Class Of Its Own

As I began to inspect the wings, it occurred to me that the singleslotted Fowler flaps cover a large proportion of the trailing edge (67 per cent, to be precise) and that – unsurprisingly – this didn’t leave much room for the ailerons.

The reason for the big flaps is to keep the stall speed down, but as small ailerons often result in reduced control authority around the longitudinal axis, I wonderedif spoilers were fitted to augment the lateral control (as they are on the TBM series). I was surprised to see that they aren’t, and made a mental note to check the roll rate. The wings feature elegant winglets, and I wondered if perhaps the winglets contributed to the aileron’s efficiency, possibly by constraining span-wise flow.

The Honeywell weather radar is housed in a neat pod at the starboard wing tip, while de-ice protection is provided by Goodrich pneumatic boots on the wings and tailplane, and engine bleed-air to the intake. The windscreen and prop are heated electrically, a much better method than ducting engine bleed-air onto the screen.

Not for the last time, I could see that in many respects the PC-12 has been designed and built to far higher specifications than are required. In fact many of its facets are more reminiscent of a transport category aeroplane.

The next item to catch my eye was the undercarriage. As the Royal FlyingDoctor Service puts to good use every day across outback Australia, the PC-12 is approved to operate from unimproved landing strips and, having inspected the rugged-looking double trailing link main undercarriage and low-pressure tyres, I could see why. The wheel track is also commendably wide (as the main gear retracts inwards into the wings), while the nose leg retracts backwards into the fuselage. While studying the nosewheel I’d already spotted that (for a tricycle undercarriage) it really did seem to provide a lot of ground clearance for the prop. Indeed, I believe that this is maintained even with a flat tyre and the nose leg compressed – very impressive.

Another aspect of the aircraft that indicated it is designed to be used from airstrips as well as airports is that not only does it have powerful LED landing and taxi lights on each undercarriage leg but there are more lights in neat underwing ‘blisters’. I now understand why the aircraft is such a firm favourite with RFDS.

As I moved towards the tail I noted the two ventral strakes and large dorsal fin, but what really got my attention was the giant cargo door aft of the wing. At 1. 32m by 1. 35m it is absolutely enormous, and as it opens wide and is hinged at the top it makes loading and unloading very easy. It is opened hydraulically and closed electrically. I could now clearly understand why the PC-12 is a favourite with freight companies, air ambulance operators and the military, as well as with private owners.

The cargo door is complemented by a pilot’s ‘airstair’ door forward of the wing, immediately aft of the cockpit. Both doors are on the port side.

I really like this arrangement, for a number of reasons. Firstly, if you’re using the aircraft as a freighter you can fill the cabin to capacity without having to leave space for an aisle. (Most small freighters ‘bulk out’ [run out of space] before they ‘gross out’ [run out of weight-carrying capacity] which is why the Cessna Caravan’s cargo pod is such a popular option). Secondly, most

The control harmony was also good, while the stick-free stability is outstanding.

private owners probably prefer to personally check that the door has been shut and locked correctly.

I next studied the large T-tail with its ‘bullet’ fairing and as I already knew the PC-12 is fitted with a stick shaker and a stick pusher, asked Jan what the stall was like. He replied with a grin that I would soon find out for myself! As always, I was keen to get to the cockpit, but as the big cargo door and large cabin have always been a major part of the PC-12’s success story, I thought I’d better examine the cabin first. And once I’d got to the top of the airstair and entered the aircraft I could see why – it’s huge! The cabin’s length (excluding the cockpit) is an impressive 5. 16m, and with a width of 1. 52m and a height of 1. 45m, it really is extremely spacious. At the back of the cabin is the baggage compartment, which has a cubic capacity of 1. 13m3. It is heated, pressurised and fully accessible in flight.

Another excellent feature is the design of the lavatory. This is immediately aft of the cockpit, and is closed off on both sides by folding doors. Many aircraft use curtains instead of doors, which is certainly not as private. The PC-12’s is a much better idea.

Jan and I now made our way into the cockpit. The seats are extremely comfortable and offer plenty of adjustment (even the armrests move, while the headrests have six positions) The rudder pedals also adjust over a good range, while I fully approve of the fact that although the passenger seats have three-point restraint systems, the pilot’s seats have four-point harnesses.

In common with other large single-engined turboprops, such as the Caravan and TBM, one of the PC‑12’s biggest selling points is that it is not only certificated for single-pilot operation but is very much aimed at the owner-pilot. Consequently, as I began to study the instruments and controls I was curious to see how ‘user-friendly’ the cockpit was.

The instrument panel is fitted with the advanced Honeywell Primus Apex suite. This consists of four identically-sized liquid crystal display screens. These are arranged as a primary flight display (PFD) in front of each pilot, with the other two (functioning as MFDs, one for systems and the other for situational awareness) mounted vertically in the centre of the panel. Each screen has a diagonal size of 255mm and is easy to read, even in bright sunlight.

Each screen can be sub-divided into 1/6, 1/3 or 2/3rd sections, with each containing different data, such as engine parameters or navigation information. Aircraft configuration, such as trim, undercarriage and flap position, is also shown here. It’s a very elegant and intuitive system, yet although each one of the three individual undercarriage position icons can show seven different displays, I’d still also like three lights adjacent to the undercarriage selector.

There are no analogue instruments at all, as the back-up instrumentation consists of a small, self-contained emergency standby instrument system to the left of the captain’s PFD. This neat little unit displays attitude, speed and altitude, and can run off its own integral battery in the unlikely event of a total electrical failure.

The installation of the Apex system has also meant that an alpha/numeric keypad for the flight management system is located below the lower MFD, with a large cursor control device aft of the power control lever. Jan then demonstrated how to program the FMS by moving the cursor with the track ball, while inputs are confirmed by using the ‘enter’ softkey, just like any computer. It really did appear to be both easy and – more importantly – intuitive. A very neat feature is as the flight deck is ‘wireless’ it is possible to input data swiftly and simply. I could see that this would be a very useful feature when programming the FMS with multiple sectors or a particularly complex flightplan.

Interestingly there isn’t a prop lever. Instead, prop control is automatic, and prop speed never exceeds a nice, slow (and quiet) 1,700rpm.

Another transport category-type feature fitted to the aircraft is the crew alerting system. There are red ‘master warning’ and orange ‘master caution’ lights, sensibly sited just above the PFDs, while the actual nature of the out-of-limits condition is displayed on the systems MFD.

As on many turbine-powered aircraft, the switches for most of the electrical systems – such as the external lights, starter and generator – are in the overhead panel. The centre console carries just a few switches and rheostats forthe internal lights, along with the power lever, fuel condition lever and flap selector. As mentioned earlier, there is no prop control, so I now turned my attention to the control yoke. This is liberally studded with switches, buttons and even a trigger (which must be pulled to allow use of trim control).

One aspect of the cockpit that I did particularly notice was how big and robust the switches (mostly large rockers) were. Although the PC-12 is a big aircraft, the cockpit actually feels as if it is from an even larger machine. However, I did wonder if perhaps the switches would be better colour-coded (they’re all a somewhat anonymous grey).

Jan started the engine, while I watched closely. The start sequence is very straightforward – simply switch on the batteries, then press ‘start’, and at 15%Ng move the fuel condition lever to ‘ground idle’. The engine lit promptly, and we moved on to the pre-takeoff checks. These included checking the stall protection system (remember it has a stick-shaker and a stick-pusher) lowering the flaps to 15° and setting the trims.

Taxiing from the Pilatus factory to Buochs airport is an unusual and possibly unique experience as you cross a busy road. However, the traffic lights are (properly) biased in the pilot’s favour, and I’ve never had a long wait! As the nosewheel steers through the rudder pedals and the hydraulic brakes are both powerful and progressive, taxiing was very easy. Although I ensured that the power lever was on the idle stop, in common with most turboprops there’s so much thrust that it wanted to taxi faster than I did. Rather than ride the brakes, I pulled the power lever up over the gate and back into the ‘beta’ range. Approaching therunway I pushed the fuel condition lever to ‘flight idle’ and carefully taxied into position.

Having lined up on Buoch’s 2,000m runway 07 I brought the power up against the brakes. A glance at the windsock showed a gentle crosswind from port, while as ambient conditions are essentially ISA we had a density altitude of about 1,500ft. With two POB, no baggage and 750kg of Jet A-1 in the tanks we were around 1,040kg below the 4,740 maximum takeoff weight, with a fairly forward CG. With 1,200shp at my command the acceleration is unsurprisingly excellent, while unlike most of the other turboprops that I’ve flown, in the PC-12 you don’t have to monitor the torque gauge, as the torque limiter automatically protects the engine. Instead, I just smoothly pushed the power lever forward to the stop and concentrated on keeping straight.

The acceleration was excellent, and tracking the centreline was easy, despite the crosswind. The airspeed increased quickly, and I rotated at 85kt. It was interesting to note how little the pitch attitude seems to change at rotation, but this could be an optical illusion, as the long cowling slopes down and away from the cockpit. I then retracted the undercarriage, engaged the yaw damper and raised the flaps. The undercarriage comes up with no discernible change in pitch trim, but as the flaps retract the trim changes and the aircraft seems to ‘settle’ slightly, although it’s easily trimmed out (as long as you remember to pull the trigger before operating the trimmer).

As you’d imagine, the combination of 1,200shp turning a big four-blade prop produces considerable amounts of precession and P-factor. Consequently, without the yaw damper you’d have to adjust the rudder trim whenever you changedeither the airspeed or power setting if you wanted to keep the pedal forces neutral and the slip ball centred. With the yaw damper engaged, the automatics keep the slip ball centred, although initially it’s slightly disconcerting to feel the rudder pedals moving under your feet.

I let the aircraft quickly accelerate to 130KIAS, and as we’re relatively light the rate of climb is phenomenal, and we’re soon at 10,000ft.

An examination of the general handling revealed the roll rate to be brisk, and with surprisingly low stick forces. I had read that earlier models were rather heavy in roll, but one of the changes Pilatus installed in 2006 was a servo-tab in each aileron. For such a big machine, I thought it very pleasant to hand fly, and noted that the control harmony was also good, while the stick-free stability is outstanding.

Jan encourages me to make full use of the PFD, and I find that if I place and hold the flightpath marker icon on the horizon’s ‘zero-pitch’ reference line then I don’t lose a foot of altitude! We then move onto slow flight. As mentioned previously, because the PC-12 has a T-tail it is fitted with both a stick-shaker and a stick-pusher. There is an electrically heated AoA vane in the outboard leading edge of each wing, and when this senses the alpha is approaching a critical value the stall warner sounds and the stick-shaker actuates. If no recovery action is taken then the stick-pusher fires. This pushes the control yoke forward with a force of around 28kg.

As we were a good way below MTOW, with the flaps at 40° I managed to get the IAS down to almost 65kt before the shaker activated, while the pusher fired at about 60. These are pretty slow speeds for an aircraft this big that can cruise at up to 270KTAS and 30,000ft, so with this in mind we climb up to FL300. The PC-12 is very much a ‘going places’ machine, and not only is it in its element at altitude but sometimes favourable winds can add 100kt to the groundspeed. From 30,000ft above the Alps the view is stupendous! From our lofty perch Jan points out Austria, France, Germany and Italy, before we get back to the serious business of evaluating the aircraft. The maximum cruise speed is 280KTAS, but a more representative (and efficient) speed is between 250-260. With an OAT of -44C conditions are essentially ISA, and at 255KTAS we’re only burning around 225kg/hr.

Jan then directs me to perform an emergency descent as if the pressurisation has failed. As with most turboprops, if you pull the power right back the prop generates loads of drag, and it was easy to achieve a very high descent rate (8,500ft/min) without excessive speed. As for the pressurisation, all I can say is that I never noticed it working – which is exactly what you want.

I level out at 12,000ft and Jan takes control.

“There’s a way we can burn even less fuel,” he grins, and I nod enthusiastically. During the briefing Jan had explained that during production test flights and engine change-related maintenance flights, company test pilots perform an in-flight shutdown and re-light within the glide-cone of Pilatus’s base airfield. I can see we’re practically overhead Buochs, so having informed ATC of our intentions he pulls the fuel condition lever back, the prop disc turns into four blades which slow and feather – and we’re in a 3,600kg glider, high above the Alps. As an experienced sailplane pilot I automatically note our speed, sink rate and altitude, and then do a quick ‘final glide’ calculation. We’re gliding at 115KIAS, while sinking800ft/min (‘eight down’ in glider parlance) which means that we would have 30 minutes from 30,000ft cruising altitude to restart the engine, and in the extremely unlikely event of it not restarting we could glide around 60 miles, enabling us to not only reach many suitable airports, but even several different countries! It does restart, of course, and we carry on with the test.

Pilatus PC-12 NG

Technical specifications

Powerplant
Pratt & Whitney Canada PT6A-67P turboprop, producing 1,200shp (895kW)
Performance
Max cruise 280kt
Stall speed 67kt IAS
Rate of climb1,820ft/min
Range inc IFR reserves 1,715nm
Takeoff distance over 50ft obstacle 808m
Service ceiling 30,000ft
Weights
Max takeoff 4,740kg
Empty 2,800kg
Useful load 1,960kg
Fuel capacity 1,226kg
Dimensions
Length 14.40m
Height 4.26m
Wing span 16.28m
Wing area 25.81m2
Cabin height 1.47m
Cabin width 1.52m
Cabin length 5.16m

Jan is keen for me to see the automatic side of the PC-12, so we head off to Grenchen, a less than 1,000m GA airfield close to Bern, where the autopilot flies a perfect precision approach, (aka ‘coupled baro-VNAV’) even though the ground-based navaids make this particular runway non-precision (it only has VOR/DME).

I really like flying with Jan. As both a production test pilot and instructor he knows the PC-12 NG and its systems both inside out and back-to-front.

Returning to Buochs was easy in the outstanding visibility, but in more inclement weather the exceptional situational awareness provided by the ‘Apex’ system would’ve been much appreciated, particularly as the 7,000ft-tall Mt Pilatus is inside the circuit when you’re downwind for runway 25! Jan demonstrates an impressive short-field landing with full reverse and then it’s my turn. The takeoff is easy but with so much power it’s imperative to be in front of theaircraft as circuit altitude is reached very quickly! The undercarriage and flaps both extend smoothly, although the aircraft does balloon slightly as the flaps reach 40 degrees. Jan recommends placing the flightpath marker symbol on the virtual runway’s threshold (remember the PFD uses synthetic vision) and then controlling the speed with power. This works out pretty well, and after a smooth touch and go the second landing really is very gentle, pull the power control lever into reverse and we stop very quickly.

I’m really quite pleased with my second landing, although Jan deflates my ego somewhat by pointing out the trailing-link undercarriage is a real flatterer, and that you actually have to apply yourself to make a bad landing.

No matter, I can now clearly see why the PC-12 is so popular. It’s a real ‘pilot’s aeroplane’, with good performance and fine handling. There’s always a temptation to compare an aircraft with another, particularly if they are both powered by the same engine. However, I cannot think of any other single-engined turboprop that I’ve flown which is capable of hauling such a heavy load (or nine passengers) or flying over 1,800nm – from a short, unprepared runway. Comparisons are meaningless – the PC-12 NG is, quite literally, in a class of its own.