11 December to 15 March 1995
BOULDER--Do you glance anxiously at the wings as the deicing equipment pulls away minutes before your flight takes off? Do you sigh with frustration over another delayed departure? Now there may be hope for winter fliers. Takeoff accidents and delays could be significantly reduced while airlines save money on deicing procedures if a new icing prediction and display system now being tested at Chicago's O'Hare International Airport proves useful to airline and airport personnel.
The accumulation of snow on aircraft prior to takeoff can be a serious safety hazard. As little as .8 mm of ice on the upper wing surface can knock 25% off an airplane's lift and increase the drag. To help reduce takeoff hazards due to ice accumulation, the Federal Aviation Administration has supported ground deicing research at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, since 1991.* Now the fruits of that program have emerged in a prototype system being tested between December 15 and March 31 at O'Hare.
During the test, surface weather stations, snow-weighing gauges, and Doppler radars will measure snowfall accumulation, temperature, humidity, wind speed and direction, and the water content of snow. The data will be processed instantly and displayed graphically on video monitors at the American and United airlines station controls, the city of Chicago snow desk, and the United Airlines Meteorology Department.
Short-term "nowcasts" (0 - 30 minutes) based on the data are expected to aid airport officials, including ground personnel deicing the planes, airline station control managers coordinating flights, airport managers in charge of plowing the runways, and air traffic controllers deciding how long to hold planes at the gates.
The new technology is a direct result of scientific research. Roy Rasmussen, head of NCAR's ground deicing program, recently found that the potential of snow to form ice on an airplane's wings and fuselage corresponds to the amount of water in the snow (called the liquid- equivalent snowfall rate) rather than to visibility, which has traditionally determined deicing and takeoff decisions. In studying a number of takeoff crashes due to icing (see list below), Rasmussen found that visibility at the time of the accidents varied widely. He determined that large, dry snowflakes hampering visibility were less of a threat than small, heavy flakes holding more water. The snow- weighing gauges used in this winter's test at O'Hare will measure the liquid equivalent snowfall rate. The data will allow airport and airlines officials to make decisions based on quantitative measurements indicating the real potential of snow to form ice on aircraft rather than on estimates taken from visibility.
"Pilots have already become more aware that visibility can be misleading when it comes to aircraft icing," says Rasmussen. "My hope is that providing the most up-to-date snowfall information will result in safer winter flying and greater confidence for the public."
During November, two snow gauges were placed at O'Hare itself and three more 8 to 17 miles northeast, northwest, and southwest of the airport. The outlying gauges are designed to give the liquid- equivalent snowfall rate of snow bands approaching the airport 30 to 60 minutes in advance.
A prototype ground deicing and snowfall display system was demonstrated at Denver's Stapleton International Airport (now closed) and the new Denver International Airport (DIA) last winter. Compared to Denver, Chicago snowfalls are typically wetter and heavier, and Chicago's weather is generally more like that of several East Coast airports. O'Hare also follows different procedures from those at DIA for deicing aircraft and plowing runways. Results from this winter's test at Chicago should extend the usefulness of the Denver-developed system to other airports around the country.
The new system awaiting this year's winter storms in Chicago won't prevent shutdowns due to heavy snowfall, like the one that closed O'Hare on November 11. But more accurate information could make winter takeoffs safer and help airlines stick more closely to their schedules while saving money through efficient deicing procedures. Soon you may find you relax during preflight snowfalls, and you may even arrive in time to make that meeting.
*This research is sponsored by the National Science Foundation through an Interagency Agreement in response to requirements and funding by the Federal Aviation Administration. NCAR is managed by the University Corporation for Atmospheric Research under sponsorship by the National Science Foundation. The views expressed are those of the authors and do not necessarily represent the official policy or position of the U.S. government.
Date Aircraft Type Location Icing Conditions ---- ------------- -------- ---------------- 12/68 DC-9 Sioux City, Iowa** Light, freezing drizzle; fog 11/78 DC-9 Newark, N.J. ** Snow, fog 2/79 Nord 262 Clarksburg, Wyo. Frozen snow 2/80 Bristol 253 Boston, Mass. ** Light snow, fog 1/82 B0737 Washington, D.C. ** Snow 2/85 DC-9 Philadelphia, Pa. ** Light, freezing drizzle, ice pellets 12/85 DC-8 Gander, Newfoundland Light, freezing drizzle 11/87 DC-9 Denver, Colo. ** Snow 3/89 F-28 Dryden, Ontario Snow 3/92 F-28 New York, N.Y. ** Snow**Weighing snow gauge data available
A wide range of weather and weather-related images is available through NCAR's Visual Communications program. View NCAR's Digital Image Catalog on the World Wide Web at http:/www.ucar.edu/DMC/DMCHome.html or call Linda Carbone at 303-497-8612 (e-mail firstname.lastname@example.org) or Nita Razo at 303-497-8606 (e-mail email@example.com ) for a print version of the catalog or for assistance
This press release lives on the World Wide Web at http://www.ucar.edu/ucargen/press/deicing.html