A Radical rotor boosts helicopter speed to 288 mph
The top speed of helicopters hasn’t increased much since the 1960s, but that will change when the prototype of Sikorsky’s newly unveiled X2 takes flight late next year. It will travel at up to 288 mph (compared with the 220mph limit of conventional ‘copters) using two four-bladed, low-drag rotors spinning in opposite directions and an airplane-like propeller in the rear that significantly increases the forward thrust. The stacked blade configuration incorporates new control techniques and stiffer composite construction that allow the rotors to be set closer together for less weight and drag.