The first flying prototype of the BO 105 light helicopter completed its maiden sortie in 1967, introducing the world to a pioneering hingeless rotor system designed by Ludwig Bölkow. That system became synonymous, not only with the legendary BO 105 but also the BK117, EC145 and H145 that followed. Now, Airbus Helicopters has taken the next evolutionary step.
“We’ve eliminated the rotor head,” Nicolai said, “and installed five blades directly onto the rotor mast. On this size of helicopter, the rotor head typically adds between 700 and 1,200 parts. The D-3 has less than 100 parts, which means 56kg less weight, reduced maintenance and lower cost.” The result is a 150kg increase in the H145’s useful load and improved passenger comfort thanks to a smooth ride.
“The rotor is still rigid but contains no oil or grease. A composite flex control unit inside each blade controls blade movement, with lead and lag dampers installed externally. The result looks similar to the H135 blade but we’ve included a break point where two bolts connect the inner and outer blade. It simplifies our production process and reduces maintenance costs. When a rotor blade is damaged, it’s normally the outer, aerodynamic section that is involved and now this can be detached and replaced without affecting the whole blade. All blades are interchangeable and manufactured to a weight tolerance of +/– 1g, based on a so-called ‘master blade’.”
Aside from changes to the tailplane and forward cross tube for the skid undercarriage to accommodate the new rotor’s vibration frequency, the rotor itself is the primary engineering change between D-2 and D-3. Otherwise, a small software revision smoothly incorporates the D-3’s performance characteristics into the Helionix cockpit avionics that are common with the D-2, although the D-3 also introduces an entirely new connectivity capability.
The wireless airborne communication system (wACS) enables Helionix to communicate wirelessly with a server while the helicopter is on the ground and via LTE when it is in the air. The process enables transfer of key data between helicopter and server, as well as communication and data handling between Helionix and cockpit devices, including iPads containing navigation, weather or mission data. LTE internet connectivity is also available to cockpit and cabin devices.
D-3 delivered
Some 326 D-2s have been delivered. In 2019, the operational H145 fleet accumulated 85,800 flying hours, a figure of little obvious significance until Nicolai explained that the 1,400-strong H135 fleet flew 375,000 hours over a similar period. Clearly, H145 utilisation is high and the aircraft work hard. With 4,400hr behind it by 31 August 2020, the high-time H145 is a UK-based, ex-HEMS airframe.
Until the third quarter of 2021, D-2 and D-3 helicopters will continue down the Donauwörth production line, at which point the final D-2, serial 20360, will mark the end of the four-bladed H145; Nicolai expects to see the aircraft completed in September or October. He anticipates delivery of a further seven D-3s in 2020, with between six and eight machines handed over per month thereafter from a production rate of around 80 helicopters per year.
Considering that more than 300 D-2s had been delivered by 2019, five years after the type’s introduction, the D-3’s achievement of 115 contracted orders by mid-October 2020 is quite remarkable. It also means that a customer ordering a D-3 in December 2020 is likely to have to wait until spring 2022 for delivery.
Or perhaps not, or at least not entirely. Airbus is also offering a D-3 retrofit for the D-2, a prospect that has already tempted operators into placing more than 80 orders.
The initial retrofit installation, for Rega, Swiss Air-Rescue, began at Donauwörth late in October. However, parts are sold as a kit and any approved Part 145 maintenance organisation will be able to complete the work in future. “We’re doing the retrofit together with Rega’s technicians,” Nicolai said, “in order to verify its content and ensure our service bulletin (the document that accompanies the upgrade) is fully accurate. Essentially, we’re refining the process with our first customer.” Ultimately, the upgrade is expected to take 250 man hours if completed as part of an 800hr inspection.
Launching the new model and D-3 upgrade while still building the D-2 might have been a challenge at the best of times. However, with Covid-19 impacting operators and suppliers, and Airbus Helicopters’ staff, Nicolai admitted: “The orders are very positive but providing all the components we need for production and the retrofit kits in the current situation is stressing our logistics system.” Nonetheless, Airbus Helicopters announced delivery of the first production D-3 on 30 September 2020. Given the H145’s HEMS legacy, it is fitting that the airframe went to the Norwegian Air Ambulance Foundation (see next feature) .
Airbus Helicopters
Proven capability
The H145 is classed as a light twin-engined helicopter. However ‘light’ should not be confused with limited. The cabin comfortably seats eight passengers behind the one- or two-pilot crew, or as many as ten in high-density configuration. However, the H145 is the tool of choice for special missions – Nicolai likened it to a Swiss Army knife – and regularly flies with heavy role equipment rather than a cabin full of passengers. Useful load is therefore more relevant to many of its real world operators.
“The BK117D-3 is a 3.8-tonne machine at maximum take-off weight,” Nicolai highlighted. “Empty weight is 1.9 tonnes, which means we’ve achieved a 1:1 ratio between empty weight and useful load. I think it may be the only helicopter on the market with that ratio. It comes through the use of technology and lightweight materials, including composites and carbon fibre. Essentially, you can load in as much fuel, equipment and as many passengers as the aircraft weighs.”
Main rotor diameter is reduced by 0.2m with the five-bladed unit, a saving Nicolai termed ‘negligible’ compared to the D-2 for pilots landing a D-3 in a confined space. Otherwise, the aircraft is towards the large end of the HEMS scale, yet sufficiently compact to make it a machine of choice. The ability to land in a city centre pocket park, parking lot or even on a traffic roundabout is especially prized for crews delivering critical healthcare.
Less obviously, the five blades of the D-3 may be folded to an ‘all-back’ position, reducing overall length compared to the D-2, where two blades fold forward and two aft. The H145 is popular with superyacht owners and the D-3 is more easily housed in the small hangar spaces of the better-equipped vessels.
When it comes to performance, in the urban environment or in the field, the H145 has always impressed, especially under hot-and-high conditions. Airbus proved the point with a recent trip to Aconcagua, landing the D-3 on the mountain at 22,840ft. Nicolai explained that while it was a first for a light-twin helicopter, the feat was also within the D-2’s reach. He said, “Here in the UK, even loaded to 3.8 tonnes, the aircraft will do a Cat A vertical take-off with no problems.”
As the D-3 enters service, it will commonly do so alongside existing D-2s. Operating variants of the same type can generate headaches in terms of differences in tools, technician training and spares holding. However, Nicolai confirmed: “Except for the rotor system and extra payload, there’s no difference. The aircraft are technically almost identical, with the same maintenance schedules and requirements.”
Five-star experience
Ralf Nicolai said that, for him, the biggest takeaway from experiencing the D-3 in flight is the smoothness of the ride. Offering the chance to fly in the demonstrator aircraft, Airbus provided the opportunity to test his claim.
Light though it may be, on walking up to it, the H145 does not seem like a small helicopter at all. Climbing into the back requires a reasonable reach up onto the skid step and then on into the cabin.
The result is a high seating position that combines with an exceptional view through the huge cabin window.
Aside from the two cockpit seats and pair of passenger seats bolted to the cabin floor, D-HADW was relatively austere inside, as befits its trials and demonstrator role. The lack of fittings allowed a real appreciation of its capacity though and the empty cabin is surprisingly large – think good-sized van – and usefully shaped.
We donned headsets, which is usual for helicopter travel, allowing the pilot’s excellent commentary and description of the helicopter’s systems to be heard, as well as shutting out aircraft noise. I exposed an ear soon after take-off to better judge cabin noise levels and, considering there was no sound insulation in the semi-finished cabin, found them surprisingly low.
Hover taxiing us away from the ramp, our pilot established the helicopter in a low hover, ready to demonstrate Helionix’s ability to deliver training modes. A simulated single-engine failure created no drama at all, just a slight dip towards the ‘failed’ engine before the aircraft adjusted power automatically and recovered. Later, an automatic descent into another very low-level hover, initiated when we were already some distance out from the airfield, also impressed, although not as much as the power demonstrated as we climbed out in a simulated helipad take-off profile.
Pockets of turbulence in the air around Oxford made the flight a little bumpy at times. Besides that, the flight was remarkably smooth. Your author has no previous H145 experience but understands that HEMS veterans have been impressed. Someone unfamiliar with helicopter flying would definitely notice the vibration; I found it comparable to the ACH130 Aston Martin Edition, a luxurious single-engined machine, although not as smooth as the Sikorsky S-76D. That is not an entirely just comparison though, since the US type boasts a highly capable vibration suppression system, while the D-3 has none at all. Indeed, the D-2’s vibration suppression system is removed as part of the D-3 retrofit, which makes its smooth ride all the more impressive.
Airbus Helicopters