An executive favorite gets a makeover — again.
Flying the S-76D
offered BCA an opportunity to fly the new S-76D at its West Palm Beach, Fla., facility in late November 2012. While conditions on the appointed day were perfect for flying — winds light, about 17 kt., temperature a balmy 78F (26C), MSL a mere 20 ft. — they were terrible for an evaluation flight. And the aircraft weighed in at 9,494 lb., well below its 11,700-lb. max takeoff weight.
With the twin PW210S FADEC-controlled engines producing 1,077 shp each, pushing the aircraft to its limits was unlikely. But what I really wanted to see was just how much the pilot's workload was reduced by the newTopDeck system. And as it turned out, an hour's flight with Greg Barnes, project pilot for the S-76D program, more than satisfied my curiosity.
The initial part of the demonstration flight was fairly standard, with me sitting in the right seat and Barnes in the left. The aircraft, N767J, was being used as an experimental/test aircraft, configured for flight tests, so no passenger accommodations were installed in the cabin.
Start-up was simplicity itself. Start-up power is supplied by a lead-acid battery capable of providing up to three starts. Power is controlled by two overhead “T”-shaped throttles, each having a start button at the end of one arm of the “T.” Push the button and the engine starts. If the engine senses anything amiss, it will automatically shut down. A hot start will cause the fuel flow to stop, but the engines continue to motor in order to cool down.
Push the throttle forward and you've got full power. The power can be applied slowly, in stages or in one quick thrust — pilot's choice. It's probably ill-advised to make it one quick thrust on an icy helipad.
Taxiing from the helipad to the runway was similar to the experience with most wheeled helicopters — pull in a little power, push the cyclic forward a bit to get it rolling, then steer with the pedals while giving just a bit of cyclic during a turn to keep it level. We taxied out to the active runway, where Barnes started by showing me that the aircraft can do a 360-deg. turn around its own axis.
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.
We climbed to 2,000 ft. holding 100 kt. in the climb, then accelerated to 130 kt. and engaged VNAV and RNAV (airspeed and area) to hold us on a steady course and altitude.
An assortment of charts is available to the pilot on the digital map (DMAP) display, to include Jeppesen approach charts and Thales multifunction moving maps. Barnes pulled up a vector chart to demonstrate the aircraft's flight path control. He simulated a large storm cell directly between our points A and B, then used the cursor control to mark a point to the right of the storm cell. The aircraft automatically turned toward that mark. He then remarked the original Point B, noting that when the aircraft reached the new point in space, it would automatically track to Point B, avoiding the storm. This was all done using the trackball and pushing a single button.
Sikorsky initially installed thePrimus 440 weather radar on its S-76s but discovered customers were replacing that with the 660 system. So, the Primus 660 is now the standard weather radar for the S-76D. The Thales system also offers XM Weather for on-screen satellite weather service as an option. Also available as an option is ADS-B and GPS precision approach capabilities.
To test basic flight characteristics, we took the aircraft up to its 155 kt. Vne, pulling only 50%. Barnes noted that while Vne is 155 kt., because of the efficiency of the Pratt & Whitney engines, maximum cruise speed for best range is 154 kt. He also noted that Sikorsky already has the data to expand the 155 kt. Vne limit “down the road.”
For steep turns, Barnes “beeped” the aircraft over into a 30-deg. angle of bank and put it on automatic hold. The aircraft held steady at 110 kt., pulling only 40% torque. The 30-deg. angle of bank is the maximum for automatic hold. That can be manually overridden to allow up to a 60-deg. bank — with a warning voice letting you know when you are reaching power limits.
Virtually all aspects of the flight can be done using the push-button controls on the autopilot control panel (APCP) located directly behind the trackball housing on the center console.
Barnes programed a flight plan for the approach back to Sikorsky's field and then coupled in the heading, airspeed and altitude using the push buttons on the APCP. The aircraft flew itself to the ILS and then automatically transitioned to ILS mode. The navigation, glideslope and deceleration commands are coupled to the primary commands in the autopilot, allowing the aircraft to fly hands-off down to the runway.
Repair work was being performed on the approach end of the runway, so we had to take over and land manually. However, by engaging VHLD and plunging the trim switch, you can program the system so that the aircraft descends to a specific altitude and comes to a hover over a specific spot, still hands off.
The aircraft also automatically decelerates. Once below 130 kt., the gear can be dropped and the aircraft settles on to the ground. The green line on the PL indicator automatically drops to 130 kt. when the gear goes down, one of the results of pilot input during the initial planning stages for the new D model.
Once on the runway, I taxied back to the pad with no trouble.
For shutdown, the book says that no cooldown time is needed for the PW210S engines. However, Barnes said he always cools them down for 1 min. Old habits die hard. I would have waited two.
The flight lasted 70 min., with a fuel burn right at 650 lb. Sikorsky shows a fuel burn of 578 pph in its charts, so our 557 lb. was very close. A lot of factors affect fuel burn, but the figures came out about right.
As for transitioning into the D model, Barnes said that a new guy could be using the aircraft “within a few hours,” and that after one or two flights, “the guys are doing things on their own.” I can see why. It's just a matter of learning which buttons to push. BCA
|2 Pratt & Whitney PW210S|
|Dual Channel FADEC|
|OEI (30. sec.)||1,241 shp|
|Continuous OEI||1,077 shp|
|Max Takeoff||1,050 shp 5 min.|
|Max Continuous||1,077 shp|
|Max. Gross Weight||11,700 lb.|
|Max. Cruise Speed||155 kt,|
|Max. Cruise Speed Vbr||154 kt.|
|Max. Range No Res.||441 nm|
|HIGE Ceiling||9,700 ft.|
|HOGE Ceiling||5,000 ft.|
|OEI Service Ceiling||7,550 ft.|
|CAT A — 100 ft. Deck||11,700 lb.|
|Cabin Length||7.92 ft.|
|Cabin Width||6.25 ft.|
|Cabin Height||4.42 ft.|
|Cabin Volume||204 cu. ft.|
|Baggage Volume||38 cu. ft.|
|Exec. Seating||2 + 6/13|
|External Noise||92 dBA||86 dbA|
|Internal Noise||87 dBA||83 dbA|
|CAT A, 100ft. Elev. Deck|
|Fuel Burn||94 gph||94 gph|
|Rig Approach Upgrade||N/A||✔|