Versions of the Beech King Air have been in the air since the 1960s. Flight International flew the latest variant of the twin turboprop
Peter Henley/WICHITA
In 1964, when Beech produced the original King Air, it obviously came up with a winner. That winning tradition continues, 36 years later. Rugged, reliable and comfortable, yet offering a measure of challenge in piloting, the latest King Air range combines vintage quality and regular technology improvements to remain a favourite with single-pilot flyers.
Flight International flew the latest top-of-the-range King Air 350 from the Beech facility at Beech Field, Wichita, to sample the turboprop's handling characteristics and to learn the secret of its continuing pilot appeal. This appeal is important for the King Air range: about 60% of them have been bought by owners who fly the aircraft themselves. It is a sophisticated aircraft to fly and the basic price tag for a King Air 350 is about $5 million.
Climbing into the cabin and moving forward to the cockpit is a nostalgic experience. There is a whiff of leather upholstery and the space is thoughtfully and symmetrically laid out (doubtless incorporating the opinions of numerous pilots over the decades). Although there are obvious concessions to the march of time, such as the Collins Pro Line II electronic flight instrument system (EFIS) screens, the overall impression is vintage 1960s.
Collecting a new King Air 350 from the Raytheon plant could be a similar experience to collecting a 1960's Mark II Jaguar car straight off the production line today. There are rows of toggle switches; the control quadrant, housing the power levers, pitch levers, engine condition levers and trim wheels, finished in gloss black with smartly engraved legends in crisp white. It is a miniature version of what would be found in a Constellation or a DC-6. There are elegant columns of analogue dials and the systems control panels are similarly fashioned in black and white with round dials and robust switches.
There is an air of quality about the whole cockpit: it feels as if the same craftsman had fitted the panels and proudly secured them in place for the past 35 years. Perhaps the analogy with the Jaguar is apt; Raytheon recently offered a promotion featuring a special external paint finish and a Jaguar Cars logo on the tail.
Climbing into the seat involves stepping over the centre console and the seat cushion. The console is low compared with that of most modern cockpits and a strap handle in the roof helps. Demonstration pilot Tom Sifford compares it to climbing into his MGB GT sports car.
Snugly comfortable
The task is made easier by the location of the control column, which emerges from the instrument panel rather than the floor. Familiarity would doubtless make it easier still. A small pocket outboard of each pilot's seat provides document stowage. The seat is snugly comfortable and is adjustable fore and aft, for height and for recline. There is a four-point harness and an adjustable arm rest. The field of view is adequate, but compared to a modern cockpit, the windscreens are a little shallow and the glazed area less generous. The view in a turn at 30° or more of bank is abruptly cut off by the top of the side windows. There is an excellent view of the left wing, engine nacelle and propeller from the left seat.
The King Air 350 is certificated for single-pilot operation and the cockpit layout is oriented around the left-hand seat. The aircraft used for the flight appraisal belongs to a customer and its Collins Pro Line II EFIS has three screens - an attitude director indicator (ADI) and horizontal situation indicator for the pilot and a central multifunction display. The right seat flight instruments are electro-mechanical round dial items, but a matching pair of EFIS CRTs can be specified as an optional extra. On both pilots' panels the airspeed indicators, altimeter and vertical speed indicators are round dial, separate instruments (ie, that information is not included in the EFIS display except for a small window showing a rolling figure digital read-out of instantaneous air speed on the left side of the EFIS ADI.)
Each engine merits a column of six analogue instruments with windows showing digital repeats of the analogue reading where appropriate, eg, torque. The radio and navigation controllers are on the centre instrument panel. A clock is at the centre of each control yoke, there is a choice of headset or speaker and hand-held microphones, and emergency oxygen masks are stowed in the cockpit roof.
Starting the Pratt & Whitney PT6A-60A engines, rated at 780kW (1,050shp) each, using the aircraft battery to power the electric starter motors, was a straightforward series of manual operations. The engine start panel was by my left knee. The right engine ignition and start switch was selected ON and the engine condition lever selected to low idle at 12% N1 and then the ITT (intermediate turbine temperature) and N1 were monitored (the peak ITT was well below the 1,000°C maximum), the oil pressure checked and the condition lever set to high idle.
Straightforward operations
The generator was switched on and the battery charged before following the same procedure to start the left engine.
The avionics were turned on and Sifford entered a simple flight plan in the Universal flight management system panel on the centre console between the seats. The parking brake (which locks the pedal brakes once they have been depressed) was released via a pull-push knob, also by my left knee.
Maintaining taxi speed was easy enough using propeller pitch and wheel brakes. The nosewheel steering, controlled through the rudder pedals, was slow to respond to demands and was imprecise. Sifford said it needed lubrication. Differential power and brake could be used to tighten turns.
Before take-off, an engine run-up was required - a chore inescapable with a turbo-prop aircraft. Here, the overspeed governors, rudder boost, low pitch stops and autofeather all have to be checked. At this point, a turbojet's simplicity, as compared with a turboprop's complexity, becomes abundantly clear. But in the 350's case it rewards its pilot through a metamorphosis once it is airborne. Also some of the run-up items are for "first flight of the day" only and not all must be repeated before each subsequent take-off; an experienced pilot would accomplish them quickly and slickly.
Accelerate smartly
The take-off weight was 6,375kg (13,900lb) compared with a maximum permitted of 6,804kg. Beech Field is about 1,400ft (425m) above the ground and the recently completed new runway 18 was in use. The outside air temperature was +2°C and the surface wind about 230° 5-8kt (9-15km/h). The relevant speeds were V1, 102, VR and 107. Before take-off the propeller levers were set and the flaps put to "take-off and approach". The power levers were advanced to static take-off power against the wheel brakes. The autofeather lights were checked and the brakes released. The 350 accelerated smartly and was easy to keep straight despite the recalcitrant nose wheel steering. At 102kt it was rotated to a pitch attitude of about 10° for the climb. The undercarriage was retracted and the flap brought up at 135kt. There was a nose-up trim change as the aircraft settled into the climb, but it was easy to re-trim.
Although the 350 has electric pitch trim switches on the left grip of the control yoke, the mechanical trim wheel to the left of the power lever quadrant comes so easily to hand and is so pleasant to use that I favoured it for pitch trimming throughout the flight. The undercarriage lever would usually be by the pilot's right knee. In this case it was fitted on Sifford's side of the centre instrument panel but was still reasonably easy to reach from the left seat. The undercarriage is hydraulically powered by an electric motor-driven pump which emitted a high pitched whine during the 6s or so that the undercarriage takes to travel up or down.
Generally, however, the cabin and cockpit of the 350 were remarkably quiet and free from vibration. Sifford and I wore lightweight headsets with no noise attenuation and used the intercom but could converse without it. The smoothness comes from the synchrophaser which electronically matches the RPM of both the dynamically balanced four-bladed Hartzell propellers and phases the blade tips so as to eliminate simultaneous shockwaves from the blades impinging on the fuselage sides. The synchrophaser works during take-off and landing, as well as while airborne, and, in addition to reducing vibration, eliminates the cycling drone of desynchronised propellers. The quietness stems from the Ultra Quiet active noise control system (ANCS) which uses 24 microphones and 12 loudspeakers strategically located about the cabin to detect noise and broadcast an eliminating counter noise.
The claimed, resultant, average cabin noise reduction is 3-8.5dB (A). When the ANCS was switched off the cabin and cockpit became instantly much noisier. Both the propeller synchrophasing and ANCS are standard equipment in the 350. The aircraft has conventional ailerons and rudder and a T-tail with the tailplane (horizontal stabiliser) and elevators mounted on the top of the fin (vertical stabiliser). These primary control surfaces are operated by push-rods, cables and bell cranks. The three-position Fowler flaps are electrically operated and controlled.
The controls have a pleasant, natural feel but the control forces are noticeably heavier in pitch than in roll. Once in any stable phase of flight, the aircraft can easily be trimmed "hands-off" using the three excellent trim wheels. Its subsequent stability until disturbed is an asset to single pilot operation, helping the pilot to hand-fly accurately while re-tuning radios and navigation aids or copying ATC clearances. A snapshot look in the climb showed the 350 to have good longitudinal static stability (also an asset to single-pilot hand flying) and a rudder doublet at 175kt passing 10,000ft provoked dutch roll which was naturally damped in four cycles or in 1.5 cycles with the yaw damper on.
At 15,000ft, the rate of climb was 2,200ft/min (11.17m/s) and, at 27,000ft, 1,500ft/min. A brief cruise was established at flight level 280 (temperature -31°C) which stabilised at 300KTAS and 195KIAS. A simulated emergency descent was then initiated by closing the power levers to idle, setting the propeller levers fully forward, the flaps to Take-off and Approach just below the 202kt limit and the undercarriage down at the 184kt limit. The resulting rate of descent was "off the clock" beyond the maximum calibrated 3,000ft/min. The a penalty for having the propellers generating their maximum drag at full fine pitch was a significant increase in noise.
Stall testing
We found clear air between 14,000 and 16,000ft to try two stalls at an all-up weight of about 6,000kg. The first was power off, clean. The aircraft was trimmed at 130kt and the speed reduced at 1kt/s. At and near the stall the 350 demonstrated the common characteristics of a straight wing multi-turboprop and benefited from agile use of the rudder to keep the wings level. This technique's effectiveness would doubtless improve with practice. Additionally, at low indicated airspeed, with the power at flight idle, there was discernible "hunting" from the propellers, which caused minor fishtailing.
There was good natural buffet at 100kt (almost simultaneously with the audio warning) and the stall was defined by a gentle g break and nose drop; minimum speed in the stall was 97kt and a left wing drop was effectively countered with rudder. With "approach" flap and the undercarriage down, the characteristics were similar, with a g break from a higher pitch angle and speed of 92kt (buffet) and 88kt (minimum).
At 140kt and 14,000ft, Sifford demonstrated a simulated engine shut down and propeller autofeather. At this speed and altitude the process was smooth and undramatic. Because of the weather it was not possible to try an autofeather and single engine handling at or near the more realistic V2 speed. The 350 has a rudder boost, operated by an electric servo, which functions automatically to reduce foot force on the rudder pedals when a reset difference between engine torques is detected.
A global positioning system, coupled approach to Beech Field was made. The autopilot flew the aircraft smoothly and accurately, but as the flight director heading select knob and auto-flight mode switches are on the centre console, inboard of the pilot's thigh, using them was a significant head-down task compared with using similar controls on or below the glareshield.
Discernible thump
The 350 was easy to fly on the latter part of the approach and into ground effect. Closing the power levers to flight idle caused a slight nose-down pitch change. The classic, straight-legged undercarriage was not as compliant as a modern trailing link main leg. The touchdown was light, but caused a discernible thump. Retracting the power levers to "Ground fine" generated sufficient propeller drag to slow the aircraft effectively and quietly.
The King Air 350 proved to be a likeable aircraft of considerable character. Its appeal lies in its classic appearance, handling and build quality. Its virtues included the skilful blending of modern technology, such as EFIS, propeller synchrophasing and ANCS into a 36-year-old design. Less attractive were the inherent turboprop need for a run-up before take-off and, in extremis, noise - despite the revolution ANCS has brought during normal operations. Also, refuelling is overwing rather than through a single point pressure system and the occasional modern addition, like the auto flight mode controller, is not ideally positioned. For conservative operators, for whom reliability, turboprop short-haul economies and the undeniable but subtle appeal of a "pilot's aircraft" are all important, the 350 is a good choice. That it sells well in its 36th year acknowledges there are still plenty of operators in that category at large.
Source: Flight International
