SP Guide Publications puts forth a well compiled articulation of issues, pursuits and accomplishments of the Indian Army, over the years

— General Manoj Pande, Indian Army Chief

I am confident that SP Guide Publications would continue to inform, inspire and influence.

— Admiral R. Hari Kumar, Indian Navy Chief

My compliments to SP Guide Publications for informative and credible reportage on contemporary aerospace issues over the past six decades.

— Air Chief Marshal V.R. Chaudhari, Indian Air Force Chief

Sikorsky R-4 – The First Mass-Produced Helicopter

The Sikorsky R-4 was the only Allied helicopter to serve during the War and it became the first helicopter in the world to enter series production

Issue: 06-2021By Joseph Noronha

The Sikorsky R-4 was a two-seat helicopter with a single, three-bladed main rotor. It was primarily used by the United States (US) Army Air Force, the US Coast Guard and the British Royal Air Force. Being introduced into service at the height of World War II, it came in handy for search and rescue in the Burma campaign and in other areas with forbidding terrain. The Sikorsky R-4 was the only Allied helicopter to serve during the War and it became the first helicopter in the world to enter series production. A total of 131 R-4s were built.

But the R-4 was not the world’s first helicopter. There are numerous claims and counterclaims about who built and flew the first helicopter, not least because autogiros were also invented around the same time. The Spanish engineer and pilot Juan de la Cierva invented the autogiro in the early 1920s, making it the first practical rotorcraft, according to aviation historians. In 1928, de la Cierva flew an autogiro across the English Channel from London to Paris. The German Focke-Wulf Fw 61, first flown in June 1936, is often considered to be the first practical, functional helicopter. The experimental machine had a transverse twin-rotor configuration and could fly above 8,000 feet at speeds of 190 kmph. There was also the Flettner Fl 265, another experimental helicopter that first flew in 1939. But the helicopter really came into its own thanks to the genius of the Russian-American engineer Igor Sikorsky.

In 1939, Sikorsky designed and flew the Vought-Sikorsky VS-300. It was the first practical single lifting-rotor helicopter. After experimenting with various configurations to counteract the torque produced by the main rotor, Sikorsky chose a single, smaller rotor mounted on the tail boom. It is the configuration used by most helicopters even today. Sikorsky’s R-4 was developed from the VS-300. It had a framework of heavygauge steel tubing and all but the extreme rear end of the fuselage was fabric-covered, as were the main rotor blades. A new feature was the fully-enclosed cabin with side-by-side seating and dual controls for the two-man crew. Powered by a 165hp Warner R-500-3 engine, the prototype XR-4 first flew on January 14, 1942. It soon set new endurance, altitude and airspeed records for helicopters including a peak altitude of 12,000 ft and maximum airspeed of 145 kmph.

On April 20, 1942, a flight test was conducted to show that the R-4 was ready for delivery. It included a power-off autorotation – something that had never before been done in a Sikorsky helicopter and for which no procedure existed. However, test pilot Les Morris successfully demonstrated that the R-4 was both safe and controllable in autorotation. There were other interesting manoeuvres to demonstrate control accuracy and other capabilities of the new machine. For instance a 10-inch ring was “speared” with the pitot tube by lifting it off a pole, and then delivered to Igor Sikorsky’s hand while hovering a few feet off the ground. Similarly, a net bag of raw eggs was hung from the pitot tube at the end of a 10-foot rope. The R-4 climbed high into the air, then descended slowly to lower the eggs to the ground, intact. More practically, a passenger was taken aboard the hovering helicopter using a rope ladder and was later returned to the same spot with the ladder. Another passenger showed how easy it was to exit a helicopter by jumping out while the machine hovered a few feet above ground. The Army observers were impressed and requested that the helicopter be flown to Dayton, Ohio.

Till then the R-4 had never been taken beyond a mile from the factory at Bridgeport, Connecticut. Consequently Les Morris began making short cross-country flights to prove the viability of the engine and transmission over longer distances. He finally departed on May 13, 1942 and arrived in Dayton on May 17. The trip covered a distance of 1,225 km. The total time airborne was 16 hours and 10 minutes through 16 separate flights. During the journey, an endurance record of one hour and 50 minutes was also set. A sedan carrying technicians, tools and spares, with a large yellow circle painted on the roof, followed the R-4’s route on the ground as a “chase” vehicle. The R-4 was accepted by the US Army on May 30, 1942.

On May 7, 1943, a Sikorsky R-4 flown by Colonel Frank Gregory became the first helicopter to make a landing at sea. On January 3, 1944, a major accident on the USS Turner left 150 crewmen seriously injured. The nearby hospital soon exhausted its supply of blood plasma. With many lives at stake, Lieutenant Commander Erickson attached two cases of plasma to the floats of an R-4 helicopter and delivered them directly on the hospital grounds in 14 minutes. Delivery by car would have taken hours.