The tail rotor also a tapered blade tip, high-lift airfoil and a chord increased by “about an inch,” Hunter says. “This allows us to slow the tail-rotor tip speeds down through changing the gear ratio in the intermediate gearbox. This gives us the same performance, because it's an increased efficiency rotor, while substantially lowering the acoustics of the aircraft.” Sikorsky has measured the noise levels of the D model at 86 dBA externally and 83 dBA internally, compared with 92 dBA and 87 dBA, respectively, for the C series.
Both the main- and tail-rotor blades have built-in electrical heating mats for the rotor ice protection system (RIPS), which will allow flight into known icing. RIPS has not yet been certified, but provisions for the system can be built into the aircraft as an option. Certification is expected in the 2014-15 timeframe.
But perhaps the most significant improvement to the D model, certainly for the pilots, is the fully digital glass cockpit. The earliest S-76s had virtually no digital instruments, while the previous C++ model had only a limited glass cockpit provided by Parker-Gull.
With the exception of the Rockwell Collins Pro Line navigation/communication radios and Honeywell's Mark XXI enhanced ground-proximity warning system, all of the avionics are from Thales, including the four-axis autopilot.
The TopDeck avionics suite involves a “click to fly” concept that has never been used on a helicopter before, according to Thales. Essentially it reduces most, but not all, of the commands required from the pilot to no more than two button pushes, significantly reducing workload.
The system is designed to provide everything that could be needed by a single pilot, particularly for instrument flight-rules flying, requiring the minimum of effort. Basically, it does everything for the pilot except brew coffee in the cockpit, something that will have to wait for a future S-76.
While the system is sophisticated and complex, it is user friendly, says Hunter. An hour-long demonstration flight showed how simple it is.
The instrument panel features two 8 X 6-in. screens for each pilot that can serve as either a primary flight display (PFD) or multifunction display (MFD). In the center of the panel are the pilots' multipurpose control and display units. Directly below each pair of displays is a PFD control panel and a Cobham 380 audio control panel.
Two changes made to the D model's instrument panel compared to the C++'s were to reduce its size, taking about an inch off the bottom and trimming the glareshield to improve visibility, and moving the landing-gear control from the center console to the upper center of the main panel for easier access.
A major factor in reducing the pilot's workload is the cursor control device (CCD), a raised housing containing a roller ball sitting toward the front of the center console. Each pilot has a CCD, and uses the trackball to move a cursor around the display screens. The pilot can rest his hand on the housing to provide stability in flight, then use his fingers to move the cursor wherever he wants on the MFD or PFD. Once the cursor is positioned, a button is pushed and the command inputted, just like a left or right click with a mouse.