The R-5 was originally built by Sikorsky as its model S-48. It 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 by having an increased rotor diameter and a new, longer fuselage for two persons in tandem, though it retained the R-4's tailwheel-type landing gear. Former USAAF 43-46607. Operated by the RTAF 1953-1970. The plane was designated Helicopter No. 1A (H.1A ฮ.๑ก).

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.