How Lasers Will Help Us Make Planes Quieter and More Fuel-Efficient

DLR

Over the past century, the airplane has revolutionized the way we travel and do business, and made enormous technological advances. But modern jetliners burn gobs of fuel and are still loud, especially if you live near an airport flight path. So plane manufacturers (with extra encouragement from government regulators) are always on the lookout for ways to make their aircraft quieter and more efficient.

One way to save fuel and reduce noise is to land at lower speeds, which calls for a more detailed understanding of how air moves over plane wings. Normally, aircraft designers model airflows in computer simulations and in wind tunnels, because it’s difficult to track air moving over a wing at 400 MPH. Now, a German research team is finally getting that detail from in-flight measurements. And it’s doing it with lasers.

During two nighttime flights this week, a team at the German Aerospace Center (the country’s NASA equivalent) shot bright green lasers from the window of their test plane out onto the wing of their specially equipped Airbus 320 Advanced Technology Research Aircraft. The lasers (which are so bright, the pilots wear goggles) illuminate the water droplets moving across the wing, enough for high-speed cameras to capture the movement of the droplets airstream in real time.

By analyzing the images captured by the two high-speed cameras, the researchers can visualize real water droplets—and thus airflow—as they move over the wing. It’s a more accurate and realistic data set than what you get from a computer simulation, and better than past in-flight systems, which were attached to the wing itself, interfering with the airflow and only allowing for a measurements at a few points. One of the most useful aspects about this approach, called Particle Image Velocimetry, is that it allows scientists to compare real-world airflow with their simulations, to ensure that the computer models are accurate.

The team is focusing on analyzing the aircraft’s flight just before landing, when all the flaps are open to maximize lift at low air speeds. Thanks to custom software, the entire airflow around the wing can be visualized in three dimensions. “We want to acquire an understanding, in hitherto unachieved precision, of how the airflow behaves around the wings and flaps, and especially around the engine” during low-speed flight, says Ralf Rudnik, the scientist in charge of the High Lift In-Flight Validation Project.

Increasing lift allows planes to throttle back more, saving fuel and allowing for a quieter approach. That’s important for quality of life concerns for those living near airports, as well as airlines that want to save on fuel bills. If the research is successful, future aircraft designs could allow for a reduction in the minimum speed required on approach for landing. French airline manufacturer Airbus is involved in this research as well, and the FAA is approaching it from another angle, improving flight paths at airports in Houston to minimize throttle use on approach.

So if you live near an airport, these green lasers could make your life a little quieter in a decade or two.