"Rotors, rotors everywhere: 54 homebuilt rotorcraft gathered for the 3rd International Fly-in of the PRA in Raleigh, N.C. representing 26 states and 6 foreign countries.
In the front row are 25 pilots who participated in flight competitions.
Most taught themselves to fly in their own whirlybirds and had no previous airplane flight training. The convention established a new world record in the number of private rotorcraft to be assembled at any one time.
Popular Rotorcraft Association photo. FIgure 12 from Verti-flite, August 1965