S-49/R-6A/hos-1/Hoverfly Mk II helicopter sikorsky s-49/R-6a army Serial No. 43-45379

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S-49/R-6A/HOS-1/Hoverfly Mk II HELICOPTER

Sikorsky S-49/R-6A Army Serial No. 43-45379

The Sikorsky S-49/R-6/HOS-1 model was a follow-on to the successful R-4 helicopter with the first flight on October 15, 1943. It was designed as a streamlined R-4 with an all metal fuselage, a larger engine, and a planetary gear main gear box. The XR-6 helicopters featured the R-4B 38 foot 3 bladed fully articulated main rotor and a 3 bladed tail rotor powered by a 225 hp Lycoming O435-7 six cylinder horizontally opposed engine. The Lycoming engine was replaced by a 235 hp Franklin O-405-9 engine in the XR-6A and all subsequent R-6 models. The S-49 had 2 place side by side seating in the cockpit. One Experimental XR-6 and five XR-6A/XHOS-1 helicopters were initially built by Sikorsky Aircraft.
On March 2, 1944 a Sikorsky XR-6A helicopter flew non-stop from Washington, D.C. to Patterson Field in Dayton Ohio a distance of 387 miles in 4 hours 55 minutes with a ground speed of 80 mph. The flight crossed the Allegheny Mountains at an altitude of 5,000 feet. The pilot was Colonel Frank Gregory and the passenger was Ralph Alex, the Sikorsky project engineer. World records for speed, distance and endurance by a helicopter were eclipsed by this flight.
Since Sikorsky Aircraft was at maximum production capacity with the R-4 and R-5 models, the USAAF, Production Division at Wright Field directed that the S-49/R-6 production be License built by Nash-Kelvinator. Nash-Kelvinator was selected since they were already producing Hamilton Standard Propellers and Pratt and Whitney Double Wasp R-2800 engines under Licenses from United Aircraft Corporation. Sikorsky Aircraft was very reluctant to release control over helicopter production and showed little interest in accepting a contract to furnish the engineering and design data while another manufacturer did the fabrication. Sikorsky eventually complied with the government decision.
Nash-Kelvinator was awarded a contract for 26 YR-6A developmental helicopters followed by a production contract for 900 R-6A helicopters. Since the Kenosha and Milwaukee Wisconsin areas (Nash-Kelvinator’s home) had labor shortages, the War Production Board directed Nash-Kelvinator to build the R-6 helicopters elsewhere. Nash-Kelvinator built cabins in Grand Rapids, Michigan and performed final assembly in Detroit Michigan. Other components came from suppliers across the country including Sikorsky Aircraft providing Rotors, gearboxes, blades, and most drivetrain components. Production was slow in coming mainly because Sikorsky made countless changes to the original design which delayed the delivery of drawings for long periods of time. The XR-6A prototypes were still in Testing and Sikorsky wanted the helicopter to be as perfect as possible before releasing the production drawings. As a result Nash-Kelvinator did not test its first production model until mid-September 1944 with the first delivery on October 23, 1944. Nash-Kelvinator had 4 assembly lines producing 16 helicopters at a time. At peak production Nash-Kelvinator was producing 50 helicopters per month. Production was halted in 1945 with Nash-Kelvinator producing 219 R-6 helicopters.

Nash-Kelvinator R-6 production line in Detroit Michigan
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