It was evaluated for use in coastal patrol and light transport roles; in 1934 it was redesignated C-28 and assigned as a liaison aircraft to the United States Military Academy.

This was part of a fleet of civilian aircraft flown by volunteers along the Atlantic and Gulf Coasts, searching for both German submarines and for allied ships in distress.

[4] A surviving CAP S-39, previously based at Rehoboth Beach, Delaware, is currently on display at the New England Air Museum.

The aircraft was intended to allow Deeds to quickly travel from his yacht to business and events ashore.

[5][6][7] Data from Aerofiles : Sikorsky,[14] American flying boats and amphibious aircraft : an illustrated history[15]General characteristics Performance