A Real ‘Sovereign of the Skies’
King Air. Even the name suggests a certain regal air of superiority, and when Brian Jones of NAC at Oxford told me that the only C90GT in Europe was stopping by and asked whether I would I like to fly it, you can be sure that I didn’t need asking twice.
When photographer Steve and I arrived at Oxford the King Air was already there, and over a coffee Brian introduced us to the two pilots who had just flown it over Casey Davis and Mark Mohler. Casey and Mark began to brief me on the forthcoming flight, and their enthusiasm for the aircraft was infectious. So much so that I was impatient to get going, so as soon as we’d finished our coffee we walked out to the aircraft.
I soon noticed that it was parked on the grass and asked Casey if the aircraft was approved for operating from unpaved surfaces. Casey confirmed that it was, and my eagerness to get behind the controls increased still further. Why? Well, there are quite a few turbine-powered aircraft that are cleared to operate from unpaved runways, and a good number that can cruise fast, at high altitudes and over long distances, but there are very few aircraft that will do all these things.
As we commenced the pre-flight Casey briefed me on the many differences between earlier C90s and the new GT. As befits any vehicle with GT in its name the main difference is the engines they’re bigger. Well, sort of. In fact, the GT has the same amount of power available as earlier aircraft, but the new engines are 750 shaft horsepower PT6A-135s, which are flat-rated to 550shp. This means that as the aircraft climbs, the engines continue to produce 550shp, which of course greatly enhances performance. The props are also new. These are four-blade constant-speed Hartzells, which are restricted to a maximum of 1,900rpm. This is 200rpm slower than on previous C90s, and while I could easily see (or hear) that this would make the aircraft quieter, I was curious to find out what it would do to the take-off performance. Although the maximum power available is the same, there would be less static thrust produced, which would obviously degrade the acceleration.
As we moved around the aircraft it quickly became apparent that Beechcraft intends to retain its well-earned reputation for quality. The C90GT is not only extremely well designed, it is equally well made. As mentioned earlier, the C90GT was created to operate from unpaved strips, but just how rugged is the undercarriage? The answer is very. I also noticed that while the nosewheel retracts backwards, the mainwheels retract forwards into the long shapely nacelles. I wondered if this was to reduce pitch trim changes during undercarriage extension and retraction, and made a note to check for this during the flight.
While moving around the aircraft I noted that de-icing of the wings, fin and tailplane is done pneumatically, and that there were trim-tabs in both elevators and the rudder, but only on the port aileron.
Access to the cabin is via an airstair, and once aboard I took the time to examine the cabin and try to ascertain just why the King Air series has been such a success. I also wanted to see how the cabin compared with that of a VLJ (Very Light Jet). It was not found wanting. The cabin is a squared-oval and has a maximum width of 1.37m and a max height of 1.45m. And although it is more than 50% larger than any VLJ, it actually appears even bigger, mainly because the generously sized windows create a very airy feel. Another outstanding feature of the cabin is the baggage bay. Not only is it large, heated and pressurised but most importantly it is accessible in flight. I also thought that the chairs were excellent. They were extremely comfortable and offered plenty of adjustment I particularly liked the way that they angle inboard, as this greatly increases both leg and elbow room.
The impression of a large aircraft continues from the cabin into the cockpit. And though the overall feel is of a much bigger aircraft, conversely as soon as I adjusted my seat I became increasingly aware that the C90GT has been specifically designed with the owner/pilot in mind. All of the controls are easy to both see and reach, while the various systems and sub-systems are logically located. That said, I was surprised to discover that the flight and engine instruments were mostly analogue and electro-mechanical. Having flown a number of piston-powered aircraft fitted with either the Garmin G1000 or Avidyne Entegra glass cockpit, the plethora of electro-mechanical analogue gauges was something of an anomaly. In fact the only electronic instruments were the attitude direction indicator (EADI) and horizontal situation indicator (EHSI) that make up the Collins EFIS 84, and a Sandell altimeter. As the C90GT is approved for single-pilot operations, only the Captain enjoys these digital delights.
The engine monitoring gauges are also on the left side of the panel, and consist of 12 dials in two columns (one column for each engine). These are (from top to bottom) Inter-Turbine Temperature (ITT), torque, propeller speed (displayed as RPM) N1 (gas generator RPM, displayed as a percentage of the maximum allowed) fuel flow and a combined oil temperature/pressure gauge. All the dials (except fuel flow, obviously) are colour coded and the torque and turbine speed gauges have a small digital readout above the analogue presentation. The centre of the panel contains a Collins ProLine II avionics suite, which includes weather radar. I liked the way that the various toggle switches were grouped together, but did feel that colour coding would have made the functions of each switch clearer particularly for someone transitioning onto type.
While I’d been studying the panel I’d had a sneaking feeling that it looked very familiar. Then I suddenly realised why it bears a very strong family resemblance to Beechcrafts classic Baron. I began to realise why the C90GT doesn’t have a glass cockpit. I’d bet that a lot of customers for this aircraft are transitioning up from a Baron, and the cockpit lay-out would certainly make them feel right at home. A clever strategy but, in my opinion, a double-edged sword, as a pilot who is moving up from a Diamond TwinStar, Cirrus SR22 or Lancair Columbia 400 might not be so impressed. However, as the latest version of the Baron (the G58) features a fully integrated panel with G1000 avionics I suspect that it wont be long before the C90GT follows suit.
A large centre console carries the power condition levers, trimmers, flap switch and position indicator plus cabin pressurisation gauges and controls. The console extends aft between the seats, and this is where we find the autopilot. Having approved of the Beechcraft Premier IAs glareshield-mounted FGP (Flight Guidance Panel) I did rather feel that this aspect of the C90GT was less than satisfactory (a very comprehensive annunciator panel dominates its glareshield). I also wondered if perhaps angling the GPS moving map in slightly towards the pilot might make it easier to see under awkward lighting conditions. The fuel quantity gauges, transfer pump controls and the essential circuit breakers are to the pilots left below the side window, with the bulk of the circuit breakers on the right side of the cockpit. All of the controls and gauges for the electrical system are grouped in a neat panel directly above the windscreen.
Having completed the Before Engine Starting checklist, it was now time to start the engines. Well used to the vagaries and idiosyncrasies of piston engines, it never ceases to amaze me just how easy it is to start a powerful turbine. Simply check that the fuel is On and the low fuel pressure light is Off, then move the right engines ignition and starter switch to Start, while at the same time checking that the oil pressure is rising and the Ignition On annunciator has illuminated. Then, as soon as the N1 (gas generator rpm) has stabilised at or above 12%, move the Fuel Condition Lever over the detent to Low Idle, check the fuel flow gauge, and the engine should light almost immediately.
As the N1 accelerated rapidly towards 60%, I kept an eye on the ITT gauge. Should the ITT rise towards its limit of 800C it is imperative that the Fuel Condition Lever is promptly closed; otherwise there is a very real danger of cooking the hot section. I made another check of the oil pressure and ITT, and then set the Fuel Condition Lever to High Idle, turned the ignition and starter switch off and the generator on, then repeated the sequence for the left engine. Compared to (for example) trying to persuade a hot IO-360 to start, it is incredibly easy.
As mentioned earlier, as the aircraft is cleared for operations from unprepared surfaces I’d started the engines where it was parked. (The PT-6s are fitted with inertial separators, which stop these very expensive turbines ingesting something that is likely to disagree with them.)
Taxying out to the active runway soon revealed both good and bad points. On the plus side the nosewheel steering is positive and precise, while the toe-operated hydraulic disc brakes are powerful and progressive. On the negative side, it quickly became apparent that the C90GT tends to taxi quite fast. Indeed, even with the power levers pulled back into the Beta range, it was still rolling along at a fair old rate. Casey could see that I was slightly uneasy, and suggested that rather than riding the brakes the best way was to brake almost to a complete stop (to kill all the energy) and then let it slowly gather speed, before braking again. I’m sure that experienced King Air pilots probably don’t even notice, but it was faster than I was comfortable with.
Out at the run-up the well-designed cockpit continued to impress. As Casey talked me through the pre-take off checks, I noticed that I seemed to find the relevant switch, lever or control with no effort at all. Clearly, the Human Factors people have done an excellent job. One significant difference to the checklist is that the first stage of flaps is now used for take-off. As I’d suspected, the reduced rpm of the new props has reduced static thrust, which of course has degraded the acceleration. However, not only has the use of flap meant that a take-off from sea level uses the same amount of runway as earlier C90s, but in a hot n high situation, the GT actually uses less runway. This is because the derated engines are still producing 550shp at high-density altitudes. Checking the speeds to be used for take-off revealed that the VMCA of 85kts is actually lower than the Vr of 93kts! The King Air series has always enjoyed an enviable safety record, and I was becoming increasingly aware of why.
Out on the runway I lined the GT up, stood on the brakes and slowly increased the power until both props were at the 1,900rpm red line, before releasing the brakes and alternating my attention between the ASI, centreline and torque meters. The ambient conditions were about 5C over ISA, while Oxfords 1,319m runway 01 had a slight crosswind from the right. With five POB and full fuel I would guess that we were within 10kg of the 4,608kg MAUW, and while the initial acceleration was, as I’d anticipated, nothing startling, it rapidly improved.
The needle of the ASI soon swung past the Vr of 93kts, and with a smooth rotation the GT was off the ground and climbing swiftly. I would guess we probably used about two-thirds (800m) of the runway. Retracting the flaps and undercarriage produced negligible changes in pitch trim and we rapidly accelerated past the blue line speed (Vyse 108kts). As I followed the flight director I was impressed to note that the VSI was indicating just over 2,000ft/min! Furthermore, the climb performance did not even begin to degrade until we had passed through 15,000ft, and even then it was in excess of 1,800ft/min.
During the briefing Casey had described it as the sportiest of the King Airs, as with its relatively short-coupled fuselage and powerful, flat rated engines it was a GT by nature as well as name. Consequently he encouraged me to sample the fine handling, and how could I resist? In fact, the roll rate is pretty lively (the ailerons are excellent) and as I rolled swiftly from a steep bank to port into an even steeper one to starboard the boys in the back laughingly reminded me that I had passengers on board! Suitably chastened, I assessed the stability and control in a more responsible fashion! Overall, I thought the handling was excellent, with powerful, well-harmonised controls and low break-out forces. Stability around all three axes was also good, while the visibility was fine. This is a fun aeroplane to hand-fly.
With such a prodigious climb rate we very rapidly reached our assigned altitude of 23,000ft, where I engaged the autopilot and let the aircraft accelerate to its max cruise speed, which at this altitude was 189kts. This gave us a TAS of 270kts, while a glance at the fuel flow gauges revealed that the engines were burning 250lbs (113kg) a side. As we still had just over 1,000kg of fuel in the tanks I calculated that we could easily fly for over 1,000 nautical miles and still have adequate IFR reserves and this was at max cruise! (This, incidentally, is around 40kts faster than earlier C90s.) Furthermore, as the GT is certified to 30,000ft we could have climbed another 7,000ft. However, as the maximum cabin pressure is only five PSI this would mean that at 30,000ft the cabin altitude would be around 12,500ft. This is probably a bit too high for an unfit middle-aged cigar-smoking, overweight executive, and I suspect that a more viable cruise altitude is around the mid-twenties. I then disconnected the autopilot and hand-flew the GT back down to 12,000ft.
As my experience with the aircraft grew, my confidence increased exponentially. Indeed (and despite my initial reservations about all the analogue instruments), I was rapidly becoming very comfortable with the C90 and its systems. Once level at 12,000ft I re-engaged the autopilot, as Casey was keen for me to see just how well it handled an engine failure. As we cruised along, he turned off the fuel to the starboard engine the engine flamed out and the GT did yaw a little, but the autopilot didn’t drop out and it held our heading and altitude perfectly. The propeller auto-feathered, the automatic rudder bias worked as advertised absolutely everything was as simple and easy as Casey had said it would be, leaving me with nothing else to do but shut down everything as per the check list. Once again, I could see why the King Air has such an enviable safety record, even when being flown by owner/pilots. I then disengaged the autopilot and flew around for a while, which simply proved that cruising on one engine in a C90GT is very easy!
While Casey read the checklist I went through the air start procedure. This was perfectly straightforward and the engine lit almost immediately. All I had to do then was increase power slowly, to avoid producing a big yaw, before turning the starboard engines generator and associated accessories back on. I would have loved to have stalled the aircraft, but I suspect the passengers probably wouldn’t have shared that instinct, so instead I headed back towards Oxford.
As we drew nearer and changed to the Tower frequency it became obvious that this was a very busy day. Consequently both Casey and I were kept fully occupied scanning for traffic. In fact, it was only after the flight that I suddenly realised that I’d extended the flaps and lowered the undercarriage without even hunting for the controls. More proof that this is an intelligently and intuitively designed cockpit. Incidentally, another excellent feature is that the limiting speeds for the undercarriage and the first stage of flap are both very high. Consequently, should you have to lose height in a hurry its easy to add plenty of drag.
As I turned onto final I could see that I was a bit high and so pulled the power right back to flight idle. As the props were still set to 1,900rpm, the GT practically fell out of the sky, courtesy of the braking effect of the prop discs. This promptly got me back on the glideslope and at the right speed, and I bumped the power back up to about 300ft/lbs. During the briefing Casey had mentioned that the GT was not the easiest King Air to land, as the relatively short fuselage made quite sensitive in pitch. However, as the PAPIs indicated a perfect two reds, two whites, and the needle of the ASI settled on exactly 100kts I was feeling very confident. In the interests of honesty, I have to say that on short final I sank slightly, the third PAPI started to turn red and I had to add a touch more power to stay on the slope. This got it all sorted out nicely, and we flashed over the fence with two reds, two whites, at exactly 100kts. As we crossed the threshold I start squeezing the power off while holding the nose up and absolutely squeaked it on. If I say so myself (and I will), it was good. I pulled the power levers back into reverse and the deceleration was so great that I had to be quick to get the props back out of reverse as the speed sank towards 40kts.
I was hugely impressed by the C90GT, although I suspect that with the introduction of the new VLJ class some of you may be wondering, why would you want to buy a turboprop? However, a more apposite question is why wouldn’t you want to buy a turboprop? The difference in speed isn’t that critical, turboprops are certainly more fuel-efficient and the King Airs cabin is also larger. However, for me at least the real clincher is that this aircraft is as much at home at Hedgerow airstrip as it is at Heathrow Airport. The ability to land at relatively small, unprepared strips (something no jet can do) is a real plus, and in my opinion really does give the C90GT the edge. Beech has been selling King Airs for more than 40 years, and on the basis of flying the C90GT, I’d have to say I can’t see that stopping any time soon.