Thursday, June 11, 2009
The Pilot Decides
Controllers offer assistance, but it’s the pilot’s responsibility to manage the flight
The pilot of a twin-engine Mitsubishi MU-2B-40 received a weather briefing on the morning of August 25, 2006, which indicated that there’d be widely scattered rain showers and thunderstorms along portions of the planned route of flight from Bloomington, Ind., to Eleuthera Island in the Bahamas. The flight was cruising at FL280 when the pilot made contact with Jacksonville Air Route Traffic Control Center (ARTCC) in Florida at about 12:22 p.m. When the pilot was switched to a different sector, he heard several aircraft requesting course deviations due to weather. The controller asked the Mitsubishi pilot if he needed to deviate from course before reaching the vicinity of Ormond Beach, Fla. The aircraft was equipped with weather radar, and the pilot said that he wouldn’t need any deviations.
At 12:52 p.m., the ARTCC controller announced that a convective SIGMET was in effect for South Carolina, Georgia, Florida and Florida coastal waters. The pilot advised the controller that he had reconsidered a deviation, but whether he’d change course depended on when the controller would allow him to proceed direct to his destination. The controller said that because of traffic, he needed the pilot to reach Ormond Beach before he could proceed direct to Eleuthera Island. The pilot then radioed that if he needed to deviate, he’d have to go 10 degrees to the right, but wouldn’t have to alter course for about 60 miles. When the pilot needed it up ahead, the controller approved the deviation, asking if the pilot would be able to make it back over Ormond Beach. The pilot replied that he wouldn’t, and it looked as if Ormond Beach was being affected by the weather at the moment. The controller commented that the airplane had better weather radar than he did and asked the pilot to advise when he could proceed direct to Melbourne, Fla. The pilot replied, “Ten [degrees] right now and direct Melbourne when able—I can handle that.”
At 1:06 p.m., the pilot radioed the ARTCC controller that he couldn’t maintain altitude. The controller tried to call the pilot, but there were no further radio transmissions from the airplane, which experienced an in-flight breakup and crashed near Bunnell, Fla. The commercial pilot and passenger were killed.
Investigators found the power switch for the airplane’s radar turned on. They also found that the radar antenna’s tilt control had been set at approximately four degrees up. A meteorological study found that very strong to intense thunderstorms existed around FL200, which was below the aircraft’s cruise altitude. With the antenna tilted up, the returns likely wouldn’t have appeared on the pilot’s display. Investigators noted, however, that they couldn’t determine whether the aircraft’s weather radar was depicting the stronger returns or if the pilot was aware of the stronger storms below his cruise altitude.
Controllers at the Jacksonville ARTCC had displays of NEXRAD weather radar returns. The weather displays had four settings: below FL240, between FL240 and FL330, above FL330, and from sea level to FL600. The display used by the controller handling the Mitsubishi was set to display weather returns between FL240 and FL330 because he was controlling traffic within that altitude band. The controller’s display showed only weak to moderate echoes above FL240.
The NTSB indicated that the accident’s probable cause was the pilot’s inadvertent encounter with thunderstorms.
Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other NTSB news. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.
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