The Lockheed CL-475 was a rigid rotor design based on the ideas of Lockheed engineer Irven Culver. The aircraft flew 5 months from initiation of the design following remote controlled model tests of the concept. It was the first helicopter to be built and flown by Lockheed.

The successful testing of this aircraft led to a US Army/Navy contract to build the XH-51 high speed demonstrator.

Source: "Rigid Rotor Rewind: Lockheed Helicopters Come Full Circle", Raymond L. Robb, VERTIFLITE March/April 2017, Page 50