PETER GRAY / DONAUWÖRTH, GERMANY
The EC145 10-seater helicopter was built to use the best features of two previous models. But has it been a happy marriage?
A manufacturer wanting to enter the 10-seat helicopter market can either start with a clean sheet or use the best features of existing models. Eurocopter and partner Kawasaki chose the latter option, combining the front section of the new-technology EC135 with the proven rear section of the BK117C-1.
The resulting EC145 is 90% a combination of these two aircraft. The remaining 10% is clean-sheet design, and includes the main and tail rotor blades, and a wider, longer cabin with bigger doors. Compared with the BK117C-1, the new main rotor and other aerodynamic improvements increase range from 540km (290nm) to 700km, and provide an additional 150kg (330lb) of payload. The extra 0.85m3 of cabin volume permits the proposed increase from eight to 10 seats (one pilot and nine passengers or two and eight).
The new hingeless main rotor blades, with their curved tips, reduce noise and vibration. The aircraft is more than 5dB below US and international noise limits on the approach and more than 7dB below on take-off and fly-over. This is 60% lower than the BK117C-1, says Eurocopter. Redesigning the tail rotor rather than fitting a fenestron avoided costly main gearbox modifications to handle the higher power and speed demands. A full certification programme was also avoided and, although the helicopter is marketed as the EC145, the type certificate says BK117C-2. Ultimately, certification will be for single-pilot instrument flight rules operation.
The big sliding doors, the lack of door posts and the large cabin have proved attractive, particularly to emergency medical service customers. REGA of Switzerland, German automobile club ADAC, DRF of France, and the French Gendarmerie and German police have all placed orders. The biggest customer so far is Sécurité Civile, the French civil defence and emergency organisation, with an order for 32 aircraft. Operators of the EC135 and/or the BK117 will find there many interchangeable components and also that pilot and technician conversion time is minimal. Plans are afoot to provide two full flight simulators, probably based at Donauwörth in Germany close to the production line.
Flight International was invited to evaluate the EC145 at Eurocopter's airfield at Donauwörth in early January. The sky was overcast with a 700ft (200m) cloudbase, which ruled out the autorotations and vortex-ring entry I had wanted to try. There was snow everywhere. So although our pressure altitude was 1,340ft, the air temperature of -3ºC (26ºF) meant that our density altitude was -500ft . Visibility was an adequate 4km, and wind was 5-10kt (10-20km/h).
The aircraft was a pre-production model, not entirely representative of a production EC145, and one of the aircraft with which Eurocopter has accumulated over 2,000h of test and certification flying. Our take-off weight with full fuel, ballast and a flight engineer was 195kg below the maximum of 3,585kg. The EC145 is one of the few helicopters that can take full fuel (695kg) and a full load (1,085kg) and still have weight and space for extra equipment.
Test pilot Rudolf Kappeler did a full pre-flight inspection. Access to the relevant areas is good - Eurocopter has provided sufficient retractable steps and handholds to climb over the aircraft and enough access panels and sight glasses to do a comprehensive inspection. Provided the pilot has had some training, an engineer is not required until the aircraft has flown over 100h since the last pilot inspection, says Eurocopter. Another design criterion was low and affordable maintenance, so few components are life-limited and most are on-condition only. Scheduled checks are few and far between. Accessibility of components was a major objective, as was the concept of replacing modules and submodules instead of a whole component.
The elimination of door posts and provision of sliding doors gives good access to a cabin 2.16m (7ft) long and 1.13m high.
There is a long, level and unobstructed floor from the rear baggage compartment through to the cockpit. The centre post, common in other helicopters, has been eliminated by using a unique flight control system with flex-ball cables running from the cockpit controls up between the two windscreens to the overhead mixing unit. Four rails run the length of the cabin, allowing seats to be attached in just about any position. There are freight tie-down rings every 25mm. Our aircraft had just the flight-test engineer's seat and telemetry equipment installed in the cabin.
The main and tail rotors are high off the ground, keeping them out of harm's way. This is important when loading freight, baggage or stretchers through the rear clamshell doors with the rotors running.
Latches on the many panels are designed to prevent inadvertent opening in flight, but can be operated by someone wearing gloves in cold weather conditions - an example of attention to detail.
Production models will have crash-attenuating seats and shoulder harnesses for all occupants.
The Turbomeca Arriel 1E2 turboshaft engines are unchanged from the BK117C-1, and give 575kW (770shp) maximum contingency power (single engine), 550kW take-off and maximum continuous. The main gearbox is limited to 550kW, 405kW and 370kW, respectively, which means that published engine power is available throughout a wide range of temperatures and altitudes. The flat main gearbox has a redundant oil system - an excellent safety feature.
Landing skids are attached to the belly and do not intrude into the fuselage as on the C-1, allowing a larger fuel tank and easier maintenance (for example, a fuel pump can be replaced without draining the tank). The tanks are crash resistant and the belly and undercarriage are designed to absorb most loads in an excessively heavy landing. Other safety features include the duplication of electric and hydraulic systems. There are fittings on both sides of the cabin for a 270kg-capacity winch with a 90m cable.
Kappeler offered me the right-hand pilot's seat. Access via the long steps which stretch from the cockpit along the length of the cabin was easy. The seat was comfortable and adjustable fore and aft, as were the pedals. An up/down adjustment is optional. I found a position where I could rest my right arm on my right thigh for precise hovering. I could reach and see everything I needed. I liked the various controls positioned on the cyclic stick and collective lever grips. Somewhat like the military "hands-on" control concept, this is a good design for single-pilot IFR flying. The first impression looking around was the excellent visibility. Within the big cockpit there are several potential storage areas for documents and other equipment needed for single-pilot IFR.
Although the engines are not digitally controlled, their management is almost as good. To start, the pilot only has to select the prime pump and start switch, then sit back and watch the slow, cool start, adjusting the twist-grip throttle as required. Fuel control units monitor all the parameters and present the pilot with two matched engines and the ability to adjust them manually. There are generous overspeed, overtemperature and overtorque limits should the pilot need them to escape a difficult situation. There is a mini health and usage management system (UMS instead of HUMS), which records exceedances and other parameters. The information is available to the pilot and can be downloaded.
The instrument panel layout is state-of-the-art and reflects Eurocopter's research into providing the pilot with an easy to interpret presentation of where he is, where he will be and the state of his aircraft. Information is presented directly in front of the pilot on two flat-panel screens called the vehicle and engine management display (VEMD), which I recognised from my EC135 test flight. The scan area is minimal. Then there is the central panel display system (CPDS), the contents of which can be seen at a glance. The cockpit is compatible with night vision goggles.
One criticism is that in the remote event of a total display failure in instrument meteorological conditions, the pilot would have to use the standby instruments mounted line-abreast to the left of his main display. The standby artificial horizon, altimeter and airspeed indicator are to the left of the rotor/power-turbine RPM instrument. The standby compass is a long way out on this already stretched and unusual scan, on the pillar between the two windscreens. Unless a pilot has recently flown the aircraft using these instruments, he might be hard-pressed to interpret his position in space and control the aircraft accordingly. There are standby instruments available which could present all the information on one gauge.
After following Kappeler through the engine, rotor and systems start - straightforward and without checklist - he handed over control and, after a quick glance at the warning and caution advisory panels to ensure everything was in order, I pulled up into a hover. With a comfortable seat/controls position established, I had no trouble holding a precise 1m hover, just watching the attitude and not doing much to hold it. A glance at the excellent first limitation indicator (FLI), which combines turbine outlet temperature (T4), gas generator rpm (NG) and torque (TQ) on a single indicator, showed immediately that power required was well below maximum continuous. Digital readouts of actual T4, NG and T are presented alongside the FLI. Attention-getting warnings appear when any of the limits are approached.
Kappeler performed some vigorous nose-down accelerations and other manoeuvres for the photographer, positioned 100m in front of us. This displayed the EC145's positive main-rotor crispness. During transition to forward flight, as we passed 50kt, the rotor/power-turbine RPM (NR/N2) automatically reduced from 100% to 98%. This is a "fly neighbourly" design feature. Rotor RPM automatically increases as the aircraft decelerates through 50kt. Similarly, NR increases when the aircraft is carrying out Category A operations or operating at high-density altitudes.
Once in level flight at 2,000ft with -5ºC outside air temperature, and while still fairly heavy, I selected maximum continuous power and noted 142kt (263km/h) indicated airspeed. This was better than the brochure value of 135kt. Most modern helicopters will cruise above 140kt at maximum continuous. As 142kt also coincided with our never exceed speed (VNE) at this weight, altitude and temperature, we took the opportunity to do some turns.
The airspeed indicator on the LCD goes to red if VNE is exceeded. As part of an ongoing vibration analysis test, the anti-vibration equipment had been removed so we were flying a "raw" aircraft, but the resultant vibration level, a slight high-RPM buzz, did not increase. The maximum VNE is 150kt.
While still heavy, 60º steep turns were performed in both directions at a sustained 90kt. The most common problem in steep turns is the door pillar getting in the way of visibility. Not so in the EC145. The pillars are so far back that even at 60º bank they do not impede the pilot's vision.
To check single-pilot friendliness, Kappeler retarded one engine suddenly from maximum continuous to flight idle. Rotor RPM droop is a critical parameter but NR reduced to 95%, well within limits, and held. Kappeler lowered the lever slightly and we continued with hardly any loss of airspeed and no loss of altitude. Engine power restored, he lowered and raised the lever viciously from high power to low power settings: NR/N2 fluctuated wildly, but stayed well within limits.
Kappeler demonstrated an engine fire drill. The master caution and relevant warning light on the instrument panel illuminated, accompanied by the gong.
Lifting the cage over the warning light and pressing the button does everything - shutting down the engine and firing the extinguisher bottle. There is no need to close the throttle, eliminating the possibility of shutting down the wrong engine - another good safety feature. Eurocopter's research into pilot-friendly warning and caution advisory systems has, in my view, been successful.
Heading back to the airfield, Kappeler disengaged the automatic flight control systems so I could fly the helicopter "raw". With the systems off, handling in turns, climbs and descents was benign, hardly any different to the stabilised state. Our aircraft had the full autopilot. This is not just a stabilisation system, but allows the pilot to programme the aircraft for hands-off instrument flight. There are convenient coolie-hat trim switches on the stick to adjust altitude, heading, airspeed and vertical speed and a go-around button on the lever.
Kappeler then switched off the number two hydraulic system, which powers the tail-rotor pitch change mechanism. In the cruise, including level turns, climbs and descents, only a little extra pedal power was required. The ultimate test, however, is an approach to the hover and a landing. In some other helicopters I have had difficulty establishing a safe or even manageable hover with no tail-rotor hydraulics. Similarly, I have had some trouble trying to hover with all artificial stabilisation removed. Neither were a problem with the EC145. With the number two system switched off I performed a 360º spot turn, approach to the hover and landing. It was the same for an approach and landing with the raw aircraft, which flies very well.
There were no flight manual limits or sideways and backwards flight so I went fairly quickly then handed over to Kappeler, who went very fast - at least 30kt, I estimated. We still had plenty of tail rotor control available. This is good news in strong crosswind or even downwind conditions. During fast rearwards flight, fuselage attitude remained stable with no tendency to pitch forward. Although the flight manual limits for rate of spot turn are modest, Kappeler showed that fast turns produce no handling ill effects. I hovered and landed the aircraft in various directions with no difficulty.
The electronic instruments allow a small panel. Not only does the pilot have a much reduced scan, but also visibility is excellent. As expected, I had no problem carrying out extremely steep and even vertical approaches to a spot on the runway.
This also helps when performing rooftop Category A departures and arrivals which require a rearwards and upwards take-off with the abort back on to the rooftop. We tried these on a marked-out area on the runway. Because of the helicopter's high power-to-weight ratio, a Category A take-off from a clear heliport has a decision height of only 20ft and 30kt. This comes quickly, so Eurocopter are considering a time limit instead.
Kappeler wound one throttle back and carried out a gentle single-engine run-on landing on to the snow alongside the runway. Finally he demonstrated a stuck-pedal situation by taking his feet off the pedals during a fast cruise and attempting to line up the aircraft with the runway at the bottom of the approach. As we came over the runway with the nose cocked hard left, he raised the lever slowly, bringing the nose round to the right. If this had been for real, he could have planted the aircraft onto the runway and accepted the swerving slide before coming to a stop. This is where a simulator will be useful.
The rigid rotor offers many advantages including low maintenance and long-life or on-condition components, but with the rotor installed so high above the airframe the pilot must be careful of mast stresses. As a result, there is a mast limit gauge which is referred to when carrying out sloping ground landings and take-offs. Kappeler demonstrated these in all directions. The limits are generous and the stick had more than adequate limits of movement. To prove the manoeuvrability of the rigid rotor conclusively, Kappeler threw the aircraft around vigorously within the confines of the small airfield, demonstrating the high main rotor power and response.
With a price of $3.6 million for the basic aircraft, the EC145 represents a significant upgrade of the BK117. Pilot workload in managing the aircraft is low, allowing more time to concentrate on other things such as flying in busy airspace. A malfunction should not overwhelm the pilot. Engineers will appreciate the ease of maintenance, the long overhaul intervals and many on-condition components. Eurocopter puts direct maintenance costs at €270/h ($230/h) and the maintenance burden at 0.44h for every hour flown. Although our aircraft had neither passenger seats nor fully insulated cabin, I am sure passengers will be conveyed with comfort, speed and safety. The low noise signature will be especially relevant for EMS operators in built-up areas. The many proactive and reactive safety features will benefit passengers, pilots and operators.
Source: Flight International