Piasecki PV-3 / HRP "Rescuer"
1945
Although it was built only in modest numbers and had an unspectacular (though useful) service career, the Piasecki HRP-1 has its place in the history of rotorcraft by virtue of being the world's first practical tandem-rotor helicopter and, at the time of its appearance, the world's largest helicopter of any kind. Frank N. Piasecki, holder of the first helicopter pilot's licence to be issued in the United States, became interested in rotorcraft development before America's entry into World War 2, and in 1943 he formed a company known as the P.V. Engineering Forum whose first design, the PV-2, was a single-seat, single main rotor helicopter with a 90hp Franklin engine. This machine, which flew for the first time on 11 April 1943, was Piasecki's first and only single-rotor helicopter, for on 1 February 1944 he received a contract to develop a tandem-rotor utility transport and rescue aircraft for the U.S. Navy.