helicopter
Sikorsky S-76C+

Sikorsky's S-76C+

The race to capture the corporate twin-engine helicopter market began in earnest in the 1970s. In 1979, Sikorsky introduced the S-76, which quickly established itself as the gold standard within the niche. It has sold more than 850 copies and remains in production today, with virtually the same airframe it brought to market in 1979.

One reason for its enduring popularity is that few competing helicopters convey as much elegance. Buyers also appreciate its futuristic styling, roomy 204-cubic-foot cabin, speed, and solid all-weather capabilities.

That said, some S-76s are better than others. The original A, A++, and A Mk II models are arguably underpowered to some degree—especially for missions that involve urban­ environments with lots of tall glass canyons. These models also have a lower maximum takeoff weight than others—900 to 1,200 pounds less.

The B model, with its more powerful Pratt & Whitney Canada PT6-B36A engines and beefier airframe, has plenty of power but gulps jet-A the way a sailor on shore leave might guzzle beer.

The C model with its Turbomeca/Safran engines offers better fuel economy and more power than the As, but not quite as much as the B. (The discerning eye can differentiate As from Cs: A models have a wide tail and a wide horizontal stabilizer; they’re narrow on the C.) There is also a little problem with all S-76 A, B, C, and C+ models produced before 2004: they’re loud, inside and outside.

One reason for its enduring popularity is that few competing helicopters convey as much elegance.

Sikorsky introduced the S-76C+ in 1996 and produced nearly 200 of them over a decade. The aircraft—which was rated for single-pilot instrument operation—features a composite main rotor system that delivers enhanced performance, active noise canceling and vibration control, and a pair of Turbomeca Arriel 2S1 engines with full authority digital engine control.

During and after the C+’s production cycle, Sikorsky incorporated many improvements into the model, including an integrated instrument display system, and a four-screen Honeywell electronic flight information system. The most important add-ons for the C+ came in 2004, when Sikorsky began offering its Quiet Zone main transmission gearbox; in 2007, when Keystone Helicopter Corporation (now part of Sikorsky) debuted its Silencer interior; and in 2016, when Sikorsky introduced its C++ engine-upgrade program. Collectively, these three modifications—all available via retrofit—can turn what is already a capable helicopter into a very good one.

Building on NASA-funded research from the 1980s, Sikorsky engineers determined that the majority of interior noise in the S-76 originated from vibrations in the main transmission. Further investigation showed that the vibration resulted from meshing of specific gears in the transmission and that these vibrations were transmitted to the transmission housing and then to the entire ­airframe, producing a distinctive high-pitched whine.

Sikorsky explored various solutions to the problem. The most effective proved to be chemically superfinishing the gear flanks to make them smooth and thereby reduce their friction coefficient. Superfinishing the gears reduces cabin noise to the point where pilots and passengers can hold normal conversations without benefit of headsets and hear aircraft noises not previously discernable. The superfinished gears are at the heart of the Quiet Zone transmissions.

In 2007 Keystone installed its first Silencer cabin shell on an S-76C+. The Silencer not only cuts cabin noise, it shaves 100 pounds off the weight of a standard interior and makes maintenance inspections faster and easier. Because it has pre-engineered access points, mechanics no longer need to remove an entire interior to perform scheduled maintenance.

The system uses an advanced carbon-fiber skeletal structure that incorporates air conditioning ductwork as structural cross members and attaches to the airframe with isolators. The outer framework supports the interior for improved rigidity and reduced vibration while permitting easy access for airframe inspections and allowing room for acoustic blankets. Silencer has proved so effective and popular that it is now standard on all new S-76s, including the S-76D.

In March 2016, Sikorsky announced that S-76C+ operators could upgrade to S-76C++ configuration with a Safran 2S2 engine upgrade kit. Doing so provides greater takeoff and ­cruising power and increases useful load limits by 350 to 450 pounds. It also allows operators to incorporate new technologies, including dual digital engine control units and engine inlet barrier filters that prevent ingestion of debris and particulates, thereby improving reliability and lowering maintenance costs. Upgraded aircraft become eligible for enrollment in Sikorsky’s Total Assurance or Power Assurance fixed-costs maintenance plans. Upgrading the engines provides a power increase of about 8 percent, delivering 923 shaft horsepower on takeoff and 823 at cruise power.

Of course, a new S-76D has even more power than a C++ (14 percent more on takeoff) and burns less fuel (8 percent). But a nicely equipped one will set you back at least $12 million to $15 million, while you can buy a newer C+ for around $3 million.

You can give an S-76C+ other retrofits to make it more contemporary, adding LED lighting, satphone, monitors, beverage drawers and snack nooks, Blu-ray players, high-end speakers, luxurious leathers, and expensive veneers.

One final point. As you may have heard, Lockheed Martin acquired Sikorsky from United Technologies Corporation in 2015. For several years before that, United Technologies acted in ways that left little doubt about its desire to dispose of the helicopter maker. Sadly, one sign of UTC’s intentions was its level of product support for civil helicopters as measured by the annual ­product-support survey in our sister publication, Aviation International News.

The good news is that Lockheed Martin has committed to keeping both sides of Sikorsky—civil and military—running and healthy; and the commitment appears to have some teeth. In this year’s AIN survey, Sikorsky moved up a notch, from fourth to third place among major helicopter manufacturers.

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