Contra-rotating main rotors were a feature of the HH-43B in service with the Air Force from the 1950’s to the 70’s
.Misc Helicopters
Co-Axial Rotors. as on the Hiller-copter illustrated in the December Mechanix Illustrated, eliminate noise and vibration on this new helicopter designed by Vincent Bendix. The inventor claims it will be easier to operate and safer than an automobile. Two levers control the machine’s flight, and continuous autorotation makes it possible to fly it with safety at altitudes of only 100 to 200 feet.