The R-6/Hoverfly II was developed to improve on the successfulSikorsky R-4. In order to enhance performance, a completely new streamlined fuselage was designed and the boom carrying the tail rotor was lengthened and straightened. The main rotor and transmission system of the R-4 were retained.[1] Sikorsky allotted theirModel 49 designation to the new design. Later, dynamically balanced modifications to the rotor were carried out by Doman Helicopters Inc. The new aircraft could attain 100 mph (160 km/h) compared with 82 mph (132 km/h) by the earlier design.
Initial production was by Sikorsky, but most examples were built byNash-Kelvinator. Some of the later aircraft were fitted with more powerful engines.
A Sikorsky R-6A transport ferries a wounded soldier from the battlefield during June 1945 in Luzon, Philippines.
The first R-6s were delivered to theUnited States Army Air Forces (USAAF) in late 1944 and some were transferred to theUnited States Navy (USN). It was initially intended to pass 150 R-6s to theRoyal Air Force (RAF), but delays caused by the switch of production from Sikorsky's factory atStratford, Connecticut, to Nash-Kelvinator atDetroit,Michigan, meant that only 27 R-6As were actually delivered to the RAF as theHoverfly II.[2] Fifteen of these were passed on to the Royal Navy'sFleet Air Arm (FAA).[3]
Some of the RAF examples were allotted to 657 Squadron RAF for proving the use of helicopters in the Army Co-operation role, and two external stretchers could be fitted to the fuselage. 657 Squadron operated their Hoverfly IIs as Air Observation Posts, spotting for Army artillery units. The Hoverfly IIs remained in operation with the RAF until at least 1956 in the SAR role at RAF Leuchars, and one squadron example was displayed at the September 1950Farnborough Air Show.[4]
The FAA used their Hoverfly IIs in the training and liaison roles. Naval units to use the type included771 Squadron from December 1945, followed by705 Squadron.
The USAAF operated their R-6s in secondary roles and the survivors were redesignatedH-6A in 1948. The USN examples were designated theHOS-1 and a further 64 were intended to be transferred from the USAAF, but this did not take place.
Disposals of surplus military S-49s were made in the civil market in the late 1940s but none now remain in operation. Four are currently displayed in US museums.[5]
