Sikorsky tests counter-vibration system
Sikorsky and Lord have completed the flight demonstration of a hub-mounted vibration suppressor (HMVS) intended to address crew fatigue and reduced equipment reliability caused by helicopter vibration. Eventually, the HMVS could be part of a larger system integrated into all Sikorsky helicopters.
The flying testbed was a UH-60A Black Hawk, which accelerated from a hover to 150 knots, performed autorotations and made 60-degree-bank turns. The two companies collaborated on the evaluation at the U.S. Army’s Aviation Applied Technology Directorate (AATD) at Fort Eustis, Va., as part of the AATD’s active rotor component demonstration program. The effort involved 30 flight hours logged between August 2012 and March this year.
The HMVS cancels the largest vibratory loads near their origin–the main rotor hub–William Welsh, Sikorsky technical fellow for dynamic systems, explained. By acting at the source, the system prevents the loads from propagating into the airframe.
A control computer receives vibratory acceleration levels throughout the cockpit and cabin. Using these inputs, an algorithm commands the relative positions of the actuators to subdue these vibrations. The actuators consist of four eccentric masses, each controlled by a brushless electric motor. The motors spin the masses at the blade passage frequency (17.2 Hz for the Black Hawk).
In flight-testing, the HMVS was found to reduce vibration significantly, while reducing weight by 30 percent compared with current, passive systems.
In fact, Sikorsky is working on the HMVS as a component of Zero-Vibe, a wider-ranging system for vibration suppression. “We anticipate that Zero-Vibe will produce a jet-smooth ride in Sikorsky helicopters, resulting in low crew fatigue and reduced direct maintenance costs,” Welsh said. The full Zero-Vibe will start flight-testing in the fourth quarter of this year, under the AATD Combat-tempered Platform Demonstration program.