January 22, 2009
By Thomas A. Horne
Hartzell Propeller Inc. has earned a type certificate for a new, lightweight composite-construction propeller hub. The first such hub was delivered to Cirrus Aircraft, for use with Hartzell’s ASC-II composite propeller blades. It will be installed in Cirrus’ SR22.
The composite hub weighs four pounds less than the hubs previously used, and the blades save another 12 pounds over the earlier aluminum prop blades. This lighter weight meant that Hartzell could certify the propeller-hub unit to a lower centrifugal load limit—25,000 pounds, versus the 50,000 pounds of force required by metal prop blades. Future propeller system weight reductions will vary depending on the number of blades and the length of the hub extension.
“In aviation, every ounce counts,” said Mike Disbrow, Hartzell’s senior vice president of marketing and customer service. “Four-plus pounds carried far forward on the airframe can make a real difference in center of gravity and loading.”
The ASC-II composite blades are made of a proprietary layup of carbon fiber and Kevlar, with integral stainless steel shanks and co-molded, electroformed nickel leading edges.
With the success of the new prop and hub in Cirrus aircraft, Disbrow said that the new design will be used in other, future propeller applications.
AOPA Pilot Editor at Large Tom Horne has worked at AOPA since the early 1980s. He began flying in 1975 and has an airline transport pilot and flight instructor certificates. He’s flown everything from ultralights to Gulfstreams and ferried numerous piston airplanes across the Atlantic.
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