When air flows around the wing of an airplane, it creates vortices of swirling air. When that wing accelerates suddenly, two vortices form and circle in opposite directions. Sometimes these circles link with one another to create knots. Knots occur in nature and physicists have theorized for the last hundred years that they could be created in liquid, too. Physicists have now figured out a way to create them and have 3-D footage of the results, which were published in Nature Physics on Sunday.
The researchers used a 3-D printer to make cross-sections of tiny airplane wings. Then they put the wings in a tank of water that was electrically charged to have lots of tiny bubbles. The bubbles show movement in the tank. When the wing was pulled through the water, it created knots in its wake which were recorded in 3-D with a high-speed laser scanner.
If you’ve ever been stuck in an airport for hours on end, you know that explanations for such delays are often lacking. A new study of U.S. air traffic helps explain why minor delays spread through the system, and how to prevent them from doing so.
Researchers began with 2010 data from more than 6 million U.S. domestic flights, including their scheduled and actual times of departure and arrival. They were especially interested in how minor delays at a few random airports produced further delays across other parts of the network—i.e., not so much what might happen if a massive storm closed many regional airports, but what might happen if a random scattering of planes across the country each needed 10 extra minutes on the ground to fix
mechanical problems. To investigate, researchers produced a computer model, similar to ones used in the past to predict how infectious diseases are carried by air travel.
The number one cause of plane crashes used to be controlled flight into terrain (pdf), accidents where pilots unintentionally collide with an obstacle. A pilot unable to see through fog, for example, could fly straight into a mountain, crashing an otherwise perfectly functional plane. Such accidents killed over 9000 people—until aviation engineer Don Bateman’s crash-avoidance technology changed all that.
Bateman invented the original Ground Proximity Warning System (GPWS) in the 1970s. Using information from the altimeter. airspeed indicator, and other devices already standard in planes, the original GPWS warned pilots with increasing urgency—first “Caution—Terrain,” then “Pull up! Pull up!”—if the plane was due to crash. Bateman, now 79 years old, still works at Honeywell and he’s still perfecting the GPWS. The modern warning system integrates GPS locations of potential obstacles. In a profile of Bateman for the Seattle Times, Bob Voss, chief executive of the Flight Safety Foundation, says, “It’s accepted within the industry that Don Bateman has probably saved more lives than any single person in the history of aviation.”