http://en.wikipedia.org/wiki/Sikorsky_H-5
The H-5, originally designated the R-5 by Sikorsky, was designed to provide a helicopter having greater useful load, endurance, speed, and service ceiling than the Sikorsky R-4. The R-5 differed from the R-4 in having increased rotor diameter and a new, longer fuselage for two persons in tandem. Larger than the R-4 or the later R-6, the R-5 was fitted with a more powerful Wasp Junior 450-hp radial engine, and quickly proved itself the most successful of the three types
The Sikorsky R-5 was the second helicopter type to go into full production for the U.S. Air Force. The R-4 used in the last stages of World War II was primarily a trainer while the R-5 was intended for observation and rescue duties. The R-5 prototype first flew in August 1943. When the US Air Force became an independent service in 1948 the designation letter for helicopters was changed from "R" to "H" and the Dragonflies were re-designated H-4. In June of that year the Air Force ordered 39 Dragonflies specially equipped for rescue operations with a hoist mounted on the left side of the helicopter. The H-5 remained in service up to the early 1960s, but is best known for its service rescuing downed pilots during the Korean War.
http://www.pimaair.org/collection-detail.php?cid=246
Don't know if this helps or not
Walt