76D Heads for Certification
Announced at Heli-Expo in 2005, the S-76D is moving out of its protracted development phase and into certification flight-test and low-rate production. Initial certification is expected by year-end, with deliveries to begin in the first quarter of 2012—a four-year delay.
The D model is a major upgrade to the S-76, more than 800 of which have been delivered since it first flew in 1977. With more-powerful engines, improved rotor and integrated avionics, the S-76D is designed to combine the single-engine performance of the corporate-preferred S-76B with the cruise fuel-efficiency of the offshore-favored S-76C.
“We get the power of the B with the efficiency of the C family, which is attractive from an operating cost perspective,” says Tim Fox, S-76 senior program manager. Increased power and rotor lift improve hot-and-high performance, dual-speed rotors reduce noise and a rotor ice protection system allows the D to operate in more challenging environments.
“We have power, performance, best-in-class fuel burn, and the D is extremely quiet for its size,” he says. Priced about the same as a similarly equipped C++, the D can lift 1,000lb more and fly 400nm versus 375. These improvements will allow Sikorsky to offer a single model across markets that previously were segmented, Fox says.
“The D gives us openings into new markets and areas of the world, hotter environments where the C could not operate and the B had the power, but not the specific fuel consumption,” says David Franc, S-76 marketing manager. Improved high-altitude performance opens up VIP and EMS markets such as Denver and Mexico City, while “we can go further offshore with greater launch reliability”.
Powered by a pair of digitally controlled, 1,050-shp Pratt & Whitney Canada PW210S turboshafts, the D model introduces flaw-tolerant all-composite blades, a Thales TopDeck cockpit with large-format displays and four-axis autopilot, and optional electrically deiced rotors that allow flight into known icing. Active vibration control and health and usage monitoring systems are standard.
After the delays, caused by unexpected and unspecified discoveries during development, the S-76D is on track to meet its performance targets. “Shake-down tests identified weaknesses, which we have fixed,” says Fox, adding “the helicopter is quieter than predicted, rotor lift is slightly greater than predicted and fuel efficiency is on plan.”
Two prototypes, D1 and D2, have logged more than 300hr since the first flight in February 2009, with certification testing getting under way in November 2010. The third aircraft, D3, will join the 750hr. flight-test program later this year, tasked with avionics certification. D1 is moving into powerplant certification from system development, and D2 into performance testing from avionics and autopilot development.
S-76 airframes are manufactured in the Czech Republic by Aero Vodochody and in China by Changhe Aircraft Industries. Aero delivered the first production S-76D airframe to Sikorsky’s final-assembly plant in Coatesvillle, Pa., in December and, with the last S-76C++ to be delivered this December, Changhe is expected to transition to the new model late this year. “We envision dual-sourcing on the D, but this is to be worked out,” says Fox.