As you known, most helicopters are able to flying at speeds up to 250km/h (a hundred thirty or a hundred and forty knots or about 160 mph), however Eurocopter has allowing go up to 430km/h (267 mph). it is called the Eurocopter X3 that claimed as the arena fastest helicopter ever constructed.
As considered, Eurocopter X3 has brings one additional engine, which is able to drive the extra propellers and like a standard helicopter. The Eurocopter X3 is utilized a hybrid machine, new modern know-how for impressive climb and descent charges.
This hybrid helicopter will be on hand in search and rescue, medivac, and armed forces operations, the place requires excessive velocity and acceleration capabilities.
source: eurocopter web site
Eurocopter X3 hybrid quickest helicopter
The Eurocopter X3 hybrid helicopter exceeds its pace problem: 232 knots (430 km/h.) is attained in stage, stabilized flight