Ordered in 1943, the Sikorsky XR-6 prototype (43-47955) made its maiden flight on 15 October 1943. As its manufacturer's designation indicated, it was essentially a refined and developed version of the R-4, and the same rotor and transmission system was used in both types. A 225hp Lycoming O-435-7 engine provided the power, and the fuselage was transformed into a highly streamlined, metal-skinned unit with a one-piece moulded plexiglas cabin for the 2 crew members. On a March 1944 the XR-6 set new helicopter distance, endurance and altitude records when it made a non-stop flight of 623km from Washington, D.C, to Dayton, Ohio, in 4 hr. 55 min, climbing to 1524m over the Allegheny Mountains en route. The XR-6 was followed by five 2-seat service test XR-6A's for the USAAF and U.S. Navy, built by Sikorsky with 240hp Franklin O-405-9 engines, and twenty-six generally similar pre-production YR-6A's built by the Nash-Kelvinator Corporation. The latter company also carried out the production of the one hundred and ninety-three R-6A's built from 1945. Thirty-six of these were delivered to the U.S. Navy as the HOS-1, and formed the equipment of that service's first helicopter squadron, which commissioned in July 1946. Forty R-6A's were supplied to Britain under Lend-Lease, these being named Hoverfly II in British service. Fifteen of them were allocated to the Fleet Air Arm for communications and training in 1946; others served with No.657 (AOP) Squadron RAF and the Airborne Forces Experimental Establishment. Like the R-4, the R-6 could be fitted with pontoons as an alternative to a wheeled landing gear, and was employed on a variety of duties including air/sea rescue, casualty evacuation and observation. Its career was, however, a short one: it was frequently beset by engine difficulties, and soon gave way to the more reliable R-5 and its derivatives. A proposed Lycoming-powered R-6B version by Nash-Kelvinator was cancelled.

K.Munson "Helicopters And Other Rotorcraft Since 1907", 1968

The R-4's rotor and transmission system was installed in a new streamlined fuselage with an all-metal semi-monocoque tail boom to become the VS-316B or XR-6, powered by a 168kW Avco Lycoming O-435 engine. Some 193 production helicopters were built for the USAAF as the R-6A, for the US Navy as the HOS-1 and for the British as the Hoverfly Mk II.

D.Donald "The Complete Encyclopedia of World Aircraft", 1997

Photo Gallery

	The Sikorsky R-6 was developed parallel with the improved R-5 but was basically a refinement of the R-4 design. Note its four-wheel landing gear arrangement, streamlined structure and improved frontal visibility.
	An R-6A assigned to SAR operations, with Rescue painted on the top of the tailboom and high-visibility markings. Beginning with the R-6, helicopters flown by the U.S. Coast Guard had Navy designations with the suffix letter G (as HOS-1G) until the 1962 redesignation of U.S. military aircraft.
	Sikorsky R-6

Technical data for Sikorsky R-6 Crew: 1, passengers: 1, engine: 1 x Avco Lycoming O-435 rated at 168kW, rotor diameter: 11.6m, length: 11.7m, height: 3.2m, take-off weight: 1317kg, empty weight: 923kg, max speed: 161km/h, cruising speed: 120km/h, rate of climb: 4.0m/s, service ceiling: 3050m, range: 185km

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