Peter Gray/DALLAS
When Bell Helicopter Textron decided to re-engine its Bell 222 helicopter with Allison 250-C30G/2s, it took the opportunity to incorporate more than 70 other refinements and modifications. The result is the Bell 230.
As Bell senior experimental test pilot John Ball and I approached the 230 outside Bell's Fort Worth, Texas, factory, my first impression was of the machine's aesthetically pleasing lines. One of the changes from the 222 is the reshaping of the cowlings, not for the sake of appearance, but to provide a good flow of air for engine cooling, to create less drag and to preserve the in-flight stability of the 222.
The result adds even more flair to an already good-looking and stylish helicopter. Helicopters, with their requirement to have the engines drive both main and tail rotors and with their complex rotor hubs, cannot be expected to look sleek, but the 230 does.
PRE-FLIGHT INSPECTION
Bell wanted single-pilot instrument-flight-rules (IFR) certification for the 230, with no stabilisation or autopilot system, and there are various devices attached to the airframe to help achieve this. Ball and I noted and checked several features on our walk-round.
The 230 has a Bell JetRanger-like vertical tail to assist directional stability and provide some sideways force to off-load the tail rotor. Unlike the JetRanger's fin, however, the 230 tail has long, slim flaps on the trailing edges at 90¡ to the airflow to provide yaw damping and improve stability in forward flight.
in other Bell aircraft, the horizontal stabiliser on the tail is fixed, with no pitch-change mechanism to maintain. I recognised the usual Bell inverted aerofoil. As well as providing some stability in pitch, its main purpose is to pull down the tail as the forward speed increases and so avoid an uncomfortable nose-down attitude. This situation allows a greater range of centre-of-gravity limits and a more centralised cyclic- pitch stick position, which means, for example, that at high speed the pilot does not have to hold the cyclic almost at arm's length.
In addition, compared to the many other Bell helicopters I have flown, there are two vertical plates on the ends of the stabiliser, also offset, also fixed. Slats on the stabiliser leading -edge improve stability and reduce main-rotor mast-bending stresses during low-speed climbs with high power settings - always a problem for designers, particularly of modern helicopters with their vastly increased power-to-weight ratios (the 230 has a 5.5kg/kW [9lb/shp] ratio).
These devices, and other characteristics, provide a remarkably stable aircraft without the use of additional electronic stability-augmentation equipment which most other helicopters require to be certificated by civil-aviation authorities for single-pilot IFR operations. Helicopter manufacturers are addressing ways of improving built-in stability which has, until recently, been almost ignored and left to the pilot to deal with. Even during visual-flight conditions, long hours spent flying an unstable helicopter can be excessively fatiguing.
Another important factor for IFR operations is low vibration levels. Vibration is yet another element of the fatigue-causing factors. Two-bladed helicopters are notorious for their inherent high vibration levels and are thus usually poor to fly under instrument-flying conditions. Bell has developed its vibration- suppression systems over the years and, in the 230, has produced an impressive result. The main gearbox is mounted on Bell's Noda-Matic suspension system which has two nodal beams attached to the fuselage through rubber-like bearings. The main-rotor hub has heavy pendulum weights top and bottom of the blade roots, which not only help to dampen vibrations, but also give a degree of stability.
The downside of this is that the aircraft is very unstable in yaw, in the hover, without hydraulic boost to the tail-rotor pitch -change mechanism, as I was to find out during my flight.
As Ball and I approached the aircraft, I stopped to compare the main rotor movement, in the 12kt (22km/h) wind, with a Bell 212 parked nearby. Neither of the aircraft's blades were tied down. The 212's blades were rocking constantly against the stops, while the 230's were hardly moving. This is because of the elastomeric bearings on the main rotor head which stiffen the otherwise freely flapping blades.
These bearings also allow more responsive handling and better stability. Another advantage is that the aircraft can be started up safely in winds up to 60kt, which would not be normally considered in a two-bladed helicopter because of the danger of the main rotor "sailing" low as it accelerates and striking the airframe, usually the tail-rotor drive-shaft cover. A wind speed of 40kt is a more usual maximum limitation.
We climbed up the conveniently located stepping points to examine and check the main-rotor head and blades. The only lubrication required is to the pitch-change rod bearings. The blades are of modern design and have swept tips to help overcome the aerodynamic problems of high-speed flight. I particularly noticed the three trim tabs on each blade and the large weights above and below the blade roots - all smoothing devices.
The basic airframe is made to accept wheels or skids. The wheels are retractable and, thoughtfully for those helicopter pilots who may have flown most of their hours on skidded aircraft and few on a retractable undercarriage, Bell has provided a warning system - a loud blast in the headset and a warning light on the instrument panel - when the speed drops below 55kt and the wheels are up.
I noted the small chin windows by the pilot's feet for evaluation during steep approaches. The windscreen wiper-blade motors are at the bottom of the screen, instead of at the top. The passenger doors are 750mm wide and open through 170¡, which is useful for offering up stretchers when the helicopter is being used in the ambulance role. Sliding right- and left-hand passenger doors are available to accommodate a winch. All the doors, which can be closed by just slamming them, have flush handles with locks.
We had a look inside the voluminous (1m3/227kg) baggage compartment and noted the smoke detector. There is also another 0.17m3available for bags behind the rear seats. The avionics are stored in the nose.
Although my aircraft was equipped with instrument-landing system (ILS), stability-augmentation system (SAS), four-axis digital automatic flight-control system (AFCS) and radar, there was still room for more, there and in the tail.
There is provision for a flotation gear, but no thought has been given yet to the stowage of a life-raft. The aircraft does not have an icing clearance. At 3.6m above the ground, the main rotor is well out of harm's way, particularly for medical stretchers, and is unlikely to flap lower than 2.8m.
THE INTERIOR
The aircraft I flew was a VIP version, with four passenger seats in the 3.8m3 cabin and two seats in the cockpit. Comfort is first class. There is an entertainment centre between the seats and a cocktail cabinet (which I was not allowed to test), additional sound proofing and a glareproof retractable privacy screen separating the cabin from the cockpit. Communications between the crew and passengers is by telephone. In other interiors it is by hand signals.
All passenger seats, no matter in which interior, have shoulder harnesses. The pilots' seats are crashworthy.
Getting in and out of the pilots' seats was easy with the low floor and the shape of the cyclic, which allows you to slide in behind it, rather than the usual cocking of the leg over. This, I was told, was to cater for women in skirts. The low floor also gives easy access to the passenger cabin. Aircraft of this size usually have high floors necessitating steps, which may be retractable and complicated, to make room for fuel cells underneath. The fuel in the 230 is stored in the crashworthy sponsons and under the rear seat.
I installed myself in the left-hand seat which is adjustable fore and aft and up and down. The pedals, too, are adjustable. When I had found a comfortable position which allowed me to rest my right forearm on my right thigh when holding the cyclic (the best arrangement for good control), I could not, however, see the master caution light, which was obscured by the instrument-panel cowling, so I had to lower my seat more than I liked. This did not occur in the right-hand seat.
I looked around and liked what I saw - an extremely well-designed cockpit, with everything conveniently at hand and in a sensible position and well grouped. The collective lever for the right-hand pilot's seat was nearly upright, requiring more of a push/pull movement than the usual up/down. The two twist-grip throttles were side by side on the lever - a much more sensible and natural arrangement than one above the other. The collective on my side was the more conventional up/down arrangement, with one throttle above the other.
I liked the exceedingly clear presentations of the electronic flight-instrumentation system. I am always amused at Bell's insistence in giving the various limitations to the nearest decimal point and attempting to mark small instruments accordingly. The 230 is no exception: for example, "86.4%" torque and the even more extreme "926.7 degrees C" measured gas temperature (MGT) - and these on instruments of less than 40mm diameter. The 926.7degreesC is red-lined and represents the maximum for engine starting, a useful reminder to the pilot.
The comprehensive bank of warning and advisory lights, neatly grouped along the top of the instrument panel, contains all the usual signals, plus overtorque and overspeed warnings, and there is an audio as well as a visual warning for low-rotor RPM. Another good design feature is the plate holder for instrument let-down charts. The helicopter instrument-pilot frequently has to make do with trying to balance charts on his lap while trying to fly an instrument approach, unlike the fixed-wing pilot, whose aircraft will have plate holders.
START-UP AND HOVERING
Management of the throttles during engine start is a little different in this aircraft. Allison prefers the throttle to be used to take the MGT up into the high range quickly and have a short warm start, rather than the usual cooler, longer one. This is better for the engine, says its manufacturer. Taxiing was a delight with the fully swivelling nosewheel. My first take-off and hover was uneventful in the 12kt wind, the controls being well balanced and the aircraft very stable. I was impressed by the low vibration level and noise, and the smoothness and comfort. All-round visibility was good.
Our weight was 3,785kg, just 25kg short of the maximum operating weight of 3,810kg. This weight is restricted to 3,570kg for public-transport category "A" operations. Although we were heavy, we were using only 80% torque. The outside air temperature was 16¡C, with pressure altitude at 300ft (90m) - very nearly a standard-atmosphere day. This power margin was to be expected, with the Allisons capable of producing 520kW (700shp) each, but restricted to a combined dual-engine take-off power of 690kW.
These engines will provide excellent performance throughout the aircraft's flight envelope including hot, high and heavy operations, where older designs suffer so badly from lack of power.
Sideways and backwards flight up to the limit of 30kt was benign, with no handling difficulties. Many helicopters suffer from directional instability when in the hover, if the wind blows from certain directions, but the Bell test pilots have not discovered any such areas with this aircraft. Spot turns, and hovering crosswind and downwind, were also problem-free. Attitude control, visibility and vibration levels were good throughout.
The transition into forward flight and climb were straightforward and we levelled at maximum continuous power, which gave us a healthy 134kt indicated and true airspeed, just 3kt short of what the brochures say what the 230 will do. While still close to maximum weight, I took the aircraft to the never-exceed speed (Vne) of 150kt and carried out some turns.
I was pleasantly surprised by the aircraft's responsiveness to the cyclic throughout the whole flight envelope, from the hover to the Vne. This is because of the unique design of the main-rotor head, with its elastomeric bearings, which almost give it the characteristics of a rigid rotor. All the controls were well balanced, vibration levels (even at Vne) were remarkably low. Bell has made a big effort to achieve this.
There is a different torquemeter presentation philosophy in every helicopter I have flown, and the 230 has a separate needle and scale for each engine and a total-torque indication of power being delivered at the rotor mast.
AUTOROTATION
Autorotation and powered recovery to the hover gave us a rate of descent of 2,000ft/min (10m/s) at 70kt, which is normal for an aircraft of this weight and size. Because of the low drag and good streamlining of the fuselage, the flare must be started rather sooner than expected and given plenty of bite to get the speed off for a low-speed engines-off landing. Control and handling were good.
We returned to the cruise and I asked Ball to put us on one engine. The speed settled to a healthy 100kt and, although we lost about 3% rotor RPM, they were still well within limits, a very satisfactory performance. There is a beeper switch on the lever for adjusting RPM. Although there are twist-grip throttles, there is no manual throttle, the engines being managed automatically throughout. Engine matching is achieved by a sideways movement of the beeper switch. I flew the aircraft "raw", with no SAS or AFCS, and found the handling benign.
We were carrying one passenger and I asked him about comfort, noise, vibration and visibility in the back. He was happy with everything.
Ball engaged the autopilot and demonstrated hands-off heading, height, attitude and speed control. The aircraft can be used for an automatic ILS and, if necessary, an automatic go-around. I carried out a steep approach on to a ground target. There was insufficient visibility through the chin window so I yawed the nose slightly right, out of the way, and flew it down to the target with no difficulty while looking through the bottom of the windscreen.
When back in the cruise, I asked Ball to switch off the number one hydraulic system which powers the tail-rotor pitch control and is used by the SAS and AFCS. The pedals were quite stiff, but not unpleasantly so. Provided there is no lever movement, there is no footwork required.
I elected to carry out an approach to the hover with the intention to land. I flew a shallow approach, making as few movements on the lever as possible. When I came to the bottom of the approach, applied lever and attempted to hover in to the wind, however, I had a lot of difficulty trying to hold the heading steady.
The pedals required about 30kg of force to move them. The aircraft started to swing, so I applied a little opposite pedal, but the swing continued. I applied more pressure. The nose suddenly swung the other way, past the original heading.
Application of opposite pedal initially had no effect, so more was applied, and the same thing happened again - an overswing. I was unable, even after a minute or so, to hold a steady heading. At one stage, we were 90degrees out of wind. Ball eventually took over control and managed to hold it more or less into wind. I restored the hydraulic pressure for him and we returned to base. This experience spoiled otherwise impeccable handling and control characteristics. Apparently , even experienced pilots do not attempt to hover in this condition, but aim to run the aircraft on with minimum lever movement.
CONCLUSION
The Bell 230 fills a useful place in the increasingly complex and demanding world of the intermediate twin-sized helicopter market. It has been carefully designed to be operated in a variety of roles, from corporate and emergency medical-services (EMS), to utility, in a wide range of environments.
Bell appears to have achieved more than its design objectives of changing the engines and has produced a capable aircraft, with a competitive initial purchase price ($3.4 million), low operating costs, increased safety and flexibility.
Operators will appreciate the much improved reliability, high-lifed items and the long times between overhaul of many of the major components. The aircraft is easy to maintain and operate, with simple fuel and electrical systems, automatic engine controls and a finely tuned, lubrication-free, main-rotor system.
I enjoyed flying the aircraft because of its inherent stability, crisp and well-balanced handling (apart from the number-one-hydraulics off case) and excellent performance, which gives plenty of power in hand, especially in hot, high and heavy conditions. I was impressed by the attention to detail in the design of the cockpit, which made it easy, for example, to get in and out; provided a chart holder for instrument flying; and presented the instrumentation clearly.
Engineers will be pleased by the low maintenance-hours-to-flight-hours ratio, increased reliability and the quality of the engineering.
Passengers will appreciate the quiet, spacious comfort and high-speed, vibration-free ride. The aircraft's stability and ability to be flown accurately on instruments will allow it to carry them into airspace where others cannot go with only one pilot and without the expense, extra weight and extra maintenance of a stabilisation system. Sophisticated equipment to allow hands-off flight can also be installed, however.
Technical revelations
At a speed of 134kt (248km/h), which we got at maximum continuous power and 315litres/h (83USgal/h), the range, with no reserves on full fuel, is 720km (390nm), which equates to 3km/3.8litres.
The Bell 230 has been designed for simplicity, low cost, low maintenance and reliability. It incorporates a simplified electrical and fuel system; does not require fuel-boost pumps for flight, only start-up; it has no manual throttle and no lubrication of the main rotor head.
The cost for a basic visual-flight-rules (VFR) aircraft on skids is less than $3.4 million. This includes training for two pilots and one engineer. FlightSafety International has a simulator.
Direct operating costs (excluding insurance, hangarage, workshop, pilot and finance) are about $500 an hour, or $600 if using Bell's total-support plan.
The 230 requires 1.15h maintenance for every flight hour.
The hook will carry 1,270kg - there is plenty of power available for this.
The basic VFR aircraft weighs 2,270kg, leaving 1,550kg for fuel and payload for non-public-transport operations and 1,300kg for public transport. The aircraft I flew, with VIP interior, four-axis autopilot and additional soundproofing, weighed 2,810kg, allowing a payload of 1,000kg and 760kg respectively.
Four-bladed 430 offers smoother option
Flight testing of the Bell 430, a stretched, four-bladed derivative of the 230, "is going extremely well" at Bell Helicopter Textron Canada's Mirabel, Quebec, plant, says programme manager Gilles Laflamme. The 430 incorporates several design changes aimed at increasing the market appeal of Bell's intermediate twin.
The major change is a new four-blade, all-composite, bearingless main-rotor, derived from the Model 680 experimental rotor Bell first flight-tested a decade ago on a Model 222, forerunner of the 230. The hub consists of two glassfibre-reinforced-plastic yokes which accommodate blade motion by bending, eliminating the need for hinges and bearings. Pitch-change forces are transmitted to the ends of the yokes via stiff aerodynamic cuffs.
Bell says that the design offers simplicity, high reliability and almost unlimited life. The 430 rotor has roughly the same number of parts as the 230's two-blade rotor. Vibration and noise are reduced significantly and, although diameter is unchanged, the four-blade rotor produces 10% more thrust. Never-exceed speed is 150kt (280km/h), unchanged from the 230, but may be increased, Laflamme indicates.
The entire dynamic system from engines to rotors is uprated by 10%. The Allison 250-C40 engines provide 10% more power than the -30s used in the 230. The -40 also introduces a Chandler Evans full-authority digital engine-control system. The rotor-pylon support-structure is simplified, with the 230's anti-vibration nodal beams replaced by lighter, simpler fluid-elastic dampers.
The second major change is an 460mm fuselage stretch aft of the crew seats. This gives airliner-standard legroom in the cabin, but the stretch was driven primarily by the emergency-medical-service (EMS) market, Laflamme says. EMS operators wanted a longer cabin so that attendants could sit at the head of the patients. For utility missions, an optional 460mm-wide hinged panel alongside the passenger door provides an opening wide enough to accommodate a 1.2m pallet, loaded via fork lift.
The third major change is in the instrument panel. A Rogerson Kratos integrated instrument display system (IIDS), consisting of two liquid-crystal displays (LCDs), replaces all the round-dial engine- and rotor-related instruments used in the 230. The centrally mounted IIDS also performs some of the functions of a health- and usage-monitoring system, Laflamme says. A Rogerson Kratos LCD electronic flight-instrument system (EFIS) will be available as an option on the 430.
The first prototype 430 was flown on 25 October, 1994, followed by the second prototype, equipped with the EFIS, IIDS and AlliedSignal Bendix/King KFC-500 automatic flight-control system, on 20 December. The first production 430 will be flown in October and will be used in the flight-test programme leading to certification in November. Series production will begin in the first quarter of 1996 at a rate of two a month. At $3.7 million, the 430 is more expensive than the $3.4 million 230.
Source: Flight International
