The latest innovative research program involving Airbus and its partners could help airlines reduce fuel consumption by as much as 5 percent.
In a hangar in Tarbes, France, resides the Blade project, one of the most advanced research and development programs underway by the European manufacturer and its partners. The goal of Blade (which stands for Breakthrough Laminar Aircraft Demonstrator in Europe) is to "demonstrate the laminarity [laminar flow] for commercial aircraft," explained Axel Flaig, senior vice president of Airbus Research and Technology.
Airbus has transformed its A340 prototype (MSN 001) by adding a new outer wing section angled 20 degrees higher than the inner section. A bullet-shaped pod is mounted at the tip of the wings.
A true laminar-flow wing applies the principle of aerodynamic organized flow and reduces friction and drag. The principle has been known for decades but could not be applied effectively on commercial aircraft for technical reasons, Flaig explained, although it is hoped that the modified A340 will demonstrate the feasibility of this technology. The potential drag reduction could reach 8 percent on short-range aircraft when compared to a standard turbulent (non-laminar-flow) wing, but this would occur at an optimum speed of Mach 0.75, a little less than the current typical cruise speed of Mach 0.78.
Two Concepts, Two Wings
On this A340 there are two different outer (semi) wing sections, so the partners can test two manufacturing concepts. The left wing was manufactured by Saab in Sweden and Aernnova Aerospace in Romania. This section is made of a single panel that covers more than 50 percent of the wing in order to improve laminar flow. The right wing section is made of different panels, and the joint in the leading edge has been carefully assembled and polished to improve the laminar effect. This wing's leading edge was provided by GKN in the UK and integrated by Aernnova. The right wing section, which Airbus aerodynamics specialist Laurent Mallard describes as "more perfect," is less expensive to manufacture than the left one. By testing both wings in the same flight conditions, the research team will be able to determine how much each is able to benefit from the laminar-flow effect. If the difference between the two is small, the right wing concept will be more cost effective to manufacture, the engineers explained.
The A340 has been equipped to enable capturing a massive amount of data during a planned 150-hour flight campaign. More than 2,000 parameters will be measured and analyzed, said Philippe Seve, flight-test engineer. Cameras have been installed in the vertical stabilizer and on the pods on the wingtips. There are 34 cameras in total, three of which have infrared sensors. The infrared cameras will measure the deformation of the sun's reflection on the wings, which are covered in a striped pattern. To allow the wing to reflect the sun, they have been painted gray. “If they were white, it would have made thermal visualization impossible, so we decided on gray,” explained Daniel Kierbel, leader of the Blade project.
Airbus expects to conduct the first flight by the end of September, flying the airplane from Tarbes to Toulouse, where it will be stored during the flight campaign. Because of the sun’s angle needed for measurement and visualization, there will be no flights during winter. Seve expects flight testing in normal conditions to be completed between spring and autumn 2019.
The so-called “mosquito flights” are scheduled during spring and early summer of 2019 to test the cumulative impact of insects crashing on the wings and affecting its laminar profile. The test aircraft will mostly fly in circles over Camargue, a marshland area on the French Mediterranean coast formed by the delta of the Rhône river. During this campaign, a Krueger device, a lift-enhancing surface mounted under the leading edge, will be deployed in front of the wing during takeoff and landing to try to repel the insects.
The research team, including members from all over Europe, expects validation of the concept as a result of the flight tests. No timetable has been given yet, but the technology could quickly move into industrial implementation if the Blade experiment delivers the expected positive results.
The project will cost about €180 million ($216 million), and Airbus has invested €90 million ($108 million).
The Blade project is part of the Clean Sky initiative, aimed at reducing noise and emissions in Europe by 50 percent by 2050 compared to 2005. Blade started in 2008, and after the concept was selected, wind tunnel testing was performed in 2014 before the wings went into production in 2016 and were installed in 2017.