Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: MONDAY, May 15, 1995 TAG: 9505160022
SECTION: NATL/INLT PAGE: A-1 EDITION: METRO
SOURCE: Associated Press
DATELINE: WASHINGTON LENGTH: Medium
Called Terminal Doppler Weather Radar, it's one of 45 units planned across the nation. The $380 million project is designed to give busy airports warning of weather like the violent storm that downed a USAir flight in Charlotte, N.C., last July, killing 37 people.
New radars in Houston, Memphis, St. Louis and Denver are in use. Charlotte's new radar is under construction, as are a dozen others. Raleigh-Durham will have North Carolina's other system. National and Dulles International are the Virginia airports awaiting theirs.
A Doppler radar system in Floyd County, Va., is being used to help detect wind shears around airports in Roanoke and the New River Valley. It is part of a National Weather Service station built in Virginia Tech's Corporate Research Center in late 1994.
Fifteen more systems are installed and being checked out, the Federal Aviation Administration says.
One is in Brandywine, Md., only a few miles from National Airport. It watches over Andrews Air Force Base, where on Aug. 1, 1983, Air Force One, carrying President Reagan, landed just six minutes after a violent wind burst.
Besides the Charlotte accident, deadly crashes caused by sudden powerful wind bursts include a 1985 Delta crash near Dallas that killed 133 and a 1982 American Airlines accident that killed 153 near New Orleans.
Although safety is the prime goal of the new system, it is also expected to reduce weather-related delays, said Robert W. Meyer of Raytheon Corp.
The frequency of severe weather was the major factor in deciding where new units were needed, said Donald H. Turnbull, FAA's program manager for weather radar. Thus, most are in the central, eastern and southern states where thunderstorms often produce vicious winds that can drive an airliner into the ground.
Airplanes are most vulnerable when taking off and landing because they have little room to maneuver. The radars will scan the area below 1,000 feet, out to three miles for planes approaching the airport and two miles for those leaving.
The new units track wind movement by following tiny dust particles and insects to detect violent microbursts and wind shear, the conditions blamed for the Charlotte crash. The unit sounds an alarm when it spots dangerous conditions.
Microbursts often occur in thunderstorms when rising air cools and suddenly sinks back toward the ground. This can create a downward torrent of wind, which hits the ground and bursts sideways, like water from a faucet hitting the bottom of a sink.
In wind shear, air movement changes suddenly, shifting between a strong wind from the left to one from the right, for example.
by CNB