Peter Gray/MUNICH
Everything about the Eurocopter Tiger is modern - the design, materials, the technology and even the way it is operated and managed. The rotor head has no hinges to lubricate and is made of composite materials. The main rotor blades are also made from composite materials, and especially at the blade tips, are of modern design. The tail rotor, too, is modern in design and materials. I recognised it as being similar to that of the Aerospatiale Super Puma, but with three blades. It is very powerful, as I was to find out.
All the gear boxes have a dry run capability the main gearbox for 66min. The MTU/Turbomeca/Rolls-Royce 390 engines are prototypes also, so we had to be careful. Visitors like me are not yet allowed to do single engine landings. I did, however, examine a reversion to single engine in the cruise. The engines produce a huge amount of power - 1,160kW (1,550hp) "super emergency power" and 958kW each for takeoffs - yet they weigh only 170kg.
The Tiger, like all the other combat helicopters, has a high power-to-weight ratio. What I found remarkable is that the modern engines can produce the same, or even more power than, their predecessors, but weigh a lot less. Gone are complex axial compressors and their complex variable air-inlet guide vanes, which are fine when everything is well adjusted, but can cause dramatic power losses and other undesirable characteristics when they go wrong.
Instead, with this engine there are two very powerful centrifugal compressors of modern shape, design and materials pouring the power into just a single gas-generator turbine. Their robustness reminded me of operating in primary jungle clearings in South America, where our centrifugal compressors would suck in all sorts of bits and pieces of undergrowth and vegetation and spit them out at the back with no ill-effect. The engineers were convinced that they gave the engine a clean-up on the way through.
After a pre-flight study of the flight manual, and other documents and a long question and answer session with Andrew Warner, Eurocopter's chief test pilot and Tiger project pilot, and Manfred Kaminski, flight-test engineer in charge of the Tiger, I was ready to fly.
WALK AROUND AND START-UP
The weather was fine, with a gentle breeze, plus 7°C air temperature, and a pressure and density altitude of about 2,000ft (600m). I had asked for a heavy aircraft, so Warner chose 5,700kg, which would be a representative weight after taking off at the maximum of 6,000kg with the appropriate weapons and fuel for the job to be done, and arriving in the vicinity of the first target or targets. We spent a long time going round the aircraft. I was aware of the various design philosophies and saw now how they were achieved.
The first of these is "Do Not Be Seen By The Enemy". So there is the very thin fuselage with 1.1m-wide cockpits, the signature-reducing paint, no glare from the large areas of cockpit glass and plexi glass, the infra-red/TV sight right on the top of the main rotor to allow the rest of the helicopter to remain hidden, the diffused engine-exhaust gases, low-radar-signature blades and low overall noise.
Also apparent, were the measures taken to satisfy the second criterion, of any combat helicopter - "If Seen, Do Not Be Hit". Dotted around the fuselage are devices for detecting laser and radar illumination, and alerting the crew. The aircraft's agility, with its limits of +3.5g to -0.5g, also helps it to stay out of trouble.
Another of the design criteria is, "If Hit, Survive The Impact And Stay In The Air". For example, the tail-rotor drive shaft on a commercial aircraft of this size would normally be about 40mm in diameter and of solid metal. The Tiger's horizontal drive shaft is made of aluminium alloy; the inclined drive shaft is made of composites.
If hit, by even a small-calibre round, it will easily shear, giving a severe, often fatal, control problem. On the Tiger the solution, brilliantly simple but effective, is a hollow composite shaft of almost 130mm diameter, through which a round can pass without necessarily fatal damage. The load will pass around the resulting two holes and the shaft will continue to drive the tail rotor. The engines, too, are designed with the same philosophy - that is, in one side, out the other and contain the damage. They are separated however, by an armoured bulkhead to protect the remaining engine after a failure.
Finally, if it is one of those days and a crash is inevitable, the designers and manufacturers have made a real effort to protect the crew. The rearward-sloping main undercarriage legs will contain an enormous amount of vertical speed impact; likewise the aircraft belly and the crew seats. The cockpits are strengthened to protect the crew should the aircraft roll over. Each crew member has a window-jettisoning system, which blows out the appropriate panels on either side. The panels can also be blown out, by an outside rescuer, a nice touch.
The main gearbox and engines have containment, so that components do not penetrate the cockpits, a lethal occurrence with older-generation helicopters. The fuel tank is self-sealing. There are cable-cutters top and bottom, essential for low-level nap-of-the-earth flying. The horizontal stabilizer also serves as a work platform. We noted, too, the good lightning protection, plus the gravity refueling point on one side and the pressure refueling point on the other. The aircraft can be refueled and re-armed in the field in less than 20min by three men.
With all these reassuring factors in mind, I climbed up eagerly into the front cockpit, which is for the pilot. I looked around and liked what I saw. Eurocopter has eliminated as many switches as possible. What remains are just a few on each side panel. The engines are full-authority digitally controlled - that is, fully automatic, so there are no twist-grip throttles or speed-select levers, just a small single management panel on the left-hand console which does it all.
Engine management is straightforward, foolproof and simple. I noted the usual scratch-pad liquid-crystal-display (LCD) screen and associated keys to change, update or enter new information. The instrument panel is dominated by two, 150 x 150mm multi-function displays (MFDs), which show everything that the crew requires, at the appropriate time to operate the aircraft, including navigation information, check lists, emergency procedures, a moving map and weapons information, not only yours, but those coming at you, along with other useful and vital items.
I was impressed by the fuel-contents-versus-range management: the pilot can programme the system for ground speed, track or other parameters and he will then be given the amount of fuel/time remaining to complete a task and other bits of useful fuel information.
MFD presentations can be selected in metric or imperial units. The crew will be alerted automatically of any malfunctions or necessary warnings such as low fuel - orally for most of the malfunctions and warnings, and also visually. One of the MFDs will identify automatically the problem and suggest corrective action. The alerting system is geared to the severity of the problem.
The rest of the cockpit equipment is strategically placed in a logical, sensible fashion, giving a well-designed and functional layout in a fairly confined space. To allow the pilot to look out and fly the aircraft (the most important quality of a combat helicopter), the important systems can all be managed using the devices on the cyclic stick and collective lever. There is a set of standby conventional analogue flight instruments alongside the MFDs in the front cockpit. The small wide-angled mirrors on both sides of both cockpits allow the front crewman to observe the rear one and both to view the rear of the aircraft.
For the flight, I occupied the rear cockpit, designed for the gunner. The aircraft can be flown from either cockpit - the controls are identical. The gunner has access to all the sighting and sensing systems and weapons including the Tiger's primary armament - the TRIGAT fire-and-forget anti-tank missile. The pilot in front can fly everything except the anti-tank weapons, and has access to all the sensors.
For really rapid departure, the crew can get into the cockpit, select "start" on both engines simultaneously, then strap in. By the time they have done this, the engines and rotor are at flying speed, the avionics are self-tested and on-line and you are ready to lift-off - after engaging the automatic flight-control system if you wish.
We, however, did things slowly. The left-hand engine was started, showing benign acceleration and temperature peaks - no drama here. With this running, we were able to use it to give us hydraulic power and full electric to check out all the systems. Full and free movement of the controls was performed using the auxiliary hydraulic pump before the start of the first engine. I noted that the cyclic stick has a relatively small range of movement because there is a large amount of power available to the rotor with only a small amount of cyclic movement. The number-two engine was then fired up, the warning system showing us that everything was on line and serviceable. I pulled up into my first hover.
TAKE-OFF, HOVER AND CRUISE
I deliberately relaxed both arms and feet as we lifted off. There were no surprises, and we came to a neat hover. I noted from the power indicator on the MFD that we had plenty of power in hand. The aircraft is designed to have at least a 17% power margin when hovering out of ground effect.
Warner took over briefly and gave the official photographer some unusual hover attitudes: 20¡ nose down; nose up; 45° left and right back. I resumed control and tried the usual hovering manoeuvres of sideways, backwards and spot turns, with and without the duplex four-channel automatic flight-control system (AFCS), stabilization-augmentation system (SAS) and trim-augmentation computer. The latter is a special handling augmentation system for nap-of-the-earth flying to give better handling at moderate speed.
These manoeuvres were to be repeated later to the aircraft's limits, when we had more space. The message, which came through loud and clear, was of the effects of a rigid four-bladed rotor and 10% equivalent offset hinges. They give an outstandingly stable aircraft, even with all the stabilisation systems off - and there are three levels of automatic stabilisation. The Tiger hovered almost hands-off: I merely held the stick and lever very lightly, did nothing with my feet and just gave the occasional suggestion of a push-pull on the controls. The hover was rock-steady. Vibrations were benign, visibility was superb and I felt comfortable and relaxed.
Eurocopter has made a big effort to provide the crew with a comfortable cockpit. The environment system should deal with most extremes of weather, and the seats are comfortable and adjustable, so that you can see the top line of the instrument panel display (this is important because there are warning lights here) and over the 21° drooped nose. From the rear cockpit, the gunner can see over the occupant of the front cockpit and over the nose.
Best of all, from a handling point of view, is good control, especially with the cyclic stick. This is so important in combat helicopters with the enormity of their combined tasks of staying low, going very fast, identifying the target, firing at it and staying out of harm's way. The cockpit is so designed that I could find a position where I could rest my right forearm on my right thigh and thus achieve extremely accurate handling. The small cyclic movements give vast rotor-control power, allowing precise, but relaxed control of the helicopter.
I pulled maximum continuous power and we shot out of Eurocopter's small operating area and into the cruise. While we were still fairly heavy, I held maximum continuous power to check the speed. We were at 5,000ft pressure altitude, slightly over 5,000ft density altitude in slight turbulence. We got 140kt (260km/h) indicated air speed, 150kt true speed. The brochures say 145kt sea level, so this was quite close. While the Tiger was still quite heavy, I pushed over and went to the published Vne of 160kt. The aircraft specification calls for 160kt for our configuration. The air-to-air and ground-support version goes to 170kt. Given the sophistication of the main-rotor system, I was curious as to how fast Eurocopter had actually flown the Tiger. "Much faster," said Warner. There was a slight increase in the low vibration level as we passed through 150kt, but nothing significant. I rolled left 30°, and snapped over to 30° right again. All the responses were benign. Warner gave me a few system failures so that I could assess the warning systems. Pilot-head failure produced a mild gong and warning lights. I asked for the more serious situation of a generator failure (loss of nearly 50% of electrical power): the warnings were the same, but the MFD showed us the situation automatically. More serious events, such as high/low-rotor RPM, have an even more urgent attention getter.
AUTO ROTATION
Next, we entered auto-rotation with a powered recovery at the bottom. Auto-rotation characteristics are a minor consideration for a combat helicopter, which will rarely be at such a height as to be able to take advantage of it. No test pilot report is complete without one, however. The best rate-of-descent speed of 70kt gave us a rate of descent of 2,600ft/min (13.2m/s), which is to be expected in such a helicopter.
Helicopter performance, like many things, is a compromise between adequate or (better still) more-than-adequate rotor power available to the pilot to do the job, and having a benign rate of descent in auto-rotation. The plus side is that, although Eurocopter has not yet carried out engines-off landings, I strongly suspect that when it does there will be more-than-adequate rotor power available to achieve a successful benign landing.
Having by now got used to interpreting the power parameters on the MFD, I explored the effects on the rotor RPM (NR) on raising and lowering the lever quickly. With a poor system, you can get an unwanted loss of NR just when you need high RPM most.
The readability and interpretation of the MFDs was excellent: the only slight niggle I had was that the engine torque representation did not identify which needle applies to which engine. Warner agreed, and said that he would get it changed.
Flight through very mild turbulent air coming off the snow-capped Alps gave sudden mild attitude disturbances that were easily controlled. I was now flying the aircraft raw with no stability augmentation.
BACK TO LOW LEVEL
Eurocopter has clearance to fly low in this zone, so we dropped down to a large open area to explore the limits of sideways and backwards flight, and spot turns. I was allowed by Warner, to go sideways in each direction to such a speed, as to reach full pedal travel. This resulted in about 60kt, plus or minus 10kt - an impressive demonstration of tail-rotor power and the suppression of other aerodynamic nasties, which can occur at these sideways speeds.
There was a very slight rocking as we went through about 20kt, but nothing significant. Fast back-wards flight (60kt) was benign. Warner says that he has been up to 70kt: his visibility from the front cockpit looking aft is excellent. Fast back-wards flight is not an operationally necessary manoeuvre, but does give the pilot a lot of confidence in the quality of control. The aircraft's specification calls for a 40° heading change after 1s, hence the powerful tail rotor, which gives a rate of turn of 120°/s.
AGILITY AND AEROBATICS
As we climbed up, I gave my five-point harness and chinstrap an extra tug and handed over control to Warner for him to demonstrate the Tiger's agility. Accelerating using maximum continuous power, he got up to 120kt in a steep climb and pushed it over the top into a vertical dive. For good measure, he then rolled the Tiger through 180°.
Next came a manoeuvre I have carried out only in an aerobatic fixed-wing aircraft, pointing vertically up until the aircraft stops, kicking it around 180° to point vertically down and then, to demonstrate the rotor power available in this extreme position, do a 180° turn, very impressive. We then did a couple of loops, pulling 2g.
As I followed him through on the controls, I noted that he did not use a lot of cyclic movements, as you would in a fixed-wing aircraft, thus proving the high rotor-control power with only a small cyclic-stick movement. I noted out of the corner of my eye that, as we became inverted, my MFD artificial horizon toppled but, miraculously, as we leveled out the right way up, it was back to normal.
The next demonstration, which shows the rotor-control power available, was coming to the hover at a safe altitude, and whacking the helicopter over to 90° of bank.
Air-to-air combat is in the specification, and Eurocopter has found that in such a role, with the crew concentrating on keeping the other aircraft in sight, you can get into some very unusual attitudes - hence the Tiger's ability in this area. The rigid rotor, as well as, giving superb stability, also gives lots of control power, especially during low or negative g manoeuvres. Recovery from unusual attitudes is not a problem.
NAP OF THE EARTH FLYING
We next explored rapid accelerations and then quick stops from the hover, followed by a low-level run below the treetops. The rotor disc diameter is intentionally small, at 13m (the Bell SuperCobra's is 14.6m and the Atlas Rooivalk's is 15m). The aircraft can therefore be taken through very narrow gaps and is very agile around the 90° bends.
With its mast-mounted sight, the Tiger can hide behind an obstruction, preferably solid, and the hover hold is engaged using the Doppler and radar altimeter. The gunner looks through the sight on top of the mast, and can take the helicopter up so that he can see the target. Only the sight is exposed, the rest of the aircraft remains masked.
He can then take the aircraft back down, sort out the weapons and pop up again to fire them. He can fire four anti-tank weapons in say, 4s - the total exposure time of the aircraft. It would be extremely unlikely that the enemy would see the Tiger. The mast-sight vibrations have been suppressed to within the specified limits.
If the cannon is to be used on a target which is not on the line of flight (it can be pointed at least 90° either side), the resulting powerful kickback is prevented from rocking the aircraft by the automatic flight-control system. This receives signals, before the first round has gone out, of the angle, direction, rate of fire and other parameters to kick the heading of the aircraft to point directly at the target before the first round actually leaves the gun. Hence the powerful tail rotor.
We returned to base and I carried out a steep approach on to the H: visibility from the rear cockpit looked good. Warner also demonstrated a sloping ground landing: the aircraft was not equipped with the appropriate telemetry for this so he could not take it to the specification limit of 12°. The specification also calls for the aircraft to be shut down for up to four days on a 12° slope, so a special braking system has been adopted, to avoid relying on hydraulic brake pressure, which can dissipate.
Finally, we examined a single AC generator failure, followed by a double failure. The warning systems alerted us, although we lost the use of the MFDs. The aircraft was still perfectly flyable, however, using the front cockpit's stand-by instruments. There are two batteries. Shut down, if necessary, can be accomplished in 30s.
CONCLUSIONS
The four basic Tiger criteria of: not being seen; if seen, not being hit; if hit, staying airborne; if a crash is inevitable; to survive it; were proven to me. Other design parameters, such as HOCAS (hands-on cyclic and stick) were also proven, plus the essential ability of being able to fly the aircraft while looking out the whole time, even at night and in bad weather.
With its lightweight, powerful engines and superb flying ability, the Tiger can take full fuel, full air-to-air weaponry and full TRIGAT weaponry and get you to the target and back.
Maximum endurance is 2h 50min, including reserves. Range with the fuel pods is 1,300 km. The aircraft will probably remain unseen and possibly unheard. It is designed to fly in all weathers, except icing conditions, but it has several anti-ice systems, although not on the blades or engines. There is plenty of potential for increasing engine power, or raising weight, speed and other performance criteria. I was impressed with everything I examined.
Source: Flight International
