Airtest – Pilatus PC-12

To put its performance into context, Terry Wesley-Smith, the Australian Pilatus representative who accompanied the aircraft during its recent in-country demonstration tour, reported that on the Jandakot/Essendon segment, elapsed time was 5 hours 12 minutes with start fuel at 1085kg, end fuel 230kg, fuel flow FL 290 (-34C) 152.5kg/hour, TAS 262kt, IAS 161kt, and a ground speed of 306kt (567km/h).

As I was the last of three pilots to be given the opportunity to fly the aircraft on the demonstration day, I had the opportunity to sit back in the cabin and assess the aircraft from a passenger’s point of view. I found the ride comfortable with a biggish aircraft’s reaction to the turbulent conditions on the day. The standard passenger seats, with which the demonstration aircraft was equipped, are stressed to 19g and have a three point restraint system with an inertia reel shoulder harness, a reclining backrest, sliding headrest and armrest. The seat pitch is particularly generous with plenty of leg room.

A number of different interior configurations are offered by Pilatus including the executive option with seating for six with upmarket leather seats and a private chemical toilet facility, the Combi conversion kit which has four standard seats leaving a large space for freight, and finally the freighter (PC-12XF) version which can be fitted with one or two crew seats if required.

On being invited to take the right hand seat it was again apparent that the PC-12 is a large aircraft with sufficient room to mount the engine control console between the two seats. Access to the seats, however, requires a careful lifting of the leg over the console but no doubt this would not be a problem with practice.

The view over the nose and to both wings is good, as is sighting back into the cabin. The seats, which are stressed to 25g deceleration, are comfortable, with fore and aft and vertical adjustment, and a four point restraint system with adjustable lap strap and inertia reel shoulder harness. The rudder pedals are adjusted for leg length by rotating a small control under the instrument panel.

The manual flight control system is conventional using push-pull rods and carbon steel cables and the aircraft is fitted with an internal pilot operated gust lock system. The control column is loaded with various operating buttons including the trim “coolie hat” which will only operate after pulling a trigger at the back of the spectacle. Once again it struck me that it would be a sensible move to standardise the trim coolie button release system. I am used to the military system where all the aircraft I flew had direct operation of the trim switch without any safety cutout device. The Beechjet 400A requires the button to be depressed before operation, no doubt there are other devices. Perhaps a trivial point but one that I find annoying, like left and right hand operated traffic indicators!

The cockpit is designed for single pilot operation although a copilot’s full panel as fitted to the RFDS aircraft is available as an option. A master warning system displays faults on a central annunciator panel with red for a hazardous condition, amber for caution and blue for advisory. An audible tone accompanies warning and caution conditions.

The engine was running when it came my turn to fly the aircraft under the guidance of RFDS pilot Peter Hartwell, however I had observed the automatic start sequence from the passenger cabin. The start half of the starter/generator initiates the sequence and it is then just a case of watching the ITT gauge for the indication of a start. The generator automatically comes on line once the engine is stabilised at 46%.

The PC-12 is powered by the 1600shp (1195kW) Pratt & Whitney Canada PT6A-67B reverse flow, free turbine engine, flat rated to 1200shp (895kW). Engine power is controlled by two levers, the Power Control lever and the Condition lever. The Power Control lever controls engine power during ground, flight and propeller reverse operations. The Condition Lever sets the fuel control unit operating conditions for the three positions of fuel cutoff/feather, ground idle, and flight idle. A manual override control allows the pilot to control engine power through direct manipulation of the fuel control unit.

The propeller assembly consists of a four bladed aluminium constant speed (1700rpm in flight) fully feathering and reversible unit. The propeller blades are set to zero when the Power Control lever is in the ground range and full propeller reversing can only be obtained when in this condition.

Once on our way I found taxiing easy and pleasant through the well coordinated steerable nosewheel. There is little need for brakes, ground speed being controlled by occasional use of reverse thrust in the Beta range.

Takeoff was straightforward with no discernible tendency to swing. I was advised to set the power to 46psi rather than fire-walling the lever and relying on the automatic torque limiter, a sensible handling technique. Prompted by Peter Hartwell, I applied slight back pressure on the control column as we commenced to roll; this took the weight off the nose wheel as the aircraft accelerated to 80 knots (148km/h) for rotation, which made for a more comfortable ride. Following lift off the aircraft accelerated fairly rapidly to the undercarriage retraction speed of 100kt (185km/h) and to the climbing speed of 120kt (222km/h). Undercarriage and flap operation are straightforward with the Fowler flaps having three primary positions of up, 15 degrees (takeoff) and 40 degrees (land). My one criticism is that I found the calibration of the ASI between the crucial arc of 100 and 120kt (185 & 222km/h) too detailed but as usual got used to it with the passage of time.

I had previously asked to sample the stall observing the T-tail configuration which required the installation of a stick shaker and pusher for certification, so had the opportunity to try a few turns on our way to our assigned flight level of 120. I found the controls well coordinated although a little heavy as might be expected observing the size of the aircraft, and the fact that they are manually operated. As I was to confirm later in the circuit, the PC-12 is a slippery beast and I found it reluctant to slow down in the clean configuration. As we approached the stall at idle the stick shaker began to operate with a very positive vibration and as I continued to pull back to maintain height, the stick pusher cut in, very firmly pushing the control column forward with its design force of 23kg. It would be advisable not to practice this manoeuvre with cabin occupants as it would be a most uncomfortable negative ‘g’ ride in the back. Recovery was straightforward with not much height loss (couldn’t have been much as there was no cry from ATC!) using power and the usual gentle easing back.

Because the aircraft is a single, it has to meet a FAR 23 stall requirement of 59kt (109km/h) in the full dirty configuration, which it does with the stick pusher inoperative. The published figures at MAUW (pusher on) are 61kt (113km/h) dirty and 85kt (158km/h) clean.

During our climb to height and subsequent return to the circuit we had occasion to fly through a reasonable amount of cloud which gave me the opportunity to fly the aircraft on instruments. I found that it stayed where I put it making it a comfortable IFR platform. The instruments, which apart from the EFIS attitude indicator (ADI) and heading and situation indicator (HSI), are conventional round dials and are easy to read and interpret. I didn’t have the opportunity in the short time available to explore all the information that can be fed into the EFIS displays, but my impression was that it would be hard to get lost with all the navigation data available, including GPS.

We were some distance out when we obtained our ATC clearance for descent and return to the circuit and shortly after lowering the nose, I found that I had to pull the Power Control lever almost back to the idle stop to stay below 210kt (390km/h) as directed. However the relatively high maximum undercarriage lowering speed of 177kt (328km/h) and first stage of flap speed of 163kt (302km/h) provide for a fast descent if required.

Our entry into the circuit was via a straight in approach which ended up slightly steeper than I had planned because of an apparent reluctance on the part of the aircraft to slow down. I made a mental note to use full flap earlier next time to ensure a proper powered approach. I needn’t have worried about the landing, it was a non event due to the very forgiving trailing link configuration. On the second approach I had the opportunity to experience a go-round due to a tardy Fokker 50 using the full length of the strip but, as should be expected, it presented no problems.

My final approach was again a little fast but I managed to get it back to the recommended speed of 80kt (148km/h) over the fence in time to arrive in a powered configuration with a gentle flare resulting in an ego boosting landing due to the trailing link undercarriage.

Following touchdown, Peter Hartwell selected reverse pitch and we slowed down rapidly as advertised in time to turn off comfortably to the GA section at Canberra.

I think my problem with speed control was adjusting to the propeller/turbine configuration, where deceleration on reducing power is not as marked as a piston. One final handling point is that the Power Lever needs to be firmly on the rear stop on touchdown as the slightest trickle of power will keep the aircraft rolling.

The PC-12 has been designed to perform both as a passenger carrier and for cargo work, or a combination of both. The large volume cabin can be quickly converted from one role to the other, and access for both is provided by the port side forward passenger, and large rear cargo doors. The passenger door, which is hinged at the bottom, has a generous width and height of 0.64m and 1.34m respectively and incorporates an integral folding steps/handrail assembly which automatically extends and retracts as the door is opened or closed. The door can be operated internally or externally and requires little effort, with locking of the six pins confirmed visually and on the pilot’s Central Advisory and Warning (CAWS) panel.

The structural cargo door, which is hinged at the top, is 1.32m high and 1.4m wide and is designed to accept a standard pallet. Operation of the door is automatic at the press of a button and again door locking is confirmed visually and on the CAWS. The high T-tail is specifically to keep errant forklifts well clear of the tailplane when loading through the cargo door. The final means of egress is an overwing emergency exit (0.69m high x 0.48m wide) incorporating a window, which is located over the right wing.

As already mentioned, a feature of the design to aid unimproved field operations is the trailing link main undercarriage which as I discovered, certainly makes for smooth soft landings; no doubt a major asset in ambulance/medical work. Although the aircraft is certificated to FAR 23 standards, it also meets the later requirements for spin resistance (amendment 42), reliability of critical systems (41), and crash worthiness (36). Other features include known icing certification, a backup generator, and the latest engine fire detection system.

Comment

The traditional high design standards of Pilatus plus an engine with a proven reliability five times greater than any piston equivalent certainly qualifies the PC-12 for RPT work. Among many of the comments made about the latest Pilatus product, perhaps the most telling observation was “This isn’t a GA aircraft, this is a real airliner”.

At a price of around $US2.2m-$US2.3m (depending on options and the exchange rate), once the emotional stumbling block of it being a single is overcome, there is little doubt that the Pilatus PC-12 should feature large on the Australian third level RPT and charter scene.

My thanks to Pilatus and the Royal Flying Doctor Service for the opportunity to fly an outstanding aircraft.