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-46Bs 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.