The U.S. FAA has directed Bombardier to comply with special conditions for the use of an aluminum-lithium (Al-Li) alloy on the Global 7000/8000. The alloy is similar to the materials used on Bombardier’s C Series, a company spokesman said, noting that the manufacturer is replicating the same certification requirements it did with the regional jet program.
Bombardier is constructing the fuselages of its new Global family with Al-Li. The FAA noted that the alloy “may provide different levels of protection from post-crash fire threats than would similar airplanes constructed from traditional aluminum structure.” The special certification conditions are designed to ensure an equivalent level of protection, the FAA said, adding, “The applicant must ensure that the material being installed on an airplane does not introduce a new hazard that would reduce the survivability of the passengers during a post-crash situation, or that would provide levels of toxic fumes that would be lethal or incapacitating, thus preventing evacuation of the airplane in a crash scenario.”
The introduction of lithium, a less dense material, is designed to provide a lighter-weight, strong material that improves the efficiency of an aircraft. Arconic (formerly Alcoa), one producer of Al-Li, characterized the material as “an outstanding combination of strength, toughness, stiffness, corrosion resistance and high-temperature performance, and at a lower cost than titanium or composites.”
The material has shown the ability to reduce weight by as much as 10 percent versus composites on single-aisle transport aircraft, the metals specialist said, adding this could produce up to a 20 percent gain in fuel efficiency. Bombardier is not detailing specific gains of its use for competitive reasons.
Al-Li is used on transport-category aircraft such as the Airbus A380 and A350, Boeing 787 and the C Series. It also is used on the Gulfstream G650, among other applications.
The conditions continue the certification process for Bombardier's Global 7000, which is expected to enter service late next year. By mid-July, three flight-test aircraft had accrued 500 hours, and two additional flight-test aircraft were in final assembly.