The commercial flight was cruising at an altitude of 38,000 feet when the flight crew made a public announcement to the passengers (and a separate call to the flight attendant) that they may encounter turbulence, and the fasten seatbelt sign was turned on. The captain said they entered clouds and the flight was smooth for about 10 minutes when they noticed a very small red return (thunderstorm cell)on the radar about 5 miles in front of them. The crew did not have enough time to take evasive action and they penetrated the cell, encountering moderate rain with a strong updraft followed by one instance of a severe downdraft. The autopilot disengaged and the captain assumed control of the airplane. Shortly after, the flight attendant called on the interphone and said that she was assisting an elderly passenger in the lavatory when the upset occurred and they were both seriously injured. The captain immediately declared an emergency and landed without further incident. Weather Surveillance Radar (WSR) imagery identified a discrete cell of strong reflectivity values coincident with the airplane's position at the time of the turbulence event. A review of recorded weather data from two separate air traffic control centers handling the flight showed that moderate to extreme intensity precipitation existed ahead of the airplane for an extended period. However, the controllers did not recall seeing any displayed precipitation in the accident location, although they did recall seeing precipitation in other locations around the area. Review of display settings in use by the controllers showed no reason that the weather would not have been displayed, and there was no indication of a system malfunction. Review of ATC communications between the controllers and the flight crew revealed there were no discussions of the precipitation and thunderstorm activity ahead of the flight as required per Federal Aviation Administration (FAA) Order 7110.65, paragraph 2-6-4, "Weather and Chaff Services."
The inadvertent encounter with convective weather during cruise flight. Contributing to the accident was the flight crew's failure to detect and avoid the thunderstorm cell earlier in the flight, and the failure of air traffic controllers to provide the convective weather information to the flight crew.
— 9,300 samples, 15 parameters, SRN 192,940 to SRN 193,240.
| Time | Event | Page |
|---|---|---|
| SRN 192,940-193,240 | Five-minute event window plotted (figures 1 and 2) | 2 |
| SRN 193,074 | Master warning on for 6 seconds | 3 |
| SRN 193,090 | Master caution on for 10 seconds | 3 |
| SRN 193,091-193,092 | Lowest vertical acceleration about -0.8 g at SRN 193,091, highest about 1.7 g at SRN 193,092 | 2 |
| SRN 193,153 | Autopilot disengaged at about 36,750 ft pressure altitude | 2 |
Docket: data.ntsb.gov/Docket/?NTSBNumber=CEN10LA363. This brief is an analytical aid assembled from public records; it is not an investigative finding.