Sikorsky H-5, HO3S-1 helicopter The Sikorsky H-5/HO3S was a
four-seat, utility helicopter used by the US Air Force, Navy,
and Marine Corps during the Korean War. An XR-5 prototype first
flew on 18 August 1943, and the S-51 first flew on February
1946. The US Air Force acquired several dozen S-51s with the
designation H5. The US Navy and Marine Corps also acquired
several dozen with the designation HO3S-1. The US Air Force 3rd
Air Rescue Squadron, based in Japan, possessed 9 H-5s at the
beginning of the Korean War, and they quickly proved their value
for evacuation of casualties. Marine Corps Helicopter
Observation Squadron 6, VMO-6, accompanied the 1st Marine
Brigade when it arrived in Korea, and it began flight operations
in Korea on 3 August 1950. US Navy HO3S-1 helicopters,
originally intended for air-sea rescue, operated from most US
aircraft carriers throughout the war. The H-5 and HO3S-1
helicopters proved so versatile for light transport, casualty
evacuation, air-sea rescue, and rescuing downed pilots