First flight may have slipped by around 12 months, but at production sites across Europe components for the Airbus Helicopters Racer high-speed technology demonstrator are beginning to come together.
In early April, the slender nose of the new helicopter was revealed as the three sub-assemblies making up its canopy were joined into a single structure.
While the development has been relatively untroubled, it has not been without its challenges, and has also required a weight-saving drive by the manufacturer.
Clearance for manufacturing was triggered by the conclusion of the critical design review in December 2019. Assuming the coronavirus outbreak does not add significant delay to the programme, then final assembly should begin by mid-year at Airbus Helicopters’ facility in Marignane, France.
“To be precise it is almost all the aircraft which is ready for production but there are some topics that have some delay, although nothing really critical at the moment,” says Brice Makinadjian, Airbus Helicopters’ chief engineer for the Racer.
Part of the EU-funded Clean Sky 2 programme, the Racer – or Rapid and Cost-Effective Rotorcraft, to use its convoluted acronym – should now make its maiden sortie in the fourth quarter of 2021, later than the original 2020 target.
The design builds on research conducted with Airbus Helicopters’ X3 demonstrator in the middle of the last decade, but features V-shaped box-wings for additional lift, twin pusher propellers and technology to allow one of the two engines to be idled – and rapidly restarted – during the cruise.
Given the project’s ambitions from both technical and industrial standpoints, it should probably come as little surprise that the timeline has slipped a little to the right.
The Clean Sky project seeks to foster innovation and grow competencies in companies across the continent, all of which means that the development chain for each programme is more complex than usual.
For the Racer, while Airbus Helicopters is the project lead at the vehicle level, it has 17 core partners and 35 other partners in the effort. Crucially, none of these are selected by the airframer but by the Clean Sky joint undertaking following an open call process.
Some are more familiar to it than others, such as long-time propulsion partner Safran Helicopter Engines, which is supplying twin Aneto-1X powerplants for the technology demonstrator.
There are also consortia of industry and research bodies or academia: Romaero and Romania’s INCAS aerospace institute are building the fuselage, while Magnaghi Aeronautica and Italian aerospace council CIRA are developing the landing gear.
And at the other extreme come businesses never previously involved in aerospace, like German automotive specialists KLK Motorsport and Modell und Formenbau Blasius Gerg, which have teamed as the FastCan consortium to produce the Racer’s canopy.
The time and effort required to manage this multi-headed beast is largely the reason for the programme’s delay, admits Makinadjian.
“There are 50 entities that we have to manage in order to build an aircraft that will fly. This brings a bit of complexity in terms of management and it is probably slowing down a little bit the way we can develop,” he says.
His comments are echoed by Antonello Marino, project officer for the Fast Rotorcraft Innovative Aircraft Demonstrator Platform within the Clean Sky programme. “The major challenge is that it is a programme that is built in a way that is co-ordinated by the leader but receives contributions from a number of complementary grants and partners,” he says.
“That means that a very minor delay at one level may affect the overall plan of the Racer.”
While the majority of the Racer is on track, development of the new gearbox is running late, admits Makinadjian. He stresses that this is not due to “technical issues” but simply trying to align its methodologies with those of co-developer Avio Aero.
“There are many discussions made between specialists to understand each other. Especially in the field of the main gearbox these are taking a bit longer than for other designs,” he says.
However, Makinadjian is at pains to point out that the lateral driveline, a key part of the new transmission, remains on schedule.
Comprised of flexible shafts rotating at 3,000rpm, the drivelines transfer power from the main gearbox down the wings to the lateral gearboxes in order to drive the pusher propellers.
Makinadjian says endurance tests of a flight-representative example of component are ongoing. “We have already produced the shaft – this is a real achievement,” he adds.
When developing the X3, Airbus Helicopters re-used components from other aircraft in its range, such as the fuselage from an AS365 Dauphin.
But Makinadjian says the level of re-use is dramatically lower on the Racer: around 10% of the gearbox components are from previous designs and certain elements of the avionics are drawn from existing helicopters, but the rest is entirely new.
Although for its first flight the Racer will be fitted with a main rotor from an H175 super-medium-twin, Airbus Helicopters intends to swap the blades for those with an “optimised” design at a later stage.
The new blades are being developed as part of a French-funded research project and will not be ready in time for the maiden sortie. While he declines to elaborate on the shape of the new blades, Makinadjian says the “evolution” will take into account “all the experiences we have on the X3 and the design of the Racer.”
One additional capability will also not be used during the early stages of testing: the stop-start function on the Aneto-1X engines.
Explaining the decision, Makinadjian stresses that although the Racer’s development has been informed by the X3 effort, it is “quite a new formula” and as such “we have to take it step by step”.
“Before stopping one engine in flight and having only one remaining I would like to demonstrate the Racer’s formula and the way it is behaving first,” he says.
“We have to measure the formula and every detail of how it is behaving and then introduce any major modification. I am more comfortable if every other parameter is measured and we only have the one to test.”
In addition, budget and resource limitations are also pushing the programme towards sequential rather than parallel testing, he says.
The Racer will weigh in at about 7-8t maximum take-off weight. In comparison, the conventional H160 being developed by Airbus Helicopters carries 12 passengers but is 2t lighter. But the difference in their respective maximum cruise speeds is pronounced: 220kt (407km/h) versus 155kt.
Speed, as Makinadjian points out, comes at a cost; the addition of the box-wing, propellers and specific canopy all add weight to the structure. To achieve the target 220kt cruise speed and have the same weight and capacity as the H160 “is not feasible”.
However, Airbus Helicopters is trying to keep that weight trade-off as “affordable” as possible for any end customer should a programme eventually be launched.
Managing the Racer’s mass is such a crucial factor that Marino says that during the design phase, Airbus Helicopters “was obliged to launch a sort of weight-saving campaign, bringing that closer to the original target.”
This has been achieved through the use of innovative materials and manufacturing processes, he says. For example, the composite-reinforced canopy is some 7% lighter than the original design requirements.
In addition, the “very, very innovative” tail structure, produced by Aernnova of Spain, uses for the first time “very light” primary structural components produced via additive layer manufacturing, alongside external parts made through resin-transfer moulding.
Similar efforts across the helicopter have resulted in an overall weight that is acceptable for a technology demonstrator, says Marino.
Key aims for the around 200h of flight testing planned, lasting around two years, will be to validate the Racer’s performance against the Clean Sky goals – a 220kt cruise speed but with 20% lower emissions of CO2, NOx and noise than current helicopters.
But the airframer will also use the flight-test phase to give “concrete demonstrations” of the helicopter’s utility for current civil and parapublic missions: increasing the area that can be covered during search and rescue operations or cutting the time required for emergency medical services.
Although the Clean Sky programme restricts the development to technology readiness level 6, short of full industrialisation, the mission demonstrations are clearly aimed at gauging the market potential of the technology.
While he stresses it is his opinion, not that of the company, Makinadjian believes that by the middle of the decade Airbus Helicopters will be in a position to see if it makes sense to launch a commercial development programme.
“In five years from now we will definitely have all the parameters to take decisions,” he says.
