1954 tests conducted at NASA Langley Research Center’s Full Scale Tunnel and Free Spinning Tunnel building. The model being tested was 0.4 scale . Researchers looked at the models maneuverability during hovering, take-off, and landing. Langley catalog #L-23.
Free Spinning: http://gis.larc.nasa.gov/documents/646/historic/WebApp.html
Full Scale: http://gis.larc.nasa.gov/documents/643/historic/WebApp.html