TheSikorsky S-76 is a medium-size commercialutility helicopter designed and produced by the American helicopter manufacturerSikorsky Aircraft. It is the company's first helicopter specifically developed for the civilian market.
The S-76 was developed during the mid-1970s, originally being designatedS-74 but renamed in honor of theU.S. Bicentennial. Drawing upon its recently developedS-70 helicopter, it features twinturboshaft engines, four-bladed main and tail rotors, and retractablelanding gear. On 13 March 1977, the prototype performed itsmaiden 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-shoreoil drilling industry; later on, demand shifted towards theVIP 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, as newer helicopters such as theAgustaWestland 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.
The development of the S-76 commenced during the mid-1970s as theS-74. The S-74 was subsequently redesignated the S-76 in honor of theU.S. Bicentennial. The company had set the design goal of producing a medium helicopter suitable for corporate transportation and theoil drilling industry. Sikorsky's design work on theS-70 helicopter (which was selected for use by the United States Army as theUH-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 Despite this, Sikorsky planned to design it to conform with either the relevantFAR or military standards, whichever was more stringent, with the goal being the production of a rugged civil helicopter which could be used "off-the-shelf" for military purposes.[7]
It was announced on 19 January 1975, before it had even been designed and Sikorsky began taking contracts; they would use these already signed operators for market research during development.[7] The intended engine had also not yet been designed and was to be purpose-built alongside the S-76. Prototype construction began May 1976, with the first flight scheduled for May 1977, and deliveries scheduled to commence July 1978.[7] On 13 March 1977, two months ahead of schedule, the prototype performed itsmaiden flight.[8] On 21 November 1978, initial USFederal Aviation Administrationtype certification was granted, while the first customer delivery took place on 27 February 1979.[9]: 142, 144 During late 1978, the S-76 was officially named "Spirit",[9]: 144 however, this name was officially dropped by Sikorsky on 9 October 1980, reportedly due to translation issues into some foreign languages.[5][10]
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 byPratt & Whitney Canada PT6B-36A andPratt & 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.[8]
During the early 2000s, the S-76C+ was the main version in production; it was equipped with twinTurbomeca Arriel 2S1 engines withFADEC and aHoneywellEFIS suite.[8] This version also incorporated active noise suppression, vibration dampers and acomposite main rotor. On 3 January 2006, the S-76 C++ replaced earlier versions in production; it is powered by twinTurbomeca Arriel 2S2 engines and incorporates an improved and quietertransmission 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, andtype 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.[11][12][13]
The rate of manufacturing noticeably declined during the 2010s; only a dozen S-76s were delivered between 2016 and 2020.[14] During September 2013, it was announced that the Chinese manufacturerChanghe Aircraft Industries Corporation had been contracted to produce the S-76D airframe.[15] 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 andlicensing 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.[16][17] Sikorsky has stated that it will continue to actively manufacture spare parts for the S-76 at itsConnecticut facility.[14]
The S-76 is of a conventional configuration, with a four-bladed fullyarticulated main rotor and a four-bladed anti-torque rotor on the port side of the tailboom. It is powered by a pair ofturboshaft engines, which are located above the passenger cabin.[18] On the prototypes and initial production aircraft, these engines wereAllison 250-C30s, a variant of the popular Allison 250 engine that was developed specially for the S-76. It had a single-stagecentrifugal compressor instead of the multi-stageaxial/centrifugal compressor of earlier models of the engine, rated at 650 shp (480 kW) for takeoff.[9]: 113–114 These engines are connected to the main rotor by the main gearbox, a three-stage unit with abull gear as its final stage, rather than theplanetary 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][9]: 114
The main rotor is furnished with a single piece aluminum hub fitted withelastomeric bearings, which are designed not to require lubrication or any other kind of maintenance throughout its design life.[5][9]: 114 The main rotor blades have titaniumspars and incorporate a ten degree twist to provide an even loading when hovering, while they use a non-symmetricalairfoil section with a droopedleading edge. The rotor tips are tapered and swept back.[6]: 1378 [9]: 114 The rotor blades on later-build S-76s feature ice protection measures.[14] The flight controls areservo-assisted and have a Stability Augmentation System fitted.[9]: 114,116 A retractablenosewheel undercarriage is fitted, the reduceddrag 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 useshelium-filled bags to increasebuoyancy in the event of a forced landing on water.[6]: 1377
The fuselage of the S-76 is made from both metal andcomposite materials; while the nose is composed offiberglass, the cabin area primarily employs a lightalloyhoneycomb structure, the semi-monocoque tailboom is also constructed of light alloy.[18] 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.[9]: 114 Later models can be flown by a single pilot when provisioned with an appropriately configured cockpit.[14] 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.[17]
Early on in its commercial career, the S-76 became popular for offshore operations, such as tooil rigs.[19] Numerous operators have either purchased or leased the type specifically to operate in this sector.[20]
During 1982, the S-76A set multiple class records for range, climb, speed[21][22][23] and ceiling.[24] In June 1995, the S-76 became the first helicopter tocircumnavigate the world in an east-to-west direction, piloted by the Australian adventurerDick Smith.[25]
During the campaigning in the run up to the2005 United Kingdom general election, both theLabour and theConservative parties dispensed with conventional 'battle buses' in favour of S-76 helicopters to quickly transport their leaders around theBritish Isles.[26] According to Jason Lambert, Sikorsky's vice president of commercial and military systems, the S-76 had proven itself to be particularly popular amongstVIP customers.[17] By 2020, according to Sikorsky, ten countries operated S-76s to carry theirheads of state.[19]
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 theRAH-66 Comanche armed reconnaissance helicopter programme.[27] 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 atablet computer, the take off and landing phases were also performed autonomously.[28]
During the 2010s, many S-76 operators elected to replace the type with newer medium-lift rotorcraft, such as theAgustaWestland AW139.[17] 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.[14]
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 twoTurbomeca Arriel 1S turboshaft engines. 17 manufactured.
Armed utility transport version of the S-76 Mk. II. Delivered in 1983 to thePhilippine 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.[31][32]
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.
The Advanced Composite Airframe Program (ACAP) was an all-composite Sikorsky early LHX proof of concept aircraft. DesignatedS-75, it mated a newcomposite airframe with S-76 engines, rotors and powertrain components.[34]
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 prototypeRAH-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.[27]
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 byCHC Helicopter Corporation.[2]
Ornge / Ontario Air Ambulance Corp. (originally owned byCanadian Helicopters and eventually o/o by Ornge and replaced by AW139 in 2012). 1 donated to Centennial College in Toronto (C-GIMZ) and 1 to Canadian Aviation and Space Museum (C-GIMB).
On 17 July 2002, S-76AG-BJVX, operated byBristow Helicopters,crashed into the North Sea due to the failure of a main rotor blade. The operator temporarily halted all helicopter flights over theNorth Sea until operations resumed on 3 September 2002.[53]
On 26 January 2020, S-76BN72EXcrashed in Calabasas, California, killing all nine occupants, including the retired professional basketball playerKobe Bryant and his daughterGianna.[19] The cause was determined to be the pilot Ara Zobayan experiencing spatial disorientation due to heavy fog, as well as pilot error.[57][58]
^abcdDevine, Vinny (11 September 2012) [April 2012]."S-76 Helicopter".Sikorsky Archives.Archived from the original on 13 March 2022. Retrieved25 April 2022.
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