European airliner manufacturer Airbus is preparing for the imminent start of the assembly of its first A350 XWB flight test aircraft, the company’s latest design, on its final assembly line (FAL) in Toulouse, in the south of France. Subassemblies and other important components have started arriving at the FAL and the final assembly process is expected to start within days. But this aircraft, designated MSN1, will not be the first complete A350XWB airframe. It will be the third.
On May 24, the first complete fuselage of the A350 XWB was rolled out from the fuselage assembly station of the FAL and towed to another FAL station, where it is currently being fitted with its wings, main undercarriage and other components. This first-ever A350 XWB airframe will, however, never fly, but be placed in a special test rig for static fatigue testing.
The second complete airframe will also be for ground testing.
These developments represent significant milestones in the European aircraft manufacturer’s current new technology wide-body airliner programme. The MSN1 is due to make its maiden flight in the first half of next year. In all, there will be five A350 XWB flight test aircraft (Airbus does not use the term prototypes), two of which will be fitted with a complete cabin.
The entry-into-service (EIS) of the launch version of the aeroplane, the A350-900, is scheduled for the middle of 2014 – just two years from now. Airbus’s Customer Services division is already preparing for the EIS of the new aircraft, making use of lessons learnt from the EIS of the A380 Superjumbo. This preparation includes the development of training courses for both operations and maintenance personnel, the writing of technical documentation and the develop- ment of the spares and equipment supply chain organisation.
There are three planned versions – the 314-seat A2350-900, the 270-seat A350-800 and the 350-seat A350-1000, although each would be able to carry more seats in high-density configurations (a high-density A350-1000 would be able to carry 440 passengers, for example). The suffix XWB stands for eXtra Wide Body and was adopted to distinguish this aircraft from the original A350 project – a very different and much less advanced design.
The A350, along with the Boeing 787, which entered revenue service in October, represents not only a new generation of aircraft, but also a new generation of airliner manufacturing technology. The airframes of both aircraft are composed overwhelmingly of composite materials.
The A350 XWB is 53% composites (carbon-fibre-reinforced plastic) by weight – the figure for the 787 is 50% – which, because composites are lighter than metals, means that composites form the bulk of the fuselages and wings and key structural components. The other materials used in the manufacture of the A350 XWB are aluminium and aluminium-lithium alloy (19% by weight), titanium (14%), steel (6%) and ‘miscellaneous’ (8%).
“Airbus certainly does not lack innovative ideas,” pointed out then Airbus CEO Tom Enders in May, addressing international aerospace journalists at the Airbus Innovation Days in Toulouse. (Enders is now CEO of Airbus’s parent group, EADS.)
“This is a company brimming with innovation. We have plenty of contacts with universities – more than 600. And we work with many of our [research] institutions. Innovation is clearly in our DNA. Innovation is one of the four pillars of Airbus.”
Among the research institutions the company works with is South Africa’s Council for Scientific and Industrial Research, which has undertaken studies into the predicted aspects of the A350 XWB’s in-flight performance and characteristics.
Airbus has long been a world leader in the use of composites to manufacture airframe components. The company first employed composites to make secondary structures in the A300B from 1972. Airbus first used composites to make primary structures on the A310, which made its maiden flight in 1982. With the A380, the proportion by weight of composites in the airframe reached 22%.
In the A350 XWB, composites are employed in the fuselage, the wings, the belly fairing, and the empennage (vertical and horizontal tails); aluminium and aluminium-lithium in the fuselage frames, ribs, floor beams and landing gear bays; titanium in the leading gear, pylons, and attachments; and steel mainly in the landing gear.
“We have the world’s most efficient twin-aisle aircraft in the making,” asserted Airbus executive VP and head of strategy and future programmes Christian Scherer.
“In the A350 [XWB], we have [further] developed a lot of our ways of working,” affirmed then Airbus COO (and now CEO) Fabrice Bregier in May.
“Yes, there are contracts [with suppliers], but we try to work beyond the limits of contracts. We will depend more and more on partners. You won’t find a company in this field that is more international than Airbus. We have more than 100 nationalities working for Airbus. We are working with 2 000 suppliers across the world.” One of those suppliers in South Africa’s Aerosud.
“This programme is like a book. Every day we’re writing a new page,” affirmed Airbus executive VP and A350 XWB programme head Didier Evrard. “We have a lot of innovation on this programme – a lot of innovation, [for example], in the cabin design, in its comfort. We’re very much changing the rules everywhere.”
Learning from bitter experience on the A380 programme, which suffered expensive delays because different units of Airbus had used different design software, the A350 programme has, from the start, used a single design software tool not only for all Airbus divisions but also for all suppliers involved in the programme. Extensive modelling was carried out on the design of the aircraft, its components and subcomponents. There is a digital mock-up of the entire aircraft, which amounts to a huge store of data which is shared with all the A350 XWB risk-sharing partners. This, for example, allowed a fully three-dimensional design of the complete electrical system of the aircraft.
The modelling was followed by tests of components and subcomponents. Demon-strator units of major structures were built and tested, including a fuselage barrel section demonstrator in Toulouse and two wing box (that is, main wing structure) demonstrators in Broughton, in the UK. There is a landing gear test rig in Filton, in the UK, a test cabin layout in Hamburg, in Germany, an ‘iron bird’ rig for all A350 XWB systems in Toulouse and an air systems integration bench in Mexicali, Mexico, among other test and development facilities. Demonstrator units of subcom- ponents have also been built and tested, such as the cargo hold substructure, which was built and then subjected to crash tests.
Then there was more, and more refined, modelling. “There was very strong cooperation between modelling and testing,” reported Evrard. Thanks to increasing powerful systems and software, computer models are getting bigger and more detailed. Airbus now has a computer model of the entire A350 XWB airframe and its test rig. This means that engineers can model static tests as well as run the actual tests on the real airframe. All this has been done to reduce risk as much as possible.
Meanwhile, new buildings for the production or assembly of large A350 XWB components have been erected in France, Germany, Spain and the UK, and even in the US. Worldwide, some 5 000 people are currently working on the A350 XWB programme.
The A350 XWB fuselage is composed of a nose section, three barrel sections and a tail section. The nose section is of metallic construction, in part because of the threat of bird strikes (metal parts are easy to repair) and in part because it makes the integration of certain avionics systems easier. The nose section includes a crew escape hatch in the roof.
All the other sections are overwhelmingly made of composites. Unlike the 787, whose fuselage barrel sections are each made in one piece, the A350 XWB’s barrel sections are each composed of four panels – top, bottom and two sides. To form a barrel section, these four panels are fastened to circular frames and longtitudinal ribs. The fasteners used to do this are called frame clips and are manufactured by Aerosud. A laser tracking system ensures that the panels are exactly positioned for the assembly of the barrel sections.
The use of panels allows Airbus to make longer barrel sections. This, in turn, means that the number of orbit joints – the circumferential joints which link the barrel sections – is reduced and that these joints are kept away from the centre wing box and out of the highly stressed region of the fuselage. The tail section of the fuselage is a single composite unit. The vertical tail plane started fatigue testing before the first fuselage was assembled.
The wings have composite skins and aluminium-lithium ribs. “It’s a brand-new assembly system we’ve developed at Filton,” highlighted Evrard. “It’s automated, with complex machinery. This is necessary for the long term.”
The wing is built in a horizontal position and not – as with all previous Airbus aircraft – in a vertical one. The materials used in the construction of the A350 XWB wing are different from those used in the A380 wing and the construction processes are also different. So the company is not expecting a repeat of the A380 wing rib feet cracking problem.
“The experience of the A380 is being taken into account,” he assured. The wing track cans – which contain the machinery which extends and retracts the wing flaps – are also Aerosud products.
The components and subcomponents for the A350 XWB are manufactured at Airbus risk-sharing partner and supplier plants across the world, and not just in Europe. These are assembled into major structures, such as the nose, fuselage and tail sections, wings, under- carriage and vertical and horizontal tail planes, at various major Airbus plants, such as Saint Nazaire, in France, Hamburg, Stade (Germany), Broughton and Filton, and then brought to the FAL, in Toulouse. Each of these structures is fully fitted with all its requisite wiring and piping before it arrives at the FAL.
Many of these major structures are flown to Toulouse on board Airbus A300-600ST Beluga transport aircraft. Once unloaded, the major fuselage structures are placed in the FAL’s Station 59, where workers will start the fitting-out process for the fuselage sections. They are then moved to Station 50, where the main fuselage sections are joined to form the complete fuselage, and the nose wheel gear is fitted. At the same time, the outfitting of the cabin starts. Once assembled, the fuselage is moved to Station 40, where it is joined to the wing and the main undercarriage is fitted. The airframe is then towed to Station 30, for further cabin outfitting and various aircraft system tests (including of flight controls, landing gear, flaps and slats). Thereafter, the aircraft is taken outside for ground tests that cannot be done indoors, including pressurisation tests. Then it is taken to Station 20, where its engines and economy-class seating are fitted.
At the moment, there are some 300 workers assigned to the A350 XWB FAL, but this will rise to between 1 200 and 1 500 when full production is achieved. At a production rate of ten aircraft a month – expected to be reached in 2018 – it will take about two-and-a-half months to complete an A350 XWB on the FAL.
“The programme objectives are still very challenging,” said Evrard. There is only one year until the first flight and only two years until EIS. That Airbus has succeeded in developing close relationships with A350 XWB programme suppliers helps.
“It’s feasible, but it’s tight, for sure,” he stated. “We have three challenges ahead – one of them is the assembly of the MSN1, then testing; then, in parallel, we move toward the maturity of the supply chain and manufacturing process. Once we have the first flight, then we have this one-year period of flight tests. We’ve prepared a lot for this. But this is a challenge, for sure. We have to demonstrate that we can certify this aircraft in one year.” A key objective is a smooth ramp-up to full production of the new aircraft.
Currently, 34 customers have placed firm orders for 560 A350 XWBs. They are Aer Lingus (9 on order), Aeroflot (22), Afriqiyah Airways (6), Air China (10), AirAsia X (10), Aviation Lease & Finance Company (12), AP Fleet Management (12), Asiana Airlines (30), AWAS Aviation Capital (2), Cathay Pacific (48), China Airlines (14), CIT (5), Emirates (70), Ethiopian Airlines (12), Etihad (12), Finnair (11), Hawaiian Airlines (6), Hong Kong Airlines (15), International Lease Finance Corporation (20), Kingfisher Airlines (5), Libyan Airlines (4), Qatar (80), Singapore Airlines (20), Synergy Aerospace (10), TAM (27), TAP (12), Thai (4), Tunisair (3), two undisclosed customers (1 each), United Airlines (25), US Airways (22), Vietnam Airlines (10) and Yemenia (10).