Tuesday, May 22, 2012
Tackling the wilds of Utah in a do-it-all turboprop
The capability of the Honeywell Primus Apex avionics system provides features found in many business jets. WAAS, synthetic vision, keyboard input, trackball cursor control, charts, data link weather and multiple screen redundancy make data management easy. The executive cabin option features a spacious interior with a flat floor and six large leather seats that can swivel and slide to the center of the cabin for increased shoulder room.
The PC-12NG boasts the new P&WC PT6A-67P engine with 1,744 thermodynamic hp, flat-rated to 1,200 hp. It's important to understand that turboprop engines work like non-turbocharged piston engines, losing power as they climb. By limiting or flat rating the engine to a power well below the maximum possible power, it's possible to produce full flat-rated power during the climb.
Most turboprop engines are limited by maximum torque values at low altitudes but become temperature limited during the climb as the engine has to work harder to compress thinner air. The new -67P engine features single crystal alloy turbine blades with higher temperature limits for increased thermodynamic power. This provides additional power during the climb and during cruise over the previous -67B engine. At gross weight, the NG climbs at over 1,900 fpm and boasts a maximum cruise speed of 280 KTAS. Climb to FL 300, and at maximum power, you can cover 1,560 nm with NBAA reserves. Slow down to around 250 KTAS, and you can go nearly 2,000 nm on a full tank of 402 gallons of Jet A. For our mission, this kind of range makes it easy to hop between numerous unattended fields all over southern Utah before even coming close to running low on fuel.
PC-12/47NG takeoff and landing performance is remarkable. At max gross weight, the takeoff ground roll is only 1,450 feet, and a 50-foot obstacle is cleared in only 2,650 feet. At max landing weight, only 1,830 feet is required to clear a 50-foot obstacle and get stopped. With reverse and maximum braking, the landing ground roll is an astonishing 945 feet.
From the beginning, a unique safety feature of the PC12 has been the use of an angle-of-attack (AOA) indicator. The Honeywell Primus Apex system makes it particularly easy to fly optimum AOA for each phase of flight by simply lining up indicator carrots. If you like, you can forget about recommended airspeeds and simply fly AOA to achieve the proper airspeed for any weight and configuration. If you really aren't paying attention and you do manage to get close to stalling the airplane, the PC-12 is equipped with a stick shaker and pusher to help even the most inattentive pilot keep the AOA within safe boundaries. So as we climbed out, I merely held the AOA at the optimum value for the climb.
In a few minutes, we leveled off at 10,000 feet, and in cruise, the airplane is a delight to fly. With the NG model, Pilatus has added servo tabs to the ailerons to improve the heavy roll forces characteristic of the older PC-12s. This change helps produce much more harmonized controls. Still, it takes more than a light touch to move the controls, but that's pretty normal for an airplane in this category.
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