Sikorsky VS-316A / S-48 / R-4 Hoverfly / HNS / H-4
In 1941, the Vought-Sikorsky Division of United Air-craft was awarded a development contract for an experimental helicopter, designated XR-4. The Sikorsky R-4, or VS-316A, was a definitive development of Igor Sikorsky's successful pre-war VS-300. Like the VS-300, it had a framework of heavy-gauge steel tube, and all but the extreme rear end of the fuselage was fabric-covered, as were the 10.97m diameter main rotor blades. It retained the single three--blade rotor and anti-torque rotor of the VS-300, driven through transmission shafts and gearboxes. A completely new feature was the fully-enclosed cabin, with side-by-side seating and dual controls for the 2-man crew.
Powered by a 165hp Warner R-500-3 engine, the prototype VS-316A flew for the first time on 14 January 1942; later, with the military designation XR-4 and serial number 41-18874, the aircraft was handed over to the USAAF for evaluation. It arrived at Wright Field, Ohio, on 18 May 1942, having completed, in stages, the 1225km trip from Bridgeport, Connecticut, in 16 hr 10 min flying time.
Les Morris, was the Chief Test Pilot on the Sikorsky VS-300 starting in March, 1941 (and on the XR-4, XR-5 and XR-6 which followed).
An experimental R-4 was fitted with a tilting tail rotor.
Later in 1942 an order was placed for three service test YR-4A's with 180hp R-550-1 engines and main rotors of 11.58m diameter, and similar changes were made to the XR-4 in 1943, after which it was redesignated XR-4C.
These were generally similar to the YR-4A's except for an enlarged cabin, and were used inter alia for winterisation and tropical trials in Alaska and Burma. In the latter theatre one of the YR-4B's carried out the first recorded casualty evacuation operation by helicopter.
Other 1943 developments included the first-ever landing by a helicopter on a ship at sea (by Colonel Frank Gregory on 7 May 1943) on the tanker Bunker Hill in Long Island Sound, USA, and the production of twenty-seven pre-series YR-4B's for further evaluation by the USAAF, the U.S. Navy (three), U.S. Coast Guard (three) and the RAF (seven). The Navy designation was HNS.
Thirty production machines (YR-4As and YR-4Bs) were ordered in total.
In 1944 the R-4 became the first helicopter in the world to be placed in series production.
One hundred production R-4B's were built, similar to the YR-4B except for a more powerful engine; thirty-five were delivered to the USAAF for observation and liaison duties, and twenty to the U.S. Navy as HNS-1 reconnaissance and air/sea rescue aircraft. The US Navy established its first helicopter squadron, VX-3, at Floyd Bennett Field NAS.
The remaining forty-five were supplied to Great Britain under Lend-Lease, most of them going to the Royal Navy. The R-4B was known in British service as the Hoverfly I. In the RAF the Hoverfly I replaced the Rota (Cierva C.30A) autogiros of No.529 Squadron from August 1944, and some were supplied to the Helicopter Training School at Andover early in 1945. By the end of the year the type had passed out of RAF service, some aircraft being allocated for radar calibration work with the Telecommunications Research Establishment; others undertook snow and flood reporting duties, and one was allocated to the King's Flight to carry mail and freight. The Joint Experimental Helicopter Unit, established in 1954, was equipped initially with R-4B and R-6A helicopters handed on from the Royal Air Force and Fleet Air Arm.
A U.S. Navy HNS-1 was flown by the Coast Guard, which was given responsibility for Navy helicopter development and operations during World War II. A float-equipped HNS-1 operated the icebreaker Northwind (AG-89) during Rear Admiral Richard E. Byrd's 1947 expedition to the Antarctic.
It was not long before Sikorsky's predictions about the lifesaving capabilities of the helicopter came true. U.S. Coast Guard Cdr. Frank Erickson flew the R-4 on the first helicopter mercy mission in January 1944, delivering blood plasma for injured sailors after an explosion occurred aboard a U.S. Navy destroyer outside of New York City's harbor.
The first helicopter rescue during combat occurred in March 1944. Army Air Corps Lt. Carter Harman flew an R4 in Burma to rescue four men from behind enemy lines.
A Navy-Coast Guard HNS-1 was "stuffed" into a C-54 transport of the Air Transport Command at the Coast Guard air station in Brooklyn, N.Y. The helicopter was flown 1,000 miles on 29 April 1945, to Goose Bay, Labrador. It was then reassembled and rescued 11 Canadian airmen from two separate crashes in rugged territory, carrying them to safety one man per flight.
The first civilian helicopter rescue took place in November 1945, in Long Island Sound near Fairfield, Conn. An Army R-5 flown by Sikorsky pilot Viner rescued two men from an oil barge during a storm.
The R-4 did not enjoy a long service career, either in Britain or the United States, being supplanted in the early post-war years by the Sikorsky S-51 and its British-built equivalent, the Westland Dragonfly. Those still in American service were redesignated H-4B in 1948.
By the time production switched to the improved R-5/S-51 series, a total of 130 Sikorsky R-4s had been built.
Engine: Warner R.550, 180 hp / 134kW
Rotor dia: 38 ft (11.58 m)
Fuselage length: 10.35 m
Length: 48 ft 2 in (14.68 m)
Height: 12 ft 5 in (3.78 m)
Empty weight: 952kg
Max TO wt: 2535 lb (1150 kg)
Max level speed: 75 mph (121 kph)
Max speed @ 1150 kg: 65 kts
Rate of climb: 3.3m/s