S-76 Rebirth

With the S-76D, Sikorsky takes a classic and makes it state of the art.

(March 2011) — As an icy wind whipped from the Hudson River and buffeted the heliport’s aluminum chain-link fence with an unrelenting ferocity, settling into the cockpit of a Sikorsky S-76 instead of some lesser machine made me stop and appreciate the size and power of one of the best-selling helicopters of all time.

“I’m a strong swimmer and might make it back to dry land,” said the S-76 captain buckling in beside me, “but I doubt you could.”

Those were the _dis_comforting words offered as simple statement of fact masquerading as a “safety briefing” just in case we ended up in the frigid water on takeoff. I was about to get a demonstration of a new helicopter terrain and obstacle warning system in an older S-76B model, and the pilot was teasing, wasn’t he?

Perfect, I thought.

Thank goodness for good, old-fashioned Pratt & Whitney reliability and the stellar safety record of the S-76, which rates significantly better than most other turbine-powered helicopters. Combine this with a roomy cabin, comfortable ride and 155-knot maximum cruising speed, and it’s no wonder the model has succeeded as a mainstay of corporate, offshore oil and medevac fleets for more than three decades.

What Sikorsky designers didn’t realize when they were developing the S-76 in the mid-1970s, of course, is that the model would still be a top choice of helicopter buyers more than 30 years later, thanks to a long list of improvements that have boosted the model’s gross weight, useful load and range while bringing incremental advances to the cockpit and passenger compartment.

Now, with the introduction of the S-76D, featuring an all-glass integrated avionics suite (based on the one in the Airbus A380 super jumbo jet), dual-speed composite main rotor, additional fuel capacity, icing certification (a first for an S-76) and 1,077 shp Pratt & Whitney Canada PW210S turboshaft engines, Sikorsky appears on the verge of guaranteeing that the helicopter will remain relevant for decades to come.

First, though, the S-76D design team will need to cross the certification goal line. Development setbacks have delayed the helicopter’s first delivery by four years to 2012. Sikorsky blames the wait on supply chain issues and unspecified design changes. The protracted development and lingering economic downturn have conspired to put the brakes on production of the current S-76, the C++ model, production of which stands at less than half of what it normally should be.

Sikorsky announced the S-76D in 2005 after completing an 18-month market study that uncovered a laundry list of design improvements customers said they wanted — many of which Sikorsky’s competitors were already offering in their helicopters. The S-76D’s launch also came two months after Sikorsky bought Keystone Helicopter, an engineering and completion specialist in Coatesville, Pennsylvania, the site of the S-76D final assembly line. The former Keystone operation is now fully integrated into the new Sikorsky Global Helicopters, but getting there took longer than expected, the company acknowledged.

Aero Vodochody of the Czech Republic — a former builder of military jet trainers and a longtime Sikorsky partner that has produced more than 250 S-76 airframes — is being tasked with manufacturing S-76D fuselages and delivering them to the Coatesville factory, where the rotors, engines and gearboxes will be fitted before customer completions and acceptance test flights. The first production S-76D fuselage arrived in Coatesville last November. That completed helicopter now joins two prototypes for the certification program, which is taking place at Sikorsky’s flight test center in West Palm Beach, Florida, and in Coatesville. This triumvirate is forming the core of an accelerated test program expected to culminate with FAA certification by the end of the year. Assuming all goes according to plan, the first new helicopter will be delivered shortly afterward to Falcon Aviation Services, an air charter operator based in Abu Dhabi, United Arab Emirates, that has snapped up the first two S-76D delivery positions.

Technology Enhancements
Sikorsky has completed more than 300 hours of flight tests since the S-76D’s first trip aloft in February 2009. The development program will involve about 800 hours of flying before the helicopter — and a massive amount of test data — are handed over to the FAA for validation flight-testing this summer.

While the S-76D sports a new look with the redesign of the helicopter’s engine air inlet and aft cowls, the really big differences come from a compendium of new technologies packed into the model, all of it centered on improving performance, boosting efficiency, reducing noise and giving S-76D pilots better tools in the cockpit.

Sikorsky chose to scrap the mix of Rockwell Collins and Honeywell avionics in the S-76C++ and start fresh by partnering with Thales, a French company that also supplies avionics systems to helicopter makers Eurocopter and AgustaWestland. Dominating the S-76D’s instrument panel are four large-format, flat-panel displays measuring 6 by 8 inches each, two integrated flight management systems, an electronic standby instrument and two beefy cursor-control devices mounted between the pilots on the center pedestal.

Unlike the various soft keys you might be used to in Garmin’s G1000 or Avidyne’s Entegra cockpits, the Thales TopDeck cockpit instead incorporates trackball controls that pilots use to access most any cockpit function, from setting the radios to calling up Nexrad weather images. Simplified drop-down menus ensure the pilots can access needed information as quickly as they can open a file on their PC.

TopDeck components take up less physical space in the cockpit, allowing Sikorsky designers to streamline the instrument panel and provide more legroom and better visibility, both of which should be welcomed improvements for pilots who complained they’d bang their knees in earlier S-76 models or they had trouble seeing over the glareshield. Ergonomic improvements aside, the ease of use and tremendous capability of the Thales suite should have pilots falling in love, designers say.

“The technology Thales has developed in the airline world for Airbus and the advanced integration of its avionics were really the two factors that led to our decision to go with the TopDeck cockpit,” said Tim Fox, Sikorsky S-76D program manager. “Thales was able to offer features our customers said they wanted, such as advanced digital maps, integrated flight management systems and an architecture designed to keep the pilots’ heads up and to present information so that typically they’re no more than two mouse clicks away from any given function.”

The Thales dual-channel digital autopilot in the S-76D will incorporate operating modes similar to those in the C++, in addition to a number of search-and-rescue modes offered as an option. One such mode, based on GPS input, lets the pilot press a button on the cyclic when directly over a rescue scene, such as a boat in trouble, and command the helicopter to fly a descent pattern putting it directly over that location in a hover at 50 feet — without the pilot ever having to touch the controls. This capability, Sikorsky stressed, will be included in a future TopDeck software load, probably about a year after initial certification, as will functionality more familiar to general aviation pilots such as GPS RNAV WAAS LPV approaches, XM satellite datalink weather and automatic dependent surveillance-broadcast (ADS-B).

Equally as important as what’s being added in the cockpit are the improvements on the outside, and nowhere are the changes more apparent than atop the helicopter. The S-76D incorporates all-new composite main rotor blades with a wider chord and swept tips, enabling the use of less power to yield the same performance. The S-76D’s introduction will also mark a switch to Pratt & Whitney Canada power after a 15-year hiatus, during which S-76 models have rolled off the production line with Turbomeca Arriel-series engines. The new main rotor blades enable the S-76D to lift about 500 pounds more than the C++ model does, though Sikorsky has decided against increasing the helicopter’s maximum takeoff weight, currently 11,700 pounds, choosing instead to focus on performance improvements in challenging operating environments.

“Our customers told us they wanted more power to be able to operate higher and hotter, so rather than increasing the max gross weight, we went after the ability to operate the helicopter in a wider range of environments,” Fox said. “The S-76D has more power than the S-76B and better fuel efficiency than the S-76C, so the engine change is bringing extra power to the helicopter in a very economical platform.”

For pilots concerned about the structural integrity of the composite rotor blades, Sikorsky describes them as being “flaw tolerant,” meaning that if cracks begin to form, they do so in a controlled way — in other words, when the rotor blades start to fail, they shouldn’t tear apart in flight with potentially catastrophic consequences. Don’t worry, though: The chance of the rotor blades developing cracks in the first place is said to be between slim and none.

The improved rotor design substantially reduces noise, to the point that Sikorsky has set a goal of marketing the S-76D as the quietest helicopter in its weight class. More flight-testing is needed before Sikorsky can make that claim, but designers promise the S-76D will exceed the Grand Canyon National Park standard — the world’s strictest noise rule. Indeed, when the S-76C+ chase aircraft is heard flying overhead followed by an S-76D test helicopter, the difference is obvious. The S-76D’s main rotor actually operates with lower lift, while the tail rotor, thanks to a number of design changes that allow it to rotate more slowly, essentially has disappeared from the noise signature.

The S-76D also incorporates rotor icing-protection technology borrowed from the larger S-92. The system uses electric heater mats embedded within the main rotor blades to shed ice automatically without pilot input — something you’d probably love to have on the wing and tail surfaces of your airplane. Sikorsky expects the S-76D to gain certification for flight into known icing after the full regimen of winter flight-testing is completed in early 2013.

Another improvement to the S-76D is the introduction of an automatic dual-rpm main rotor that switches from high to low speed based on a set of predetermined airspeed and altitude criteria. You can think of it sort of like the single-lever power in a Cirrus that adjusts throttle and propeller rpm simultaneously. The S-76D rotor operates in high-speed mode during takeoff and automatically transitions to low-speed mode when crossing certain altitude and airspeed thresholds, squeezing more range and reducing noise in cruise flight. The opposite happens when transitioning from cruise to approach and landing. Pilots and passengers — as well as people on the ground — can tell when the change occurs by the difference in sound, but there is no obvious performance difference, Fox noted.

S-76 Lineage
To create the S-76 Spirit (unveiled in 1976 and named in honor of the U.S. bicentennial), Sikorsky took the main rotor of the UH-60 Black Hawk and mated it to a streamlined composite fuselage that still allowed it to offer a large passenger compartment and baggage area. Designers then added a retractable tricycle landing gear and two 650 shp Allison 250-C30 engines. The prototype flew for the first time on March 13, 1977, and, designated the S-76A, found a ready home with scores of corporations, offshore oil operators and others during an initial production run that included 284 helicopters. The first S-76 customer delivery was made to Air Logistics of Lafayette, Louisiana, on Feb. 27, 1979.

Sikorsky sold a handful of special-order A+ models with Turbomeca Arriel 1S engines and A++ helicopters with Arriel 1S1 engines, while also introducing the baseline S-76 Mk II in 1982 with a more powerful version of the Allison 250 engine. The company then introduced the P&WC-powered S-76B in 1985, which quickly became a favorite choice of blue-chip companies in the Northeast, especially around New York City. The introduction of the S-76C in 1991 marked the addition of the Arriel 1S1 to the production line, which was later replaced by the Arriel 2S1 in the C+, and finally the Arriel 2S2 in the C++. Sikorsky built S-76B and S-76C/C+ models concurrently from 1991 to 1997. (In case you’re wondering, Sikorsky chose to add plus signs to S-76 models that primarily featured only an engine change, reserving new letter designations for major upgrades to the line.)

As an interesting aside, while it’s true that a number of Sikorsky models have been introduced in the years that correspond with their model numbers (for example, the S-61 in 1961, S-76 in 1976 and S-92 in 1992), there are many more examples in Sikorsky’s history in which the naming convention fits a serial pattern rather than a year. The Sikorsky S-47, the world’s first production helicopter, for instance, was introduced in 1940; the S-58 debuted in 1954; the S-70 (the civil version of the Black Hawk) first flew in 1974; and Sikorsky’s newest helicopter, the S-97, a proposed high-speed light attack/scout helicopter based on the X2 high-speed twin-coaxial-rotor demonstrator, was unveiled in October 2010.


The S-76D faces two tough competitors in the medium-twin helicopter market: the $10 million Eurocopter EC155 built in France and the $11 million AgustaWestland AW139 produced in Italy, both excellent helicopters that have garnered loyal customer followings in their own right. The S-76D and EC155 typically can seat a maximum of six passengers, while the larger AW139 can hold eight comfortably. In fact, with a cabin volume of 204 cubic feet, the S-76D is the smallest of the bunch while also being the priciest at $12 million to $13 million (depending on the configuration). But the S-76D’s maximum range of 450 nautical miles is quite respectable and proves the engineers have done a good job of squeezing every last mile and ounce of fuel from the design.

Helicopter industry insiders see the helicopter market turning around in 2012, putting the S-76D in prime position to capitalize when tire kickers again become buyers. Sikorsky holds about 70 deposits for the model and anticipates an initial production run of 30 to 35 helicopters per year, which matches the historic average for the S-76 over its 32-year history. While last year saw the delivery of only a handful of C++ models, more than 40 were delivered in 2006, the model’s first year on the market. Later this year, Sikorsky will deliver the 800th S-76 produced.

Sikorsky expects 25 to 30 percent of new S-76D sales will go to the corporate/VIP market and a similar percentage to offshore oil operators. A global trend that has led to the commercialization of search-and-rescue operations in developing nations (many of which have witnessed firsthand the effectiveness of helicopters in disaster relief roles) should lead to growing sales in this segment, to about 15 percent of the total. An additional 7 to 10 percent of sales are anticipated from EMS operators, with the remaining sold for multimission/utility functions such as homeland security and border patrol, especially in areas of the world with hot-and-high operating requirements.

Now all that’s left before the S-76D makes it to a heliport near you is a whole lot of flying and the FAA’s stamp of approval. For more information visit sikorsky.com.

**Check out this extra feature to find out more about the technology behind the S-76D. **


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