He then picked it up to 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 (ITT) and gas generator (Ng), displaying the one closest to the limit. In the S-76D, the gauges are based on 100%. In the event of an engine out, however, the remaining engine power can go up to 140% for 30 sec.
Rotor rpm is rated at 107%. It was originally set at 100% but was later increased to 107% of the original rpm, so that's where the limit rests.
If the aircraft enters a non-standard situation, such as operating 30 sec. with one engine inoperative, the scale moves the green line to the percentage limit for that condition with the time limit shown in amber.
As expected, at no time during our hovering exercise did the PL get close to 100%. The aircraft automatically computes its own weight, and at 9,494 lb., a stable hover showed 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 authority with the tail rotor stuck into the wind since the wind was minimal. There was a slight increase in vibration, but that was it.
I found the aircraft to be a bit tight on the controls during a standard hover, and Barnes recommended using the force trim release buttons to loosen it up. That helped a lot — although it then seemed to be a bit too sensitive. But like pilots, every helicopter has its idiosyncrasies. A pilot simply gets used to each aircraft's, and it didn't take long to figure out how to handle this one.
The aircraft has force trim on both the cyclic and collective, so the pilot can adapt either or both controls to his own “pilot technique” feel for flying the aircraft. All hovering can, however, be done by simply “beeping” it where you want it to be by engaging the autopilot's velocity hold (VHLD). There is also a beeper trim button to move the aircraft up or down.
Placing a green circle at a point on the map display of the runway 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. To change position, the pilot simply dials in where he wants to go. If it's 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 max performance, were without drama. Climb-out for a normal takeoff was at 75 kt., 750 fpm at 59/60% torque. The aircraft can monitor OAT and aircraft weight to determine best rate of climb, for both normal and OEI climb-outs, and indicate that rate by a little white triangle on the airspeed indicator.
Vibration level was moderate — acceptable but not great — although Barnes pointed out that the test aircraft only had one vibration suppression unit, whereas standard S-76Ds would likely have three or four, reducing vibration levels much further.