03/31/2015. Remarks by Johan Visschedijk: "Two three-seat Army R-5As were accepted by the Navy at Floyd Bennett Field in December 1945 for trials as HO2S-1s (BuNo 75689, 75690). Production orders were placed for developed four-seat versions of the same basic Sikorsky S-51 design, designated HO3S-1 and equivalent to the USAF's H-5Fs, with Pratt & Whitney R-985-AN-5 engines. Despite observation designation, the HO3S-1s served in a wide variety of roles, and gave outstanding service with Helicopter Utility Squadron HU-1 'Pacific Fleet Angels' in Korea. Deliveries began in November 1946, and VX-3 received its first aircraft of this type in May 1947; at least 88 were procured (BuNo 122508 to 122529, 122709 to 122728, 123118 to 123143, 124334 to 124353). One XHO3S-3 had a new rotor head and blades, in 1950."