Sikorsky R-4 Explained

The Sikorsky R-4 is a two-seat helicopter that was designed by Igor Sikorsky with a single, three-bladed main rotor and powered by a radial engine. The R-4 was the world's first large-scale mass-produced helicopter and the first helicopter used by the United States Army Air Forces,[1] the United States Navy, the United States Coast Guard and the United Kingdom's Royal Air Force and Royal Navy. In U.S. Navy and U.S. Coast Guard service, the helicopter was known as the Sikorsky HNS-1. In British service it was known as the Hoverfly.

Development

The VS-316 was developed from the famous experimental VS-300 helicopter, invented by Igor Sikorsky and publicly demonstrated in 1940. The VS-316 was designated the XR-4, under the United States Army Air Forces' series for "Rotorcraft". The XR-4 first flew on 14 January 1942[2] [3] and was accepted by the Army on 30 May 1942.[4] The XR-4 exceeded all the previous helicopter endurance altitude and airspeed records that had been set before it.[5] The XR-4 completed a 761miles cross-country flight from Bridgeport, Connecticut, to Wright Field, Ohio, set a helicopter peak altitude record of 12000feet, while achieving 100 flight hours without a major incident and top airspeed approaching 900NaN0[6] [7]

The British Admiralty, having learned of the VS-300, made a ship available, Empire Mersey, fitted with an 80x landing platform, intended to show the USN their work with ship-borne autogyros.[8] After her loss in 1942 to a U-boat, she was replaced by SS Daghestan.[9] The first deck-landing trials aboard Daghestan were carried out in 1944. The British received two of the first eight helicopters built.

On 5 January 1943, the United States Army Air Forces ordered 29 prototypes.[6] The first three were designated YR-4A and used for evaluation testing. The YR-4A benefited from a 180hp Warner R-550-1 Super Scarab engine, compared to the 165hp Warner R-500-3 in the prototype, and a rotor diameter increased by 1feet. Evaluation of the YR-4A demonstrated a need for further improvements, including moving the tailwheel further aft on the tailboom, venting the exhaust to the side instead of downward, and increasing the fuel capacity by 5USgal. These and other design changes led to the designation of later prototypes as YR-4B, which were used for service testing and flight training.

United Aircraft announced on 5 November 1944 that the one hundredth helicopter had been completed, and that the production rate had reached five every six days.[10]

Operational history

Following the explosion and sinking in January 1944 of USS Turner, U.S. Coast Guard Commander Frank Erickson flew the first U.S. helicopter rescue in a Sikorsky R-4 carrying life saving blood plasma for the casualties from New York City.[11] On 22–23 April 1944, U.S. Army Lieutenant Carter Harman of the 1st Air Commando Group conducted the first combat rescue by helicopter using a YR-4B in the China-Burma-India theater.[12] Despite the high altitude, humidity, and capacity for only a single passenger, Harman rescued a downed liaison aircraft pilot and his three British soldier passengers, two at a time.[13] On 22–23 January 1945, another rescue by the R-4 involved several legs for refueling and navigating through passes between mountains nearly 10,000 feet (3,000 m) tall, to reach a weather station located at an elevation of 4,700 feet (1,400 m). The higher-than-normal altitude required a downhill run of 20 ft (6.1 m) to get airborne.[14]

While the R-4 was being used for rescues in Burma and China, it was also being used to ferry parts between floating Aviation Repair Units (part of Operation Ivory Soap) in the South Pacific. On 23 May 1944, six ships set sail with two R-4s on board each vessel. The ships had been configured as floating repair depots for damaged Army Air Forces aircraft in the South Pacific. When the helicopters were not being used to fly the parts from one location to another, they were enlisted for medical evacuation and other mercy missions.[15] Helicopter pilot 2LT Louis Carle was assigned to the Brigadier General Clinton W. Russell, the Fifth Aircraft Repair Unit. From June 15 to July 29, 1945, Carle and five other pilots evacuated 75 to 80 wounded soldiers, one or two at a time, from the highlands northeast of Manila. They were the second group of helicopter pilots after Lieutenant Carter Harman to evacuate wounded via helicopter during World War II. Unlike Harman, they were targeted by Japanese soldiers who tried to shoot them down with machine guns. Their six-week effort constitutes the largest combat helicopter operation before the Korean War.[16]

On June 15, 1945, the Fifth Air Force received a request from the 38th Infantry Division to evacuate two soldiers with head injuries from a spot east of Manila. Carle flew one of his ship's Sikorsky R-4 helicopters and landed near the front lines, much to the amazement of the soldiers, who had never seen a helicopter. The helicopter was not configured to handle stretchers, and they removed a seat and placed the wounded man on the aircraft floor. Carle flew the soldier to the 311th General Field Hospital near Manila. Once word got out of their availability, they were called on again and again. Carle flew seven hours and made six evacuations on the same day.[16]

In Royal Air Force service, the R-4 was called the Hoverfly.[17] The Helicopter Training School, formed January 1945 at RAF Andover, was the first British military unit to be equipped with the helicopter. Many RAF Hoverfly Mark Is were transferred to the Royal Navy for training and one was used in 1945–46 by Fairey Aviation to develop rotor systems for their Gyrodyne helicopter.

Piloting difficulty

The helicopter was difficult to fly. The aircraft's blades were made of wood ribs around a steel spar and covered with doped fabric. The blades were difficult to keep rotating in the same plane and vibrated excessively. The cyclic made continuous small orbits, vibrating continuously. There was no governor to control rotor speed, and the pilot had to correlate the throttle continuously with collective pitch inputs.[16] The Chicago Tribune reported on Carle's efforts to transport the wounded. They wrote that the "control stick shakes like a jackhammer, and the pilot must hold it tightly at all times. Should he relax for even a minute the plane falls out of control. Pilots of regular planes say it's easy to identify a helicopter pilothe has a permanent case of the shakes."[18]

Variants

XR-4
  • One prototype Model VS-316A with a crew of two and dual controls, Warner R-500-3 165hp engine, became XR-4C
    YR-4A
  • Version with larger rotor diameter and a Warner R-550-1 180hp engine; three built.
    YR-4B
  • Version with detailed changes; 27 built for development testing followed by a further batch of 14, seven to US Navy as HNS-1s.
    R-4B
  • Production version with a Warner R-550-3 200hp engine; 100 built including 20 for the US Navy and 45 for the Royal Air Force.
    XR-4C
  • Prototype XR-4 re-engined with a Warner R-550-1 180hp engine with the larger YR-4A-type rotor.
    HNS-1
  • Three YR-4Bs and 22 R-4Bs transferred to the US Navy; three diverted to the United States Coast Guard.[19]
    Hoverfly I
  • UK military designation of the R-4 for the Royal Air Force and Royal Navy; 52 delivered and one later transferred to the Royal Canadian Air Force. 133 were built[20]
    Sikorsky S-54
  • An R-4B modified as a sesqui-tandem helicopter with an observer's seat aft of the main rotor gearbox for trials. First flown on December 20, 1948.[21]

    Operators

    United States

    Surviving aircraft

    Canada
    United Kingdom
    United States

    References

    Notes
    Bibliography

    External links

    Notes and References

    1. http://www.nationalmuseum.af.mil/Visit/MuseumExhibits/FactSheets/Display/tabid/509/Article/195868/sikorsky-r-4b-hoverfly.aspx "Sikorsky R-4B Hoverfly"
    2. Gunston 2005, p. 88.
    3. Mondey 2005, p. 29.
    4. Web site: Sikorsky R-4B Hoverfly. National Museum of the US Air Force™. en-US. 2019-03-24.
    5. Web site: Sikorsky R-4B – Canada Aviation and Space Museum. ingeniumcanada.org. en-CA. 2019-03-24.
    6. McGowen 2005, p. 29.
    7. Web site: Sikorsky Archives First Delivery. www.sikorskyarchives.com. 2019-03-24.
    8. .
    9. Cocker 2008, p. 114.
    10. Associated Press, “Firm Completes Its Hundredth Helicopter”, The San Bernardino Daily Sun, San Bernardino, California, Monday 6 November 1944, Vol. 51, p. 1.
    11. Web site: Sikorsky HNS-1 Hoverfly . 2022-05-05 . United States Coast Guard . en-US.
    12. Dorr, Robert. History in Blue, Air Force Times, 22 March 2004.
    13. McGowen 2005, p. 34.
    14. Williams 2005, pp. 30–31.
    15. Williams 2005, p. 31.
    16. Web site: Magazine . Smithsonian . Connor . Roger . Medevac From Luzon . Smithsonian Magazine . 9 February 2022 . en.
    17. Web site: Flight 1946. flightglobal.com. 3 April 2018.
    18. News: Veysey . Arthur . Lift Yanks out of Luzon by Helicopter . 9 February 2022 . Newspapers.com . Chicago Tribune . 21 Jun 1945 . en.
    19. Web site: Drucker. Graham. Sikorsky R-4B Hoverfly (HNS). www.fleetairarmarchive.net. 31 March 2013. usurped. https://web.archive.org/web/20121031163118/http://www.fleetairarmarchive.net/Aircraft/Hoverfly.htm. 31 October 2012.
    20. Web site: Sikorsky R-4B Hoverfly 1 . 2023-11-07 . RAF Museum . en-GB.
    21. Web site: S-54 Sesque Tandem Experimental Helicopter. 7 December 2021.
    22. Web site: R-4/H-4. globalsecurity.org . 2014 . 21 October 2014.
    23. Howard/Burrow/Myall 2011, pp. 3-9
    24. Sturtivant 2007, p. 203
    25. Web site: S-47/R-4 Helicopter . sikorskyarchives.com . 21 October 2014.
    26. Web site: History of Coast Guard Aviation pg. 25 . uscg.mil . 21 October 2014.
    27. Web site: Sikorsky R-4B . Canadian Aviation and Space Museum . 14 March 2021.
    28. Web site: Sikorsky R-4B Hoverfly 1 . Royal Air Force Museum . 14 March 2021.
    29. Web site: Simpson . Andrew . Individual History [KL110] ]. Royal Air Force Museum . 14 March 2021 . https://web.archive.org/web/20101223040326/http://www.rafmuseum.org.uk/london/collections/aircraft/aircraft-history/66-AF-765%20%20Hoverfly%20KL110.pdf . 23 December 2010 . 2007.
    30. Web site: Vought-Sikorsky XR-4C . National Air and Space Museum . Smithsonian Institution . 14 March 2021 . 28 March 2021 . https://web.archive.org/web/20210328205425/https://airandspace.si.edu/collection-objects/vought-sikorsky-xr-4c/nasm_A19600307000 . dead .
    31. Web site: Sikorsky R-4B (S-47) 'Hoverfly' . New England Air Museum . 14 March 2021 . 6 November 2020 . https://web.archive.org/web/20201106214844/http://www.neam.org/shell.php?page=aircraft_collection_detail&name=sikorskyr4b . dead .
    32. Web site: Sikorsky R-4B Hoverfly . National Museum of the United States Air Force . 14 March 2021 . 20 April 2015.
    33. Web site: Airframe Dossier – Sikorsky R-4B Hoverfly, s/n 43-46521 USAAF . Aerial Visuals . 15 March 2021.
    34. News: Hanging around in Ft. Belvoir . 15 March 2021 . Fairfax County Times . 9 February 2019.
    35. Web site: Our Collection – Restoration Hangar . Yanks Air Museum . 14 March 2021 . https://web.archive.org/web/20110718140911/http://www.yanksair.com/RestorationHangar.html . 18 July 2011.
    36. Web site: Sikorsky R‑4B Hoverfly . Yanks Air Museum . 5 February 2017 . 14 March 2021.
    37. Web site: Rotary Wing Collection . United States Army Aviation Museum . 15 March 2021 . https://web.archive.org/web/20120713050320/http://www.armyavnmuseum.org/museum/collection/rw3.html . 13 July 2012 . 2 January 2003.
    38. Web site: HNS Hoverfly . National Naval Aviation Museum . 14 March 2021 . https://web.archive.org/web/20181203192630/http://www.navalaviationmuseum.org/attractions/aircraft-exhibits/item/?item=hns-1_hoverfly . 3 December 2018.
    39. Web site: Airframe Dossier – Sikorsky HNS-1 Hoverfly, s/n 39047 USCG, c/n 104, c/r N75988 . Aerial Visuals . 14 March 2021.
    40. Web site: Aircraft : R-4 Sikorsky Hover Fly . CAF Operations.org . 7 May 2021.
    41. Web site: FAA Registry [N4605V] ]. Federal Aviation Administration . U.S. Department of Transportation . 7 May 2021.

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