The S-61R is a medium transport and search and rescue helicopter manufactured by the Sikorsky company as well as under license by Agusta.
The first flight of the S-61R occurred in 1959 and it was introduced in 1961.
The S-61R is derived from the S-61 Sea King and was built as a prototype for a private venture. The S-61R of course shares much of its base technology with the Sea King, but there are significant changes between the models.
The S-61R has a hydraulic rear ramp which allowed for wheeled vehicles to be loaded straight into the helicopter. A 2000-pound winch for internal cargo handling was added as well as retractable tricycle-type landing gear and a gas-turbine auxiliary power plant.
This power plant allowed for independent field operations, a design concession that is carried over into other areas of the S-61R. For example, the pressurized rotor blades allow for easy inspection and the helicopter is equipped with facilities to remove and replace almost all major components in remote place, making the S-61R practical for deployment as a single unit.
Sikorsky no longer manufactures the S-61R, but variants of it are still made under license by Agusta. The S-61R served in the United States Air Force as the CH-3C/E Sea King and the HH-3E Jolly Green Giant. The Coast Guard used it under the name HH-3F "Pelican".
Poduction ran from 1959 into the 1970s and despite decades having passed since new models were made, the S-61R remains in service today.