Airbus flew its first laminar-flow wing test flight early this week for the EU-sponsored Clean Sky “Blade” project. The A340 flown in the test, a jet called ‘Flight Lab’, took off from the Tarbes Aeródromo in France at 11am local time on Tuesday. After a series of tests, it landed at an Airbus facility in Toulouse, France 3.5 hours later.
With this flight, the A340 became the first aircraft in the world to combine a transonic laminar wing profile with a fixed internal primary structure. The plane used in the test used two transonic laminar outer wings (one on each side) and an enhanced flight-test instrumentation (FTI) station in the cabin. The wing additions are part of Airbus’ attempt to improve the airflow over the wings of planes.
Fixed laminar wing testing is part of Airbus’s estimated €330 million ($392 million) contribution to the EU’s Clean Sky II initiative, which is a multi-year project that includes various tests to advance aircraft engines to be more efficient.
Ten specially trained pilots and engineers have been planning for this achievement for months, including spending time in simulators and receiving training with FTI systems. A team of an additional 70 mechanics have been working on installing the FTI system in the plane that was used as well as installing the new outer wings.
“We began by opening the flight envelope to check that the aircraft was handling correctly,” said Philippe Seve, a flight-test engineer for Airbus that was on the Blade test flight. “We achieved our objective to fly at the design Mach number, at a reasonable altitude and check everything was fine. We also checked that the FTI was working as expected, to identify further fine-tuning for the next flights.”
Airbus used specialized sensors to track the flexibility of the wings to help engineers gauge the influence of the laminarity. Some of the tests used on the wing include infrared cameras measuring wing temperature, acoustic generators that measure the influence of acoustics on the laminarity of the wings, and a reflectometry system that measured real-time wing deformation during flight.
Blade, the name of the project, is an acronym for Breakthrough laminar Aircraft Demonstrator in Europe. Blade is tasked with assessing the feasibility of introducing laminar technology in commercial aviation. The project aims to achieve a 50% reduction in the wing friction of planes and a 5% reduction of the CO2 emissions of aircraft.
“[These savings] sound small, but for this is huge,” said Charles Champion, Executive Vice President of Engineering at Airbus.
Blade also tries to measure tolerances and imperfections present while laminarity is sustained. Airbus says that it intends to simulate every type of imperfection in the laminarity in a controlled environment, which will reveal the tolerances for building a laminar wing.
“Laminar flow” is a term used in fluid dynamics that characterizes a flow featuring high momentum diffusion and low momentum convection, in contrast with “turbulent flow”.
Though this is one of the first flights by an aircraft with fixed laminar wings, the idea isn’t uncommon in the aviation industry. Boeing’s 787 Dreamliner features a hybrid laminar flow wing, which is artificially induced through hardware. Axel Flaig, senior Vice President of Research and Technology at Airbus’ Commercial Aircraft Division, says that the benefits of laminar airflow have been known about for decades but never practically applied. Flaig argues that this is because it hasn’t been possible to produce industrial scale wings smooth enough to achieve a laminar airflow that are also robust enough to achieve the desired effect in daily airline operations. Laminar wings need to be extremely smooth and have precisely finished surfaces, which means that wings can’t have rivets or other factors that could disrupt airflow.
In Airbus’ recent flight, the new wing section was fully functional despite not having a fuel supply. The additions included the aircraft’s ailerons on each side.
The ‘Flight Lab’ is expected to fly at least 150 hours by the end of the year.
All photos from Airbus unless otherwise noted