“Turbulence is normal. It’s part of the sky,” said Smith. “It’s not about the plane but where the plane is.”
Turbulence follows a rating system similar to that of a spice-o-meter at an Indian restaurant — light, moderate, severe and extreme. Cornman describes the stages, from mild to serious, as water rippling in a glass, liquid flowing out of the vessel and the cup flying through the air. Most passengers experience the swirling and spilling phases, but never the most intense situations, which can cause injuries and structural damage. When a weather system threatens such peril, pilots do their utmost to avoid the roiling air. If stuck in an ugly patch, they will attempt to steer the plane toward calmer air, climbing to a higher altitude or changing course.
Pilots rely on numerous systems to track turbulence, including weather forecasts, radar, communication with air traffic control and updates from other planes in the vicinity.
“In general, we have a reasonably good idea of where the rough air is,” said Smith. “But it can be more of an art than a science.”
Getting a bead on it
To help take the guesswork out of the pin-the-tail-on-the-turbulence game, physicists and other industry specialists are working on innovations that detect unsettled air. For instance, Boeing installed the Vertical Gust Suppression System in the new 787 Dreamliner. VGSS acts like a super-beagle: Sensors in the plane’s nose detect volatile air, then relay the message to the aircraft’s brain, which automatically makes adjustments to reduce the bump. Passengers will probably sleep right through the tweak.
In May, the company received a patent on another invention, a GPS unit that can read the “twinkle” of the radio waves for more than 200 miles, thereby identifying erratic air flow. (Quick debriefing: Stars appear to twinkle when upset air bends and bobbles the light as it travels through the atmosphere; same deal with radio waves. Apologies for crushing the fantasy of stargazers who thought that little aliens living on stars were flicking their bedroom lights on and off.) At this early stage, no planes are equipped with the GPS unit.
Cornman, who was instrumental in the GPS program, is also tackling the turbulence issue at the federally funded center. Under the sponsorship of the Federal Aviation Administration, he and collegues developed the In Situ Turbulence Reporting Program, detection software that allows participating airlines (Delta, United and Southwest so far) to share reports on rough air. Also in his bag of new tricks: radar software that can track “stuff embedded in the air,” a useful tool for recognizing convective turbulence, and “lidar,” lasers that detect small particles in visibly clear air and measure their motion. Delta uses the new radar capability, and the Hong Kong airport has installed the uber-lasers. Researchers are also throwing some brain cells at improving weather forecasting, which could inform pilots of upcoming chop.
“Turbulence is pretty dynamic,” he said. “Pinning it down is pretty hard.”