Pilatus PC-12: Cabin Size Really Does Matter

No airplane offers more cabin room or range for the money. And because it is a single the PC-12 is more economical to operate than any turbine airplane of similar size. Sales of the PC-12 have been accelerating rapidly and backorders are building because no other airplane can deliver so much for the money. When the PC-12 entered service in the mid-90s it was most attractive to owner pilots who appreciated the benefits of a turboprop single and to utility operators who needed the cabin space and rough field capability. Those groups still represent big chunks of the PC-12 customer base, but in the past couple of years the number of nonpilots and charter and fractional operators on the order list has been growing fast. In every case, it's for the same reason-size and comfort of the cabin.

Over the dozen years of PC-12 production Pilatus has made many improvements to the original design, increasing its capability and performance. For 2006 the company made changes that every pilot will appreciate, but are also important to the owner, whether he flies the airplane or hires a professional pilot. The big change in utility is another maximum takeoff weight increase to 10,450 pounds, up 530 pounds with no significant change in empty weight. With full fuel tanks, that leaves more than 1,400 pounds of payload available in a standard airplane with an executive interior. Over shorter distances where full fuel is not required, the new PC-12 can carry more than 2,600 pounds of stuff. More payload is always good because it translates into more range when the cabin is full, or the ability to cruise faster because more fuel is available.

The PC-12 airframe has always been extremely rugged, actually overbuilt for its previous lighter max takeoff weights, so structural change was not an issue with the recent weight increase. The big deal is stall speed at maximum weight, which in singles is restricted to 61 knots. The logic of the maximum stall speed is that in a forced landing a lower approach speed improves the odds of a successful outcome. However, Pilatus has shown the FAA that its structure, stronger seats and restraint systems deliver the same level of crashworthiness at 66-knots stalling speed as a conventional single does at 61 knots. Of course, the higher stalling speed is only at the new maximum takeoff weight, which won't be an issue on most trips, and as soon as fuel burns off the stalling speed will drop, so even after a max weight takeoff stall speed will be down to 61 knots or less before long.

The extra available payload does not change the unusually large CG range the PC-12 enjoys. Even with a single pilot and no passengers, or a single pilot and 400 pounds all the way back in the cargo area at the rear of the cabin, the airplane is still within limits. All fuel is carried in the wings so there is no significant CG position change during a flight. Cabin room is great, but the CG range to use all that space is equally important.

The easiest way to identify a new PC-12 is to look at the winglets. The original winglets stood close to vertical and had a fairly wide chord. The new winglets-which grew out of Pilatus' development of its new military trainer, the PC-21-are smaller, less upright, and more smoothly faired into the wing. The new winglets reduce drag, and by smoothing airflow at the tip, they improve aileron effectiveness.

The ailerons have also been changed with the addition of a servo tab. Roll control force in the PC-12 has always been heavy, too heavy to harmonize with the pitch and rudder forces, but the new ailerons reduce force by as much as 60 percent at low airspeeds and up to 72 percent at high indicated airspeed. The servo tab moves opposite the direction of aileron travel, thus reducing control force in the same way a trim tab relieves force on a conventional control surface. Similar tabs were the norm on large propeller airplanes years ago, and even some jets, and are a good way to reduce forces without adding weight and complexity.

Other external improvements are a switch to LEDs for position lights, giving many thousands of hours of bulb life, and a new, smoother fairing of the dorsal fin to the fuselage.

Important changes have been made under the cowling since we last reviewed the PC-12, chief among them an engine condition monitoring system and an oil debris monitoring system. The condition monitoring system automatically records all important operating parameters of the engine and can provide early warning of any degradation so preventative maintenance can be performed. The oil debris monitoring system counts metal particles that circulate past a chip detector and issues a warning when a threshold is exceeded. A normal chip detector, which the PC-12 engine also has, uses a magnet to snag larger chips and then issue a warning, which is important, but the debris monitor can find a trend before a serious problem develops.

Much of the ready acceptance of flying such a large airplane on one engine comes from the unrivaled reputation for reliability of the Pratt & Whitney PT6A-67B engine that has powered all PC-12s. The engine is one of the largest in the PT6 family, producing 1,605 shp at sea level, but the PC-12 uses only 1,200 shp for takeoff and 1,000 shp for climb and cruise. That means full rated power is available for takeoff and climb even with air temperature at the takeoff airport above 120º F.

The design, workmanship and materials used to finish the PC-12 cabin have improved greatly over the years and now rival the interiors of other business airplanes. Most people order the airplane with six cabin seats, with a club arrangement forward. The huge baggage door in the rear is standard, so you can easily take your Harley along if you like, and the aft two seats can be quickly removed to carry oversize cargo. One very well done cabin feature is the potty that is located just aft of the copilot. What makes it work so well is that Pilatus devised a system of hard doors that fold out, sealing off the potty from both the cabin and cockpit, leaving plenty of space for comfortable use. It is one of the better potty arrangements in any light jet or turboprop.

New for 2006 are Ipeco pilot seats with their huge number of adjustments and long-term comfort. The seats are also more compact than the previous crew chairs, so there is even more room in an already spacious cockpit.

The PC-12 cockpit feels like it belongs to an even bigger airplane, certainly something of the transport category. All the controls, knobs and switches are big and sturdy. This is the place for some serious flying, with no detail overlooked, down to the diagram on the center of the control wheel that identifies each of the many control buttons and switches mounted on the wheel.

Even though the cockpit at first appears complex, there is a high degree of automation. For example, there is no propeller control because the prop is automatically regulated to 1700 rpm. Fuel is balanced automatically by boost pumps that turn themselves on or off. The start sequence is automated, and you push the power lever full forward for takeoff, something that is not universal in PT6 powered airplanes.

Pilatus has switched from carbon brakes to conventional steel brakes. The carbon brakes had more stopping power, but it turns out that with its low approach speeds and propeller reversing, brakes are not much of an issue. Carbon brakes have a tendency to grab and chatter when they are cold-a phenomenon sometimes called morning sickness-so a smooth taxi was not always easy. The new steel brakes are easy to manage on your first try.

For takeoff from Centennial Airport near Denver we had about 1,600 pounds of fuel and three people onboard, bringing takeoff weight up to about 8,600 pounds. It was hot, nearly 90º F, so the density altitude was out of sight at Centennial's 5,883-foot elevation, but the PC-12 needed less than 4,000 feet of runway, a very short distance under such demanding conditions.

Over the years Pilatus has modified the various warning and annunciation lights in the cockpit, so now it has the desirable "dark cockpit" for takeoff. That means no lights are showing when everything is normal, so if you see a light during takeoff roll, you know it's an abnormal situation. The PC-12 is one of those airplanes that changes pitch attitude very little at liftoff. It just seems to levitate with only a little back pressure on the wheel. With so much horsepower into a single propeller you may expect it to be difficult to control the PC-12 during takeoff roll. It isn't. With rudder trim set in the takeoff position the airplane is no more demanding than any high performance piston single during takeoff. The rudder trim switch is on the power lever, but the yaw damper takes care of most trim requirements when it is engaged, which I did immediately after liftoff.

ATC gave me an immediate left turn after takeoff and I was astonished at how little control force was required to roll briskly into the bank. The new servo tabs on the ailerons really work. The PC-12 does, however, retain it's unusual trigger switch to arm the electric trim. You squeeze the trigger with your index finger and then move the rocker switch under your thumb to trim in pitch or roll.

Initial climb was around 1,800 fpm and decreased only a little as I approached 17,000 feet. At that altitude it was 15º C above standard, but with max cruise power set the PC-12 posted a true airspeed of 269 knots on 480 pph of fuel flow. From there a climb to FL 250 took less than seven minutes, and when level the true airspeed settled in at 261 knots, but fuel flow was down to 365 pph. The tanks were about half full, but the engine instrument system calculated that we could fly for three hours and 40 minutes to dry tanks. A rule of thumb for fuel burn in the PC-12 is 450 pounds in the first hour and 350 pounds per hour after that. With 2,704 pounds of fuel in full tanks, range with IFR reserves can stretch out to just under 1,500 nm while flying at high speed cruise. Pull the power back and range, particularly downwind, stretches out several hundred more miles.

And that's with the seats, as well as the tanks, full.

The PC-12 has Bendix/King electronic flight instruments (EFIS), and most people opt for the optional larger five-inch displays. Garmin GNS-530 combined nav, com, GPS systems and a Garmin multifunction display are also options that nearly everyone orders. Some all-glass panels have been approved for older PC-12s under STCs (see related article) but Pilatus has not yet made a decision to do a complete overhaul on the avionics. The company wants to select a system that integrates all avionics functions and expects to do that sometime in the future. The EFIS-50 in the airplane now uses solid-state gyros, and the altimeters are electronic air data computers to meet RVSM requirements, so many of the benefits of a glass panel are already there. The KFC 325 automatic flight control system does an excellent job of flying the airplane with smoothness and precision, so everything a pilot wants and needs is there, except for the pizzazz of the big flat-panel displays.

The PC-12 is a stable and easy airplane to fly at any altitude or airspeed. Pilots transitioning out of high performance piston singles will find the indicated airspeeds and flying qualities to be not that much different, particularly with the new, lighter roll forces. The Vmo indicated airspeed limit is 240 knots, and that decreases with altitude. And, like other turboprop singles, the propeller provides loads of drag when the engine is in flight idle, so it's easy to come down at a high rate if the situation requires. The airplane is certified to 30,000 feet and achieves its lowest fuel flows at that altitude, but the cabin hits 8,000 feet when the airplane is at 25,000 feet, so many will find it most comfortable to fly in the mid-20s where you find a good compromise of fuel efficiency, speed and cabin comfort.

The only problem I have with the PC-12 around the runway is making myself fly slow enough. I think it's the sheer size of the airplane that makes me feel as though 90, or even 80 knots, is not fast enough on final approach, even though those are correct, with 80 or less being the Vref for typical landing weights. The Pilatus people say pilots like me who are used to flying twins and jets are the ones that don't want to slow to the proper approach speed, while pilots coming out of other singles find that the numbers feel normal.

The long nose exaggerates a pilot's impression of pitch attitude when you are near the ground, so at first it looks like you are approaching with the nose way down, and then in the flare it looks like the nose is pointed very high. The fact is the PC-12 approach and landing attitude is like any other single, but the sight picture is different. After a few tries, the picture starts to look normal and the tendency to flare too high goes away. The stroke on the trailing link main landing gear is enormous, so it's tough to make a hard landing in the PC-12, and the airplane is at home on grass, gravel or other unimproved landing strips. And with the drag of the propeller when you reduce power, it's easy to put the airplane on target. Once the nosewheel is down, propeller reverse is very effective with little need for brakes except to turn off the runway.

The PC-12 is a breakthrough airplane. Its size for the purchase price and low fuel flow are propelling demand, but the fact that it has only one engine is mattering less and less, to more and more people, is indeed a big change. Pilots were, naturally enough, the first to know the facts and trade the tiny risk of a forced landing for the many cost and efficiency benefits of a single, but now nonpilots are making the same decision. If there was ever any doubt, size does matter, and it's the size of the cabin, not the number of engines, that matters most to many.__