This is a Significant Operational milestone.
The aircraft was tethered to a plate that could be dragged around. The flight lasted only a few seconds and flew to a height of a few inches.
The site of the first flight is now recognized as an Historic aerospace site.
(Source: The History of Sikorsky Aircraft, Journal of the American Helicopter Society, Vol. 1. No. 1, January 1956, Page 27)