A new turbulence detection system under test is alerting pilots to patches of rough air as they fly through clouds, according to RAN’s sister publication Air Safety Week. The development is an advance on current technology which can only track certain types of turbulence but not that related to thunderstorms, which the National Center for Atmospheric Research (NCAR) says accounts for two thirds of turbulence.
The system, designed by NCAR and tested by United Airlines on commercial flights, is designed to better protect passengers from injuries caused by turbulence while reducing flight delays and lowering aviation costs. National Traffic Safety Board statistics from 1992 to 2001 show that turbulence was a factor in at least 509 accidents in the United States that resulted in 251 deaths in general aviation flights. In addition, more than 1,000 injuries occur aboard commercial aircraft every year.
“Turbulence associated with thunderstorms is really dynamic and changes very quickly," said John Williams, a scientist with NCAR. “Getting that information to pilots in the cockpit is absolutely essential. What we're doing that's really new is applying artificial intelligence to get rid of data that contaminate the measurements. The idea is to mimic how a human expert would look at the information. Our hope is that it will help reduce unnecessary delays and diversions and guarantee passenger safety and comfort.”
The new system uses a mathematical method developed by NCAR scientists, known as the NEXRAD Turbulence Detection Algorithm, or NTDA, to analyze data obtained from the National Weather Service's network of 83 Next-Generation (NEXRAD) Doppler radars for information on precipitation, cloud density and gusts within clouds. The new program’s official launch date is 2011 when its in-flight updates would come every 15 minutes.
Pilots in the past have lacked accurate measurements of turbulence that develops in clouds and thunderstorms, partly because turbulent areas may be small, evolve quickly, and occur outside the most intense parts of the storm. As a result, FAA guidelines suggest that planes avoid thunderstorms by at least 20 miles when possible, even though large sections of that area may contain relatively calm air. The NTDA does not measure clear-air turbulence, such as that caused by the jet stream or by wind flowing over mountainous terrain. But about two out of every three turbulence encounters are associated with clouds and storms, the focus of NTDA detection.
FAA and National Science Foundation are funding the development program which has already cost $2 million. The new system tracks the severity of turbulence 100 miles ahead of an aircraft as well as 40 miles from its wingtips. A software program then filters out information that can distort the data - such as flying insects and birds - and creates a three-dimensional map of turbulence for a given area. The resulting real-time or "nowcasts," of turbulence can be transmitted to pilots in the cockpit and made available to airline meteorologists and dispatchers via a Web-based display for immediate and, more fuel-efficient, re-routing.
These radar measurements create a three-dimensional mosaic showing turbulence across the country that can help pilots avoid hazardous areas or at least give them warning of trouble ahead. "The messages I've received in the cockpit gave a very accurate picture of turbulence location and intensity," says Captain Rocky Stone, chief technical pilot for United. "The depiction of turbulence intensity provides an unprecedented and extremely valuable new tool for pilot situational awareness." Depending on the results of this year's tests, which run through October, the next step may be to expand the system to additional United aircraft or other airlines.