In 1944, twenty-one (Y)R-5A helicopters were converted to R-5D standard through the addition of a nosewheel and a rescue hoist. This one wears post-1947 roundels. It is seen here in North Carolina. We have a nice colour photo of this H-5D, as the designation then was, at Selfridge AFB in 1953. On 14 December 1953 it had an accident at Ellington AFB, Texas while with the 47th ARS. The last H-5s retired from US military service in 1957. Photo from: Iredell County Public Library

Despite FY 1943 serials, production R-5A helicopters were not delivered until after the end of World War II. Photo by: Peter Stackpole / Life

Mail helicopter experiment in the Chicago area. The closest bridge is Cass Street Bridge, the second Jefferson Street Bridge and the third the Des Plaines River (railway) bridge in Joliet. Photo by: Mark Kauffman / Life

The first XR-5 prototype, 43-28236, suffered significant damage following a tail rotor failure on 12 October 1943. Test flying resumed with the second XR-5, 43-28237, in the last week of November 1943. 43-28327 assigned to 4020th Base Unit, Wright Field, Dayton, Ohio. It fatally crashed at Alachua Field, Gainsville, Florida on 2 December 1944, when welds in the main rotor failed. Photo by: Rudy Arnold / Smithsonian Institution

The Sikorsky R-5 (S-48) was an improved R-4 (VS-316), the first of five XR-5s flying on 18 August 1943. The first 26 out of 60 production R-5As were given the YR-5A designation and 43-46604 must have been one of nine YR-5As delivered before the end of WWII. The design was enlarged and further improved in 1946 as the R-5F (S-51). Redesignated as an H-5A in 1948, 43-46604 was involved in an accident in New Mexico on 20 September 1949. Photo from: Wright State University

Crews of the 5th Air Rescue Squadron posing with their equipment. The early helicopter was originally an YR-5A. A Grumman SA-16 Albatross is on the right and a Fairchild SC-82A Packet, 45-57737, on the left. The C-82 Packet was the progenitor of the C-119 Flying Boxcar. The SC-82 carried the tracked amphibious rescue vehicle behind the helicopter - stuff of the Thunderbirds! Photo from: Wayne State University

The forerunner of the Sikorsky S-51 was the S-48. This is the fourth of five XR-5A prototypes which seems to be tested here with no less than four external litters. This airframe had been ordered by the Royal Navy as FT848 but was requisitioned by the USAAF. Note the affluent parking lot in 1944. Photo from: National Archives at Boston

I find it really fascinating to see these old helicopters/aeroplanes and to understand how the types in service today have evolved from them. The boom in helicopter development is particularly interesting as the rapid advances post-WWII quickly opened up possibilities that couldn't be contemplated previously. The improved capabilities of the H-5 became extremely useful during the Korean War for the timely rescue of downed pilots and for Medevac missions.