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Although not generally known, the helicopter was much more than an experimental aircraft during World War II. The United States Army Air Corps used the Sikorsky R-4 for important missions during the War. The potential for helicopters used for military operations quickly became apparent. One of its first missions was in search and rescue, where it proved invaluable.
The Sikorsky R-4 was the first helicopter built in numbers. Its protoype first took to the sky in 1939 and production helicopters were eventually deployed with the U.S. Army Air Corps, U.S. Navy, Royal Air Force, and Royal Navy.
Mass production of the Sikorsky began in 1942 at their plant located in Stratford, Ct. Soon after, the Royal Air Force and Fleet Air Arm tested the helicopter and found it met or exceeded their expectations. The Sikorsky R-4 was eventually deployed to the U.K. just prior to the end of the War. There they were designated the Hoverfly Mk I.
It was 1939 when Igor Sikorsky successfully flew his helicopter design. The prototype was designated the VS-300. The helicopter was capable of a 70 mph top speed. It led the way to the production of the Sikorsky R-4.
The Sikorsky R-4 differed from prototype helicopters in that it had an enclosed cockpit with the pilot and co-pilot seated side by side. It was initially powered by a Warner R500 piston engine producing 165 h.p.
The U.S. Army Air Corps soon placed orders for the helicopter after its successful testing. More powerful R550, 180 h.p. engines were fitted to the production helicopters.
Pilots found that the Sikorsky R-4 was a relatively easy aircraft to fly. They were able to solo in the helicopter after only a few hours.
Although it didn't look strong, the Sikorsky R-4 fuselage proved durable. Diagonally mounted spars provided additional strength. The undercarriage of the R-4 could be fitted with floats for ship board use. Due to its upward tapering fuselage, the R-4 needed a lengthy tail wheel to keep it level while on the ground.
On May 17, 1942 a Sikorsky R-4 prototype helicopter flew a record 760 miles. On May 6, 1943 a R-4 landed on a ship at sea, the USS Bunker Hill aircraft carrier. The was the first time this had been done successfully. On April 21, 1945 the R-4 became the first helicopter to perform a rescue in the Arctic.
A total of 131 Sikorsky R-4 helicopters were produced.