rules as early as possible," said Jeff Hawk, the Boeing executive who oversees 787 certification.
The FAA is expected to soon issue a second proposal that would require Boeing to assess the crashworthiness of composites. Hawk said Boeing is preparing for that request as well.
A handful of other special FAA conditions for the twin-engine 787 mirror requirements Boeing had to complete for the 777 wide-body, which first flew in the mid-1990s. But the composite fuel tank and wing test is new, as would be any proposal on a crashworthiness standard.
Boeing wants no certification surprises once flight tests begin in August. Hawk said the special FAA conditions would not slow the 787's delivery schedule for May 2008.
Carbon-based composite fibers bound by epoxies have been used for years in military aircraft and have gradually made their way into tail fins, flaps, interior panels and stabilizers on commercial jets. They appeal to manufacturers wishing to satisfy airline demands for powerful, yet lighter aircraft that use less fuel.
But the 787 will be the first jetliner to feature composite fuselage, wings and fuel tank.
Safety experts say fire is the chief threat to passengers in most accidents.
Containing or delaying flames from reaching the cabin and engines or penetrating fuel tanks is a priority.
The FAA cited a "major shift" in aircraft construction with the 787 and acknowledged that it needs to know more about composites.
"The use of composite structure should not decrease this existing level of safety," the FAA said in its proposal for new fire tests for fuel tanks and wings. "Boeing must demonstrate that the 787 has sufficient post-crash survivability."
The FAA wants Boeing wings and fuel tanks to withstand fire for five minutes without failing after a survivable crash, the same amount of time regulators accept for metal tanks.
Mark Shuart, a composites expert at NASA's Langley Research Center in Virginia, said Boeing has taken a bold step with the 787 design and expects the company materials to be certified.
"Some of the most conservative engineers in the world are chief engineers of airplane companies. They're betting the company when they build a new plane," Shuart said.
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