Flight International first test-flew the H135 in 1998 – when it was still known as the EC135 and manufactured by Eurocopter – so I was curious to see what improvements have been made since.
Our invite from Airbus Helicopters was to fly the latest Helionix-equipped variant at its Donauwörth factory in Germany.
One of the biggest changes for the current P3/T3-standard helicopter from earlier iterations is the increase in maximum take-off weight (MTOW), from 2,720kg (5,600lb) to the present 2,980kg.
The flight-test aircraft was fully loaded to this figure, although Airbus Helicopters went even further, putting in another 20kg of fuel to take account of time spent on the ground receiving a through briefing from chief experimental test pilot Alexander Neuhaus.
This ensured that when we pulled up into our first hover, we were at 2,980kg – a nice touch. No doubt operators will be encouraged to do likewise to get maximum range and endurance for their flights.
Our aircraft was a prototype to test various systems and equipment, so there were no passenger seats to try, but as with most all-rounders, there are a variety of interiors available. The standard passenger transport layout comes with five rear and two cockpit seats.
The H135 will be capable of carrying an underslung load of 1,400kg and internal configurations can be changed from one role to another in about 10min, the manufacturer says.
Airbus Helicopters has accumulated 300h of flight testing on the new Helionix system and, at the time of writing, certification was imminent ahead of first delivery next year.
Neuhaus ran through the limitations section in the as-yet-unpublished flight manual, which show that the maximum all-up weight of 2,980kg can be maintained to quite hot and high conditions before being restricted. The outside ground effect and inside ground effect hover weight ceilings are also high, allowing the operator great flexibility, especially in hot climates.
The aircraft is cleared up to 20,000ft, which is impressive considering the thin air at that altitude. It can hover at up to 16,000ft in ground effect and operate in outside air temperatures from -35°C (-31°F) to ISA +39°C, up to a maximum of +50°C.
The basic payload available with full fuel plus pilot is 780kg. Standard fuel tanks give a total of 560kg. Endurance with no reserves is about 3.4h, but additional fuel tanks are available as an option.
Although the flight manual forbids all aerobatic manoeuvres, loads from -0.5g up to +2g at maximum aircraft weight have been demonstrated by the test pilots, running up to 3.5g at lighter weights – close to the 4g I have pulled in a combat/attack helicopter.
These g levels are undoubtedly sustainable due to the bearingless, rigid rotor system. The design requires little maintenance, has few moving parts and provides long-life rotor blades and low drag levels.
The H135 can be started and stopped in winds up to 50kt (93km/h), a rare attribute for a helicopter. These characteristics will undoubtedly give pilots confidence that they can, if need be, indulge in some vigorous handling to recover, say, from a potentially hazardous situation. In addition, the rotor also helps landing on slopes: the H135 will take 14° sideways on, 12° upslope and 8° downslope. The main rotor blades are 10cm longer than those on the previous P2/T2 iteration and also incorporate an increased twist.
Another advantage of this modern rotor is the swift recovery from vortex ring state/settling with power. This is a phenomenon peculiar to helicopters when a high rate of descent with little forward speed causes the airflow over the main rotor to be disturbed enough to, in extreme cases, cause loss of control. The H135 can be quickly flown out of this condition, says Neuhaus, by moving the cyclic stick forward.
Although there are some wind speed restrictions in some sectors, the H135 can be hovered and landed in all directions. This is useful for search and rescue, offshore and other operations where the pilot may not have any choice. Because it can be started in relatively high winds it is good for search and rescue operations when the helicopter has to go, no matter what the weather conditions.
While the aircraft cannot be flown with no hydraulics for the pilot’s controls, the two systems are fully redundant, says Neuhaus, so the loss of both is very unlikely.
The other unlikely loss of both systems is with the engines. Neuhaus says Airbus Helicopters has not required engines-out landings to be performed by its test pilots, as a double failure is considered a remote possibility.
While we did not carry out an autorotation during our flight, Neuhaus says the average rate of descent for the H135 is 2,200ft/min. This is fairly high for a helicopter of its size, but could be useful if the pilot needs to get down quickly for some reason.
The H135’s engines – either the Pratt & Whitney Canada PW206BB or the Safran Helicopter Engines Arrius 2B2+ – are the same as the earlier version, but the full-authority digital engine control (FADEC) management has been adjusted. My test aircraft was fitted with the French-built turboshafts.
The aircraft is equipped with an ice detector, but flight in icing conditions is prohibited. Western helicopter manufacturers have not yet caught up with the Russians, who manage to operate theirs in fairly severe icing.
Airbus Helicopters has tried hard to make the H135 environment-friendly by reducing its noise signature, cutting airframe and other sources of drag so as to require less power, adding more efficient engines, dropping empty weight and other measures, such as lowering the rotor speed in certain conditions thanks to the modified FADEC.
As well as the optional traffic collision avoidance system (TCAS), there is a helicopter terrain avoidance, awareness and warning system (HTAWS), which alerts the pilot if the aircraft is getting too close to an obstruction. If, say, carrying out a mountain rescue close to a cliff, the HTAWS can be muted, but only for 5min.
The never-exceed speed (Vne) is the same as the earlier model: 150kt. It is calculated automatically in flight and the pilot warned if it is exceeded. As usual, the test pilots have taken the aircraft to Vne +10%. The H135 is quite benign at 165kt, says Neuhaus, even at maximum weight. A Vne short red line is displayed on the airspeed strip for the pilot to see.
Airbus Helicopters has computerised many tasks. This includes the pre-flight authorisation and acceptance. I went with Neuhaus to accept the aircraft, which he did by just offering his card to a computer screen. If the aircraft has not been prepared and signed for by the technician, the system will not accept the pilot’s input – a clever but simple safety feature. If on an operation with no engineer, the system can be modified for the pilot to pre-flight the aircraft and accept it.
Our density altitude for the flight was a mere 500ft with only about 3kt of wind. Visibility was good, the cloud base high. I followed Neuhaus round his pre-flight inspection. No panels are opened, essential oil and other levels are evident and it takes just a few minutes. I noted the wire strike protection at the front and the wide sliding passenger doors which close totally flush. Litters can be loaded easily through these or the two rear clamshell doors.
Neuhaus pointed out the modified fenestron shrouded tail rotor, which is high enough to allow the loading of litters, baggage and freight through the rear clamshell doors with rotors running.
Another safety feature is that the main gearbox has a dry-run capability of at least 25min, which should give enough time to land somewhere in the unlikely event of total loss of oil. The belly and undercarriage are crash resistant, and the fuel system is designed to survive a heavy or crash landing without spillage.
The floor is level all the way to the cockpit. The panel dividing the cabin from the rear bay can be removed quickly to provide a voluminous storage area. It has numerous tie-down rings and is stressed for 600kg/m². The Helionix version allows the rear baggage bay to be removed to give additional floor space.
Experimental flight test engineer Jurgen Steiner accompanied us on the flight and was very helpful explaining some of the design features.
I climbed easily into the right-hand seat with its five-point harness. All the seats will be crash resistant and have shoulder harnesses with an automatic locking system and headrests to help prevent whiplash injuries. The pilot’s seat and tail rotor pedals can be adjusted to allow full access to all the cockpit equipment and displays. This is important since the aircraft, like its predecessor, will be certified for single pilot instrument flight rule (IFR) conditions. The left-hand cockpit seat can be turned 180° for a systems operator.
The instrument panel is of the latest Airbus Helicopters design and completely computerised. It belongs to the same Helionix family as found on the H145 and H175. It can provide whatever information the pilot selects. The outstanding feature is the single 15.5cm x 20.5cm (6in x 8in) panel in front of the pilot which contains all the information required to operate the aircraft: attitude, heading, speed, rate of climb/descent, route, altitude, power, terrain and collision avoidance, for example.
This makes flying it much easier than in other aircraft where the pilot has to continually scan through various instruments. The pilot can bring up whatever is required on to the screen, and there are no dials or needles.
All presentations are colour coded – green for normal, amber means caution, pilot awareness and subsequent response, white requires pilot awareness and may require pilot response, and red is for getting the pilot’s attention and immediate response.
Every limit is associated with an audio cue. This is good for a pilot who has his head out of the cockpit for, say long-line underslung operations. There are no temperature and pressure gauges on the display. These parameters are monitored discretely and brought to the pilot’s attention only if there is an anomaly.
Both the cyclic stick and the collective lever have enough buttons on them for the pilot to be able to conduct the whole flight without removing their hands from them. The exception is when the aircraft is flown by the four-axis autopilot: it is then operated with hands and feet off all the controls.
In among the screens is the standby attitude indicator. In the event of a total loss of all the displays, this small instrument (5cm x 9cm) has enough information for the pilot to continue to fly, approach and land safely. It shows attitude, airspeed and height/altitude. It has its own battery supply, so is independent from the main systems.
All-round visibility is good. I was to take particular advantage of this when we went vertically down on to the landing spot from 200ft.
Unlike some other similar-sized helicopters I have flown, there is plenty of storage space for the various articles that we pilots like to take on board, plus the essential manuals.
The aircraft is fully equipped with all the latest aids and communications equipment. Switches and other equipment on the overhead panel are, thankfully, kept to a minimum and are easily reached from the pilot’s seat. Vital systems have backup or redundancy, thus providing a high level of safety of operations. This is especially important and relevant for single-pilot IFR flights.
Neuhaus went logically through the cockpit to set it up for engines start. He did it from memory using a simple flow pattern and took just a few minutes. He started both engines in quick succession by moving two switches and sitting back to observe and monitor. If in a hurry, such as for a rescue mission, the aircraft can be made ready to fly within about 2min. Once all the automatic pre-flight checks have been done, the pilot is presented with a green “all systems go” light, another nice touch.
My first hover was easy, requiring very little input from me. A glance at the power needle showed that we had plenty of power in hand at this maximum all-up weight. Likewise when we hovered out of ground effect. Handling during sideways, backwards and spot turns in both directions was similarly benign.
I invited Neuhaus to take over control and carry out these manoeuvres at high speed while following him through on the controls. He went sideways at 30kt in both directions and I noted that there was still pedal available at this speed. Rearwards at 30kt showed no tendency for the nose to suddenly drop as in some other helicopters I have flown; this can not only be disconcerting when close to the ground, but can also be hazardous.
I did not time Neuhaus’s 360° spot turns, but they were fast. There was still some pedal availability in both directions, but more importantly in recovery to the hover, when a bootfull is required.
I glanced at the power indication during all of this and found it easy to interpret. It changed colours as power was increased. Maximum power available was easily seen. The pilot does not need to memorise any numbers: it is all done with colours and presentations. We did not get anywhere near maximums during these extreme manoeuvres at maximum weight.
We climbed up to cruise altitude and did some, for me, reasonably tight turns in both directions. I invited Neuhaus to go steeper at this high weight. At 60° in both directions, there were no signs of any aerodynamic distress.
To give pilots realistic engine-failure practice in some helicopters, you have to use full single-engine power, but this reduces the life of the engine. The modern helicopters I have test flown now have a training mode, selectable on the H135 by pressing a single button.
Once done, the engine indications immediately went to a realistic single-engine presentation, with the only exception that they were highlighted with a T in a triangle. Our right hand engine – the “good” one – showed full power.
An automatic countdown started going from yellow to red when the full-power time limit was approaching. This was accompanied by real rotor speed droop, which I restored by lowering the collective lever slightly. If it droops more than 12%, as yet another safety feature, the “failed” engine power will be restored automatically. In reality, to protect the life of the engine, no more than maximum continuous power is used. Another single click restored us to normal twin-engine configuration.
To complete our flight, Neuhaus demonstrated the many hands- and feet-off automatic pilot characteristics. The autopilot has four axes – pitch, roll, yaw and collective. The pilot can adjust any of the attitude or flight modes (pitch, roll, yaw, heading, rate of descent/climb) by use of a single button. If weather conditions are so bad that the aircraft cannot be flown safely, using this autopilot should get him/her out of trouble. Likewise, if the pilot gets into an excessively unstable condition, two clicks will cause the aircraft to revert to straight and level.
Neuhaus then demonstrated auto-hover and the ability to tweak it gently left, right, backwards or heading change. Ideal for search and rescue missions when recovering someone down below, in the sea, say. Similarly, hover height can be adjusted. This was highlighted at the end of our final automatic approach back to base.
If the pilot has his/her head out of the cockpit and a malfunction or other warning pops up, they are alerted by sound. They can then return to the cockpit and press a button to bring up the message: another well thought-out safety feature.
To complete our flight, Neuhaus set up a hands- and feet-off automatic instrument approach back to the H circle at the Airbus Helicopters base. The choice of approach glide slope is up to 10° for non-precision and up to 6° for a precision glide slope such as ILS. These generous limits take full advantage of a helicopter’s capabilities. The pilot can select any parameters for acquisition of the final glide slope – direction of capture, height, speed, rate of descent and the like. The whole profile is presented on the pilot’s screen. The aircraft will automatically level off at 50ft after a precision approach such as an ILS, or 100ft for non-precision.
Because there are some high trees on the instrument approach to Donauwörth, Neuhaus selected a 10° glide slope. The autopilot followed all of the parameters set up. These were seen clearly on the pilot’s screen. The aircraft flew us down, hands and feet off, to a 200ft hover over the H. Neuhaus then wound us down to 3ft and invited me to take control and land.
The shut-down, like the start-up, was logical and easy, despite the many sophisticated systems involved. Any serious limitation deviations or mechanical issues are recorded and can be downloaded.
The overall impression is that although technically the aircraft is complex, it is extremely pilot-friendly to operate, has many safety features and, in most cases, more than enough power to carry out demanding tasks, such as a high-altitude rescue.
Passengers, no doubt, will enjoy the comfort, with good outside visibility, low noise and a smooth, fast ride.
Purchase price is from €4 million ($4.4 million) for the fully equipped basic aircraft to €6 million for more specialist configurations, such as law enforcement.