New Icing Warning System for U.S. Airplanes Debuts

John Roach
for National Geographic News
December 6, 2006
Beginning today pilots will have more reliable information about the threat of dangerous icing conditions as they fly across the continental U.S.

The information could save the airline industry more than $20 million a year in aircraft damage and fuel by guiding pilots away from areas in the atmosphere where icing can take place, according the National Center for Atmospheric Research (NCAR) in Boulder, Colorado.

The new data may also save uncounted lives. A study by the National Transportation Safety Board estimates that 819 people died from icing-related accidents between 1982 and 2000.

The new technology is part of an upgrade to a system called the Current Icing Product (CIP), which is available to weather forecasters, air traffic controllers, and, for the first time, pilots.

The project combines surface observations, weather models, satellite and radar data, and pilot reports to create maps and plots of icing conditions that are posted online.

"Pilots can now look at updates during flight," said Marcia Politovich, an in-flight icing researcher at NCAR.

The maps and plots are updated hourly and can be selected for altitudes up to 29,000 feet (8,840 meters), according to the research center. The reports can be streamed directly into the cockpit.

Prior to the upgrade the information was available only to trained meteorologists who could interpret the complicated weather data compiled by CIP, Politovich explained. The information was then relayed to air traffic controllers and pilots.

The update "puts pilots in more true command of the flight path," she said.

The Danger of Icing

Politovich said that contrary to conventional wisdom, water does not always freeze at 32 degrees Fahrenheit (0 degrees Celsius).

When it's in the form of tiny drops in clouds, water can stay liquid all the way down to minus 40 degrees, which is the same temperature in Fahrenheit and Celsius.

But when these so-called supercooled water droplets hit an object, they freeze onto it. That's why trees at mountaintops in the winter are often covered in rime—the white ice formed in a dense, chilly fog.

The same thing can happen to airplanes flying through cold, wet clouds.

"When an airplane flies through a cloud of precipitation containing supercooled water droplets, the drops stick to the airplane, changing the shape of the airflow, and that makes the plane not fly so well," Politovich said.

Gene Addy is an icing researcher at the NASA Glenn Research Center in Cleveland, Ohio. Generally speaking, he said, the more water, the thicker the cloud, and the more dangerous the icing conditions.

"Ice builds up more quickly," he noted. "Conversely, where the temperature is quite a bit below freezing, the drops freeze on impact, and it can be more of a challenge to get the ice removed, which protects the airplane from accretion."

Icing Research

The study of accretion, or how ice builds up, on aircraft wings is a major focus of icing research at the NASA research center, Addy said.

(See a National Geographic magazine feature: "The Future of Flying.")

NASA-built computer models of the accretion process are widely used throughout the aviation industry in the design of ice-protection systems, such as the placement of heaters on wings.

"We also get involved with getting a handle on how icing affects the airplanes … what happens to the airplane when it's trying to fly with ice accretion on it," he said.

To study the dangers of icing, the NASA researchers fly themselves into icing conditions on a DH-6 Twin Otter aircraft to collect data on cloud conditions, ice formation, and plane performance, he explained.

NCAR's Politovich called the data collected by the NASA team "critical" in the development of CIP. The data verifies the accuracy of their weather models.

With confidence in the CIP data, pilots of properly equipped airplanes can fly through areas of light icing knowing that the conditions will not be severe enough to cause a problem, she said, instead of taking extended, fuel-costly detours.

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