Wikipedia

Sikorsky S-76

(Redirected from Sikorsky S-76A)
"S-76" redirects here. For other uses, see S76.

The Sikorsky S-76 is a medium-size commercial utility helicopter designed and produced by the American helicopter manufacturer Sikorsky Aircraft. It is the company's first helicopter specifically developed for the civilian market.

S-76
A Galician Coast Guard S-76C+
General information
TypeUtility helicopter
National originUnited States
ManufacturerSikorsky Aircraft
StatusIn service
Primary usersBristow Helicopters[1]
Number built875[3]
History
Manufactured1977–present
First flight13 March 1977 (1977-03-13) [4]
VariantsSikorsky S-75

The S-76 was developed during the mid-1970s, originally being designated S-74 but renamed in honor of the U.S. Bicentennial. Drawing upon its recently-developed S-70 helicopter, it features twin turboshaft engines, four-bladed main and tail rotors, and retractable landing gear. On 13 March 1977, the prototype performed its maiden flight. The initial production variant was the S-76A, the first deliveries of which took place on 27 February 1979. Several improved models were produced over time, including the S-76 Mk II launched in 1982, and the S-76B in 1987. Development of the S-76D was particularly troubled, being delayed by four years of delays due to flight envelope issues; it was finally certified for operation on 12 October 2012.

The S-76 initially encountered strong demand from the off-shore oil drilling industry; later on, demand shifted towards the VIP sector of the market. It performed several noteworthy flights, such as the first circumnavigation of the world in an east-to-west direction by a helicopter, and an autonomous demonstration flight during 2016. Sikorsky also used individual helicopters, often heavily modified for the purpose, for experimental purposes and to support other programmes. Demand for the S-76 waned during the 2010s, newer helicopters such as the AgustaWestland AW139 proved to be stiff competition. During March 2022, Sikorsky halted new orders for the S-76, but stated that it was looking at opportunities for future overseas manufacturing with foreign partners.

Development

edit

The development of the S-76 commenced during the mid-1970s as the S-74. The S-74 was subsequently redesignated the S-76 in honor of the U.S. Bicentennial. The company had set the design goal of producing a medium helicopter suitable for corporate transportation and the oil drilling industry. Sikorsky's design work on the S-70 helicopter (which was selected for use by the United States Army as the UH-60 Black Hawk) was utilized in the development of the S-76, incorporating S-70 design technology in its rotor blades and rotor heads.[5][6]: 1378  It was the first Sikorsky helicopter designed purely for commercial rather than military use.[6]: 1377 

 
An early production Sikorsky S-76A owned by Canadian Helicopters and used as an air ambulance

On 13 March 1977, the prototype performed its maiden flight.[7] On 21 November 1978, initial US Federal Aviation Administration type certification was granted, while the first customer delivery took place on 27 February 1979.[8]: 142, 144  During late 1978, the S-76 was officially named "Spirit",[8]: 144  however, this name was officially dropped by Sikorsky on 9 October 1980, reportedly due to translation issues into some foreign languages.[5][9]

The first production variant was the S-76A. Several improved models were produced over time. During 1982, the S-76 Mk II, equipped with more powerful engines and other refinements, was introduced. In 1987, production of the S-76B, powered by Pratt & Whitney Canada PT6B-36A and Pratt & Whitney Canada PT6B-36B engines; it was capable to attaining a maximum speed of 155 kn (287 km/h) at sea level. By early 2001, in excess of 500 S-76s had been delivered.[7]

During the early 2000s, the S-76C+ was the main version in production; it was equipped with twin Turbomeca Arriel 2S1 engines with FADEC and a Honeywell EFIS suite.[7] This version also incorporated active noise suppression, vibration dampers and a composite main rotor. On 3 January 2006, the S-76 C++ replaced earlier versions in production; it is powered by twin Turbomeca Arriel 2S2 engines and incorporates an improved and quieter transmission as well as minor changes in the interior equipment and avionics. By January 2006, Sikorsky had secured 92 orders for this model.[citation needed]

Development of the follow-on S-76D was subject to four years of delays due to technical problems in expanding the flight envelope. On 7 February 2009, the prototype conducted its first flight, and type certification was initially expected during 2011 while deliveries were forecast to start at the end of that year. The FAA issued certification on 12 October 2012. Three prototypes were used in the certification program, with one aircraft used to certify the optional rotor electric ice-protection system. The "D" model is powered by 1,050 hp (783 kW) Pratt & Whitney Canada PW210S engines driving composite rotors and incorporates active vibration control. Performance is substantially improved with the added power, but initial certification retains the same 11,700 lb (5,307 kg) gross weight and maximum 155 kn (287 km/h) cruise speed as earlier models.[10][11][12]

The rate of manufacturing noticeably declined during the 2010s; only a dozen S-76s were delivered between 2016 and 2020.[13] During September 2013, it was announced that the Chinese manufacturer Changhe Aircraft Industries Corporation had been contracted to produce the S-76D airframe.[14] By 2022 April, in excess of 875 S-76s had reportedly been built.[3]

During March 2022, Sikorsky announced that it had halted new orders for the S-76 while potential overseas manufacturing partners and licensing opportunities were being evaluated. Reasons for the hold included decreasing sales volume, the high cost of supply and manufacturing, and the prohibitive costs associated with adapting the S-76 to meet increasing safety mandates. This move effectively ended production of the S-76 following the completion of the three orders that were outstanding, and represented a withdrawal by Sikorsky from the medium commercial helicopter market.[15][16] Sikorsky has stated that it will continue to actively manufacture spare parts for the S-76 at its Connecticut facility.[13]

Design

edit
 
S-76A++ used for Search and Rescue at Royal Australian Air Force bases operated by CHC Helicopter

The S-76 is of a conventional configuration, with a four-bladed fully articulated main rotor and a four-bladed anti-torque rotor on the port side of the tailboom. It is powered by a pair of turboshaft engines, which are located above the passenger cabin.[17] On the prototypes and initial production aircraft, these engines were Allison 250-C30s, a variant of the popular Allison 250 engine that was developed specially for the S-76l it had a single-stage centrifugal compressor instead of the multi-stage axial/centrifugal compressor of earlier models of the engine, rated at 650 shp (480 kW) for takeoff.[8]: 113–114  These engines are connected to the main rotor by the main gearbox, a three-stage unit with a bull gear as its final stage, rather than the planetary gear that had been used by previous generations of Sikorsky helicopters. This arrangement has 30% fewer parts and lower costs than a more conventional design.[5][8]: 114 

The main rotor is furnished with a single piece aluminum hub fitted with elastomeric bearings, which are designed not to require lubrication or any other kind of maintenance throughout its design life.[5][8]: 114  The main rotor blades have titanium spars and incorporate a ten degree twist to provide an even loading when hovering, while they use a non-symmetrical airfoil section with a drooped leading edge. The rotor tips are tapered and swept back.[6]: 1378 [8]: 114  The rotor blades on later-build S-76s feature ice protection measures.[13] The flight controls are servo-assisted and have a Stability Augmentation System fitted.[8]: 114,116  A retractable nosewheel undercarriage is fitted, the reduced drag from this arrangement is credited with increasing the S-76A's cruising speed by 6 knots (6.9 mph; 11 km/h). Emergency flotation gear can be fitted, which uses helium-filled bags to increase buoyancy in the event of a forced landing on water.[6]: 1377 

The fuselage of the S-76 is made from both metal and composite materials; while the nose is composed of fiberglass, the cabin area primarily employs a light alloy honeycomb structure, the semi-monocoque tailboom is also constructed of light alloy.[17] A pair of pilots are typically seated in a side-by-side arrangement in the cockpit, situated ahead of the cabin, which can accommodate a further 12 passengers in three rows of four, or between four and eight passengers in a more luxurious executive seating configuration.[8]: 114  Later models can be flown by a single pilot when provisioned with an appropriately configured cockpit.[13] The S-76 was not originally designed with crashworthy fuel systems, leading to difficulties continuing production after an FAA requirement was implemented in April 2020.[16]

Operational history

edit

Early on in its commercial career, the S-76 became popular for offshore operations, such as to oil rigs.[18] Numerous operators have either purchased or leased the type specifically to operate in this sector.[19]

During 1982, the S-76A set multiple class records for range, climb, speed[20][21][22] and ceiling.[23] In June 1995, the S-76 became the first helicopter to circumnavigate the world in an east-to-west direction, piloted by the Australian adventurer Dick Smith.[24]

Several airlines have operated the S-76A on scheduled services, including Helijet Airways of Vancouver, British Columbia, Canada.[citation needed]

During the campaigning in the run up to the 2005 United Kingdom general election, both the Labour and the Conservative parties dispensed with conventional 'battle buses' in favour of S-76 helicopters to quickly transport their leaders around the British Isles.[25] According to Jason Lambert, Sikorsky's vice president of commercial and military systems, the S-76 had proven itself to be particularly popular amongst VIP customers.[16] By 2020, according to Sikorsky, ten countries operated S-76s to carry their heads of state.[18]

S-76s have been periodically used to test new technologies and capabilities. The highly-modified S-76 SHADOW (Sikorsky Helicopter Advance Demonstrator of Operators Workload) was built to demonstrate its advanced cockpit for single-pilot operations and to study the human engineering interface between the pilot and the cockpit controls and displays; this was in aid of the RAH-66 Comanche armed reconnaissance helicopter programme.[26] During the 2010s, an S-76 was configured for autonomous operation and demonstrated this ability in June 2016, flying for a distance of around 30 miles (48 km) with no human intervention beyond limited inputs made via a tablet computer, the take off and landing phases were also performed autonomously.[27]

During the 2010s, many S-76 operators elected to replace the type with newer medium-lift rotorcraft, such as the AgustaWestland AW139.[16] In early 2020, it was observed that, while the S-76D was no longer compliant with FAA regulations to permit its sale to US-based customers, sales were still possible to several other countries.[13]

Variants

edit

Civil

edit
 
S-76C search and rescue helicopter operated by Norrlandsflyg
  • S-76A
Original production version, powered by two 650 shp (480 kW) Rolls-Royce (Allison) 250-C30 turboshaft engines. Large number modified to S-76A+, A++, C, and C+. 284 manufactured.
  • S-76A Utility
Utility transport version, equipped with sliding doors and a strengthened floor.
  • S-76A+
Unsold S-76s were fitted with two Turbomeca Arriel 1S turboshaft engines. 17 manufactured.
  • S-76A++
S-76 helicopters fitted with two Turbomeca Arriel 1S1 turboshaft engines.
  • S-76A Mk II
Improved all-weather transport version, fitted with more powerful engines, and other detail improvements.
  • S-76B
Powered by two Pratt & Whitney Canada PT6B-36A or Pratt & Whitney Canada PT6B-36B turboshaft engines. 101 built.
  • S-76C
Powered by two 539-kW (981-shp) Turbomeca Arriel 1S1 turboshaft engines. 43 manufactured.
  • S-76C+
Uprated version, fitted with improved Turbomeca Arriel 2S1 turboshafts with FADEC. 35 manufactured.
  • S-76C++
Turbomeca Arriel 2S2
  • S-76D
Powered by two Pratt & Whitney Canada PW210S. Also features a Thales Topdeck avionics suite and improved noise signature over all previous variants.[28][29]

Military

edit
AUH-76 "Dragon Lady"
Armed utility transport version of the S-76 Mk. II. Delivered in 1983 to the Philippine Air Force. Initially armed with two fixed forward firing M134 7.62 mm minigun (one each side) and a 7-round rocket pod on each side and radar altimeters. When M134 became unserviceable, the guns were replaced with M2P Machine Guns.[30][31]
H-76 Eagle
A militarised variant suitable for naval operations, based on the S-76B, it was announced during 1985 but none were ever sold.

Experimental derivatives

edit
 
Sikorsky S-76 SHADOW
Sikorsky S-75
The Advanced Composite Airframe Program (ACAP) was an all-composite Sikorsky early LHX proof of concept aircraft. Designated S-75, it mated a new composite airframe with S-76 engines, rotors and powertrain components.[32]
Sikorsky S-76 SHADOW
Boeing-Sikorsky MANPRINT study. The original concept of the LHX program was to produce a one-man helicopter that could do more than a two-man aircraft. The Sikorsky (S-76) Helicopter Advance Demonstrator of Operators Workload (SHADOW) had a single-pilot advanced cockpit grafted to its nose. The purpose was to study the MANPRINT or human engineering interface between the pilot and the cockpit controls and displays. The cockpit was the prototype of a single-pilot cockpit designed for use on the prototype RAH-66 Comanche armed reconnaissance helicopter. The cockpit was designed so sensors would feed data to the pilot through helmet-mounted displays. The MANPRINT study determined that single-pilot operation of the Comanche was unsafe, and would result in pilot overload. As result of this study, the Comanche was designed to be operated by a crew of two.[26]

Operators

edit

Civil

edit

The S-76 is in civil service around the world with airlines, corporations, hospitals, and government operators. The world's largest civilian fleet is the 79 Sikorsky S-76 helicopters operated by CHC Helicopter Corporation.[2]

Current military and government

edit
 
An S-76C of the Spanish Air Force
 
Sikorsky S-76B of the Royal Thai Navy
  Argentina

  Canada

  China
  Japan
  Jordan
  Philippines
  Republic of China
  Saudi Arabia
  Serbia
  Spain
  Thailand
  United Kingdom

Former military and government

edit
  Australia
  Canada
  Honduras
  Hong Kong
  Iceland

Accidents

edit

Specifications (Sikorsky S-76C++)

edit
 
An S-76B prototype helicopter modified as a fantail demonstrator for the RAH-66 program at the 1991 Paris Air Show

Data from Sikorsky[58]

General characteristics

  • Crew: two[a]
  • Capacity: 13 passengers
  • Length: 52 ft 6 in (16 m) from tip of main rotor to tip of tail rotor
  • Width: 10 ft 0 in (3.05 m) at horizontal stabilizer
  • Height: 14 ft 6 in (4.42 m) to tip of tail rotor
  • Empty weight: 7,005 lb (3,177 kg) in utility configuration
  • Gross weight: 11,700 lb (5,306 kg)
  • Fuel capacity: 281 US gallons (1,064 liters), with 50 or 102 US gallons (189 or 386 liters) available in extra auxiliary tanks
  • Powerplant: 2 × Turbomeca Arriel 2S2 turboshaft, 922 shp (688 kW) each
  • Main rotor diameter: 44 ft 0 in (13.41 m)

Performance

  • Maximum speed: 155 kn (178 mph, 287 km/h) at maximum takeoff weight at sea level in standard atmospheric conditions
  • Cruise speed: 155 kn (178 mph, 287 km/h) maximum cruise speed is the same as maximum speed
  • Range: 411 nmi (473 mi, 761 km) no reserves, at long-range cruise speed at 4,000 ft altitude
  • Service ceiling: 13,800 ft (4,200 m)

Avionics

See also

edit

Related development

Aircraft of comparable role, configuration, and era

Related lists

Notes

edit
  1. ^ Can operate with just one pilot in VFR conditions and in IFR when suitably equipped

References

edit

Citations

edit
  1. ^ "Fleet :: Bristow Group Inc. (VTOL)". Bristow Helicopters. Archived from the original on 20 January 2022. Retrieved 25 April 2022.
  2. ^ a b "Fleet". CHC Helicopter. Archived from the original on 2 January 2022. Retrieved 25 April 2022.
  3. ^ a b "Sikorsky S-76 Helicopter". Lockheed Martin. 17 August 2021. Archived from the original on 27 November 2021. Retrieved 25 April 2022.
  4. ^ Paul Eden, Civil Aircraft Recognition (Crowood Press, 2012)
  5. ^ a b c d Devine, Vinny (11 September 2012) [April 2012]. "S-76 Helicopter". Sikorsky Archives. Archived from the original on 13 March 2022. Retrieved 25 April 2022.
  6. ^ a b c d Lambert, Mark (6 May 1978). "S-76 in the Air". Flight International. Vol. 113, no. 3607. pp. 1377–1382. Archived from the original on 19 January 2019.
  7. ^ a b c Simpson, Rod (21 July 2001). Airlife's World Aircraft. Shrewsbury: Airlife. p. 505. ISBN 978-1-84037-115-4. OCLC 980274514. OL 8915318M.
  8. ^ a b c d e f g h "The Spirit of Sikorsky". Air International. Vol. 18, no. 3. March 1980. pp. 111–116, 142–144. ISSN 0306-5634. OCLC 907842170.
  9. ^ Kline, R. E. (9 October 1980), "Identification of S-76 Helicopter", Sikorsky Internal Correspondence P-2462
  10. ^ Trimble, Stephen. "Sikorsky explains four-year delivery slip for S-76D". FlightGlobal. Archived from the original on 23 January 2013. Retrieved 25 April 2022.
  11. ^ "First Flight for Improved Sikorsky S-76". Aviation Week & Space Technology. 16 February 2009. p. 15. ISSN 0005-2175.
  12. ^ "Type Certificate Data Sheet No. H1NE". Federal Aviation Administration. 18 March 2021. Retrieved 25 April 2022.
  13. ^ a b c d e Huber, Mark (2 March 2022). "Sikorsky Ponders Fate of S-76D". ainonline.com.
  14. ^ "Cooperative Program". Changhe Aircraft Industries Corporation. Archived from the original on 6 September 2009. Retrieved 25 April 2022.
  15. ^ Norris, Guy (8 March 2022). "Sikorsky Puts S-76D On Ice, Seeks License Production Partner". Aviation Week Network. Dallas. Archived from the original on 29 March 2022.
  16. ^ a b c d Johnson, Oliver (9 March 2022). "Sikorsky stops taking S-76 orders; looks to license production". verticalmag.com.
  17. ^ a b Taylor, John W. R., ed. (December 1982). Jane's All the World's Aircraft 1982–83. London: Janes Information Services. pp. 476–477. ISBN 978-0-7106-0748-5. ISSN 0075-3017. OCLC 496585133. OL 28152958M.
  18. ^ a b c Lyons, Patrick J. (27 January 2020). "What We Know About the Helicopter in Kobe Bryant's Death". The New York Times.
  19. ^ Shukla, Ajai (24 March 2022). "Pawan Hans leases 6 Sikorsky S-76D choppers for operations". business-standard.com.
  20. ^ "Thomas F. Doyle Jr. (USA) (1845)". Fédération Aéronautique Internationale. 10 October 2017. Archived from the original on 25 April 2022. Retrieved 25 April 2022.
  21. ^ "Thomas F. Doyle Jr. (USA) (11660)". Fédération Aéronautique Internationale. 10 October 2017. Archived from the original on 25 April 2022. Retrieved 25 April 2022.
  22. ^ "Nicholas D. Lappos (USA) (2262)". Fédération Aéronautique Internationale. 10 October 2017. Archived from the original on 25 April 2022. Retrieved 25 April 2022. Others: 1827, 1839, 1844, 2067, 2068, 2069, 2070, 2071, 2072, 2073, 2074, 2100, 2222, 2223, 3415, 10273
  23. ^ "Byron Graham Jr. (USA) (9947)". Fédération Aéronautique Internationale. 10 October 2017. Archived from the original on 25 April 2022. Retrieved 25 April 2022.
  24. ^ Gott, Robert (1998). Dick Smith: Australian Adventurer. Makers & Shakers. Port Melbourne: Heinemann. p. 46. ISBN 978-1-8639-1878-7. OCLC 38819984.
  25. ^ Wheeler, Brian (7 April 2005). "Which party is winning the air war?". BBC News. Archived from the original on 25 January 2021. Retrieved 25 April 2022.
  26. ^ a b "Historic US Army Helicopters". US Army TACOM-RI. 5 October 2005. Archived from the original on 27 June 2009. Retrieved 2 July 2011.
  27. ^ Jeffrey, Colin (3 June 2016). "Autonomous 30-mile flight for Sikorsky S-76 commercial helicopter". newatlas.com.
  28. ^ Huber, Mark (3 July 2012). "Sikorsky S-76D". Business Jet Traveler. ISSN 1554-1339. Archived from the original on 26 October 2021. Retrieved 3 July 2018.
  29. ^ "Thales develops new innovations for S-76D helicopter". Thales. 12 January 2011.
  30. ^ "15SW History".
  31. ^ "Orbats".
  32. ^ Harding, Stephen (1997). "Sikorsky S-75 ACAP". U.S. Army Aircraft Since 1947: An Illustrated Reference. Atglen: Schiffer Publishing. p. 251. ISBN 978-0-7643-0190-2. LCCN 96069996. OCLC 464218057. OL 1016558M – via Internet Archive.
  33. ^ "Fuerza Aerea Argentina VIP S-76". helis.com. Archived from the original on 25 February 2021. Retrieved 25 April 2022.
  34. ^ "Ministry of Transport Signs for Four S-76D Helicopters for Search and Rescue Mission in China". Lockheed Martin (Press release). 5 March 2013. Archived from the original on 4 March 2016. Retrieved 27 January 2020.
  35. ^ "Japanese coast guard orders helicopters". United Press International. Singapore. 14 February 2012. Archived from the original on 31 December 2019. Retrieved 21 February 2013.
  36. ^ "Sikorsky S-76D begins service with Japan Coast Guard". aerospacemanufacturinganddesign.com. 3 March 2015. Retrieved 29 July 2022.
  37. ^ "Aircraft". Royal Jordanian Air Force. Archived from the original on 24 October 2016. Retrieved 21 February 2013.
  38. ^ a b c Hoyle, Craig (4 December 2018). "Analysis: 2019 World Air Forces Directory". FlightGlobal. Retrieved 12 March 2019.
  39. ^ "S-76B". National Airborne Service Corps. Archived from the original on 5 August 2012. Retrieved 25 April 2022.
  40. ^ "Saudi Arabia's Ministry of Interior Signs Contract for 12 S-76D Helicopters". Sikorsky Aircraft (Press release). 21 July 2010. Archived from the original on 6 October 2014. Retrieved 21 February 2013.
  41. ^ "Serbian Police Aviation". Aeroflight. 11 October 2005 [25 September 2005]. Archived from the original on 11 March 2022. Retrieved 18 July 2012.
  42. ^ Llera, Luis Carlos (11 August 2010). "Los ángeles del mar de Galicia han salvado ya a 1.321 náufragos" [The angels of the Galician sea have already saved 1,321 castaways]. La Voz de Galicia (in Spanish). Archived from the original on 25 April 2022. Retrieved 3 July 2018.
  43. ^ Luaces, Antón. "Pesca tramita la adquisición del tercer helicóptero de Gardacostas" [Fishing is in progress for the acquisition of a third helicopter from Gardacostas]. La Opinión a Coruña (in Spanish). Archived from the original on 29 June 2012. Retrieved 3 July 2018.
  44. ^ "Air Travel". The Royal Household. Archived from the original on 23 December 2012. Retrieved 25 April 2022.
  45. ^ "CHC introduces half dozen AW139s for RAAF work". Business Air News. 11 March 2019. Archived from the original on 26 December 2021. Retrieved 17 June 2019.
  46. ^ "World's Air Forces". Flight International. 28 November 1987. p. 60. Archived from the original on 19 January 2019. Retrieved 21 February 2013.
  47. ^ Royal Air Force Historical Society (2003). Royal Air Force Reserve and Auxiliary Forces (PDF). Royal Air Force Historical Society. pp. 173–176. ISBN 978-0-9530-3451-2. Archived (PDF) from the original on 16 October 2015. Retrieved 11 January 2021.
  48. ^ "Civilian Rescue". Sikorsky Archives. Archived from the original on 29 January 2022. Retrieved 21 February 2013.
  49. ^ "Rán heitir nýja þyrla gæzlunnar - væntanleg til landsins eftir viku". Morgunblaðið (in Icelandic). 17 September 1980. Retrieved 13 June 2022 – via Tímarit.is.  
  50. ^ "Rig flights resume after fatal crash". BBC News. 3 September 2002.
  51. ^ "Final Report. Copterline Oy. Sikorsky S-76C+. In Tallinn Bay, Estonia on 10 August 2005". Aircraft Accident Investigation Commission, Ministry of Economic Affairs and Communications, Estonia. 6 August 2008. Archived from the original (PDF) on 15 November 2008. Retrieved 11 August 2008.
  52. ^ "Ornge, Ontario's air ambulance service, faces 17 labour code charges - Toronto - CBC News". Cbc.ca. 31 May 2013. Retrieved 30 May 2014.
  53. ^ [1] Archived 13 April 2017 at the Wayback Machine Eczacıbaşı helikopter kazası nedeni kuşku yaratan detay (in Turkish)
  54. ^ Melley, Brian; Dazio, Stefanie (9 February 2021). "Kobe Bryant helicopter crash caused by pilot's poor decision making and disorientation, NTSB says". Los Angeles Times. Retrieved 15 May 2024.
  55. ^ Melley, Brian; Dazio, Stefanie (9 February 2021). "Investigators report Kobe Bryant's pilot got disoriented in clouds". nba.com. Retrieved 15 May 2024.
  56. ^ "4 killed as military chopper crashes in Basilan amid bad weather". ABS-CBN News. 16 September 2020.
  57. ^ "PAF grounds Sikorsky choppers for inspection after Basilan crash". Philippine News Agency. 17 September 2020.
  58. ^ "S-76 Technical Information: S-76C++ Helicopter, Executive Transport mission" (PDF). Sikorsky Aircraft. 2007. Archived from the original (PDF) on 2 December 2012. Retrieved 12 August 2012.

Further reading

edit
edit
 
Wikimedia Commons has media related to Sikorsky S-76.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Sikorsky_S-76&oldid=1244606515"