Fastest speed in a helicopter (non-FAI)
Who
Eurocopter X3
What
293 mile(s) per hour
Where
France ()
When

The Eurocopter X3 clocked a top-speed of 255 knots (472 km/h; 293 mph), at an altitude of 10,000 ft (3,050 m) over southern France, during a test on 7 June 2013. This beat the previous record, set by the Sikorsky X-2, by 5 knots (9.3 km/h; 5.8 mph). The aircraft was flown by Eurocopter test pilot Hervé Jammayrac.

Most helicopters struggle to fly faster than 175 knots because of a phenomenon called "rotor blade stall", in which the forward motion of the helicopter slows the airflow over the rotor blades during the portion of their cycle where they’re travelling towards the rear of the aircraft.

The Eurocopter X3 gets around this problem by adding two conventional propellers on short wings to help pull the helicopter forwards.