The twin-engine, 12-passenger, two-crew-member DHRUV is said to be the only helicopter in the world able to fly over the Himalayas and Mount Everest.
 
The twin-engine, 12-passenger, two-crew-member DHRUV is said to be the only helicopter in the world able to fly over the Himalayas and Mount Everest.
The twin-engine, 12-passenger, two-crew-member DHRUV is said to be the only helicopter in the world able to fly over the Himalayas and Mount Everest.

An active vibration-control system damps out vibrations from the main rotor to the fuselage in Advanced Light Helicopters (DHRUVs) made by Hindustan Aeronautics Ltd., India (www.hal-india.com).

AVCS technology from Lord Corp., Cary, N.C. (www.lord.com), uses multiple accelerometers to measure airframe vibrations. A controller gages the feedback then sends compensating signals to actuators or Frahms (named after the original inventor) that cancel floor vibrations.

The system is capable of handling two to four active Frahms and weighs less than 1% of the aircraft gross weight. Early results indicate AVCS smoothes out vibrations throughout the entire helicopter under most flight conditions.

-- Lawrence Kren