Agusta power

Peter Gray/CASCINA COSTA DE SAMARATE

Although it has been said before, the statement that "if it looks good, it flies good" certainly applies to the Agusta A109 - and particularly to the Power version. The outside shell has changed little since the first-prototype days of 1971, but as I approached the A109 with Agusta senior experimental test pilot Carlo Tondi, the outstanding impression was one of unusually good looks for a functional, practical helicopter.

The outside fuselage has been shorn of all unnecessary protrusions: the panels, cowlings, doors - and even the door handles - are flush. This sleekness is reflected, as intended, in the aircraft's speed, as I was to find out.

Although the exterior still resembles that of the 1971 prototype, little else remains the same. Agusta has redesigned nearly the whole aircraft.

Unusually for this class of helicopter, Agusta has placed the fuel tanks, not under the floor, but behind the cabin and under the rear seats. This allows a smaller frontal area, with less drag, and also provides higher speed. The wide cabin enhances the aircraft's usefulness for emergency-medical-services work, with the capability of accommodating two litters and two medical attendants, with two pilots if required.

Another advantage is the high ground-clearance for operations in rough terrain, combined with a low floor making access and egress easy for passengers, crew and the litters. Electrically operated steps are also available.

There are many items of optional equipment, and Agusta's designers have ensured that the configuration can be changed efficiently and quickly to convert from one role to another.

I noted the easy access to all the fluid reservoirs, the climb-up route to a newly designed main rotor-head with fewer moving parts (lighter and easier to maintain), and the new droop stops which raise the minimum rotor-tip height to 2.45m - well clear of passengers and their gear. On tiptoe and at full stretch, I was unable to touch the tip of the lowest main rotor blade. We also saw the aerodynamically shaped vertical fin which helps offload the tail rotor.

The tail rotor has been given three extra degrees of pitch movement to an impressive 23¹, and the maximum rotor RPM increased, thus giving it extra power to allow the aircraft to operate safely in the worst "hot, high and heavy" conditions of high outside-air temperature, high altitude and high aircraft weight. A large strake on the left-hand side of the tail boom also assists control and allows for high crosswinds in the hover. There should be no chance of running out of tail-rotor authority in this helicopter.

The A109 Power which I flew has two powerful, but de-rated, Pratt & Whitney Canada PW206C turboshafts. They are lightweight (115kg each), but provide 545kW (730shp) each, although the transmission is limited to 670kW in total. Take-off power (full power on both engines) starts to limit at 9,700ft (3,000m) at ISA+30¹. The other engine option is the Turboméca Arrius 2K1 - with the same power and at the same price.

The undercarriage has been redesigned, simplified and lightened. All three wheels are identical, which makes spares holdings and maintenance easier. I noted the neat undercarriage wells - no loss of valuable fuselage space here, unlike in earlier A109s.

The forward avionics compartment cover is hinged at, and lifts up from, the front to give exceptional accessibility. Our aircraft was fully equipped with all the necessary equipment and optional extras for single-pilot operations in instrument conditions, yet there was still room for more. If space runs out, there is a an aft avionics bay too. This drops neatly down underneath the tail cone. Technicians no longer have to squeeze into the tail for access. Having everything at the front requires less wiring and therefore less weight. It also helps balance the aircraft without the use of payload-consuming ballast.

A strong box-like structure for passengers and pilots gives good roll-over protection. This is one of several safety features, such as the 30min run-dry capability of the main gearbox, dual-redundant hydraulics, electrical and fuel systems, passenger-proof door handles, jettison- able passenger-windows and cockpit doors, crashproof fuel cells and voice and visual warnings for some important failures/faults. The undercarriage is designed for heavy impacts, and the four-bladed rotor has high inertia.

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START-UP AND HOVER

Tondi offered me the right-hand captain's seat, which I eagerly accepted. Getting into the comfortable seat was easy. It is adjustable fore and aft, as are the pedals. I found a position to my liking and was able to rest my right forearm on my thigh for better cyclic-stick control. I had already noted that the stick is pivoted, not from a point on the floor ahead of the pilot's seat, but beneath it. This allows the pilot to control the helicopter throughout its performance envelope without having to stretch his cyclic-stick arm too far.

All the controls and switches are readily to hand. Agusta has provided an additional 10mm of cockpit width, so there is plenty of room.

This demonstration aircraft has an "all-glass" cockpit which is particularly efficient, user-friendly and pleasing. It gives an uncluttered presentation with just the information shown that you need to know at the time. There is a choice of instrument package, including a moving-map display.

The lower centre section of the instrument panel is dominated by two large displays, clearly visible and accessible to both pilots. The primary display presents all primary engine and rotor parameters and warning, caution and advisory annunciations when they occur - there are no large warning panels taking up valuable instrument panel space as in earlier helicopters. The maximum limits are clearly presented both by a moving line and colour change when you approach them. The secondary display presents advisory annunciations of fuel, electrical and hydraulic information, with clearly defined limits and a similar colour change when approached. The system monitors the engine, transmission, electrical, fuel, hydraulic and other aircraft functions as well as warning the pilot visually and in some cases aurally (gong and/or voice) and automatically displays the appropriate information relating to the event. The caution, warning and advisory annunciations are presented in order of priority and there is an overflow memory to store and recall those messages which exceed the capacity of the display area at the time. The aural warnings are equally smart and are activated in order of priority, even interrupting each other in the event of a higher priority occurring.

The pilot can interrogate the displays at will and access any other information. The system records exceedences, engine power-assurance checks and other vital information which the technicians can download for later study.

The pilots' flight instruments are well displayed. The airspeed indicator, encoding altimeter and instantaneous vertical-speed indicator are conventional pressure instruments.

The Power has been certificated for single-pilot instrument flight. Apart from the ease of interpretation of the displays and accessibility of everything, Agusta has addressed this by placing primary switches on the collective lever and cyclic stick, so there is no need to remove either hand to trim engines, select manual throttle, or cancel the master caution/warning lights. There is also a limit-override button for the full-authority digital engine-control (FADEC) to allow some more power in the event of an emergency where the normal maximum is insufficient. When it is used, the FADEC will still continue to limit engine power available, but to higher, still-safe parameters. One of the major advantages of a FADEC is to relieve the pilot of nearly all engine handling from start-up to shut-down - ideal for the single pilot having to cope with busy instrument conditions.

Navigation information from the single-pilot instrument-flight-rules avionics package is superimposed on the electronic horizontal-situation indicator and attitude-director indicator, saving instrument panel space.

The weather was mild - a cool 10íC at 600ft with no wind, which was a pity. I always prefer at least 20kt (40km/h) to explore better the aircraft's performance out-of-wind and in turbulence. The aircraft weight was just 4kg short of the maximum of 2,850kg.

I could not see the fuel-filler cap nor the external power access from my seat. The latter has a warning light, but the single pilot carrying out a rotors-running refuel will have to take extra care that the cap has been replaced and the bonding wire removed.

Tondi followed a simple route round the cockpit to set it up for the start. Because of the lack of clutter, the comparative simplicity of the layout and the excellent warning, caution and advisory system, this can be done without a checklist. Indeed, we conducted the whole flight without one. He reached up and selected "idle" on the first engine and we sat back to watch the slow, cool-engine start and the rotor begin turning. In the meantime, the displays automatically went to start mode. The second engine was started, "flight" selected on both and, after the usual systems checks, we were ready to go. If a quick departure is required, such as for an emergency call-out, the engines can be started one after the other in "flight" and the whole aircraft quicklymade ready for flight.

There is no provision for the pilot to check full and free movement of the controls - a disappointing, but increasingly common, omission.

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FIRST TAKE-OFF

Tondi launched me into my first take-off to the hover and hover-taxi out to the grass strip. We came to a neat, fairly high, stationary hover which produced a slightly nose-high and "left-wing-low" attitude, as expected. The initial impressions were how easy it was to hover (a very low workload), and how benign (very little vibration and noise). At this high weight, but at low temperature and altitude, we were using 80% torque on each engine, with 100% available, an impressive margin. I liked the power presentations on the primary instrument display. We were well below the maximum of 100%, which was clearly marked with a short horizontal line. Inspection of the secondary instrument display showed that all temperatures and pressures were "in the green" and that we had full fuel. We had lots of left tail-rotor pedal available.

While we were still heavy, having accustomed myself to the hover, I looked around and had a listen, I lowered us to about 2ft wheel height over the helipad. Our power required reduced accordingly to 71% torque from each engine as our ground cushion increased. This was ideal for a single-engine hover with 142% available on one engine for 2.5min, so I asked Tondi to select idle on one engine. We stayed in the hover with no rotor droop. The display changed automatically to single-engine configuration. Usually, my single-engined landings in the civilian helicopters which I evaluate require a demonstration first by the test pilot, or an arrival using two engines restricted to single-engine power (and thus no rotor droop which gives last-minute, but useful, extra energy for the touchdown) with a running landing. Not so with the A109 Power - there we were hovering on one engine at maximum weight.

Few civilian helicopters are capable of this, even at this altitude and outside temperature, with no wind to give us extra lift.

Fast sideways and backwards flight was trouble-free, with no increase in vibration and very little in workload. None of the controls, especially the pedals, approached full travel. The flight-manual limiting speeds are 40kt and 30kt, respectively. Tondi tells me that 50kt is not a problem. For offshore-support and other pilots, this means that you can safely hover and take off in a 50kt crosswind. Spot turns are also problem-free. There is no rate-of-turn restriction - just turn as fast as your own senses will allow.

With crisp control responses and low hover workloads, landings and take-offs on steep slopes are not a problem. Although the aircraft is limited by the flight manual to 10í of slope, with the senior experimental test pilot on board we went to 12í with no problems.

I moved into forward flight, gaining height with speed. We got a healthy 2,000ft/min (10m/s) and this with no conscious effort to go for maximum rate of climb .

While the aircraft was still heavy, I selected 100% torque on both engines and we got a healthy 150kt indicated (148kt true) airspeed at 1,500ft pressure altitude. This was 4kt below the advertised maximum cruise speed, but is impressive and above the norm, and reflects Agusta's successful attempts to reduce the drag. Vibration levels were benign.

The modern engines use conservative amounts of fuel at this speed and altitude (about 200kg/h), thus offering the user a good range of about 960km (520nm) at maximum weight and load, especially when two extra tanks are fitted in place of the litters .

Again at this high weight, I dived slightly to the never-exceed speed - again an impressive 168kt at maximum weight, and this is maintained up to altitude. Vibration levels increased slightly, but they were entirely comfortable, and turns in both directions caused no increase.

After levelling and slowing slightly, we went into 60í banked turns in both directions. Again vibration levels were mild. Visibility is adequate. We held both our height and airspeed. This was expected since the aircraft is agile enough and has enough of everything to do loops, positive-g rolls and push-overs to vertical dives, it cleared to -0.5g to +3.5g.

While we retained our 120kt forward speed I asked Tondi to bring back one engine suddenly to idle and warned him that, as the handling pilot, I would do nothing, just to see what happened, although would be prepared to lower the collective lever if rotor rpm showed signs of reducing below the powered-flight minimum. He complied immediately with full confidence of the outcome. There was little drama. We suffered a slight main-rotor rpm droop, from 100% to 95% where it stabilised. The "good" engine went to maximum. Our airspeed stayed the same. All the engine-out warnings came on, and the presentations on the two screens immediately reverted to single-engine-operation displays. I lowered the lever slightly to restore the rotor rpm to 100%, noted the 142% torque, then reduced power to single-engine maximum continuous - clearly defined on the power displays. There is no need to memorise actual rpm, torque and temperature figures: the displays will show all you need to know to operate the aircraft safely within the limits.

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EMERGENCY TECHNIQUES

We climbed up to try two autorotation techniques - one going for rapid descent, in the event of, say, a fire; the other for endurance, for example, to stay airborne as long as possible for an engine restart after a double engine failure. Most helicopters are limited to about 100kt in autorotation, because of rotor and fuselage drag causing handling and excessive diving-angle difficulties. This aircraft's limit is 128kt. So I lowered the lever fully and Tondi selected idle on both engines. We accelerated to 128kt, but I had to pull a little collective to prevent the rotor rpm exceeding the maximum of 110%, an indication of the rotor's high inertia and good efficiency. The rate-of-descent indicator went to slightly over 3,000ft/min: Tondi says that it will normally get to 4,000ft/min. Next, we tried the minimum- rate-of-descent autorotation at 70kt, pulling collective lever to reduce rotor rpm to the minimum of 90%. This gave us a modest 1,450ft/min and a flat glide angle.

While orbiting to wait our turn to join the circuit, Tondi effortlessly and quickly programmed the fully coupled global-positioning/autopilot/flight-director systems to take us to a nearby beacon at a set speed and altitude. I let go of the controls and off it went, climbing to the selected altitude, turning on to the required track and accelerating to the demanded speed. I am told that the aircraft will automatically carry out whatever instrument approach the pilot has selected and, if he does not take over control, will level off at 50ft above the runway centreline. If requested, the aircraft will go around at any altitude - levelling itself, selecting climb power and climbing at 750ft/min

Handling the aircraft raw with neither of the two stabilisation systems active was hardly any different from stabilised mode.

HANDLING FAILURES

The flight controls, nosewheel centring and locking, wheel brakes, rotor brake (when fitted) and undercarriage are all hydraulically powered. Since the tail-rotor pitch control is run off only the number one hydraulic system, this is the one we de-activated. Failure of the number two system produces no difference in handling and no speed reduction. There is no speed reduction required with failure of the number one system, but there is a marked difference in handling of the tail rotor.

In forward flight, although the pedals are slightly stiffer, there is no problem. As an introduction to coming to the hover later, on Todi's suggestion, I made my first approach shallow, holding the nose slightly left of centre and making as few power changes as possible. I did a gentle, fully controlled, running landing, kicking the aircraft straight for the touchdown. For my next attempt, I elected to come to the hover. Again, I used a flat approach. I did not at this early stage aim for a specific point on the runway, but just allowed the speed to drop off to zero as we came to the hover. Minimum use of lever helped reduce the workload and force required on the pedals to maintain the heading.

Once the necessary force was applied, the aircraft reacted almost immediately, with little tendency to overshoot the required heading. A landing would have been easy at this point, but I elected instead to fly away from the hover. As soon as we got translational lift at about 10-15kt, the pedal workload and physical effort immediately decreased. For offshore operations, landings on to a helideck with the number one hydraulic system out will require dedicated training and continuity practice.

We did some elevated helipad work. The Power is one of the few aircraft certified to Category A which is approved for these take-offs, approaches and landings at maximum all-up weight.

Category A means that a multi-engined aircraft can suffer an engine failure at any time and, for the remaining portion of the flight, will be entirely safe. This requires the calculation of a critical decision point (CDP) during take-off, before and up to which the aircraft is committed to landing back on the pad. At and beyond the CDP, the aircraft has enough power on the remaining engine to continue the take-off, climb at not less than 150ft/min to a pre-calculated safety height for the area, clearing all obstructions by a safe margin on the way. The Power can do all this from rooftops at up to about 20íC at sea level, without any reduction in all-up weight.

Tondi pulled up and backwards keeping the helipad in view through the same spot on the windscreen. He did not know when I was going to fail an engine. I did it just before the Power's 80ft CDP. The warning system alerted us, he lowered the lever slightly and we came back down at a modest rate of descent. He landed exactly on to the spot. At his subsequent attempt, I failed an engine at CDP. Tondi lowered the nose slightly and we flew away with about 20ft loss of height.

The overhead engine levers and their management are unique in my experience. Even though they may be out of their flight detents, the system will detect this and warn you on the advisory panel, but the engines will still give whatever matched engine power is required by the pilot. As mentioned earlier, a reversion to manual throttle does not require the pilot to remove his hands from the controls. There is a change-over switch on the lever and manual engine power can be controlled by a toggle switch, also on the lever. During our subsequent circuit, manual throttle was selected soon after transition: 25% torque was selected on the manually controlled engine and the good engine allowed to do all the rotor-rpm governing and work during the subsequent approach, hover and landing.

TRAINING MODE

Agusta has also addressed the problem of single-engine training and testing in the actual aircraft. The problem is that, when realistically simulating a single-engine landing, especially when heavy and possibly hot and high as well, one should actually use only one engine so as to be able to appreciate and judge the use of the momentary increase in lift during the last few seconds before touchdown, as the rotor rpm droops while the pilot pulls maximum single-engine power to cushion the landing or execute a single-engine go-around. In reality this has the unfortunate and expensive effect of putting a lot of extra cycles on the engine and reducing its life or even doing damage to the engine if enough of them are done.

The A109 Power pilot can select a training mode which will restrict the maximum power output, but still provide the droop and all the other sensations of single-engined operations. The pilot can quickly revert to full power, or the system itself will automatically do so if it senses this is required.

Agusta is confident that solo pilots will be able to practise safely those critical single-engined manoeuvres, unaccompanied by a training pilot. When tried, the system did indeed give all the indications of a heavy aircraft on a single engine - the rotor drooped as we came to the hover, but the "good" engine stayed well within maximum continuous limits.

Finally, Tondi simulated a tail-rotor pitch control failure. He found a power, speed (60kt), rate of descent (300ft/min) combination which kept the heading straight. It was then a question of finding a straight area to land on and, without changing anything, running it on.

A tyre or two may burst at this touch-down speed - the normal touchdown limit is 40kt - but that is what airmanship is all about: weighing up the options.

Nearing the end of our test, the aircraft was shut down and I moved to the passenger cabin. P&WC likes a 30s engine-stabili sation at idle before shut-down. If circumstances preclude this, the engines can be stopped immediately.

The other unusual feature is that they can be started again immediately, as Tondi did while I watched from the passenger compartment. Furthermore, he used internal battery power, which can give hot starts of hot engines. Without venting them, he restarted both engines. The starts were cool and slow, and he had us in the air again within about 2min.

My almost-1.8m body fitted easily into each of the six passenger seats, although the centre forward-facing position had my hair just brushing the upholstery. Comfort is excellent. I found the best visibility is from the outside rearward-facing seats, although it is good from all through the big windows. My intrepid test pilot accelerated to Vne and I removed my headset. The noise level was comfortable for conversation.

THOROUGHLY MODERN

Agusta has produced from an existing sound airframe design a thoroughly modern helicopter which should last through the beginning of the next century.

It is pleasant to fly and extremely efficient. Passengers will like the comfort, low levels of noise and vibration and the view.

Pilots, particularly solo pilots engaged in all-weather operations and those operating hot, high and heavy, will appreciate the smart design of all the systems. It makes a pleasant change to have enough power from the engines, main and tail rotor, to do the job. Even the neighbours on the ground may not object - its noise signature is 3-4dB below International Civil Aviation Organisation limits. The Agusta A109 Power looks good and flies good.

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