The Sikorsky S-61R was a company funded development of their S-61/SH-3 Sea King model. It features a redesigned fuselage with a rear loading ramp, a conventional water-tight hull instead of the S-61s boat-hull, and retractable tricycle landing gear. It first flew in 1963. While still under development, the US Air Force
placed an order for the aircraft in lieu of Boeing-Vertol CH-46B
s because Sikorsky could guarantee earlier delivery. The S-61R was designated the CH-3C in Air Force service. As well as the short-lived Texas Tower support, the CH-3Cs were also kept busy in servicing Atlas and Minuteman silo complexes. The CH-3E followed in 1965 with more powerful engines and other improvements. The Air Force pressed these into service rescuing downed pilots in SEA, which highlighted the need for more fuel, more power, a rescue hoist and armor plating. Sikorksy responded with the HH-3E Jolly Green Giant version. All surviving CH-3Es were brought up to this standarsd. It also built a similar long-range SAR version for the US Coast Guard as the HH-3F Pelican
. Agusta, in Italy, built a license version as the AS-61R
for the Italian Air Force and Navy.