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Inflight NEXRAD images may be older than pilots expect, NTSB warns


The mosaic NEXRAD weather radar images that many general aviation pilots get in their cockpits may be 15 to 20 minutes old, even when the image’s timestamp shows it’s only a few minutes old. That’s the takeaway message in a recent National Transportation Safety Board alert based on several recent accidents. The timestamp shown on the image is when the data processing company transmitted that image, the NTSB says. But it can take many more minutes before that to collect the radar imagery from multiple Doppler radar sites, stitch it together into a larger composite image, and then transmit that image to the cockpit. Many pilots figure a five-minute delay as a rule of thumb to calculate how much a storm cell may have moved, the NTSB pointed out. But even that isn’t enough of a buffer. The NTSB noted fatal accidents in 2010 and 2011 in which cockpit NEXRAD displays would have shown images purportedly only one minute old, but which were actually eight minutes old.