Delta pilots requested deviation before severe turbulence event: NTSB

Delta Air Lines pilots requested a deviation from a typical approaching before encountering heavy turbulence
Karolis Kavolelis /

The United States (US) National Transportation Safety Board (NTSB) has claimed that Delta Air Lines pilots requested a deviation from a typical approach before they encountered severe turbulence, which injured 17 people onboard the Airbus A350 on August 29, 2023.

The NTSB‘s preliminary report states that the Delta Air Lines Airbus A350-900, registered as N576DZ, was on approach to Atlanta Hartsfield Jackson International Airport (ATL) on its flight from Milan Malpensa Airport (MXP), Italy, when the pilots “identified a weather radar return about 40 miles ahead”.

Subsequently, they requested a deviation from Air Traffic Control (ATC) at about 6:27 pm local time (UTC -4). However, the controller asked the crew to continue on the “OZZZI [approach] before deviating north and the flight crew accepted this instruction noting only a small white cloud near OZZZI”.

“The flight crew stated there were no [Pilot Report (PIREP)] from preceding aircraft, no nearby weather radar returns, nor any significant turbulence indications on their Flight Weather Viewer application,” the NTSB’s report added.

Nevertheless, the relief pilot communicated to flight attendants working on the flight that they should complete their duties within five minutes, as aircraft might encounter turbulence within that timeframe.

Around four minutes after the requested deviation, “the aircraft entered about 12 seconds of instrument meteorological conditions (IMC) at about 14,000 feet and encountered about 2 seconds of severe turbulence within the cloud”.

Following the severe turbulence event, the flight attendants notified the crew of the injuries in the cabin. They proceeded to declare an emergency with ATC – without squawking 7700, the general code for emergency – and requested for emergency services to meet the aircraft upon arrival at ATL.

“EMS personnel met the aircraft at the gate, and about 11 people were transported to the hospital for further evaluation,” the report noted. The NTSB added that four people onboard sustained serious injuries, while a futher 13 people sustained minor injuries.

A post-flight preliminary weather evaluation showed the “composite radar image including the area of building convection that the accident flight penetrated during the event” which the Airbus A350 flew through.

The NTSB has said that it will continue to investigate the incident, adding that the board’s specialists within the domains of air traffic control, meteorology will be involved in the investigation. It will also look at the cockpit voice recorder (CVR) and flight data recorder (FDR) data.

Furthermore, the Federal Aviation Administration (FAA), Delta Air Lines, and the National Air Traffic Controllers Association (NATCA) are to be involved in the investigation, as are the controllers working at ATL at the time.

The French Bureau d’Enquêtes et d’Analyses (BEA) and Airbus have also been appointed to participate.

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