IN FOCUS: Eurocopter's new super-medium EC175 tested
Eurocopter has listened to customers and focused on safety for its super-medium EC175, set for certification later this year. Flight International takes it for a remarkably comfortable spin
By: Dominic Perry
Designed to fill a gap in its range between the 4.5t EC155 Dauphin and the bottom of the Super Puma line at 9t, the super-medium EC175 - with a maximum take-off weight of 7.5t - is Eurocopter's newest helicopter.
It has been pitched initially at the offshore transportation market for the oil and gas industry and will be certificated in an O&G configuration in the third quarter of 2013. First delivery, to an as-yet undisclosed customer, will follow shortly after. Search and rescue and VIP variants are likely to follow before the end of 2015, according to the demands of the market.
Eurocopter's newest helicopter has a maximum occupancy of 16 and uses a five-blade Spheriflex rotor with composite blades
Development has been shaped through collaboration with Eurocopter's Customer Advisory Team (CAT), a pool of operators that has provided feedback and guidance through the helicopter's gestation period. Given the safety-obsessed nature of the oil and gas industry - and by extension the companies flying on its behalf - it is little surprise that this was the CAT's primary consideration for the EC175. As a result, the type bristles with safety features and other systems to reduce pilot workload.
In fact, the advances the airframer has made are partly to blame for a certification slip announced late last year, which delayed entry into service by about six months. This stemmed from the difficulty of certificating its proprietary Helionix avionics system to a standard previously only used on the Airbus A380 airliner.
Other advanced features include a four-axis autopilot, derived from that found on the larger EC225, and a dual flight management system designed to keep the helicopter within its flight envelope. A TCAS II collision avoidance system is standard, too, linked in to the autopilot so the EC175 automatically takes evasive action if another aircraft is getting too close.
Eurocopter is pitching the EC175 at the offshore transportation market for the oil and gas industry
Another innovative feature is designed to prevent disorientation. If the pilot gets confused in, say, instrument flight conditions and/or puts the aircraft into an unusual attitude, two clicks of a switch on the cyclic stick will recover the helicopter to a safe attitude or condition. In the very unlikely event of a double computer failure or other problem, there is an automatic attitude-recovery mode.
A forward-looking, vertical stabiliser-mounted camera provides flightcrew with external visibility, allowing them to monitor passengers embarking or disembarking the helicopter. A second camera is located in the cockpit ceiling.
Power comes from two Pratt & Whitney Canada PT6C-67E turboshafts, the latest iteration of the type, producing take-off power of 1,776shp (1,320kW) and maximum continuous power of 1,645shp. When on the ground one engine can be declutched, allowing the other to continue running to power systems such as the air-conditioning, As well as enhancing passenger comfort, this does away with the need for, and the additional weight of, an auxiliary power unit. The engines are mated to a five-blade Spheriflex rotor with composite blades. The three-blade tail rotor features a 20˚ cant - a first for a Eurocopter model - which provides some additional lift.
Large 2,500 litre (660 USGal) fuel tanks are standard - the same size, in fact, as those fitted to the 11t NH Industries NH90 military helicopter - which eliminates the requirement for auxiliary tanks.
At 28m (92ft) long, the type boasts cabin space of 12.3m3 (434ft3) 3.9m long plus 2.7m3 of easily accessed cargo space. Maximum occupancy in the O&G variant is pegged at 16 passengers, although a higher density 18-seat model is under development, probably to be offered to the Asian market. A typical offshore configuration with full fuel and a full complement of passengers offers a radius of action of 140nm (260km).
Large cabin windows boost external visibility and aid speedy emergency egress. In tests, Eurocopter has evacuated all 16 passengers in 24s, easily beating the certification requirement of 90s. Comfort of the occupants is further enhanced by suspension on the main gearbox to dampen vibrations.
The latest state-of-the-art health and usage monitoring system (HUMS) is installed, which, as well as keeping tabs on the health of many components, is also used to increase their lives, thereby lowering operating costs and maintenance time and increasing up-time.
Data from the HUMS is downloaded and pooled by Eurocopter, allowing operators to benchmark the performance of their helicopters against that of the global EC175 fleet. To further increase availability, there are no major inspections requiring days of downtime; all maintenance is done progressively - overnight, say, after a day's flying. Some major components such as the main and tail rotors have no overhaul life but are on condition only.
ABSORBING THE IMPACT
In the event of a heavy crash landing, the undercarriage is designed to take the impact. Its strength is in excess of certification requirements, says Eurocopter. If there are residual forces, the belly is also designed to absorb these. All the seats are crash attenuating and have upper body restraints. The fuel system is also crash resistant. So the chances are that in the event of an accident, all occupants will survive, probably unhurt.
The 20˚ cant on F-WMXB's three-blade tail rotor is a first for a Eurocopter model
And should the EC175 be forced to ditch, the aircraft sits high in the water to lessen the risk of capsizing and can withstand up to Sea State 6. Two large life rafts are mounted externally and can be launched from both inside and outside the helicopter by the pilots or passengers. They can also be deployed if the aircraft is in an inverted position.
An automatically deployable emergency locator transmitter (ADELT) is installed on the tail cone. In the event of a landing on water, and, in the worst case, a capsize and sink, the ADELT will automatically detach, float and send out a location signal via satellite. Both the cockpit voice and flight data recorder are equipped with an underwater pinger/emergency location transmitter.
My crew was experimental test pilot Alain Di Bianca, the aircraft commander, and flight test engineer Alain Delavet. The day was clear but cold at +3˚C with 10kt of wind. At my request, Eurocopter had ballasted the aircraft to a weight of 7,275kg (16,000lb), just 225kg short of the 7.5t maximum.
I asked Di Bianca to show me a standard pilot pre-flight inspection. It was a simple walk around taking just a few minutes, with no requirement to climb up the fuselage.
Di Bianca offered me the right-hand, aircraft commander's seat. Steps and overhead grab handles made entering the cockpit easy. Unlike the many earlier helicopters I have flown, where little thought was put into providing a comfortable seat for the pilot, this example is a pleasure to sit in, with several adjustments available and even an arm rest. The pedals, too, can be moved fore and aft. The pilot sits high with good visibility over the low instrument panel. This would be evident when carrying out a steep approach, which on some helicopters requires the nose to be kicked sideways to allow the pilot to see the touchdown point through the lower side window.
As with the passenger cabin, both the doors and the large windows can be jettisoned to allow speedy egress. Both pilot seats have a five-point harness.
The design is so pilot-friendly that no checklist is required for start-up, although it is available on one of the large 6in x 8in (15cm x 20cm) multi-function displays (MFDs) if required. Even though the engines are large and powerful, they can be started using internal battery power. Part of the pre-start check was an automatic controls check. During this I saw the collective pitch lever, the stick and pedals all move, another unusual feature.
The cockpit environment is well laid out. Instead of the usual controls, switches and other items on the overhead panel, there is just the rotor brake. In front of the pilot on the instrument panel are two MFDs, one giving all the information I needed to fly: our position in space; where we were going; attitude in terms of height, speed, altitude, rate of climb and descent; power being used in the form of main rotor pitch; the all important rotor RPM and limits; and the fuel level. Limitations such as for speed and power were embedded on the presentations.
There is a small box at the bottom of the display showing warnings. A major alert such as low fuel will be in red and is accompanied by a spoken warning. A less serious situation such as an open door will bring up an amber warning and a gong noise. A white warning gives just information, such as approaching a limit. The final item is in green and gives an equipment status such as the external ground-station charging door being left open. This suggests to the pilot that the ground unit, which cannot be seen from the cockpit, is still connected and needs to be released before the helicopter moves. Before taxiing, this panel should be blank. The pilots can bring up additional information on this one screen such as weather radar and TCAS.
Another MDF sits alongside, on which the pilots can bring up whatever information suits them: for example, aircraft systems, checklists or weather radar. The aim is to do away with paperwork in the cockpit. There is a large space between the four MFDs, allowing the operator to incorporate whatever other information is required for their particular task. The centre console is well designed and keeps compatible systems grouped together.
After a logical flow across the instrument panel and centre console and an automatic test of all the systems, we were ready for start-up. Fuel switch on, move the FADEC (full authority digital engine control) switch from stop to idle, then sit back and watch the easy-to-interpret engine instruments display. Then the same for the second engine.
Next, move the switches to flight. Both engine starts were slow and cool. For a quick start, such as for an emergency SAR flight, both start selectors can be moved to the on position at the same time. The engines will then start in quick succession. The dual-channel FADECs are the latest technology. Failure of one is automatically managed by the other, so there is no need for manual throttles, says Eurocopter.
Checking that there were no warnings, the brakes were off and the nose-wheel lock released, we were ready to go. The autopilot holds the cyclic stick in position, so to taxi, I just raised the collective lever, thereby controlling the speed, and steered using the pedals.
The aim of the flight was to test the whole flight envelope including taxiing, hover manoeuvres, flight and maximum speed (Vne).
My take-off and hover were uneventful and easy to perform, with few control inputs required. We left Marseille Provence airport - immediately adjacent to Eurocopter's Marignane factory - and I flew the helicopter manually, albeit with all the flight management systems engaged. There was no need to use the pedals during turns to keep the aircraft balanced, as the flight control systems dealt with this task.
Although Di Bianca set a cruise speed of 160kt (296km/h) on the autopilot, the system would not allow this since it would have used more than the maximum continuous power, instead topping out at 150kt, the EC175's normal cruise speed. However, at lower weights this increases to 160kt. Vibration levels, often the bugbear of any helicopter, were benign, and noise levels, too, were unremarkable, even with my headset removed.
The autopilot is a big feature, allowing the pilot to programme the whole flight from take-off to landing, allowing a hands-off flight, while he concentrates on other tasks. We demonstrated this with an automatic, hands-off hover at 3,000ft (914m). While in this manoeuvre the pedals can be used to turn the helicopter onto any required heading. I subsequently pushed the go-around button on the stick and the autopilot accelerated the aircraft to the single-engine safety speed, raised the nose and climbed.
We went to 4,000ft to explore the Vne, which was now down from 175kt to 171kt. The EC175 can maintain 175kt up to 3,000ft, before falling by 4kt for every additional 1,000ft gained. The nose was lowered and at 171kt we got a voice warning. Remarkably, although the vibration levels had increased a little, they were still more than tolerable, even during 35˚ turns at this speed. Speaking of which, the autopilot prevents a turn greater than that at this velocity.
Certification requires test pilots to fly the aircraft at Vne+10% and Di Bianca and his crew have taken it up to 195kt without encountering any handling or other problems. And, even at this speed, vibration levels were relatively insignificant, he says.
The single-engine training mode was selected during high-speed cruise. This gave all the cockpit indications of reverting to one engine - an actual momentary rotor speed drop from 100% to 98%, then an instant recovery back to 100%. Power indications showed 30min maximum power on the remaining engine. In reality, to protect the life of the engines, this presentation is fabricated and we were actually using the two engines, both beneath maximum continuous power. The autopilot slowed us down to 130kt so as not to exceed maximum single-engine continuous power. The engines have three single-engine power levels: 30s; 2min; and maximum continuous.
A steep, level turn to my right showed excellent visibility around the thin door post. In some helicopters this can limit one's view into the turn. Not so in the EC175.
One of the advantages of flying with experimental test pilots is that they have already explored all the "no go" areas that we mere mortals cannot. Unless, of course, they are flying with us.
Take vortex ring/settling with power, for example. It's a phenomenon that has caught out some pilots who, upon leaving training school, forget about it. Three conditions apply: low forward speed below about 20kt; a rate of descent sometimes as low as 300ft/min; and quite a lot of power applied - the sort of situation that can occur on a poorly executed approach to the hover, say. The main rotor is subject to severe turbulence, destroying a lot of the lift, and the helicopter accelerates down. Vibrations can be severe with side-to-side yawing.
At this point, pilots can make the mistake of pulling in more collective pitch, but this aggravates the situation, and, in the worst case, the whole main rotor can stall. There is very little chance of recovery by this stage.
Some manufacturers do not explore this condition and, equally, some helicopters do not display the symptoms. So I was curious about the EC175.
At a safe height, Di Bianca hovered us downwind and allowed the rate of descent to increase. He pulled some power and - hey presto - the aircraft accelerated rapidly down (I last saw a descent rate of 800ft/min), displaying intense vibrations and heading waffling from side to side. He lowered the nose hard down and we flew out of the condition. Pilots should not drop into the trap with all these warning signs in the EC175, and as an added layer of security, the autopilot mode gives some protection against the phenomenon.
At high speed cruise, I invited Di Bianca to bottom the lever quickly, then, after a pause, raise it quickly back to the original power setting, while I checked for rotor speed droop and/or a change of attitude. He lowered the lever so quickly that I felt negative g. However, there was very little rotor RPM change, and nor was there much on the way back up. These modern engines and their control systems react as quickly as a piston engine, which is very comforting to a pilot who gets backed into a corner and suddenly requires a lot of power.
I flew the aircraft "raw" without the autopilot and flight management systems. In this size of helicopter, pilots can be prone to PIO (pilot-induced oscillations). There was no such problem with the EC175 and I would have been happy to fly onto an offshore platform in this condition.
An autorotation at best rate of descent speed of 80kt gives a rate of descent of between 2,000ft/min (10.2m/s) and 2,500ft/min.
We diverted to a nearby satellite airfield to test the EC175's hover qualities. Di Bianca put us onto one engine, using the helicopter's training mode, and aimed for a tiny circle in the middle of the field. Keeping the airspeed just above 35kt until the last moment and a flat approach, we landed on the circle using no more than maximum continuous single-engine power.
I hovered cross and downwind, flew sideways and backwards at high speed and carried out spot turns through 360˚ in both directions. Handling was entirely neutral, in a good way. I handed over control to Di Bianca to take us high speed in all these manoeuvres. At 40kt sideways, there was still plenty of tail-rudder control left. Test pilots achieved 50kt in this direction.
At 50kt backwards, the nose was still up, with plenty of control left. While flying backwards at speeds lower than this or hovering in a strong tailwind, some earlier helicopters tended to suddenly tuck the nose hard down as the main rotor flaps forward, leaving the pilot with a lot of rearward cyclic input with little left to raise it.
This does not happen in the EC175. The speed of rotation in his spot turns was so dramatic, I could feel the sideways g-force, demonstrating the power of the tail rotor. All of these control manoeuvres will give pilots great confidence in the aircraft's ability to sustain heavy weather conditions such as strong tail or crosswinds.
Di Bianca could not show me any tail rotor failure methods since these had not been explored. He says that as a result of the design of the tail rotor and its intended reliability, the chances of failure were extremely remote.
There was no slope to land on, but test flights have planted it on 12˚ up, 10˚ down and 8˚ to the side. These are generous numbers compared with some other helicopters.
We returned to Marseille airport and carried out a hands-off automatic instrument landing system approach. The autopilot can take the aircraft down to 80ft and 60kt. Any pilot should be able to land from this point!
The simple pre-landing checks of undercarriage down and brakes off were carried out. I hover-taxied back to Eurocopter and did a running landing onto the taxiway.
After shutdown, the MFD gave a full flight report, which can be downloaded. It shows any exceedances or other events of interest.
The aircraft and its management is indeed pilot friendly. It has all the safety features, both proactive and reactive, that the industry has developed over the years as a result of their experiences. Passengers will be pleased with the low level of vibration, excellent visibility, comfort and high speed. Operators will appreciate the low maintenance hours required. But time will tell how competitive the direct operating costs will be.