Eurocopter has drawn on operators' experience to produce a much-improved version of its Super Puma, the EC225
Based on the experience of a large number of operators of the Super Puma Mk1 and 2, and the military Cougar, Eurocopter has developed the EC225 medium twin-turbine helicopter and its military version, the EC725. The knowledge gained has resulted in a helicopter with considerable technological enhancements and much improved performance.
The EC225 first flew in November 2000. European certification is set for the third quarter and US certification will follow. This is a medium-sized helicopter - maximum take-off weight for both the civilian and military versions is 10,400kg (22,930lb) with internal load, 11,200kg with external load (maximum load on the hook will be 5,000kg). The aircraft can carry 24 passengers and will be certificated for single-pilot visual flight rules and two-pilot instrument flight rules operations.
The EC225 will be able to carry a heavier payload further and faster than the Super Puma Mk2. The main differences from the Mk2 are a new main rotor, uprated engines, reinforced main gearbox to absorb the extra power, and new integrated displays for the crew. The basic Super Puma structure remains unchanged. The nearest competitor is the Sikorsky S-92.
Our aircraft was the prototype, in military colours. It has flown over 300h, and Eurocopter expects to fly at least another 80h before completing the certification test programme. The EC225 has five main-rotor blades, where the Super Puma Mk2 has four, with a new blade profile and multibox structure. All the blades can be de-iced if required. The new rotor design increases performance and reduces vibration. The Spheriflex composite rotor hub has no bearings, for minimum maintenance.
Two Turbomeca Makila 2A engines are mounted in front of the main gearbox. This engine has a new compressor and operates at higher temperatures than its predecessor, producing 14% more take-off power - 2,100shp (1,570kW). This, plus the new rotor, allows more payload. With an empty weight for an offshore model of 6,300kg, full fuel without the centre tank of 2,085kg, two pilots and a cabin attendant, the EC225 has 2,373kg of payload available. With the centre fuel tank full, this becomes 2,117kg.
Estimated fuel consumption is 600kg/h. We used 1,245kg on our 2h flight, which was not a "normal" mission. The EC725 will be able to take on an extra 800kg of fuel in addition to the centre tank. This will be jettisonable. Eurocopter is quoting a range of 875km (475nm) without the centre tank. The company is still experimenting with where to put all the baggage.
Engine back-up
The Makila 2A has dual-channel full authority digital engine controls (FADEC) and also a back-up system to cover the unlikely event of both FADECs failing. If that happens, the power settings on both engines will freeze at the point of failure, which should be adequate to get home. Any subsequent movement of the collective pitch lever will result in slight rotor RPM (NR) changes, but the limits are enough to contain this. The engines are modular, making maintenance and inspection easier.
The main gearbox has been reinforced to take the extra power and increase in maximum take-off weight. The opportunity was taken to introduce modern technology on the bevel gears and optimise the gear teeth profiles. There is an emergency internal spray system for the hot parts should the oil system fail. This will allow flight for at least 30min with no oil - enough to get somewhere safe to land.
After the walk-around, I installed myself in the right-hand seat, with Eurocopter experimental test pilot Hervé Jammayrac in the left. The seats are designed for the military, but are comfortable, with armrests and the usual four-way adjustment. This aircraft has five-point pilot harnesses. Production aircraft may have four or five.
Eurocopter says the passenger seats will be crash-resistant, with upper torso restraint. They will also be slightly offset to allow more shoulder room - a nice touch. The floor, fuel system and undercarriage are also crash-resistant. Eurocopter performed extensive tests on an earlier cabin to prove that the main gearbox will not penetrate the cabin in the event of a crash. There will be plenty of tie-down points on the floor for freight, with quick seat removal.
In the cockpit, the main change from previous Super Pumas is the displays. The cathode-ray tubes in the Mk2 have been replaced with four 150 x 205mm (6 x 8in) multifunction liquid-crystal displays and two centre 100 x 125mm LCDs for displaying rotor parameters and other information. LCDs require much less space than CRTs, do not need noisy ventilation, are far more reliable and easier to read.
Eurocopter's experience in pilot-helicopter interface technology and ergonomics is embodied in the display system. When it came to flying the aircraft, even though I had not received the full training course, I was able to easily interpret the instruments. This equipment is particularly pilot friendly.
The two outboard LCDs serve as the primary flight displays, with a main-rotor pitch indicator to give the pilot some idea of how much power he is pulling. This one display indicates the aircraft's attitude, where it is and where it is going. The pilot no longer needs to scan several instruments to get all this information.
The inboard LCDs can display whatever other information the crew requires - a full route display, for example. Other glass-cockpit helicopters I have flown have some emergency get-home instruments on the top centre of the instrument panel. Scanning such instruments can cause difficulties for either pilot in instrument conditions. The EC225 has a single, small standby instrument with its own independent computer showing main rotor pitch, indicated airspeed and attitude. There is a standby compass overhead. Above each pilot's head is a large red emergency handle. This shuts off fuel, electrics and other systems in the event of a crash.
Into the air
The weather next day was bright, cold - 4°C (39°F) - with a wind gusting to 30kt (55km/h) and a density altitude at take-off of -2,000ft (-610m). My crew was experimental test pilot Didier Guerin, experimental test flight engineer Jean-Pierre Meunier in the jump seat and Bernard Turcat, flight test engineer, in the cabin test location. I took the right-hand aircraft commander's seat. Our take-off weight showed 10,015kg. Using all the usual seat adjustments, I found a comfortable position from where I was able to reach everything, remembering that this aircraft can be flown by one pilot in visual meteorological conditions.
The cockpit doors have an upper window and half a lower window, with another large window by the pedals, making for good all-round visibility. There is a big pocket in each door and space for the operator to fit more stowage receptacles. The aircraft comes with a full avionics suite with many optional extras, especially for the military.
The engine and rotor start procedure was merely fuel and pumps on, rotor brake off - although you can start one engine with the brake on - reach up and select ground or flight idle, sit back and watch the slow, cool start. Turcat had selected flight idle, so when the starter cut out automatically - displayed on the LCD - the rotor continued up to 100%. In a hurry, both engines can be started simultaneously. The parking brake was released and I taxied out to our take-off point on a taxiway at Marignane's international airport.
Feet off
My first hover was steady, easy and uneventful. The power required and power available indications were well presented and easily understood. We had plenty of twin-engine power in hand. After transitioning to forward flight during which the NR automatically reduced from 104% to 100%, we had a high-speed cruise to the grass satellite field 10min away. The ride was pleasant and, after trimming, I took my hands and feet off the controls. There is no need to use the pedals during turns. And you can actually take off with feet off.
I made an approach to the runway threshold and carried out the usual manoeuvres: out-of-wind hovering, landings and take-offs, turns on the spot, sideways and backwards flight. Even in the 30kt blustery wind, the aircraft handled well. High-speed sideways flight into and down wind had us going at 65kt on one occasion. There are no published limits. The aircraft will merely swing gently into wind once the pedal limit is reached. Backwards at 50kt was uneventful. All this shows that you can operate the EC225 in strong winds, such as on offshore platforms, and not run out of control when manoeuvring. The aircraft will be certificated to start in winds up to 65kt.
The limit for turns on the spot is not the amount of control available, but the amount of torque required to do the turn and recover from it. Guerin whizzed the helicopter round at high speed, occasionally entering the take-off power region shown on the LCD. In the hover, he encouraged me to trim the aircraft then remove hands and feet from the controls. The aircraft stayed put, even in the blustery wind. The helicopter can also be trimmed to move in any direction at a constant rate.
Our aircraft had an autohover capability. At 120kt we selected a height on the radar altimeter and selected autohover. The acquisition was smooth and accurate. There are two conveniently located trim wheels on the centre console for making small adjustments to the hover - sideways, backwards, left and right. You can adjust for continuous aircraft movement at a fixed rate, such as when shadowing a vessel during a rescue pick-up, or just move the aircraft and stop it - a nice touch. Where you are and where to hover are shown on the primary flight display. Pressing the go-around button on the lever causes the aircraft to accelerate and climb.
While still relatively heavy, Guerin demonstrated single-engine operations using the FADEC training mode. By selecting an overhead switch on the training panel, one engine drops back suddenly, but stays ready to come in if something goes wrong, and all the instrument indications show the single-engine configuration. The "good" engine was indicated at the 30s power rating, although in reality, so as not to use up valuable life, the engine does not exceed maximum continuous. A 30s countdown on the engine panel begins. The pilot can exceed the time limit if necessary to avoid an accident. Three of these 30s periods are allowed. By pressing another lever button, the engine will decelerate to 2min power and another countdown begins. Lastly, another button reduces power to maximum continuous. It is an excellent system, giving realistic indications and, at the training weight, identical handling characteristics.
Good visibility
We carried out a single-engine approach and, because of our weight and the strong wind, came to a hover. I carried out a very steep approach and found the visibility down and out to be good enough not to have to cock the nose sideways to see the intended target. This was followed by a vertical climb to over 100ft and a descent.
We left the airfield and carried out some upper-air work. Eurocopter has not yet defined Category A take-off profiles. The manufacturer will probably go for a vertical take-off to about 100ft, then rotation, and also a forward transition with a 10° nose-down selection using the trim button. With the amount of engine power available, I would expect critical decision points to occur soon after rotation from the hover and just before landing.
Eurocopter has put a lot of work into making the autopilot user friendly, accurate, versatile and with much redundancy. One of the best I have experienced, it is a true autopilot in the fixed-wing sense in that, as well as providing stabilisation, it can fly the flight plan or mission, intercept an instrument approach, and take you down to the runway at 80ft and slow speed. A pilot would be unfortunate indeed if he could not land safely from there.
Even in the turbulence, our machine did well, holding heading, speed and height accurately. Our planned route with all the waypoints was shown on the left-hand LCD, the path to the first waypoint on the right screen. Sustained turns of 45°, then 60°, were carried out using the autopilot, with no loss of height.
The airspeed vertical strip alongside the attitude indicator on the main LCD had bugs for all the significant speeds such as single-engine safety speed, best rate of climb, and never-exceed speed (VNE). These are computed and presented automatically. The autopilot has several devices to prevent the pilot inadvertently entering a potentially unsafe condition such as exceeding VNE. The pilot has to physically override the autopilot to achieve this.
I pulled maximum continuous power on both engines in straight and level flight and sat back to watch. The weight window showed 9,662kg. Our density altitude was still a minus figure. We got 150kt indicated airspeed, 145kt true. Total fuel flow for both engines was 640kg/h. Vibration levels were benign, as they had been for the rest of the flight. We pulled maximum continuous power, lowered the nose and went to the VNE of 175kt. Vibration levels increased slightly, but remained benign - 30° banks in both directions gave no increase.
For certification, manufacturers have to take any new aircraft to at least VNE +10%. Guerin says the EC225 has been to 210kt (+20%) with no adverse effects. There is no limit on angle of bank, just the occupants' comfort, so Guerin went to a sustained 60° in both directions, then 90°. Visibility round the door pillars was adequate. Indicated airspeed went from 110kt to 70kt.
Back in the cruise at 145kt and weighing 9,550kg, I asked the crew to close one throttle (using the training mode) and do nothing else. NR drooped momentarily from 100% to about 95%, then recovered to 100%. We lost 15kt, but still had 130kt.
Next Guerin demonstrated settling with power/vortex ring state where, in a slow-speed descent, airflow around the main rotor can cause blade stall and loss of control. The EC225 provides good warning with a slight increase in rate of descent and a marked rise in vibration. There was no fishtailing, which is unusual. Provided the pilots recognise these symptoms, the aircraft can be easily flown out of the condition by lowering the nose then increasing the power. I invited Guerin to raise the lever quickly, pause then lower it. There was a slight roll and yaw. NR moved about 5% - all very benign.
Systems deselected
I flew the aircraft with as many of the systems deselected as possible. With no automatic flight control system, the roll axis was more sensitive, but not unpleasantly so. Otherwise there was not much difference in handling characteristics. Eurocopter has introduced electrical servos into the flight controls so that, in the unlikely event of a double hydraulic failure, the pilot can still fly the aircraft safely. Should one hydraulic system fail, the other will easily power the controls. The pilot will experience no difference in handling characteristics.
Guerin demonstrated an autorotation with a flare and power recovery. He had to raise the lever slightly to keep NR at 104%. We were at 9,220kg. Rate of descent was high at 3,000ft/min (15.25m/s) at 104% and 3,500ft/min at 110%. But this is unimportant in a reliable twin-engined helicopter where you expect to be able always to fly safely on only one engine. The flare had bite and the FADECs restored the engines quickly with no overshoot when required.
We finished back at the field on the slope. The aircraft settled easily at 10°, left wheel on. The test pilots have demonstrated 12° nose-up and 8° nose-down slope landings.
We went through other malfunctions such as loss of electrical power and the engine fire drill. There have been several severe helicopter accidents where the crew have got confused and shut down the wrong engine. The system in the EC225 is such that I doubt this could happen.
Eurocopter has installed three anti-vibration units: two in the cabin and one for the cockpit. These can be switched off, so we did. At 60kt, the vibration level increased slightly, but not unpleasantly. It decreased slightly above 60kt, which is unusual.Offshore role
With its speed, high payload, range, excellent single-engine performance and low vibration levels, the EC225 promises to be ideal for offshore operations. Eurocopter already has orders for four aircraft from two major offshore operators CHC and Bristow, with options for two more from Bristow. Two unnamed governments have each ordered a VIP version.
The French air force has ordered 14 EC725s for combat search-and-rescue missions. The digital dual autopilot allows the crew to insert the mission requirements and watch the aircraft fly it, hands and feet off, while they get on with their tasks. The redundancies will enhance safety during such potentially hazardous operations.
A large amount of redundancy has been incorporated into all major systems. Apart from, say, a tailrotor failure or serious engine fire, I can think of no other malfunction that requires an instant response from the crew. They will have the luxury of being able to wait to see what has happened and then take appropriate action, if any is required. These qualities will provide an first class, all-weather search and rescue aircraft. Handling qualities in all regimes, even in strong blustery wind, are excellent.
All potential operators, including their maintenance personnel, should be pleased with this aircraft. Eurocopter has estimated the maintenance to flying hour ratio at about 2:1. There are no confirmed figures yet on direct operating costs.
PETER GRAY / MARIGNANE, FRANCE
Source: Flight International
