Winglets – the tips of aeroplane wings that curve upwards – save fuel, reduce noise and make higher rates of climb possible. They’re a popular design feature in modern aircraft. All Boeing’s 737s have winglets, as do several Airbus and all Bombardier jets.
They’re made from composite materials to achieve the right combination of shape, strength, weight and durability. However, existing production methods are only partly automated, making assembly labour-intensive and costly.
With demand growing rapidly GKN Aerospace wanted to speed up production times and reduce costs.
Redesigning winglets was just one of several collaborative R&D projects funded under the £12 million Structures Technology Maturity (STeM) programme launched by Innovate UK and the research councils in 2012.
The programme was led by GKN Aerospace partnered by Bombardier, Spirit Aerosystems and GE Aviation. Its objective was to support new concepts in wing design, pushing the boundaries of aerodynamic performance.
The existing production process had many separate steps – manually laying an upper and a lower skin using composite materials, building an internal spar structure, attaching it to each winglet and finally fastening the skins together.
Automating this process meant changing it (and the structure of winglets) from the inside out. Each partner worked on a different part of the production process.
GKN’s Isle of Wight Composites research centre redesigned the interior structure of the upper skin. The new design replaced internal spars with a ‘waffle’ sub-structure. This is applied and joined to the upper surface in a single process (co-curing) really speeding up production.
The National Composites Centre (NCC) took on the task of automating the laying of the complex, double-curvature external ‘skins’. A key challenges was getting its twin AFP (Automatic Fibre Placement) robots to work together in close proximity in a confined space.
Ben Hopper of the NCC said:
“Our operators had to synchronise the robots’ movements very carefully to manufacture 2 winglets at the same time on the same fixture. But it confirmed what we knew the AFP robots could do and we’ll be applying that knowledge to other projects.”
The AMRC created an automated cell to assemble the structure – using standard low cost assembly tools. A high-definition projection system enabled precise positioning of an automated robotic drilling unit to drill holes, apply sealant and insert fasteners, before securing the components to a lightweight carbon assembly fixture.
The partners were delighted with the results. John Cornforth, GKN’s Head of Airframe Technology for European Special Products said:
“Our target was to produce a winglet that performed the same more quickly and at a lower cost. We achieved 20% cost savings, reduced production times and improved the consistency and quality of manufacturing. We learned a lot that can be applied to other aerostructure projects.”
Tom Hitchings NCC Business Development Director added:
“It shows that UK companies, supported by Innovate UK and the resources of the Catapult network, are ahead of the game in delivering the next generation of high-performance, high-quality aircraft components – while reducing manufacturing costs and lead times.”
The companies GKN Aerospace is a leader in the manufacture of complex composite and metallic aerostructures including winglets (the tips of wings that curve upwards).