Peter Gray/YEOVIL, UK and BRINDISI, ITALY
Later this year, EH Industries, the Agusta/GKN Westland joint venture, will deliver the first EH101 for a commercial customer - the Tokyo Metropolitan Police - marking the 30-seat helicopter's debut on the civil market.
The EH101 was conceived from the outset to combine the roles of naval anti-submarine, military and civil utility, and commercial passenger helicopter in a single airframe. The result is a large and complex machine with three engines, multiple loadpaths and redundant controls, which its manufacturers claim sets new standards for helicopter safety and operability.
The protracted development programme has not been without its problems, but with its recent selection for Canada's 15-aircraft search-and-rescue requirement, the EH101 is making its presence felt in the international helicopter marketplace. Flight International was invited to evaluate the civil-standard EH101.
Jeremy Tracy, Westland's deputy chief test pilot, accompanied me throughout a programme which included 2h in the simulator at Yeovil in the UK, then a tour of the Agusta factory at Brindisi in Italy, followed by a jumpseat ride in one of two civil-standard EH101s undergoing a 6,000 flying hour programme, half at Brindisi and half on the North Sea, to establish the life and reliability of components and evaluate other aspects of operating the EH101. This was followed by an opportunity to flight-test a civil-standard pre-production aircraft.
MULTIFUNCTION MACHINE
The Royal Navy's requirement for a Westland Sea King replacement emerged in the mid-1970s, but the EH101 design did not begin to take shape until the early 1980s. Extensive market research showed that a medium lift, multifunction, machine was required which could satisfy not only the Navy's anti-submarine role, but other military missions and civilian operations such as offshore support, search and rescue and corporate transport.
The helicopter had to be safe, agile, rugged, cost effective, offer high utilisation and be easy to maintain, have a long service life and be able to withstand the electronic emissions that ships generate. A tall order, but this was how this flexible helicopter was born. The only major difference between the variants' airframes is the provision or not of a loading ramp at the back.
Westland chose a European partner, Agusta, to help share the programme costs, contribute research and development expertise, and give a wider potential customer base. Agusta test pilots fly regularly with Westland crews, and suggested changes or modifications are agreed with both parties, with costs shared.
To satisfy the several potential customer requirements, both military and civil, the aircraft has been designed with built-in redundancy in critical areas, ballistic protection, simplicity of operation and good handling characteristics. Specialist aviation psychologists, pilot seat manufacturers and other experts assisted in the design of safe and user-friendly equipment and procedures.
Would it all show? Would the three engines give excellent one engine-out power availability and performance? Would a failure of a generator, automatic flight control system or hydraulic pump cause any performance or handling degradation? I was about to find out.
SIX-AXIS SIMULATOR
Westland's EH101 simulator has full six-axis motion and a dusk visual system. The operator can induce as many malfunctions as you wish. Tracy went through the cockpit equipment, starting at the overhead panel.
This contains all the usual switches to manage lights, anti-icing, heating, hydraulics, electrics, fire extinguishers, fuel and the rotor brake. Additional controls are for the auxiliary power unit (APU) - a compact, light, but useful gas turbine providing pneumatic engine start and driving a generator and hydraulic pump. The APU has its own fire detection and automatic extinguisher systems and will shut itself down if it detects trouble. There is also a ground test panel, switches for the two avionics cooling fans and flotation bags, and the three power available levers, or "engine speed selects".
There are a lot of switches on this overhead panel and, while all are in reach of even the shortest pilot, some are quite difficult to read. I had to twist my neck and stretch my head well back to see most of the switches, some of which were too close to my eyes for my liking.
Given the constraints of the size and shape of the cockpit and the many systems involved, not a lot can be done about this. The shape and direction of movement of the more important switches has been varied and the less frequently used ones are at the back of the panel.
The instrument panel is dominated by six full colour, high resolution, cathode-ray-tube displays: two in front of the captain presenting flight instruments, engine, rotor and other information essential to conducting the flight; another pair in front of the co-pilot giving the same or similar information depending on what he has selected; and two in the centre of the instrument panel presenting whatever other information is requested, such as engine speeds and temperatures, rotor rpm, fuel distribution, temperatures, pressures, electrical system status and advisory, caution and warning messages.
The warning system is "smart" and well thought out. For example, in the case of more than one malfunction, that with the highest priority will always dominate. Serious events such as low or high rotor speed, engine failure or fire, and undercarriage up are also accompanied by an audio warning - a gong and/or simulated female voice.
Once the pilot has identified the nature of the alarm, he cancels the caution/warning light. This brings up the relevant page for that system on one of the central displays. There is no automatic call-up - the pilot has to initiate it. He thus has total control of the situation and is not at the mercy of a computer system. Similarly, there is no electronic checklist, either automatic or manual, to take up screen space. The good old handheld list is used.
Pilots will be pleased to know that there are no temperature and pressure instruments. Monitoring is automatic and the pilot is warned if something is wrong. In this case, unless the pilot is using the display for something else, the correct page will be brought up automatically. When we tried malfunctions, I found the system user-friendly and workable. The design philosophy is one of the "quiet" cockpit - if a system is on and functioning properly, nothing is shown to the pilot.
Only when certain systems are off or have malfunctioned is the pilot warned.
The centre console has all the usual controls for radios and navigation aids, undercarriage controls, parking brake and so on, plus two flight and maintenance management system (FMS) control display units. The FMS is used for programming the automatic flight control systems (AFCS) - there are two dual redundant systems - the autopilot, the navigation equipment and the built-in monitoring and self test functions. There is a slot for uploading the flight plan (civilian) or mission plan (military).
The FMS can store 100 routes, senses the location of navigation beacons, records exceedances, faults and other maintenance data (all of which can be downloaded), and provides information on aircraft performance and equipment status. The latter function tells you if there is a no-go situation. The radios and navigation aids and some other systems self test and advise the pilot if something is wrong. The FMS will not bring up any radio or navigation aid that is unserviceable. All this is particularly useful before an instrument flight - on the EH101, there is no need to test all the aids one at a time before departure.
STRAIGHT FORWARD START-UP
After my familiarisation we decided to go "flying". The start up sequence is straightforward and follows a flow pattern, so we did it without the checklist. The systems self-check and tell you if something is wrong.
Tracy showed me how to start the APU using the internal battery. I did a full and free check of the controls using the APU's hydraulic pump, and he talked me through starting the first of the three 1,430kW (1,920shp) General Electric T700/CT7-6s (Rolls-Royce Turboméca RTM322s are also available). We followed the progress of the start on one of the instrument displays. The other two engines were started, by which time all the important systems had self-checked, the advisory, caution and warning area was clear of all messages and we were ready. When a quick departure is required, the aircraft can be prepared for take-off in about 90s.
The visual system on the simulator is limited to dusk scenes only, so most of our flying was performed on instruments. I used the autopilot to get us going, selecting a rate of climb, heading and speed hold, then height hold as we levelled off and sat back to watch.
We then took full advantage of the simulator by asking for malfunctions that are difficult, dangerous or impossible to simulate or perform in the aircraft.
The first of these was an engine fire. The gong sounded, the voice called "fire", the master caution came on and a red button on the overhead speed select illuminated, identifying the culprit. Our engine fire was accompanied by an excessively high turbine temperature, notice of which also came up on the warning display. After cancelling the master caution light, I brought the speed select back to idle then to stopcock and pressed the red light. This activated the fire extinguisher.
We watched the red light for 15s and, when it remained illuminated, I pressed the same button again to activate the reserve extinguisher. There is no danger of selecting and shutting down the wrong engine, which has caused many accidents in the past in other helicopters. This procedure is a well thought-out feature which demonstrates one of the EH101's design philosophies, that of reducing the pilot's workload and giving him a better chance of reacting to the problem and carrying out the correct procedure. While all this was happening, the aircraft was flying on autopilot on the route, height and speed previously selected.
I next examined another engine fire, with an engine failure. We got the additional engine failure warnings - gong, voice, lights, captions.
One of the three main hydraulic systems was then failed. We got an audio alert, and the master caution/warning light illuminated. After identifying the failure, I cancelled the master caution light which brought up the secondary systems page on one of the centre screens. There was an excellent graphic display of what was happening. Failure of any one of the hydraulic systems produces no difference in handling qualities and there is no need to reduce speed, as in most other helicopters. This illustrates another of the design policies: that a first failure (apart from a confirmed fire or tailrotor drive failure) should require no immediate pilot action. If he does nothing, the aircraft should continue to operate safely.
FAILURE SIMULATED
We next simulated a generator failure. There are three engine-driven generators, plus one on the APU. The voice announced "caution" and the caution/warning light illuminated. I cancelled the light and checked the electrical page. We reset the generator and it came back on line. A subsequent double generator failure caused us to fire up the APU and get its generator on line. There was no loss of electrical services.
With the anti-icing switched off we asked for icing conditions. The caution system immediately warned us of our situation. There is a sophisticated ice detection system - no more peering out at ice probes. There is an option to have full de-icing and anti-icing on the main and tail rotors as well as the usual engine and windscreen services. With this installed, there is automatic ice detection and switching on of blade heating. This allows for operation in severe icing conditions.
I used the autopilot to take us back to the airfield, and Tracy coupled us to the instrument landing system (ILS) at 140kt (260km/h). The aircraft captured it neatly and drove us down. All we had to do was select the wheels down and ensure the brakes were off. At the bottom of the glideslope, with no action from us, the aircraft reduced our speed to 65kt and levelled out at 70ft (21m) over the centreline. On Tracy's suggestion, I pressed the go-around button. The EH101 immediately climbed straight ahead at 500ft/min (2.54m/s - a good one-engine-out rate), keeping the aircraft level. It will continue doing this until the pilot intervenes.
Tracy invited me to pickle the autopilot, fly the aircraft manually and perform a manual ILS approach. It says a lot for the aircraft and its systems that, although I was rusty at procedural instrument flying, I was able to intercept the ILS quite easily and accurately, and fly us down keeping well within limits, apart from one excursion from the glideslope because of my misreading of the rate of climb and descent indicator (RCDI). I misread it because I was unused to the presentation - a vertical line with two cursors, one showing the rate have selected with the autopilot, the other the actual rate. Designers tried to fit in a circular presentation, with a needle, but there is insufficient space.
One of the main reasons for my (partial) success with the ILS approach is that all the information a pilot needs is on one big screen in front of him - torque, localiser, glideslope, barometric altitude (baralt), radar altimeter (radalt), RCDI, attitude, heading, slip and even wind speed and direction. The display is uncluttered, easy to read and interpret.
Tracy had reduced us to two engines and on the subsequent go-around I was overenthusiastic with the collective pitch lever and exceeded the normal torque limits. The caution system immediately brought this to our attention. There is a transient overtorque limit of 20s to get you out of a difficult situation, where no mechanical harm is done, and an ultimate torque restriction to protect the transmission.
Should you suffer a failure of all three signal generators that power the displays, both pilots have a set of conventional get-you-home instruments alongside the main screens and additional information at the bottom centre of the instrument panel.
Finally, I asked for a sudden engine failure at 150kt, the certificated never-exceed speed, at maximum operating weight. I intended to take no action. We lost 2% rotor rpm, but stayed well within the generous limits. Our speed reduced to 145kt. The two remaining engines went to a slight overtorque condition, but within the allowable 20s limit I lowered the collective lever slightly and we continued on our way.
At the end of this 2h session, I was easily able to interpret the various presentations, manage the systems and deal with malfunctions, proving the user friendliness of the cockpit.
BRINDISI TOUR
In Brindisi, I saw the aircraft stripped bare. We saw the main airframe with its multiple loadpath stringers and how, in the event of a heavy landing, the fuselage is designed to crush from the bottom up, thus protecting its occupants.
I examined the heavy duty landing gear, designed to land on moving, heaving vessels, but also to impose no more stress on the deck than does a Sikorsky S-61. The EH101 can land on any deck approved for the smaller S-61.
For offshore operations, flotation bags are neatly stowed within the fuselage and liferafts in the sponsons. The flotation bags can be deployed using a button on the pilots' collective lever, but normal deployment is through immersion switches. A huge side-fuselage sliding door can be opened in flight at speeds up to 100kt and every window can be jettisoned. Every passenger row (there is three-abreast seating for 30 passengers in the commercial version of the aircraft) has a jettisonable window.
Four standard, crash-resistant fuel cells are located under the floor and there is space for a fifth. This fifth tank, plus an increase in the maximum weight from the normal 14,600kg to 15,500kg, for ferry flights or military operations for example, will increase the range to 1,850km (1,000nm). The tanks can be refilled by pressure, gravity, air-to-air or ship-to-aircraft refuelling.
The main gearbox is mounted on four attachment points with eight struts to provide the required damage tolerance and redundancy. It has a secondary lubrication systems in case the main one fails. All the other gearboxes, including the two tailrotor boxes, have a 30min run-dry capability. Running aft from the main gearbox is a damage tolerant driveshaft for the tailrotor. Tracy showed me the components of the EH101's unique active vibration control system.
The main rotor head needs no lubrication, is damage tolerant and its life is dependant only on its condition. The five main rotor blades, with their remarkable looking tips, are each attached to the hub by two spindles - redundancy where it counts. The distinctive tips help increase blade lift and efficiency, reduce the compressibility effects on the advancing blades and delay stalling of the retreating blades - all of which limit how fast you can fly a helicopter. The blades are of composite construction, are damage tolerant and lifed on condition only. They are stiff and so can be spun up in high winds.
Tracy pointed out the redundancy on the driveshafts to the three hydraulic pumps, and the emergency hydraulic accumulator. This aircraft can suffer a double hydraulic system failure and still continue to fly safely.
Site manager Harold Cunningham assured me that, when in service, the number of maintenance hours required for every flight hour will be in the region of 3.5. As many components as possible will be lifed on condition only. The only exception is likely to be the tailrotor hub.
EXPERIENCE BUILDING
While at Brindisi, I joined a flight which simulated naval operations - climb out, turns, return to the hover for 5min, then the same again for 2h 30min. The aircraft was flown by a Bristow Helicopters pilot, Graham Lee, and a UK Civil Aviation Authority examiner, Mike Webber, who were building experience on the type before taking up examiner and inspector duties.
The cockpit is spacious, with adequate storage for clipboards and manuals and space on the instrument panel in front of each pilot in which to hang an instrument approach plate.
The weather was bright and sunny. Each pilot has a visor which runs on a rail above one's head, so no matter where the sun is you can block its glare. There are also curtains to cover the large overhead panels.
Webber fired up the APU and switched on the two fans behind the instrument panel which keep the electrics cool. The noise created was significant. The APU is on the opposite side to the passenger door to help protect them from the noise, and production models will have only one, smaller and quieter, cooling fan running at a time. There will also be some head and wall lining - I was in a pre-production aircraft.
During the subsequent flight, I could see how EH101-experienced pilots used the equipment to their best advantage, bringing up or deselecting displays and information as required.
Lee brought up the moving map display on the lower screen, then overlaid the radar image. His minor gripe was the operation of the FMS keyboard, which requires a lot of typing.
Next came the moment I had been waiting for - an opportunity to fly the aircraft. The day was sunny and warm, almost standard atmosphere at sea level with 10kt of wind. The aircraft was at the maximum (civilian) weight of 14,600kg.
Tracy performed a typical pilot's walk-round inspection. It was brief and to the point. There is no need to check fluid levels - the caution system will indicate if any of them are low. He then offered me the right hand captain's seat. Getting into the large seat is easy, as is adjusting the five-point harness. The seat is identical to those used on modern airliners with up/down and fore/aft adjustments. There are two adjustable lumbar supports and armrests, with adjustable rakes.
The pedals, too, have fore and aft adjustment, so it is impossible not to find a comfortable position with all controls to hand. The all-round visibility, including over the nose (no long radome) and upwards, is excellent. There is a small side window at foot level.
The collective lever is conventional, with all the usual controls, plus a go-around button, autopilot release and flotation-bag release. The lever stays where you put it with a trigger nicely placed underneath to release the built-in friction lock. The cyclic stick is conventional, with the addition of a nosewheel steering control.
HOVER MANOEUVRES
After start-up I was ready for my first hover. I did not feel the aircraft leave the ground, nor did I on the subsequent lift-offs. I attribute this to the design of the undercarriage.
My hover was steady, with a left-wing low, nose high attitude (we had a slight aft centre of gravity), and required few control inputs from me to keep it steady. It was easy to see how much power we were using - just under 90% torque on each engine. It was also easy to see how much we had available - up to a maximum continuous 100%, with up to 106% available for 5min, plus a generous overtorque allowance. Hence the aircraft's good performance when hot, high and heavy.
While still at maximum weight, I wanted to explore one-engine-out performance in the hover, so Tracy snapped one engine back to ground idle. We stayed exactly where we were. The two remaining engines went above the maximum contingency power, which is limited to 2min 30s, but stayed well within the transient overtorque allowed for 12s. This level of performance will be reassuring to those crews engaged in low level hover work at high weights and temperatures.
The main rotor goes to negative pitch when the collective lever is lowered fully, providing 50kN (11,000lb) of downward thrust. This is for operations on moving decks.
Taxiing technique is different than in other helicopters - all turns are performed, not by using the pedals, but with one's thumb on a left/right switch on the cyclic. There is also a facility for selecting 90° on the nosewheel, which allows the helicopter to turn on the spot. I prefer this method of taxiing to the conventional ones of pedals, brakes and cyclic, especially with a strong crosswind.
Sideways and backwards flight was uneventful. The flight manual allows 40kt, but in reality the aircraft will go much quicker - 50kt is not a problem. Similarly, spot turns were benign - the maximum rate of turn is 45°/s.
While still heavy, we left Brindisi and set up a cruise at 150kt. We used well below maximum continuous power. For military or maybe search and rescue and aeromedical operations, there is dash speed limit of 167kt, which the aircraft will achieve quite comfortably. The EH101 has been dived to 185kt in tests. Vibration levels at 150kt were benign. I selected the height hold and made speed changes using the coolie-hat switch on the cyclic to reposition the bug on the airspeed indicator. There is a similar trim device on the collective lever to adjust altitude. The aircraft behaved immaculately with no overshoots of speed or altitude. Not having to use pedal in the turns above 60kt is another joy.
At 140kt, Tracy switched off the active vibration control. There was a marked increase in vibration levels, but they were still acceptable.
There are two Category A public transport take-off techniques available - short field and helipad. We tried the former while still heavy. The technique is easy - lift to 10ft, nose down 10¹ and add 10% torque. It would have been convenient to be able to move the aircraft symbol on the attitude indicator on to the artificial horizon line before rotation, but this feature is not available.
The critical decision point (CDP) is 40ft. After a demonstration, Tracy snapped an engine back to ground idle at CDP, giving me the choice of continuing the take-off or landing back. I continued. With no loss of height or rpm, the aircraft continued to accelerate to the best climbing speed, building up a healthy rate of climb. Next time Tracy "failed" an engine before CDP, so I was committed to reject the take-off and land back. No drama here either; I remembered to level the aircraft just before touch-down so as not to bang the tail.
INDUCED DISCOMFORT
Next Tracy invited me to switch off the stability augmentation while in a high speed cruise. I immediately went into a pilot-induced oscillation, mostly in the rolling plane. Nothing severe, but uncomfortable. I relaxed my grip on the cyclic, trying not to move the controls, but I could not stop it. The ever-vigilant Tracy noticed that I was moving the pedals as well as overcontrolling on the cyclic. After a while I invited him to take control and he shortly had us straight and level again, handing back control to me. I decided to try a turn. It worked well, with no overcontrolling. I rolled out and hoped for the best - we stayed nicely balanced, straight and level.
Next, with the stabilisation restored, I did some steep turns, after pulling back the overhead curtain. Vibration levels were still benign, pilot inputs low and the visibility excellent throughout the turn. I invited Tracy to take control and throw the aircraft around. He carried out some very spirited wing-overs.
Back to 150kt, and I asked Tracy to snap one engine back. When we did this in the simulator we lost 2% rotor speed. Now there was no loss. Nothing else happened of any significance. I next raised and lowered the collective quite brutally. Our rotor rpm varied by no more than 2%, demonstrating good engine governors. There was no change in attitude. To demonstrate the proficiency of the AFCS, I raised the nose quite high, applied some bank and let go of the cyclic - the aircraft returned gently, but immediately, to the original attitude with no overshoots: similarly for a pitch down.
Entry into manual engine throttle is achieved by unlatching the speed select lever, taking it quickly forward to the stop and back into the normal range. Subsequent management is straightforward and does not require many pilot inputs. The control system helps by adjusting the fuel flow when the lever is moved. A single pilot should be able to cope down to the hover and landing.
On the way back to the airfield, we picked up all the offshore vessels on the radar, the range of which can reduced to 0.45km.
We wanted to carry out a coupled ILS approach, but the glideslope was unavailable. Instead, we performed an aggressive coupled join on to the localiser, intercepting at nearly 90° at 150kt. Tracy was expecting three overshoots, but in fact I noted only two - an impressive join.
We rejoined the circuit at Brindisi and came to a 100ft hover, easily readable on the radalt display, followed by a vertical descent to the ground. The outside visibility was not so good and the lower window was of little use. Another window is to be installed further back on production aircraft. We went back up and, once established in the hover, I rotated gently forward with no increase of power, watching the radalt. We lost only 5ft - showing the efficiency of the main rotor.
RECOVERY WITHOUT DRAMA
We autorotated at the minimum rate of descent speed of 75kt. Control of rotor rpm was easy, the rate of descent was 2,500ft/min - quite acceptable for such a helicopter (I have experienced 4,000ft/min in other types). The flare at the bottom had bite and powered recovery to the hover was without drama.
We went off again and, to convince myself, I rejoined the pattern with the stabilisation off. I performed an accurate, wobble-free approach to the hover, landed and taxied to the refuelling point. Shutdown was straightforward.
All the design criteria were proven to me. The EH101's safety features, user-friendliness and comfort will appeal to the pilots and the aircraft's occupants. Its agility, cost effectiveness and ease of maintenance will appeal to the operators. The aircraft is a big, vice free, pussy cat.
Source: Flight International