Sikorsky R-6

The Sikorsky R-6 is an American light two-seat helicopter of the 1940s. In Royal Air Force and Royal Navy service, it was named the Hoverfly II.

R-6 / Hoverfly II
R-6A Hoverfly II at the USAF Museum
Role Helicopter
National origin United States
Manufacturer Sikorsky Aircraft
First flight 15 October 1943
Introduction 1945
Status Retired
Primary users United States Navy
Royal Air Force
Number built 225
Developed from Sikorsky R-4

Development

The R-6/Hoverfly II was developed to improve on the successful Sikorsky 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 their Model 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 compared with 82 mph by the earlier design.

Initial production was by Sikorsky, but most examples were built by Nash-Kelvinator. Some of the later aircraft were fitted with more powerful engines.

Operational history

The first R-6s were delivered to the United States Army Air Forces (USAAF) in late 1944 and some were transferred to the United States Navy (USN). It was initially intended to pass 150 R-6s to the Royal Air Force (RAF), but delays caused by the switch of production from Sikorsky's factory at Stratford, Connecticut to Nash-Kelvinator at Detroit Michigan meant that only 27 R-6As were actually delivered to the RAF as the Hoverfly II.[2] Fifteen of these were passed on to the Royal Navy's Fleet 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 until April 1951, and one squadron example was displayed at the September 1950 Farnborough Air Show.[4]

The FAA used their Hoverfly IIs in the training and liaison roles. Naval units to use the type included 771 Squadron from December 1945, followed by 705 Squadron.

The USAAF operated their R-6s in secondary roles and the survivors were redesignated H-6A in 1948. The USN examples were designated the HOS-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]

Variants
A U.S. Navy HOS-1 in January 1947
The R-6 was the basis for the Doman LZ-1A, which used the fuselage of a R-6A Hoverfly II. This example exhibited at the New England Air Museum at Windsor Locks, Connecticut in 2005
XR-6
prototype powered by a 225 h.p. Lycoming O-435-7 (one)
XR-6A
as XR-6 but powered by the 240 h.p. Franklin O-405-9 (five) of which three to the US Navy as XHOS-1
YR-6A
as XR-6A with small changes (26) built by Nash-Kelvinator
R-6A
production model (193) built by Nash-Kelvinator of which 36 to US Navy as HOS-1 and 27 to the RAF as Hoverfly II
R-6B
projected variant with 225 h.p. Lycoming O-435-7, but not proceeded with
XR-7
projected development of the XR-6 with a 240 hp Franklin O-405-9 engine, not built.
Doman LZ-1
One R-6A modified as a testbed
Doman LZ-1A
One R-6A modified as a testbed with a Doman-designed hingeless rotor blades and self-lubricating rotor hub.

Operators
 United Kingdom
 United States

Aircraft on display

Specifications (R-6A)

Data from Thetford, 1977

General characteristics

  • Crew: one
  • Capacity: one observer
  • Length: 47 ft 11 in (14.61 m)
  • Gross weight: 2,600 lb (1,179 kg)
  • Powerplant: 1 × Franklin O-405-9 piston, 240 hp (180 kW)
  • Main rotor diameter: 38 ft 0 in (11.58 m)

Performance

  • Maximum speed: 100 mph (160 km/h, 87 kn)
  • Service ceiling: 10,000 ft (3,000 m)
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See also

Related development

References

Notes
  1. Swanborough, 1963, p.529
  2. Butler, 2004, p.278
  3. Thetford, 1977, p.422
  4. Thetford, 1976, p.603
  5. Ogden, 2007, p.602
  6. "S-49/R-6A/HOS-1/Hoverfly". sikorskyarchives.com. 2018. Retrieved 15 September 2018.
  7. "Sikorsky R-6A Hoverfly II". stanakshot. 26 April 2017. Retrieved 29 May 2017.
  8. "Airframe Dossier - Sikorsky-Nash-Kelvinator R-6A, s/n 43-45473 US, c/r N5282N". Aerial Visuals. AerialVisuals.ca. Retrieved 15 April 2017.
  9. "Sikorsky R-6A Hoverfly II". National Museum of the US Air Force. 20 April 2015. Retrieved 14 April 2017.
  10. "Sikorsky R-6 Doman Conversion (LZ-1A)". New England Air Museum. New England Air Museum. Retrieved 14 April 2017.
  11. Ogden, 2007
  12. "Aircraft Being Restored". American Helicopter Museum & Education Center. American Helicopter Museum & Education Center. Retrieved 14 April 2017.

Bibliography
  • Butler, Phil (2004). Air Arsenal North America. Midland Publishing. ISBN 1-85780-163-6.
  • Ogden, Bob (2007). Aviation Museums and Collections of North America. Air-Britain (Historians) Ltd. ISBN 0-85130-385-4.
  • Swanborough, F.G. (1963). United States Military Aircraft since 1909. Putnam & Company Ltd.
  • Thetford, Owen (1976). Aircraft of the Royal Air Force since 1918. Putnam & Company Ltd. ISBN 0-370-10056-5.
  • Thetford, Owen (1977). British Naval Aircraft since 1912. Putnam & Company Ltd. ISBN 0-370-30021-1.
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