Sikorsky S-61

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This article is about the civil versions of the Sikorsky S-61 models. For the military versions, see Sikorsky SH-3 Sea King.
S-61L/S-61N
Sikorsky S-61N Mk.II.jpg
A S-61N Mk.II operating for Sociedad de Salvamento y Seguridad Marítima
Role Medium-lift transport / airliner helicopter
Manufacturer Sikorsky Aircraft
First flight March 11, 1959
Introduction September 1961
Status Active service
Primary users CHC Helicopter
Bristow Helicopters
AAR Airlift
Number built 119[1]
Developed from SH-3 Sea King
Variants Sikorsky S-61R
A Canadian Helicopters Sikorsky S-61L at CFB Cold Lake in 1992
A Bristow Helicopters S-61N operating for HM Coastguard
A Carson Helicopters Fire King drops on the 2007 WSA Lightning Complex fire.
HeliJet's S-61N at Vancouver International Airport
Irish Coast Guard S-61N in 2012
A Coulson Aircrane's S61N doing a drop during the Australia Bushfire Season.

The Sikorsky S-61L and S-61N are civil variants of the successful SH-3 Sea King helicopter. They are two of the most widely used airliner and oil rig support helicopters built.[1]

Design and development[edit]

In September 1957, Sikorsky won a United States Navy development contract for an amphibious anti-submarine warfare (ASW) helicopter capable of detecting and attacking submarines.[1] The XHSS-2 Sea King prototype flew on 11 March 1959. Production deliveries of the HSS-2 (later designated SH-3A) began in September 1961, with the initial production aircraft being powered by two 930 kW (1250shp) General Electric T58-GE-8B turboshafts.

Sikorsky was quick to develop a commercial model of the Sea King.[1] The S-61L first flew on 2 November 1961, and was 4 ft 3 in (1.30 m) longer than the HSS-2 in order to carry a substantial payload of freight or passengers. Initial production S-61Ls were powered by two 1350shp (1005 kW) GE CT58-140 turboshafts, the civil version of the T58. The S-61L features a modified landing gear without float stabilisers.

Los Angeles Airways was the first civil operator of the S-61[2] introducing them on 11 March 1962, for a purchased price of $650,000 each.[3]

On 7 August 1962, the S-61N made its first flight.[1] Otherwise identical to the S-61L, this version is optimized for overwater operations, particularly oil rig support, by retaining the SH-3's floats. Both the S-61L and S-61N were subsequently updated to Mk II standard with improvements including more powerful CT58-110 engines giving better hot and high performance, vibration damping and other detail refinements.

The Payloader, a stripped down version optimised for aerial crane work, was the third civil model of the S-61.[1] The Payloader features the fixed undercarriage of the S-61L, but with an empty weight almost 2,000 lb (910 kg) less than the standard S-61N.

Carson Helicopters was the first company to shorten a commercial S-61. The fuselage is shortened by 50 in (1.3 m) to increase single engine performance and external payload.[4]

A unique version is the S-61 Shortsky conversion of S-61Ls and S-61Ns by Helipro International.[1] VIH Logging was the launch customer for the HeliPro Shortsky conversion which first flew in February 1996.

One modification for the S-61 is the Carson Composite Main Rotor blade. These blades replace the original Sikorsky metal blades which are prone to fatigue. The Carson Composite Main Rotor blades permit a modified aircraft to carry an additional 2,000 lb (907 kg) load, fly 15 kn (28 km/h) faster and increases range 61 nmi (113 km).[4]

The latest version is the modernized S-61T helicopter. The US State Department has signed a purchase agreement for up to 110 modernized S-61T aircraft for passenger and cargo transport missions in support of its worldwide operations. The first two modernized S-61 aircraft will support missions for the U.S. Embassy in Afghanistan.[5]

Variants[edit]

S-61L 
Non-amphibious civil transport version. It can seat up to 30 passengers (13 Built).[citation needed]
S-61L Mk II
Improved version of the S-61L helicopter, equipped with cargo bins.[citation needed]
S-61N 
Amphibious civil transport version.[citation needed]
S-61N Mk II
Improved version of the S-61N helicopter.[citation needed]
S-61NM
An L model in an N configuration.[citation needed]
S-61 Payloader
Stripped down machine optimised for aerial crane work; features the fixed undercarriage of the S-61L, but with an empty weight almost 900 kg (2,000 lb) less than the standard S-61N.[citation needed]
S-61 Shortsky
Shortened conversion of the S-61L and S-61N, designed to increase single engine performance and external payload.[citation needed]
S-61T Triton
S-61 modernized upgrade by Sikorsky and Carson; Upgrades include composite main rotor blades, full airframe structural refurbishment, conversion of folding rotor head to non-folding, new modular wiring harness, Cobham glass cockpit avionics; initial models converted were S-61N[6]

Operators[edit]

 Canada
 Greenland
 Lebanon
 United Kingdom
 United States

Former operators[edit]

 Canada
 Ireland
 Netherlands
 Pakistan
 United Kingdom
 United States

Notable accidents[edit]

N300Y, the Los Angeles Airways prototype of the Sikorsky S-61L Helicopter, lifting off from the Disneyland Heliport
OY-HAI, the S-61N at Nuuk Heliport on a flight before its fatal flight on 25 October 1973
  • On 25 October 1973, an Greenlandair S-61N, OY-HAI "Akigssek" ("Grouse") crashed about 40 km south of Nuuk, resulting in the loss of 15 lives. It was en route to Paamiut from Nuuk. The same aircraft had an emergency landing on the Kangerlussuaq fjord 2 years earlier, due to flameout on both engines because of ice in the intake.[30]
  • On 10 May 1974 KLM Noordzee Helikopters S-61N PH-NZC crashed en route to an oil rig in the North Sea. None of the 2 crew and 4 passengers survived. The probable cause was a failure in one of 5 rotor blades due to metal fatigue. The resulting imbalance caused the motor mounts to fail and resulted in a fire. The uncontrollable aircraft landed hard in the water, capsized and sank. Investigation indicated that the metal fatigue crack must have spread rapidly in less than 4 hours. The rotor blades are pressurized with nitrogen gas at 10PSI to indicate the onset of a metal fatigue failure, yet no pressure loss was indicated during the pre-flight inspection. As a result of the accident it was recommended to shorten inspection intervals[31] The aircraft was recovered from the North Sea floor. It was rebuilt and currently flies as registration N87580 in the USA.[32]
  • On 16 May 1977, New York Airways' commercial S-61-L, N619PA, suffered a static rollover onto its starboard side at the heliport on top of the Pan Am Building while boarding passengers. The accident killed four boarding passengers and one woman on the street. 17 additional passengers and the three flight crew members were uninjured.[33] The landing gear collapse was a result of metal fatigue in the helicopter's main landing gear shock-absorbing strut assembly, which caused the helicopter to tip over without warning. The accident resulted in the permanent closure of the Pan Am Building heliport.[34] As the heliport was closed, the wreckage was removed by disassembling it and taking the assemblies down to street level using the building's freight elevators. The airframe was taken to Cape Town, South Africa, where it was rebuilt, certified and returned to service as the first S61 used in the Ship-Service Role off the shores of the Western Cape by the company "Court Helicopter" which was later amalgamated with CHC.[35]
  • On March 20, 1985, an Okanagan Helicopters S-61N (C-GOKZ) ditched in the Atlantic Ocean off of Owl's Head, Nova Scotia. The aircraft was en route from the MODU Sedco 709 offshore Nova Scotia to the Halifax International Airport(YHZ)when it suffered total loss of transmission fluid from the main gearbox. There were 15 passengers and 2 crew on board. There were no injuries during the ditching, however several passengers suffered from varying degrees of hypothermia. As a result of this incident, there was a dramatic increase in thermal protection and other advancements in helicopter transportation suits for offshore workers on the east coast of Canada.
  • On 5 August 2008, two pilots and seven firefighters assigned to the Iron Complex fire in California's Shasta-Trinity National Forest, were killed when Carson Helicopters Sikorsky S-61N helicopter N612AZ crashed on take-off. Of the 13 people reported to be on board, one other pilot and three firefighters survived the crash with serious or critical injuries. The NTSB determined that the probable causes of this accident was the following actions by Carson Helicopters: 1) the intentional understatement of the helicopter’s empty weight, 2) the alteration of the power available chart to exaggerate the helicopter’s lift capability, and 3) the practice of using unapproved above-minimum specification torque in performance calculations that, collectively, resulted in the pilots’ relying on performance calculations that significantly overestimated the helicopter’s load-carrying capacity and did not provide an adequate performance margin for a successful takeoff; and insufficient oversight by the U.S. Forest Service and the Federal Aviation Administration. Contributing to the accident was the failure of the flight crewmembers to address the fact that the helicopter had approached its maximum performance capability on their two prior departures from the accident site because they were accustomed to operating at the limit of the helicopter’s performance. Contributing to the fatalities were the immediate, intense fire that resulted from the spillage of fuel upon impact from the fuel tanks that were not crash resistant, the separation from the floor of the cabin seats that were not crash resistant, and the use of an inappropriate release mechanism on the cabin seat restraints.[36][37][38]

Specifications (S-61N Mk II)[edit]

Orthographically projected diagram

Data from International Directiory of Civil Aircraft[1]

General characteristics

Performance

See also[edit]

Related development

References[edit]

  1. ^ a b c d e f g h Frawley, Gerard: The International Directory of Civil Aircraft, 2003–2004, p. 194. Aerospace Publications Pty Ltd, 2003. ISBN 1-875671-58-7.
  2. ^ Apostolo, G. "Sikorsky S-61".The Illustrated Encyclopedia of Helicopters. Bonanza Books, 1984. ISBN 0-517-43935-2.
  3. ^ "The Self-Supporting Helicopter" Time Magazine December 26, 1960
  4. ^ a b Carson Helicopters (2009). "About Carson Helicopters". Retrieved 2009-01-12. 
  5. ^ Press Releases: U.S. State Department Accepts Modernized S-61TM Helicopters for Use in Afghanistan
  6. ^ Sikorsky S-61T gains new life in State Department program
  7. ^ "CHC Helicopter fleet". chc.ca. Retrieved 17 March 2013. 
  8. ^ "Cougar Helicopters". cougar.ca. Retrieved 17 March 2013. 
  9. ^ "Air Greenland fleet". airgreenland.com. Retrieved 17 March 2013. 
  10. ^ "World Air Forces 2013". Flightglobal Insight. 2013. Retrieved 17 March 2013. 
  11. ^ "Bristow Helicopters fleet". bristowgroup.com. Retrieved 17 March 2013. 
  12. ^ "Carson Helicopters Home page". carsonhelicopters.com. Retrieved 17 March 2013. 
  13. ^ "Former employees of Carson Helicopters indicted over fatal Iron 44 Fire crash". wildfiretoday.com. Retrieved 17 March 2013. 
  14. ^ "Croman Corporation Heavy Lift Svc.". croman.net. Retrieved 17 March 2013. 
  15. ^ "Helicopter Transport Services Aircraft". htshelicopters.com. Retrieved 17 March 2013. 
  16. ^ "DOD Contracts Keep U.S. Helicopter Operators Busy in Afghanistan". ainonline.com. Retrieved 4 June 2013. 
  17. ^ Press Releases – U.S. State Department Accepts Modernized S-61TM Helicopters for Use in Afghanistan
  18. ^ "Coast Guard S-61 being retired from duty in Prince Rupert". helihub.com. Retrieved 20 March 2013. 
  19. ^ "End Of An Era As Irish Coast Guard's Last S61 Retires". afloat.ie. Retrieved 12-December-13.  Check date values in: |accessdate= (help)
  20. ^ "Garda Cósta na hÉireann S-61". Retrieved 17 March 2013. 
  21. ^ "KLM / Era Helicopters history". erahelicopters.com. Retrieved 20 March 2013. 
  22. ^ "KLM-Noordzee Helikopters S-61N". Demand media. Retrieved 20 March 2013. 
  23. ^ "Pakistan International Airlines – PIA S-61N". Retrieved 17 March 2013. 
  24. ^ "British Airways Helicopters". Retrieved 17 March 2013. 
  25. ^ "British International Helicopters S-61". Retrieved 17 March 2013. 
  26. ^ "HM Coastguard S-61N". Retrieved 17 March 2013. 
  27. ^ "Flight Int’l 1969 Pg. 581". flightglobal.com. Retrieved 17 March 2013. 
  28. ^ York Airways "New York Airways". flightglobal.com. Retrieved 17 March 2013. 
  29. ^ Aircraft Accident Report. Los Angeles Airways, Inc. S-61L Helicopter, N300Y, Compton, California, Adopted: August 27, 1969
  30. ^ Police report regarding SAR of Air Greenland helicopter OY-HAI, who disappeared 25 October 1973 flight from Nuuk to Paamiut
  31. ^ Dutch Civil Aviation Authority Accident report 10.05.1974 PH-NZC Sikorsky S.61N (in Dutch)
  32. ^ Aviation Safety Network Occurrence 786
  33. ^ UPI. Helicopter Crash Kills Five. Beaver County (Pa.) Times: Tuesday, 17 May 1977, A-13.
  34. ^ Schneider, Daniel B. "F.Y.I.", July 25, 1999. Accessed September 30, 2007. "Q. Back in the 1960's and 70's, helicopters bound for Kennedy International Airport used to take off from a deck atop the old Pan Am Building. Why was the service halted? A. As many as 360 helicopter flights a day were planned by New York Airways after the 59-story Pan Am building was completed in 1963, but a bitter public outcry delayed the first few flights until December 21, 1965.... The operation proved unprofitable, however, since the helicopters carried an average of only eight passengers, and the heliport, which had cost $1 million to build, closed in 1968.... After another round of hearings – and renewed protests – flights resumed in February 1977. Three months later, the landing gear on one of the Sikorsky S-61 helicopters collapsed while passengers were boarding, flipping it on its side and sending a 20-foot rotor blade skidding across the roof and over the west parapet wall.... Within hours, the heliport was closed indefinitely."
  35. ^ Epstein, Curt. HAI Convention News "An S-61 With a Past" October 26, 2010. Retrieved: June 13, 2011.
  36. ^ ircraft Accident Report Crash During Takeoff of Carson Helicopters, Inc., Firefighting Helicopter Under Contract to the U.S. Forest Service, Sikorsky S-61N, N612AZ Near Weaverville, California August 5, 2008 NTSB/AAR-10/06
  37. ^ "USFA Fatality Notice". United States Fire Administration. 2008-08-06. Retrieved 2008-08-11. 
  38. ^ "FAA/NTSB Investigations". Los Angeles Injury Law Firm (See post #4 titled "Nine Firefighters Believed Dead After Helicopter Crash in California"). 2008-08-06. Retrieved 2009-02-03. 

External links[edit]