PORTLAND, Ore. If you have flown American skies lately, you may have noticed shorter, smoother trips east of the Rockies. That's because a new turbulence detection and avoidance system is being tested (so far with success) by select United Airlines flights.
New turbulence analysis software designed by the National Center for Atmospheric Research (NCAR) maps patches of rough air and compares the maps against the real-time flight paths of airliners. Alerts are sent to pilots giving them advance notice and presenting alternative routes that enable pilots to thread paths between turbulent regions without changing their arrival times. This should not only result in smoother flights but also save fuel and reduce delays on the ground.
"Last summer when we started testing the current system, we estimated that we could detect 80 percent of moderate-or-greater regions of turbulence," said NCAR scientist John Williams. "Since then we have improved the system further, so we expect to get even better results when we analyze the data next month."
If the results are as good as expected, the program will be expanded to other United flights and, eventually, to other airlines. 2011 is slated as the first year for nationwide turbulence "nowcasts" to all airliners flying over the United States.
Turbulence causes over 1,000 injuries on airliners each year, and over 500 aircraft accidents have been caused by turbulence, including over 250 deaths in recent years alone (1992 to 2001). In addition to the cost of insurance claims against these accidents, delays at airports and damage to aircraft caused by turbulence runs up bills of millions of dollars each year. The new system was crafted by the Federal Aviation Administration (FAA) over the last two years to help reduce these costs, as a part of its Aviation Weather Research Program.
NEXRAD turbulence detection algorithm guides flights through storms
Two out of three aircraft encounters with turbulence occur in or around storms, where cloud movements can be used to detect the rough air, according to NCAR (which has a separate system for forecasting clear-air turbulence caused by the jet stream). Turbulence from winds flowing over mountains, or turbulence from local disturbances, such as the wake common during takeoffs, is the focus of separate efforts in the Aviation Weather Research Program and at the National Aeronautics and Space Administration.
To be alerted to turbulence in cloudy regions, pilots today rely on reports from other pilots or on storm maps that turn large swaths of airspace into no-fly zones. The new system dissects storm fronts into regions of light, moderate, severe, and extreme turbulence, and automated alerts are issued to affected flights. The new, more detailed maps allow pilots to avoid turbulence by only slight course corrections.
"Today FAA guidelines suggest that a 20-mile buffer zone be kept between planes and storm fronts," said Williams. "But our system shows that only very small parts of most storm systems have dangerous turbulence, so that pilots don't have to waste so much fuel flying around the whole storm system."
Using data from the National Weather Service's network of next-generation Doppler radars, the NEXRAD turbulence detection algorithm (NTDA) can peer into clouds and analyze the distribution of winds. NTDA reprocesses the raw radar data to identify the degree of turbulence in each region, ignoring contamination factors such as sun glare and swarms of insects around radar dishes. "We use an artificial intelligence system to filter out bad data the way a human would," said Williams.
The result is a three-dimensional mosaic showing turbulence across the country, information that is distributed to airline meteorologists and dispatchers. The hot spots are then compared with real-time flight paths, and intersections are relayed to individual flights.
The current test period began last year, after NCAR demonstrated that existing NEXRAD installations would enable NTDA to detect most turbulence regions, and ends next month (October 2007). After a brief evaluation period, NCAR will gradually expand the system's coverage from the 83 NEXRAD installations east of the Rockies to all 166 installations nationwide, eventually allowing all airlines to receive real-time warnings of turbulence in their flight paths.