Piasecki PV-2
The Piasecki PV-2 was a helicopter designed by Frank Piasecki. The PV-2 is best known for being one of the first successful helicopters flown in the United States. The PV-2 first flew on April 11, 1943. Developed as a technology demonstrator, the PV-2 brought several new features such as the first dynamically balanced rotor blades, a rigid tail rotor with a tension-torsion pitch change system, and a full cyclic and collective rotor pitch control. The PV-2 is now on display at the National Air and Space Museum's Steven F. Udvar-Hazy Center