Weather radar images sent to small- plane cockpits with new technology can be as much as 20 minutes out of date and have been linked to two fatal crashes, a U.S. safety agency warned.
The National Transportation Safety Board told pilots yesterday that the so-called Nexrad radar display can mislead pilots into thinking they are viewing current weather information.
“Remember that the in-cockpit Nexrad display depicts where the weather WAS, not where it IS,” the safety board wrote.
The government is broadcasting weather and other data to properly equipped small planes as part of the Federal Aviation Administration’s broader overhaul of the U.S. air-traffic system known as NextGen.
Nexrad is a long-range weather radar system jointly owned and operated by the FAA, the U.S. National Weather Service and the Defense Department, according to a fact sheet posted on the FAA’s website.
While airliners carry weather radars on board that allow pilots to see storms, small planes typically have not had access to that technology.
The gap in weather information has arisen in two accidents that killed a total of eight people, the NTSB said.
On March 25, 2010, a pilot and two flight nurses were killed near Brownsville, Tennessee, when an air ambulance helicopter encountered severe weather.
On Dec. 19, 2011, a single-engine Piper Cherokee broke up in flight and crashed near Bryan, Texas, killing all five aboard.
In both cases, storms depicted on radar in the planes’ cockpits were between 5 and 8 minutes old and miles away from their actual location, the alert said.
Compounding the issue is that the Nexrad displays the age of the radar image. That time-stamp indicates when the image was created, not how old the data is, according to the NTSB.
“Weather conditions depicted on the mosaic image will always be older than the age indicated on the display,” the alert said.
The FAA has been alerting pilots to the time delay for several years, the agency said in an e-mailed statement. The information is contained in an online training guide, a manual for flying in different weather conditions and in the FAA Safety Briefing magazine.
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