Sikorsky S-76
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Sikorsky S-76 multi-role medium-size utility helicopter
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The Sikorsky S-76 is an American medium-size utility helicopter, manufactured by the Sikorsky Aircraft Corporation. It was principally designed and developed for CHC Helicopter Corporation, Canada. The maiden flight of S-76 took place on 13 March 1977. More than 800 S-76 helicopters have been delivered to various operators worldwide. Sikorsky's S-76 multi-role helicopter has been designed in order to perform several different missions, such as executive passenger transport (VIP), emergency medical services (EMS), search-and-rescue operations (SAR) and offshore passenger and material transportation.
Earlier versions of the S-76 helicopter include The S-76ATM and S-76A+TM helicopters (307 built), S-76BTM helicopter (103 built) and S-76CTM , S-76C+TM helicopters (191 built), and S-76C++TM helicopters (214 built). Sikorsky's S-76 variants are currently in service in armies and governments of several differents countries, including Argentina, Honduras, Hong Kong, Japan, Jordan, Philippines, Republic of China, Saudi Arabia, Serbia, Spain, Thailand, and Trinidad and Tobago. |
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- S-76A: Original production version, powered by two 485 kW (650 shp) Rolls-Royce (Allison) 250-C30 turboshaft engines. Large number modified to S-76A+, A++, C, and C+.
- 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. - 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. - S-76C: Powered by two 539-kW (981-shp) Turboméca Arriel 1S1 turboshaft engines. - S-76C+: Uprated version, fitted with improved Turboméca Arriel 2S1 turboshafts with FADEC. - S-76C++: Equipped with Turboméca Arriel 2S2. - S-76D: As an upgraded variant of the S-76, the S-76D helicopter’s baseline equipment includes powerful and efficient Pratt & Whitney Canada PW210S engines; an advanced THALES TopDeck ® integrated avionics system and four-axis autopilot; Health and Usage Monitoring System (HUMS) incorporated into fleet monitoring and analysis; active vibration control; and all-composite, flaw-tolerant main rotor blades. A Rotor Ice Protection System (RIPS) for all-weather capability will be available as an option. |
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| Design | ||||||||||||||||||||||
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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. 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. The main rotor blades have titanium spars and incorporate a 10 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. The design accommodates 2 pilots and 12 passengers.
Flight controls are servo-assisted, with a Stability Augmentation System fitted. A retractable nosewheel undercarriage is fitted, which gave the S-76A a 6 knots (6.9 mph; 11 km/h) increase in cruising speed and emergency flotation gear can be fitted, with flotation bags that can be filled with helium in the event of a forced landing on water. The fuselage is of mixed metal and composites construction, with a fiberglass nose and a light alloy honeycomb cabin structure. The semi-monocoque tailboom is also constructed of light alloy. |
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Propulsion
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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 take-off. 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 gave 30% fewer parts and lower costs than a more conventional design.
Turbomeca Arriel 2S1 engines were later deployed in the S-76C+ variant until December 2005. The main rotor of the S-76C+ was manufactured using composite material. Increased active noise and vibration dampers were used to provide more comfort for passengers. The S-76C++, which features an intake air filter and an improved and quieter transmission, was launched later. It is equipped with upgraded interior equipment and electronics. The production of S-76C++ was completed in January 2006. The helicopter is powered by a Turboméca Arriel 2S2 turbo shaft engine. D-variant of the Sikorsky S-76 features two Pratt & Whitney Canada PW210S dual FADEC-controlled optimized engines, which can produce about 1,050shp of power. Active Vibration Control System (AVCS) and four-bladed composite main rotor are installed for smooth operation. |
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Avionics
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S-76 variants's cockpit is equipped with a Honeywell primus weather radar, dual comm / nav radios, an automatic direction finder, dual attitude and heading reference systems (AHRS) and air data computers, a radio altimeter, a mode C transponder, dual VORs with glideslope, distance measuring equipment (DME) and a cockpit voice recorder (CVR).
The S-76D's cockpit is fitted with an avionics suite that includes a Thales Top Deck avionics system, four-axis fully coupled autopilot, an EGPWS, a traffic collision avoidance system (TCAS1), a Honeywell Primus 660 weather radar, a health usage monitoring system (HUMS), a Thales digital map and a Collins Pro Line 21 comm / nav radio suite. |
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