May 13

What happened on May 13 in aviation and space history.

• May 13, 1940

  First free flight of the Vought-Sikorsky VS-300

  First flight — On 13 May 1940 the VS-300, designed by Igor Sikorsky, made its first untethered free flight. With a single three-blade main rotor originally driven by a 75-horsepower engine, it was the first successful single-lifting-rotor helicopter in the United States and the first to counter torque with a vertical-plane tail rotor. That layout went on to become the industry standard for helicopters.