Barnes picked the aircraft up into a hover while I checked power levels. Like most of today's glass cockpits, the Thales system uses a power limit (PL) indicator to monitor torque, inter-stage turbine temperature and gas-generator speed, displaying the one closest to its limit. In the S-76D, the gauges are based on 100%. Only the rotor rpm is different, being rated to 107%. It was originally set at 100%, but rotor speed was increased to 107% of the original rpm on one of the earlier S-76s, so that is where the limit rests.
If the aircraft enters a non-standard condition, such as an engine failing, the scale drops the green line to the percentage limit for that condition, with the time limit at that condition shown in amber.
As expected, at no time during our hovering exercise did the power limit get close to 100%. The aircraft automatically computes its own weight and at 9,494 lb., a stable hover required 62% torque. The aircraft is limited to 35 kt. sideward and rearward flight, which required only 79-80% torque for each. There was no problem with tail-rotor authority with the tail stuck into the wind as the wind was minimal. There was a slight increase in vibration, but that was all.
I found the aircraft to be a bit tight on the controls during standard hover maneuvers, and Barnes recommended using the force-trim release buttons to loosen it up. That helped a lot—although it then seemed a bit too sensitive. But, like pilots, every helicopter has its idiosyncrasies. You get used to them, and it did not take long to figure out how to handle this one.
By engaging the autopilot's velocity hold (VHLD) function, hovering can be accomplished by simply “beeping” the aircraft to where you want it. Placing a green circle at a point on the runway map display—with zero airspeed dialed in—puts the aircraft in a stable, hands-off hover. Repositioning the green circle repositions the aircraft. Changing the heading while maintaining zero airspeed turns the nose of the aircraft without changing its position. If the helicopter is at a stable hover and the wind blows it off its hold point, it will recalculate and return to the original position.
Takeoffs, both normal and maximum performance, were without drama. Climb out for a normal takeoff was at 75 kt., 750 ft./min. at 59% torque. The aircraft monitors outside air temperature and weight to determine best rate of climb, for both normal and one-engine-inoperative climb outs, and indicates that rate with a white triangle on the airspeed indicator.
We climbed to 2,000 ft. holding 100 kt. in the climb, then accelerated to 130 kt. and engaged vertical and area navigation to hold us on a steady course and altitude. An assortment of charts is available to the pilot on the digital map display. Barnes pulled up a vector chart to demonstrate the aircraft's flightpath control. He simulated a large storm cell directly ahead, then used the cursor control to mark a point to the right of the storm. The aircraft automatically turned toward that mark. Remarking our original aimpoint, Barnes said when the aircraft reached the new waypoint, it would automatically track to the original point, thereby avoiding the storm. This was all done by using the trackball and pushing a single button.
The Thales system offers XM Weather for on-screen satellite weather service as an option. Also available as an option are automatic dependent surveillance-broadcast (ADS-B) and GPS precision-approach capabilities. The baseline weather radar for the D model is the Honeywell Primus 660.
To test its basic flight characteristics, we took the aircraft up to its 155-kt. never-exceed speed (Vne), pulling only 50% torque. Barnes notes that, while Vne is 155 kt., because of the efficiency of the Pratt & Whitney Canada engines, cruise speed for best range is 154 kt. He also notes that Sikorsky already has the data to increase the Vne limit “down the road.”