Aircraft wake surfing to reduce consumption

Like migratory birds, aircraft should be able to benefit from the wake of other aircraft to reduce their energy consumption. This could soon become a reality, thanks to an onboard intelligence system that allows the aircraft to locate itself relative to a predecessor's wake.

Some birds are capable of extreme migrations covering incredible distances, such as the bar-winged godwit, which flies from Alaska to New Zealand in seven days, a distance of 11,000 km! At the end of February, many Belgians observed tens of thousands of common cranes in flight as they migrated to Scandinavia. These impressive performances are made possible by formation flying. The trailing birds surf on 'air waves' created by the leading birds, thus expending less effort and consuming less energy.

This well-known aerodynamic phenomenon is already used sporadically in military aircraft formations. But civil aviation is also increasingly interested in it, including Airbus, with its 'Fello fly' programme, which is already testing formation flying and wants to develop the concept to an operational level. Indeed, scientists estimate that it could generate gains of 5 to 10% by reducing trailing aircraft fuel consumption. With 25 years of expertise in the study of aircraft wakes, UCLouvain's Institute of Mechanics, Materials and Civil Engineering (IMMC), in association with the Louvain School of Engineering, has been studying formation flying for the past two years as part of the European Research Council-funded WakeOpColl. Researchers* at UCLouvain have developed onboard intelligence algorithms that can be installed on an aircraft's onboard computer so that the aircraft can sense a preceding aircraft's wake and better position itself relative to it. This reduces fuel consumption and avoids entering the dangerous zones created by wakes. By way of comparison, the gains these algorithms could bring to aviation are equivalent to the gains obtained after 10 or 20 years of research and development to create new engines or new aircraft shapes with a view to reducing their consumption.

The study of bird flight, and more particularly migratory bird flight, is at the heart of the RevealFlight project at UCLouvain in which Prof. Philippe Chatelain, a fluid mechanics specialist, collaborates with Prof. Renaud Ronsse, a biomechanics specialist, and Prof. Julien Hendrickx, a mathematical engineering specialist.

In addition, the expertise acquired in a study of aircraft wakes by Prof. Chatelain and Grégoire Winckelmans's team led to the creation of the spin-off WaPT (Wake Prediction Technologies), which provides solutions to problems related to wake turbulence for the aeronautical and wind energy sectors.

* Denis-Gabriel Caprace, Ignace Ransquin, Victor Colognesi and Matthieu Duponcheel also contributed to research on aircraft and bird flight formation.

In a five-minute video, Prof. Chatelain explains the possible benefits of aircraft wakes but also their dangers, and how the creation of onboard intelligence algorithms could reduce consumption by 10%:

Another article on Prof. Chatelain's research: Planer pour comprendre l'aérodynamique.