Airbus nears flight testing of breakthrough aircraft laminar wing technology that promises substantial fuel burn reduction
Airbus A340 testbed aircraft with the Saab NLF wing attached (photo: P. Pigeyre, Airbus)
Mon 4 Sept 2017 – Flight testing is about to start later this month by Airbus on laminar wing technology that could reduce drag by 8% and decrease fuel burn and carbon emissions by up to 5% if used on future generation short-range commercial aircraft. Laminar flow – the uninterrupted flow of air over an aircraft’s wing to greatly improve the aerodynamics – is considered by many aircraft designers to be aviation’s holy grail because of the potential rewards involved. As part of the EU’s Clean Sky programme, Airbus and 21 partners have been working since 2008 on the BLADE (Breakthrough Laminar Aircraft Demonstrator in Europe] project, which has now reached the critical flight testing phase of an Airbus A340 testbed aircraft fitted with new outer wing sections. Airbus claims BLADE is the largest flight test demonstrator ever launched in Europe, if not the world.
The fuel burn of commercial aircraft has improved by around 70% on a per seat/km basis over the last 50 years but progress has become increasingly flatter and more difficult, says Axel Flaig, Head of Research and Technology at Airbus. Achievements so far have come, for example, from new engines, new materials to make aircraft lighter and new design tools to aid more efficient design.
“The next big step in aerodynamics is to work on the friction drag of aircraft wings,” Flaig told journalists at a press briefing held in a temporary Airbus facility in Tarbes, south-west France, where the testing is to take place. “The theory has been known for many years but the practical application has not been achieved so far because to make it happen you need very low tolerances in the design profile and to make the wing very robust against contamination, as this type of laminar bond layer is very sensitive to small disturbances. To make an industrial solution that can work in daily operations is now becoming more feasible and we have made strong progress over the past few years under this programme.”
The two outer wing sections of the A340 have been cut and replaced with two differently designed natural laminar flow (NLF) wings manufactured by GKN and Saab. Cameras are mounted in wingtip pods and on top of the vertical tail plane to monitor the transition in flight between laminar and turbulent flow.
Up to 150 hours of flight testing is expected in total until completion later in 2018 and initially will assess aircraft handling qualities, open flight envelope and provide first results on the laminar wing performance. Next year, the intention is to extensively test and characterise laminarity robustness in representative operational conditions, says Airbus.
A potential downside for airline operators, and why the technology might make more sense for short-range aircraft, is that to extract the maximum laminarity benefit, aircraft would have to fly at an optimum speed of Mach 0.75, slightly slower than the usual Mach 0.78 for an A320.
BLADE is part of the Smart Fixed Wing Aircraft programme within Clean Sky, an EU public-private sector research undertaking first launched in 2008 (Clean Sky 1) and aimed at developing technology to reduce aircraft CO2 and NOx emissions and noise levels. The 10-year Clean Sky 2 undertaking started in 2014 with objectives to come up with new environmentally-friendly technologies for next-generation aviation, to speed up development of technology demonstrators, underpin European international aviation competitiveness and create new market opportunities and jobs. It has a total budget of €4.2 billion ($5bn), with Airbus contributing €330 million ($400m).