Bell's 430 twin-engined helicopter looks sleek and provided a smooth flight in our test
Peter Gray/SINGAPORE
FIRST CAME THE Bell 222 intermediate weight, twin-engined, two-bladed, commercial helicopter in 1979, with a maximum take-off weight (MTOW) of 3,570kg, rising to 3,750kg, and the first aircraft to be certificated by the US Federal Aviation Administration for single-pilot instrument-flight-rules (IFR) operations without stabilisation equipment. This was followed in 1990 by the 230, with a MTOW of 3,820kg. This was also two-bladed, but was re-engined and incorporated many other refinements.. Then, at Asian Aerospace '96 in Singapore, Bell introduced two new helicopters, the 407 (Flight International, 21-27 February) and the 430.
The Canadian-manufactured 430 is a much updated 230. The main changes are that the 430 has an all-composite, bearingless and hingeless, four-bladed main rotor, yet-more-powerful engines and main gearbox to match, a 450mm fuselage stretch, a new instrument panel and a MTOW of 4,090kg, rising to 4,200kg with external cargo. The external load hook will carry nearly 1,600kg.
WALK AROUND
Helicopters are not normally designed to look good - they are functional vehicles designed to be flown where other aircraft cannot go. Stretched helicopters usually look even less appealing. As Bell chief pilot Alfred Schmidt and I approached the 430, I could not help but notice the sleek lines, even smoother than those of the 230 evaluated earlier (Flight International, 25-31 January, 1995). Someone once said of aircraft "...if it looks good, it flies good": I looked forward to good things.
As Schmidt showed me around the aircraft, I noted the simplicity of the main rotor system. There are no flap or drag hinges - these are replaced by flexible glassfibre-reinforced plastic yokes, which absorb all the loads but allow flapping and dragging to occur.
There are no pitch-change bearings, as this is again, performed by the yokes. Maintenance engineers will not have to lubricate or check/change bearings regularly. There is no required scheduled maintenance on the rotor.
Some recent helicopters have shaped blade tips. It is the tips, which cause most of the aerodynamic problems which restrict high forward speed, present handling problems and cause excessive noise. They also create problems such as stalling of the tips of the retreating blade, compressibility effects at the tips of the advancing blade and uncontrollable nose-up pitching, with the pilot left with little or no forward cyclic stick available to level the helicopter. Bell has tackled these snags by making the blades thinner at the tips. Helicopters now have to pass stringent noise tests, and the 430 main rotor is quiet.
The tail-cone, horizontal stabiliser with leading-edge slats and vertical end-plates, vertical fin and two-bladed tail rotor are the same as those of the 230. This made me wonder if the 430's heading would be as difficult to control in the hover with no number-one hydraulic system as is the 230.
The stretched cabin allows bigger windows and this was appreciated when I flew as a passenger. The left cabin door is in two parts - just like that of the Bell LongRanger. The main door is identical to the right cabin door, but is set into a panel door giving better access to the cabin for stretchers or bulky cargos.
Our aircraft was equipped with the standard nine-place interior - a three-person rear seat, two rows of two seats and two cockpit seats. This arrangement gives plenty of passenger comfort - indeed, the seats are several centimetres wider that those of the airliner in which I flew from London. Headroom, too, is adequate: the top of our 1.86m (6ft 1in)-tall photographer's head was just short of the roof. A tenth seat can be added alongside one two-person seat, if required. Every seat has a shoulder harness.
The additional 450mm fuselage length gives an extra 23% cabin volume, allows two stretchers to be carried and provides space for medical attendants to be positioned at the patient's head.
Some of the doors were difficult to operate, but this should be just a matter of adjustment. Each door has a gas strut or bracket to hold it open. The baggage compartment has space for 225kg, or 1.04m3 (11ft3), of luggage.
COMFORTABLE COCKPIT
I hopped easily into the pilot's seat, fastened the four-point inertia-reel harness and adjusted the seat and pedals using the fore and aft, up and down adjustments. Bell took inputs from many sources, including potential customers, when designing the 430. These also included their views on the cockpit.
The significant feature is the Rogerson Kratos integrated instrumentation display system (IIDS) which consists of two liquid-crystal multi-function displays slightly to the right of centre on the instrument panel, but clearly visible to both front-seat occupants. The IIDS is standard equipment and replaces 21 conventional instruments. In addition it contains, on five pages, information on the main aircraft systems, maintenance and power-assurance checks, recording of all exceedances, an engine start display and all the emergency warning and caution indicators. A malfunction will cause the master warning light to illuminate. The pilot can then scroll through the pages, using the scroll switch on either the IIDS or the collective lever to obtain more information on the malfunction.
Because the IIDS has incorporated all these functions on to just two screens, Bell has been able to lower the height of the instrument panel by 80mm to increase forward visibility. I made a note to do a really steep approach on to a small target (representative of the "H" on an offshore helideck) to evaluate its effectiveness.
Our aircraft came with the optional Rogerson Kratos electronic flight-instrument system (EFIS) for both pilots, presenting an even neater panel. There are the usual mechanical standby attitude indicator, compass and airspeed indicator in case of EFIS failure.
The glare shield is reserved for high-priority action items:
master warning-light;
engine-out warning (there is also an audio);
low-RPM warning;
fire-extinguisher panel;
engine start.
We had the additional optional extras of an automatic flight-control system, a stability and control augmentation system (SCAS) and an auto-level function which levels the helicopter at 50ft above ground-level at the bottom of an instrument approach. Unlike the 222 and 230, the 430 requires a SCAS for single-pilot IFR certification because it is harder to fly on instruments at low speeds.
The automatic direction finder, transponder, two navigation units and VHF radios are neatly positioned, easily visible and accessible above the two IIDS screens. There is plenty of space in the cockpit and in the avionics bay in the tail for any of the optional extras.
We had all the equipment on board for IFR operations, taking our empty weight from the published standard of 2,400kg to 2,720kg, 86kg lighter than the single-pilot IFR-equipped 230 test flown in January 1995. Bell is conscious of the importance of keeping empty weights as low as possible, so the basic aircraft comes with the bare essentials for flight in visual meteorological conditions: extra equipment is optional.
The overhead panel and centre console, retain the usual functions. As well as circuit breakers, lights, battery and generator switches, the fuel valve and hydraulic switches are located on the panel, the former protected by a flap against accidental selection.
Another notable feature is the Chandler Evans full-authority digital engine-control (FADEC) system for the 585kW (785shp) Allison 250-C40 turbo-shafts which provides:
engine load-sharing. The pilot can select compressor-RPM or temperature matching;
automatic start, which prevents hot starts;
overspeed and surge protection;
rotor speed control;
acceleration and deceleration control;
flame-out detection and automatic engine relight;
engine data collection;
emergency manual throttle operation.
The FADEC allows the 2.5min maximum contingency limit for single-engined operations to be exchanged for a higher limit for 30s, enough time to get you out of a difficult single-engined situation such as an engine failure just after leaving an offshore platform or rooftop, plus a 2min rating to get you up and away.
I liked the arrangement of side-by-side throttles on the captain's side, the left-hand throttle controlling the left-hand engine: the right throttle, the right engine. It is important in single-pilot IFR aircraft that vital controls such as throttles are positioned where the pilot can use them and continue to fly a degraded aircraft without too much distraction: a position at the end of the collective is ideal. It is equally important that there is as little ambiguity as possible as to which throttle manages which engine. Having them side by side avoids confusion. There have been some serious accidents where, during an engine fire procedure for example, in the heat of the moment, the pilot, having closed the wrong throttle, activates the fire-extinguisher system of the other engine which then closes down that engine. The co-pilot's throttles are in line on the 430.
Some thought has been given to stowage of documents. As well as the two door pockets - although a single pilot would not be able to reach the contents of the co-pilot's door pocket - there is a clipboard by the pilot's seat for his instrument-approach chart. There is plenty of room in this cockpit for pockets to contain all the manuals and other documents required for instrument flying and other types of operation. I liked, too, the space between the cockpit seats - the pilots can easily get up and go back into the cabin if required, or use this area for stowage.
The overall impression is that this is a very likeable helicopter to take into the air, single-pilot in instrument meteorological conditions (IMC) if needs be. It is impressively modern in so many areas.
START UP AND HOVER
Starting is automatic, and fully controlled by the FADEC. Just open the throttle to the detent, select, start with the switch on the overhead panel and sit back and watch. Remove the detent with the switch on the lever and wind up the engine to full throttle. If you are going off on a serious IMC trip, there are over 200 items in the check list to cover. We were going off for visual circuits at Seletar so were ready to go shortly after the second-engine start. The warning system will tell you if something is amiss.
Schmidt invited me to taxi, so I released the parking brake, inclined the cyclic tentatively forwards, raised the lever slightly, and off we went. There was no static ballast available, so we used as much live ballast as possible by inviting passengers on board and, with full fuel, were able to get our take-off weight up to 3,900kg - just 190kg short of maximum.
I tried the foot brakes and taxied easily out to the holding point where I came up into my first hover. There was 5kt (9km/h) of wind and, with an outside air temperature of 28°C, we were at a density altitude of about 1,500ft. The 430 came up into a near-perfect hover, and I had very little work to do to hold our position accurately while the control tower handled our request to cross the active runway. I glanced at the IIDS to establish the power being used - very little, with plenty in hand. The presentation of engine and mast torque, temperature, power-turbine RPM and rotor RPM is shown by moving vertical lines with a digital readout, of the value for each engine and how well matched they are clearly visible. The maximum continuous and take-off limits are shown as marks on the vertical lines.
Straying into these areas causes the lines and numbers to change colour - first to yellow, then to red. Only the turbine RPM has just a digital readout. All this information is on one page. I soon got used to the display and liked it. The fuel system is in blue for normal and red for abnormal. Data on other systems, such as those for engine and transmission oil, are also presented as vertical ribbons.
We eventually received clearance to cross, so I hover-taxied the rest of the way to the hover square. Hover-taxiing was also easy, but there was hardly any wind to test us.
All the sideways and backward speed limits are 30kt (55km/h), so off we went in each direction. The sideways limit is realistic since I got close to or reached maximum pedal deflection at this estimated speed. Control was good, with hardly any of the heading twitching which can occur at these speeds. I was able to hold our heading at exactly 90° to our direction of travel. Rearwards flight too was uneventful, with no unpleasant or sudden nose-down pitching.
During turns on the spot in both directions, I was able to maintain our position exactly over the "H". All this showed well-balanced and co-ordinated controls. All-round visibility was good, as was the cockpit noise level. I could converse quite easily with Schmidt. Later, the wind increased to 17kt during the approach of some rain while I tried crosswind and downwind take-offs and landings. I experienced no problems with these, and control was good throughout.
FORWARD FLIGHT
We were now ready for our first transition. Single-engine techniques have not yet been developed, so I accelerated gently, raising the nose to achieve 60kt, then applied maximum continuous power, pulling up on the collective-pitch lever until we reached the first yellow display. A collective shaker operates if you try to exceed maximum power. We shot up to our designated circuit height of 600ft. Our circuits had to be tight. Holding maximum continuous power straight and level, we achieved an impressive 145kt. This is the sort of speed which all modern turbine helicopters should achieve, provided that the fuel consumption is acceptable. Ours was - just over 270kg/h.
We were close to the never-exceed speed (Vne) of 150kt, so I went for that, too, and tried a few turns. Vibration levels, which will normally be at a maximum at Vne were benign, probably because of the effectiveness of the new main-rotor pylon mounting which has replaced the previous nodal-beam system. The test pilots have taken the aircraft to much higher speeds, with no ill effects, so I expect this limit to increase as the results are analysed.
Schmidt selected wheels down, giving us a good old-fashioned three greens on the panel alongside the actuating lever, and I made a decelerating, descending, turn on to a short finals to the airfield's only hover square. Getting the wheels down was the only action we had to take for our approach and landing. The IIDS would have warned us if anything else had needed our attention. I flew about an 8° approach and had no difficulty in keeping the "H" in sight all the way down over the top of the instrument panel. I was saving the really steep one for later.
There are no limits laid down for maximum bank angles, so Schmidt allowed me carte blanche. A sustained 75°, while uncomfortable for our four passengers, was reassuring for the pilots. With its hingeless rotor, the helicopter flies just like a fixed-wing aircraft. Earlier versions of the rotor have been looped and rolled.
SINGLE-ENGINEd LANDINGS
While the aircraft was still quite heavy, I tried to explore the single-engine capability. The aircraft which we were flying (a demonstrator) was restricted by Bell on the single-engine power which Schmidt was allowed to demonstrate, so we simulated single-engine power available by restricting the combined output of two engines to no more than single-engine power. In reality, the FADEC flags the one-engine inoperative 30s and 2min power ratings, and the IIDS adjusts the presentation accordingly.
There was, however, nothing in the flight manual to tell us what single-engine power was available at our 2,000ft density-altitude and temperature. Few manuals do - it is a weakness, which I would like the manufacturers to address. In reality, one would pull full single-engine power while still in the cruise before the single-engine landing and plan one's approach and landing accordingly. The flight manual gives a 30s available single-engine torque as 109.6%. On my first attempt, using a flat approach, and aiming for the 10 x 10m hover square, I used 120% for a zero speed, no hover, flop-on-to-the-ground arrival just outside the edge of the hover square, which is not good enough if you are aiming for an offshore platform. The arrival would probably have been entirely successful if it had really been on one engine, using the inertia in the rotor system and subsequent power droop to achieve the same effect.
We were over soggy, fairly long grass which requires more hover so, to compare, we did a 2ft hover over the runway and noted that we required 104% torque. I was confident that, even if our available maximum was already less than the 30s single-engine limit of 109.6%, we would have been able to carry out a single-engine approach to that very spot and come to the same low hover. I would like to try the more esoteric technique of a steep approach, driving the aircraft down to a confined area such as an offshore platform, using the power available to control the rate of descent and the remaining power in hand for the single-engine hover and landing. Single-engine offshore diversions would then be a safe proposition.
The FADEC controls rotor RPM to within tight limits, the manufacturer says, so I tried with enthusiastic up-and-down movements of the collective lever to beat the system. I failed. The RPM needles stayed almost immobile.
HYDRAULICS OFF
After my earlier experience in the 230, when I was unable to control the heading sufficiently well to attempt a landing with the number-one hydraulic system off (Flight International, 25-31 January, 1995), I asked Schmidt to let me try it in the 430. The flight manual states that, in temperatures of more than -20¡C, the aircraft should be brought to a hover, or a low-speed running landing be carried out. Schmidt told me to be prepared for some hard work.
At my request, he switched the hydraulics off just after take-off while transitioning into a climb. The subsequent circuit was easy to fly. The aircraft remained quite stable and continued its line of flight with only the occasional nudge on the controls to maintain the required attitude. Turns, climbs, power changes and descents were no problem. Using the pedals to achieve balanced turns required only slightly more pressure than normal (there was now no hydraulic assistance to the tail-rotor pitch-change mechanism). As a starter, I elected to do a minimum forward-speed landing off a shallow, minimum control-input approach. It worked well and we flopped down without too much effort on to the "H". I suspect Schmidt had not hovered this actual aircraft before without the number-one hydraulics, so he took the precaution of hovering it first, landing, taking off and then handing over control to me in the hover. The problem is the tendency of the 430 (and 230) to be slightly unstable in yaw in the hover: the heading wanders from left to right slightly. This is not noticeable during powered tail-rotor flight, but with no hydraulic power, it fishtails. The pilot tries to correct with opposite pedal, but because of the delay and other characteristics, over-controls and has difficulty in arriving at a constant heading.
I now took over the hover from Schmidt. After a few minor heading swings I had it under control and steady, lowered the lever and landed without any embarrassment.
An approach and landing on to an offshore helideck without the number-one hydraulics after sufficient practice and continuation training might be a possibility.
The aircraft comes with skids or retractable tricycle gear. I reduced our airspeed to below 55kt with the wheels up to try the warning system. The gong, a different sound from other audio warnings, alerted us. We also heard during our circuits the aural warning that we were at our pre-selected decision height.
Our passengers were luxuriating in the back, so we decided to wake them up with an auto-rotation and powered recovery to the hover. At 60kt, we achieved a modest rate of descent of 1,600ft/min (8m/s). Rotor RPM stabilised slowly - the flare had bite and the power was restored.
STEEP APPROACH
I now set up a steep approach. Holding the airfield "H" just on the top of the instrument panel did, indeed, give a steep approach, but not steep enough for my liking, so I kicked the nose slightly sideways and steepened it. I could now keep the "H" in sight all the way down with no discomfort to the passengers. The chin windows were not big enough to help much. We came to a neat hover with none of the shaking and shuddering that many helicopters produce during such a manoeuvre, our wheels exactly over the target.
The aircraft is flown normally with both throttles left fully open. If the FADEC malfunctions, there is a manual throttle. Bell 212 pilots will recognise the entry - wind back the throttle to flight idle, select manual and wind back up again. I kept the power of the manual-throttle engine just below the governed "good" engine to allow it to do all the governing and keep the rotor RPM constant. Unless I made large lever movements, there was little or no manual-throttle movement required. I had no difficulty in taking off, doing a circuit, approach and landing.
We finished off our flight with a quick demonstration by Schmidt of a few of the autopilot functions. After a manual take-off, the autopilot took us round the circuit. There is an automatic go-around button on the lever.
CONCLUSIONS
This is a modern aircraft in every respect. It flies extremely well and, despite the complex systems, which lie beneath its sleek airframe, it is easy to manage and operate. Pilots and passengers are delighted with it. I expect it to take Bell well into the next century.
Source: Flight International
