FLIGHT TEST: Eurocopter EC225 - Puma repowered

With the dual digital autopilot programmed to intercept the instrument landing system at Marseilles International airport at a 150° angle to the localiser and at high speed, my Eurocopter EC225 overshot the localiser once, slightly, and then captured it. It flew us down at 145kt (270km/h) as programmed, levelled us out at 80ft (25m) and continued down the centre line of the runway.

We could have programmed it to come to the hover. But instead, I pressed the "go around" button on the collective lever and off we went.

That is an illustration of the performance of the EC225. The medium-weight (11t), high-performance helicopter belonging to the Super Puma/Cougar family first flew in November 2000 and Flight International tested a prototype in February 2004. Since then, there have been several changes. While the basic Super Puma fuselage remains the same, the EC225 and its military version, the EC725, have resulted in a helicopter with considerable technological enhancements and much improved performance.

© Patrick Penna This Eurocopter EC225 is pictured flying over the Mediterranean, near Marseilles

More than 650 rotorcraft in this family have been sold and over 3 million hours flown. Sales of the EC225 are mostly to the civil market at a ratio of about 2:1. There are 122 aircraft in the fleet, plus 50 for the Brazilian military on order. Eurocopter listens to the operators and tries to satisfy all their requirements.

One of the biggest changes is the five-bladed main rotor, instead of the Puma's four. This enhances performance considerably. The blades are of composite materials and I noted the different shape, particularly at the tips. The Spheriflex composite rotor hub has no bearings to lubricate and maintain.

The helicopter's nearest competitor is the Sikorsky S-92, which Flight International also tested in January 2003.

Seating arrangements in the spacious cabin - although the cabin height is only 1.45m - vary from high-density 28 seats to a standard 19 crashworthy seats. There is an 8-12 seat VIP version, with toilet and cabin attendant, that has attracted the attention of several heads of state, says Eurocopter.

The 19 seats are offset to accommodate larger passengers more comfortably. They are attached to a reinforced floor and can be removed rapidly to convert the aircraft for freight. There are 15 tie-down points and provision for an on-board fuel tank.

The search and rescue configuration has a dry and wet cabin floor. So when you bring on board a casualty that has been pulled out of the sea, he/she is deposited initially on the "wet" floor to avoid spreading salt water over other sensitive areas. A typical example of Eurocopter's attention to detail.

SEARCH AND RESCUE

The aircraft I flew was configured for search and rescue, for which the EC225 is ideally suited with its high speed, powerful engines, excellent performance and long range. There is also an emergency medical services version.

Eurocopter has put a lot of thought and design features into the various configurations, so the aircraft has equipment, procedures and safety of the highest standard. For example, our test aircraft had a unique winchman station at the door. The winchman can fly the aircraft up to 20kt in any direction, with inputs monitored by the pilots. If the winchman overcontrols - and this was demonstrated on the flight by Christophe Skorlic, our flight engineer, by quickly stirring the winchman's cyclic control stick - the aircraft system damps down the actual aircraft movement.

There are many technical advancements on the EC225 compared with previous models of the Super Puma/Cougar family. These include modular design of mechanical components, the use of composite materials that offer strength with lower weight, modern avionics, an all-glass cockpit with large LCD multifunction displays, a vehicle monitoring system that can show the pilot everything needed about the aircraft systems, and an extremely competent automatic flight control system.

© T Rostang/Eurocopter  The all-glass cockpit is equipped with large LCD multifunction displays

The pilot has more of a monitoring role than actually handling the aircraft, as I was to find out. The new-generation Turbomeca Makila 2A1 engines give lots of power with maximum safety due to the fully redundant dual full authority digital engine controls and a back-up system in the unlikely event of both FADECs failing.

If that happens the power on both engines will not freeze at the point of failure and should be adequate to take you back to base. An engine change takes about 30min, says Eurocopter. The aircraft can be equipped with a full de-icing system, including the tail rotor, with no icing restrictions.

With the optional extra cold weather kit, the aircraft can be operated in temperatures as low as -45°C (-49°F). This is a major step forward, although the Russians have been doing this for years for their operations in Siberia.

The helicopter is so well designed that it can be flown by a single pilot in visual meteorological conditions. Otherwise two pilots and, if necessary, a cabin attendant and/or flight engineer are required.

A maximum gross take-off weight of 11,000kg (5,000lb) and an empty weight of 5,280kg gives a payload of 5,720kg. This includes crew, fuel and passengers/freight. With full fuel at 2,017kg, this allows 3,712kg payload, more than enough. The external sling load maximum is 4,750kg. Sling work allows an additional 200kg on the 11,000kg MGTOW.

I asked my pilot, Jacques Larra, an experimental test pilot, to do a standard pilot pre-flight inspection. It was thorough, but quick. No climbing up steps to check levels and the like. He opened the rear tail boom baggage compartment. This is large enough to contain the bags of 19 passengers.

ENDURANCE

The sponsons are multipurpose and contain energy absorbing (self sealing) fuel tanks. There are fittings for quick fit external pod fuel tanks on both sides of the fuselage thus increasing the range and endurance even further. Because it is a SAR aircraft, there are a bunch of downward pointing lights on the aircraft belly to illuminate the area below, plus other lights to highlight the dual winches area. The main rotor blades can be folded.

© T Rostang/Eurocopter  The reinforced cabin floor can accommodate freight and stretchers for the EMS mode

The cockpit is user friendly. The attention to detail is such that Eurocopter has drawn a black line down the side of the fuselage under the pilot's door to show where the left leg goes on the way down to meet with the step.

There is plenty of room for pilots to stow their on-board equipment, although charts and plates are not required since the aircraft system contains everything a pilot needs to conduct a flight. The seats are comfortable with a full harness and even two armrests, a nice touch. The seat can be adjusted for height and reach, as can the pedals.

After a thorough cockpit familiarisation session from Larra, flight engineer Skorlic turned on the fuel valves and pumps and selected "start" on both engine switches. We sat back and watched. Each engine started in turn and took the rotor to flying speed.

The starts were cool and gentle. Larra pressed the "test all" button, which the systems did, and we were ready to go within 3min. This is a major achievement for such a sophisticated aircraft and ideal for search and rescue when you need to get going quickly.

Eurocopter's experience in pilot-helicopter interface technology and ergonomics is embodied in the display system. The predominant instrument panel display is the large, multifunction four 6 x 8in (150 x 200mm) LCDs that give the pilot all the knowledge about the flight that is needed - where the aircraft is in space in terms of airspeed, altitude, both baralt and radalt, attitude, rate of climb and descent, where the pilot wants to go and the limits of airspeed and engine power, how much power is being used, and, most importantly, how much more is available.

Even though I had not done the full training course, I was easily able to interpret the presentations. The LCDs can display whatever other information the crew requires - a full route display for example. In the unlikely event of a full display failure (as happened to us in the Tiger) there is a "get you home" single instrument hat shows main rotor pitch, airspeed and attitude and compass heading.

When in autopilot, just like a modern fixed-wing aircraft, the automatic flight control system will not allow exceedences of the flight envelope. Larra tried to exceed the VNE during our flight, but it would not let us. It also stopped us at 100ft when diving down to achieve the VNE of 175kt. This is excellent protection and shows the attention to detail to provide a safe vehicle.

This VNE is approved up to a density altitude of 5,000ft, which is remarkable for any helicopter considering the problems of retreating blade stall, reverse flow over the retreating blade and the compressibility effects on the tips of the advancing rotor blade - although the rotor speed is low at 275rpm compared with the 300rpm-plus of other helicopters.

The engines and their FADEC management system are impressive. They deliver enough power to be able to climb on one engine at MGTOW at 5,000ft at 400ft/min, a comforting thought for the pilots (and passengers). The transmission, which can often be a limiting factor with powerful engines, is also capable of accepting even more power than the engines provide, a refreshing change from older helicopter designs. FADEC always keeps the power within the gearbox limitations.

We came to the hover on the main runway at Marseilles International airport and I pressed the "go around" button on my cyclic stick. The aircraft flew us to our first waypoint at the speed and height that Larra had inserted. He deliberately took us over some high towers. The warning system declared loudly, several times "caution, obstacle! caution, obstacle!".

The primary LCD showed a horizontal white line which crossed through the indicated airspeed, attitude indicator, rate of climb and descent indicator, baralt and radalt. This indicated that all the parameters of flight were being observed, within limits and that we were in a stable flight condition.

We were light at only just over 9,000kg compared with a MGTOW of 11,000kg. We cruised at between 140kt and 145kt although by using maximum continuous power we could have cruised at 151kt. At maximum gross weight the EC225/725 will cruise at 141kt with a fuel burn of only about 670kg/h. This is fast for any helicopter and efficient in terms of fuel flow. The rate of climb on both engines at maximum gross weight is in excess of 1,000ft/min. Range with standard tanks is 830km (450nm) and with the extra internal tank 935km.

Endurance with standard fuel tanks is just over 4h and with the extra tanks more than 5h, a useful addition when on an SAR mission, for example. There is even more endurance with the on-board fuel tank, on a ferry flight for example.

I was able to change our pre-selected height and speed using the trim buttons on the cyclic stick and collective lever. In the high-speed cruise, Skorlic selected one engine inoperative training mode on the simple overhead engine management panel. This gave us all the sensations of a real engine failure but used only maximum continuous power on the good engine instead of the 30s emergency power in the event of a real failure. This is to protect the life of the engine.

The "failed" engine sat at ground idle, ready to come into action. I saw the rotor rpm droop from 100% to 95% then slowly recover to about 98%. The on-board system then started the countdown and, after 30s, I selected the next lower 2min power setting by pressing a button on my stick - and so on, to maximum continuous power. In the event of a real engine failure, all the pilot has to do is press a button when prompted.

Since this was a SAR equipped aircraft we did a simulated mission. The aircraft flew us to the search area and fully automatically set up a search pattern. There is a choice of patterns. The pattern came up on one of the LCDs. As the search progressed, I was invited to select the hover position as we flew over the "casualty" by pressing one button and selecting the hover height. The aircraft immediately left the search pattern and came to an offset hover near the supposed casualty and into wind.

The wind speed and direction was shown on the LCD and offset so that the winchman can see the person/s below and also to avoid exposing him/her to downwash. The helicopter can be programmed to follow automatically a moving target such as a boat.

While in the hover, our flight engineer gave us an engine failure. I pressed the "go around" button on the lever. The aircraft nose dropped, we lost a little height during the acceleration before we started to go uphill.

Larra selected the VNE of 175kt. There was little increase in vibration. Turns did not affect this. The aircraft dove down to achieve it. He tried to exceed 175kt, but the flight envelope protection system would not allow it. For certification purposes, the aircraft has to be taken to VNE + 10% with no adverse properties. The EC225 has been taken to 210kt with no adverse effects, says Eurocopter. A comforting result for the crew. As we neared the ground in the dive, the autopilot levelled us off at 150ft with an aural "warning, terrain! warning terrain!".

© T Rostang/Eurocopter  Flight engineer Christophe Skorlic (left), pilot Jacques Larra (centre) and Peter Gray

Skorlic failed the number one hydraulic system. Handling the aircraft was still easy, only the lever needed slightly more effort. Nothing else changed. All the automatic systems were then taken out and I flew the aircraft raw. The cyclic stick was a bit stiff and I suffered from some slight "pilot induced oscillations", which is a well-known event in such sophisticated aircraft, but I felt that, after some practice, I would be confident enough to fly on instruments and to carry out a precision landing, such as on to an offshore platform - or hand over control to the co-pilot.

I handed over control to Larra and invited him to demonstrate the aircraft's agility. There is no published limit on angle of bank (unlike another manufacturer's combat helicopter that I tested - 60°!) He carried out sustained 90° turns at high speed, pulling more than 2g. The warning system did not like this and called "bank angle! bank angle!"

During the subsequent manoeuvres, I felt the negative g as the nose was pushed hard over to the vertical. The stall turn/wing over, also from a vertical nose-up position, was graceful, with plenty of tail rotor control and finished with a vertical dive.

CONCLUSIONS

Eurocopter has put a lot of expertise into the design of the EC225. It is truly multi-role. Although it has complex systems, it is very user friendly. There is a lot of redundancy in the major systems and a lot of protection. It is just like a modern fixed-wing airliner, where the pilot programs the flight and then sits back and monitors it.

The automatics do not allow the flight envelope to be exceeded. The high speed, high power available and excellent performance is a major step forward in the helicopter world. The ratio of flight time to maintenance is variable. I got several interpretations, from less than 1h to 4h.

Source: Flight International