Datalink weather has been available for years, but
it’s never been better thanks to improvements
(shown here on an Avidyne MFD).
Nexrad Considerations
The National Transportation Safety Board has become so concerned about the phenomenon that it recently issued a safety alert warning pilots about the inherent latency of in-cockpit Nexrad weather displays. The alert came just weeks after the crash of a Pilatus PC-12 over Central Florida after the turboprop single broke up in flight while maneuvering around powerful thunderstorms. The NTSB has yet to release its final accident report, but here’s what we know so far:
At about noon on a hot day last June, the pilot of the PC-12 departed St. Lucie County International Airport (FPR) in Fort Pierce, Florida, bound for Freeman Field Airport (3JC) in Junction City, Kansas. Also on board were his wife and four children, all headed home after a vacation in the Bahamas. Fueled up and ready to go, the pilot departed on an IFR flight plan and was cleared to climb to FL 260. As the PC-12 headed northwest in the vicinity of Lakeland, Florida, the controller advised the pilot that his radar was painting a large area of precipitation with “extreme” echoes. The controller recommended a deviation to the right. The pilot agreed, asking for and receiving a heading of 320 degrees. This was the PC-12’s last communication with Miami Center.
According to preliminary radar data, the airplane turned to the northwest and climbed to 25,100 feet before entering a rapid descent. The pilot of a nearby airplane reported hearing a Mayday call about one minute before picking up the sound of an emergency locator transmitter signal. Eyewitnesses reported seeing the airplane emerge from the clouds in a spin and shedding pieces before descending into a field, killing all aboard.
Although the NTSB has yet to rule on a cause, less than two weeks after the crash the Board issued its safety alert warning pilots who use in--cockpit Nexrad weather display equipment that the “age indicator” denoting when the data was transmitted can be misleading. In fact, the actual Nexrad data you see on the screen can be as much as 20 minutes older than what is stamped on the cockpit display. The NTSB noted that this difference can present “potentially serious safety hazards to aircraft operating in the vicinity of fast-moving and quickly developing storm systems.”
Obviously we won’t know what role weather may have played in the Florida PC-12 crash until the NTSB releases its final report, but it’s clear investigators are becoming increasingly concerned about the role cockpit technology can play in weather-related accidents.
The details of two other recent crashes highlight the causes for concern, says the NTSB. In one such case last year, the pilot of a Piper Cherokee Six experienced an in-flight breakup and was killed near Bryan, Texas, after flying into severe storms. The NTSB determined the pilot’s Nexrad cockpit weather display would have shown he was clear of severe echoes when in reality his track put him directly into the teeth of a storm due to the data-transmittal latency issue.
