Sikorsky Opens Bi-Directional Whirl Tower

Composite Technology Inc. (CTI), a Sikorsky Aerospace Services company based at Dallas Fort Worth International Airport, opened one of the world's most powerful structures to dynamically balance helicopter main rotor blades. Designed by Sikorsky to test main rotor blades that rotate either clockwise or counterclockwise, the bi-directional whirl tower will enable helicopter operators and manufacturers to rebalance their rotor blades in the U.S. regardless of the rotorcraft's country of origin. Sikorsky Aerospace Services is the aftermarket business of Sikorsky Aircraft Corp., a subsidiary of United Technologies Corp.

Among those attending the opening of the $15 million facility were Texas Lt. Gov. David Dewhurst, and Texas House Members Rep. Linda Harper-Brown and Rep. Mark Shelton.

"The addition of a high-powered bi-directional balance stand offers our customers reliable, accurate measurements for main rotor blades flown by helicopter operators across all categories, from lights up to heavy lift," says David Adler, Sikorsky Aerospace Services President. "The ability to test blades of all sizes and rotational speeds in either direction will provide significant cost savings and rapid turnaround time to our North American customers."

The whirl tower features two 3,000 shaft horsepower (shp) variable frequency drive induction motors for rotation of three blades (a precision-balanced master blade and two test blades) in either direction at a peak rating of 6,000 shp. The tower's 6,000 lb rotor head will enable Sikorsky to spin blades weighing up to 500 lb each, thereby easily accommodating blades flown by U.S. Marine Corps CH-53 heavy lift helicopters.

The whirl tower measures imbalance by spinning two test blades against a precision-balanced master blade of the same configuration. As the three blades rotate about the rotor head, a laser tracking system measures where the blades fly relative to one another. Adjustment of weights at a blade's tip and trailing edge will enable CTI to correct for tip deflection, and for any rotational twist along a blade's length.

"This whirl tower advances CTI's and Sikorsky's comprehensive rotor blade repair services in the U.S.," says CTI President Bob Ellithorpe of the two-year construction effort. "We are very pleased to open this state-of-the-art capability in Texas during our 40th year serving the rotorcraft community."