Ice buildup on aircraft waiting to depart can be a serious safety hazard. As little as 0.8 millimeter of ice on the upper wing surface increases drag and reduces airplane lift by 25%. With deicing fluids ranging from $2 to $4 a gallon, battling ice buildup can cost airlines tens of thousands of dollars in a single snowy day, in addition to the expense of flight cancellations and delays. The new system's half-hour forecasts could mean big savings for airlines through more effective deicing practices and fewer cancellations.
Funded by the Federal Aviation Administration (FAA), the Weather Support to Deicing Decision Making (WSDDM) was developed by the National Center for Atmospheric Research in Boulder.
The FAA will evaluate WSDDM at both airports through user surveys and cost/benefit analyses. If successful, it will become a standard feature for those airlines willing to pay for its operation at airports regularly besieged by winter weather.
At LaGuardia, Delta and USAir will participate from early January through March. American and United, which helped test a prototype of the system last year at O'Hare with encouraging results, will participate there again this winter, from mid- January through April.
Roy Rasmussen, head of NCAR's deicing program, comments, "Passengers can get anxious about safety and unpredictable delays in bad weather. I hope that providing the most up-to-date snowfall information will result in safer winter flying and greater confidence for the public." According to Rasmussen, four or five major storms at each site this year would be enough to demonstrate the system's usefulness.
During the demonstration, 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 both the Delta control tower and the Marine Air Terminal at LaGuardia, the New York Traffic Control (TRACON) office in Westbury, USAir's operations center in Pittsburgh, and the Delta operations center in Atlanta. At O'Hare, monitors will be installed at United's station control, tower, and flight operations center.
The monitors will show bands of snow detected by the National Weather Service's NEXRAD radar network as they move toward or away from the airports. Data from snow-weighing gauges strategically placed in and near the airports will be displayed as a simple graph showing the water content of snow at various locations--a key factor in deicing decisions. The resulting nowcasts (0-30 minutes) based on these and other meteorological 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 gates.
The new technology is a direct result of scientific research. Rasmussen 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 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), he noticed 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 and LaGuardia will measure the actual liquid content of the snow.
"Pilots have already become more aware that visibility can be misleading when it comes to aircraft icing," says Rasmussen. "Now we can give them quantitative measurements indicating the real potential of snow to form ice on aircraft."
NCAR has placed two snow-weighing gauges at LaGuardia, two at John F. Kennedy Airport, and one at Newark Airport nearby in New Jersey. In the Chicago area, gauges will be placed at O'Hare, at Midway Airport, in the city of Wilmette, and at the College of Du Page, southwest of O'Hare.
The University Corporation for Atmospheric Research manages NCAR under sponsorship by the National Science Foundation. This research is sponsored by the National Science Foundation through an interagency agreement in response to requirements and funding by the Federal Aviation Administration's Aviation Weather Development Program.
| Mo/Yr | 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 |