[2] In 1958, Irv Culver presented an idea for how to rigidly attach the rotor blades of a helicopter to the hub, to the Lockheed management.

In 1920, Juan de la Cierva had tried the same concept, but had trouble controlling the rotor, because of excessive gyroscopic moments.

Culver's research led him to believe that there was a way to control the excessive pitch and roll moments by incorporating a feedback system into the rotor.

[2] After completion at Burbank, the CL-475 was taken to Rosamond Lake on Edwards Air Force Base in the Mojave Desert for testing.

For six months, Lockheed experimented with three and four-bladed wooden rotors, but stability was finally achieved by using metal blades in a three-blade configuration and the addition of a gyroscopic control ring connected directly to the swashplate.