Pilot Debrief

BOEING 737-7CT near Gulf of America, GM — 2024-04-03

Final reportDCA24FA143
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Date
2024-04-03
Location
Gulf of America, GM, USA
Aircraft
BOEING 737-7CT
Registration
N567WN
Category
Airplane
Highest injury
Serious
Fatalities
0

Probable cause

The pilot’s inadvertent encounter with convectively induced turbulence from a broken line of embedded thunderstorms moving across the region. Contributing to the accident was the failure of the air traffic controller to issue pertinent weather information along the airplane’s route of flight due, in part, to the sector over-saturation and frequency congestion caused by damaged communication equipment and the inability to split the sector to alleviate some of the traffic volume.

Contributing factors

Contributing to the accident was the failure of the air traffic controller to issue pertinent weather information along the airplane’s route of flight due, in part, to the sector over-saturation and frequency congestion caused by damaged communication equipment and the inability to split the sector to alleviate some of the traffic volume.

NTSB narrative

The initial flight plan was created to minimize the exposure to any potential turbulence and thunderstorms. While en route, the flight crew used the available resources to deviate around visible weather; however, rapid development of cloud buildups prevented them from avoiding turbulence. The flight crew attempted to notify the flight attendants (FAs) of the potential for turbulence. The FAs were completing cabin service when the captain made the announcement, but only one FA was able to secure himself in a jumpseat before the airplane entered the turbulence. One FA and one passenger were in the aft galley area during the encounter and sustained serious injuries. Another FA was in the aisle and received minor injuries. A review of National Weather Service (NWS) products confirmed the passage of a squall line north of the location of the encounter with turbulence. Radar imagery depicted extreme intensity echoes below the airplane’s flight path, with light intensity echoes reaching the airplane’s cruising altitude at the time of the encounter. The NWS issued inflight weather advisories for the potential for severe embedded convective activity and turbulence associated with those storms, but there is no evidence that the flight crew was alerted. The convective echoes, high echo tops, and very unstable airmass defined this event as a convectively induced turbulence event. Jacksonville (ZJX) Air Route Traffic Control Center (ARTCC) had adequate radar coverage over the area at the time of the encounter to identify the severe weather hazard. The Center Weather Service Unit had issued a morning weather briefing warning of a broken line of thunderstorms that was expected to cross the area. A review of the air traffic control (ATC) audio revealed that the west radar sector (R30) controller did not advise the flight crew of the precipitation ahead of them as required, likely due to the increased workload the R30 controller experienced at the time. The R30 (NEPTA) sector at the time of the accident experienced increased traffic due to sector splits at adjacent ARTCCs. In addition, a fire in 2023 at the remote communications air ground facility (RCAG) site that serviced NEPTA caused damage to equipment that was critical to the NEPTA sector communications, so a temporary mobile RCAG was provided. The temporary frequencies were low-power 10-watt transmitters with limited coverage, which caused delays in transmissions, and multiple “dead spots.” These issues increased frequency congestion on an already overloaded sector because many transmissions had to be repeated multiple times. The need for the R30 controller on duty at the time of the accident to repeat missed transmissions increased the workload on the controller and increased frequency congestion.

NTSB coding

Evidence available

  • ATC audio
  • FDR / data
  • ADS-B / radar
  • Photos
  • 22 docket documents
View NTSB final reportView NTSB docket

Docket documents22

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