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Sunday, March 1, 2009

Rotorcraft Report: Smoother Flight for Sikorskys?

MILITARY | TECHNOLOGY

Future Sikorsky medium- and heavy-lift helicopters may be fitted with dual-frequency Hub-Mounted Vibration Suppression (HMVS) made by LORD Corporation, under a teaming deal struck between the two companies. HMVS technology cancels out rotor-induced vibrations at the hub by providing equal and opposite centrifugal forces; the direction and speed of which are dynamically adjusted using an on-aircraft accelerometer.

"The hub-mounted vibration suppressor consists of motorized imbalanced rotors that rotate at the blade-pass frequency to create centrifugal forces," said Mark Jolly, LORD’s senior staff engineer. "By phasing the two rotors, the magnitude and orientation of the centrifugal forces can be made to cancel lateral hub vibration. Compared to passive systems that rely on pendulum weight to counterbalance vibration, HMVS technology is more responsive, more accurate and weighs half as much." He added that LORD Corporation is designing HMVS systems to match existing passive systems in size and shape, so that retrofitting helicopters will be relatively straightforward.

The LORD/Sikorsky deal is being done under Sikorsky’s High Performance, Low Vibration and Low Noise Enabling Technologies Program, in league with the U.S. Army. The HVMS system is currently being packaged to work with existing Sikorsky helicopters. A ground test is planned for 2010, with flight tests (after the initial program has ended) sometime afterwards.

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