Boeing Mesa has flown all-composite main rotor blades for the first time on the AH-64 Apache attack helicopter. Aimed at the proposed AH-64D Block III modernization, the Upgraded Composite Rotor Blades are primarily intended to reduce blade acquisition costs 25% and life cycle costs 50%. As a secondary benefit, they may hike the Apache payload 300 to 500 lb and increase speed 4 to 5 kt with the existing drivetrain. Significantly, the new blades are designed compatible with a new 3,400 shp transmission to further boost the performance of a further-modernized Apache.

Today's ballistically-tolerant Apache main rotor blades have four metal spars wrapped in glassfiber skins. The new design has a single graphite/glass spar and glass skins and in live-fire testing met the same 23 mm high-explosive-incendiary ballistic requirement. All-composite construction made it possible to blend several advanced airfoils, including one developed by McDonnell Douglas Helicopters for the unsuccessful Super Team Comanche proposal. While the new design has the same span and chord as the current Apache blade, it increases twist from 11 to 15 degrees.

In addition to the high-efficiency airfoils, the new design incorporates a smaller tip with increased sweep but no anhedral. "We kept it simple to reduce the cost," explains Boeing Apache modernization program manger Larry Plaster.

Design of the new blade was influenced by Apache experience in Afghanistan and Iraq, "We've done a lot to improve the erosion capability of the blade," says Mr. Plaster. A new one-piece steel leading edge strip with twice the thickness and 12% greater chord covers the blade leading edge while a nickel leading edge with twice the thickness and 20% greater chord protects the tip. The new blades have an objective service life of 10,000 flight hours. If ultimately qualified for only 5,000 hours, they would more than double the life of their predecessors.

Work on composite main rotor blades for the AH-64 began as part of the Affordable Apache Rotor Program and initially included a composite main rotor hub later abandoned to reduce cost. Development funding was shared jointly by the Army and Boeing. Boeing Mesa has so far built 11 blades in a risk-reduction effort and expects to finish Proof Of Concept testing in January 2004. Depending on Army decisions, full qualification could be undertaken separately or as part of the Block III upgrade. With production tooling, Boeing Mesa has the facilities to manufacture the new blades in-house.

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