Sikorsky S-76

The Sikorsky S-76 is an American medium-size commercial utility helicopter, manufactured by the Sikorsky Aircraft Corporation. The S-76 features twin turboshaft engines, four-bladed main and tail rotors, and retractable landing gear.

"S-76" redirects here. For other uses, see S76.
S-76
A Galician Coast Guard S-76C+
Role Utility helicopter
National origin United States
Manufacturer Sikorsky Aircraft
First flight 1977-03-13 (1977-03-13)
Status In service
Primary users Bristow Helicopters[1]
CHC Helicopter[2]
Produced 1977–present
Variants Sikorsky S-75

Development

The development of the S-76 began in the mid-1970s as the S-74, with the design goal of providing a medium helicopter for corporate transportation and the oil drilling industry; the S-74 was later redesignated the S-76 in honor of the U.S. Bicentennial. 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.[3][4]: 1378  It was the first Sikorsky helicopter designed purely for commercial rather than military use.[4]: 1377 

The prototype first flew on 13 March 1977.[5] Initial US Federal Aviation Administration type certification was granted on 21 November 1978, with the first customer delivery on 27 February 1979.[6]: 142, 144  The S-76 was named "Spirit" late in 1978,[6]: 144  but this name was officially dropped by the company on 9 October 1980, due to translation issues into some foreign languages.[3][7]

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

The first production variant was the S-76A. In 1982, this model set class records for range, climb, speed[8][9][10] and ceiling.[11] Several airlines operate the S-76A on scheduled services including Helijet Airways of Vancouver, British Columbia, Canada. The S-76 Mk II was introduced in 1982 and the S-76B in 1987, with its top speed of 155 kn (287 km/h) at sea level. Over 500 S-76s had been delivered by early 2001.[5]

The S-76C+ was produced until December 2005. It is equipped with twin Turbomeca Arriel 2S1 engines with FADEC and a Honeywell EFIS suite.[5] This version incorporates 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 two Turbomeca Arriel 2S2 engines and incorporates an improved and quieter transmission as well as minor changes in the interior equipment and avionics. There were 92 orders for this model as of January 2006.

Development of the follow-on S-76D was subject to four years of delays due to technical problems in expanding the flight envelope. The prototype made its first flight on 7 February 2009, and type certification was initially expected in 2011, with deliveries forecast for the end of that year. It was FAA certified 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.[12][13][14] Changhe Aircraft Industries Corporation was contracted in September 2013 to produce the S-76D airframe.[15]

As of April 2022, over 875 S-76 aircraft have been built.[16]

Sikorsky halted new orders for the S-76 in March 2022 while it sought overseas manufacturing partners due to low sales numbers, high cost of supply and manufacturing, and the prohibitive costs associated with adapting the S-76 to meet increasing safety mandates. This has effectively ended production of the S-76 after the completion of three current existing orders and has resulted in Sikorsky withdrawing from the medium commercial helicopter market.[17]

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

The S-76 is of conventional configuration, with a four-bladed fully articulated main rotor and a four-bladed anti-torque rotor on the port side of the tailboom. Two turboshaft engines are located above the passenger cabin.[18] In the prototypes and initial production aircraft, these engines were Allison 250-C30s, a new version of the popular Allison 250 engine developed specially for the S-76, with 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.[6]: 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 used by previous generations of Sikorsky helicopters. This arrangement has 30% fewer parts and lower costs than a more conventional design.[3][6]: 114 

The main rotor hub has a single piece aluminum hub with elastomeric bearings designed not to require lubrication or any other kind of maintenance throughout its design life.[3][6]: 114  The main rotor blades have titanium spars and incorporate a ten degree twist to give 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.[4]: 1378 [6]: 114  Flight controls are servo-assisted, with a Stability Augmentation System fitted.[6]: 114,116  A retractable nosewheel undercarriage is fitted, which gives the S-76A a 6 knots (6.9 mph; 11 km/h) increase in cruising speed; emergency flotation gear can be fitted using helium-filled bags to increase buoyancy in the event of a forced landing on water.[4]: 1377 

The fuselage of the aircraft is of mixed metal and composites construction; the nose is composed of fiberglass while the cabin primarily employs a light alloy honeycomb structure, the semi-monocoque tailboom is also constructed of light alloy.[18] Two pilots (or a pilot and a passenger) sit side by side in the cockpit, situated ahead of the cabin, which can accommodate a further 12 passengers in three rows of four, or four to eight passengers in more luxurious executive seating.[6]: 114 

Operational history

The S-76 was the first helicopter to circumnavigate the world in an east-to-west direction, piloted by Australian adventurer Dick Smith, in 1995.[19]

Variants

Civil
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.[20]

Military
AUH-76
Armed utility transport version, developed from the S-76 Mk. II.
H-76 Eagle
Announced in 1985 the Eagle was a military and naval variant of the S-76B, none sold.

Experimental derivatives
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.[21]
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.{{refn|name="TriArmy"|"Historic US Army Helicopters". US Army TACOM-RI. 2005-10-05. Archived from the original on 2009-06-27. Retrieved 2011-07-02.</ref>

Operators

Civil

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
An S-76C of the Spanish Air Force
Sikorsky S-76B of the Royal Thai Navy
 Argentina
 China
 Japan
 Jordan
 Philippines
 Republic of China
 Saudi Arabia
 Serbia
 Spain
 Thailand
 United Kingdom

Former military and government
 Australia
 Canada
 Honduras
 Hong Kong

Accidents

Specifications (Sikorsky S-76C++)
An S-76B prototype helicopter modified as a fantail demonstrator for the RAH-66 program at the 1991 Paris Air Show

Data from Sikorsky[38]

General characteristics

  • Crew: two[lower-alpha 1]
  • 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

Related development

Aircraft of comparable role, configuration, and era

Related lists

Notes
  1. Can operate with just a pilot in VFR conditions and in IFR when suitably equipped

References
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Further reading
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