Airbus increases speed and precision
in windtunnel testing

With 4,496 orders booked to date from 182 customers worldwide, Airbus is a leading manufacturer of commercial aircraft and offers the most modern and comprehensive airliner family in the world.

Airbus' engineering division is responsible for aircraft design and for the interface with Airbus manufacturing teams. Its wind tunnel operation provides data as part of the aerodynamic design process and carries out tests in support of all Airbus aircraft programs. The wind tunnel team is using the SLA 7000 stereolithography system from 3D Systems for producing components for wind tunnel testing at its operations in Filton, Bristol.

Background
The Airbus wind tunnels carry out testing to provide data as part of the aerodynamic design process for all Airbus aircraft. The wind tunnel domain includes sites at Filton, near Bristol, Toulouse in France, Getafe (Madrid) in Spain and Bremen in Germany.

Martin Aston is the wind tunnel domain manager at Filton and describes the challenges facing the team. "My background for the last 5 years has been on the test side where we are always under pressure to meet deadlines. If we are able to build models more quickly we can enter the design cycle later, which gives the aerodynamicist more time to think before committing to a test”

We realized over a year ago that we needed to invest in some new technology of our own if we were going to improve our cycle times without lowering our standards".
                                            Martin Aston, Domain Manager, Filton

Solution
The Airbus wind tunnel team at Filton was already using 3D Systems® technology through a third party bureau and was aware of some of the advantages of stereolithography (SL). At that point, however, the team only used SL to make small, non-load-bearing components.

A project was launched to investigate buying a stereolithography system specifically for the Filton site. The result was the purchase of an SLA 7000 system from 3D Systems, which is designed to create larger models with tighter tolerances and high quality surface finish. The new machine was housed in a dedicated building at the site and the installation was overseen by a member of 3D Systems' consulting team.

Airbus at Filton is currently using the Accura® SI 10 SL material with the SLA 7000 system. This material provides the mechanical properties suitable for a windtunnel environment. The machine is currently being used within Flight Physics which encompasses the aerodynamic groups who submit new geometries for testing in the tunnel. Typical components include leading edge and trailing edge configurations, flap tracks, pylons and nacelles.

Some tests involve examining ice build-up on the wing, so ice shapes are produced to simulate the ice profile and then tests are carried out to determine the effect on aircraft performance. Other requests are driven by environmental needs. For example, airframe noise on approach to a landing can be caused by the landing gears being deployed, therefore scale models of landing gears have been produced to study these effects.

Not all requirements are wind tunnel specific. The technology is a resource that potentially the whole of Airbus can use. One such case was the commissioning of a full-scale spoiler flap that was required for a design/manufacturing review meeting. The part was presented to the team at the meeting and within 30 seconds modifications were identified to make it easier to produce. This has a very valuable effect on downstream manufacturing changes.

Build time is dependent on geometry and orientation in the process. Some builds may take 5 hours, others can take 60 hours. With experience, these are being optimized continuously.

The 3D Systems stereolithography system is being challenged by every new design to meet the strength, shape and tolerance demands of aircraft model components. The successful implementation of the SLA 7000 system can be seen throughout Airbus as more and more areas of the organization have adopted it for prototyping.

Benefits Innovation
Unexpectedly, the Airbus wind tunnel team at Filton found that one of the major benefits to emerge from the selection of the 3D Systems machine was the consultancy that came with it. Martin Aston asserts that 3D Systems' application engineer Dan Johns played a major part in the success of the project. "Dan was here to look at what we were doing and advise on how we could best use this technology. Some of the things we are doing now with our SLA system would never have been thought of without this application expertise. We can now take advantage of what the technology can do instead of just reducing the cycle time."

One such example has been the testing of leading edge venting systems. The model called for accurate representation of cavities and ducts within the wing leading edge. This particular component could not have been manufactured were it not for the SLA system.

Speed and Cost improvements
Not only has the 3D Systems SLA system improved the speed of development, but it has also reduced costs. Typically Airbus has found that outsourcing SL work costs up to 10 times more plus part quality is difficult to control. By having the technology in-house the quality, cycle time and cost can be controlled according to the project requirements.

"Having our own SLA system onsite allows us to react much quicker and it's also a lot
cheaper," says Martin Aston. "We now try things we never would have done before because we've got the technology on site. Effectively we can think of an idea, put it on to
build overnight or over a weekend and test it out. If it doesn't work we just repeat the
process. To do that through a bureau would be almost impossible as the typical turnaround time is four days.

"We've also started experimenting with models that we would never have attempted or thought possible previously", continues Martin Aston. "Producing plastic models using the SLA system enables us to cater for all of the shapes and curves of aircraft components."

"We have so much more control over the design process now. This not only leads to cost savings but means that we control the priority and error time. We no longer have the delay of waiting for returns if we need to build a new iteration, we simply re-run it on
the machine."
                                                  Martin Aston, Domain Manager, Filton

Geometric form and dimensional stability has been dramatically improved, which means the test data is more accurate. By having the technology on-site a deeper understanding of the process has been invaluable. This knowledge allows the project coordinator to define and control specific attributes of the geometry by understanding the technology. They can then communicate these constraints with the operator and part quality can be maintained.

Risk reduction
Airbus is constantly concerned with reducing risk, a principle which begins at the earliest stages of aircraft development. "Oversights in design can cost millions of pounds to fix once the aircraft is in production," explains Martin Aston. Even for a minor issue, an aircraft will be out of service while components are replaced, which could be damaging to the company's reputation as well as expensive to remedy. "The SLA system is useful for ensuring that our design engineers' calculations are accurate before we actually cut metal for the aircraft." says Aston.

Why 3D Systems?
"We chose 3D Systems not only because of the quality of the stereolithography systems, but because we see the company as much more than simply a machine tool supplier," says Martin Aston. "3D Systems is advising us on the whole process. That level of partnership is good to see - so many companies would just hand over the machine and tell us to get on with it."

Aston was also impressed by the response time from 3D Systems. "What we usually find when working with different companies is that you don't always get the rapid response you need, particularly during evaluation phases. From 3D Systems, whenever we've had a question there's always been someone there to answer straight away and advise us on the way forward."

The future
"We've been approaching people in departments which historically have not made prototypes at all," explains Aston. "Some of them have just used blocks of wood, which don't fully represent what you're trying to see. SL will give them a chance to make either a scaled-down version of the real thing, or a fullscale version to test."

As the relationship with 3D Systems develops Airbus will also look at expanding its use of 3D Systems' solid imaging systems with materials including metals and ceramics.

One of the challenges for the future will be to persuade people to change their processes. "Sometimes it can be tricky, particularly when someone's been doing something the same way for 20 years," says Aston. However, new teams have already adopted the SLA systems for their prototyping. The SILENCER project is an EU-supported research program testing aircraft landing gear for noise measurement. Historically their prototypes were made of materials such as aluminium and wood, but the team has enthusiastically adopted SL as a far more effective means of creating a representative model from plastic.

"We're not slow to move forward," says Aston. "Airbus has always been a leader in innovation and has a philosophy of technological advancement. That's a philosophy which runs through the whole company."