THY B773 near Keflavik on Feb 13th 2023, severe turbulence and uncontrolled descent cause 7 injuries

Last Update: May 10, 2025 / 04:43:10 GMT/Zulu time

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Photo of THY Turkish Airlines TC-JJJ, Boeing 777-300 — THY Turkish Airlines TC-JJJ, Boeing 777-300 (Photo credit: byeangel / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Feb 13, 2023

Classification
Report

Airline
THY Turkish Airlines

Flight number
TK-18

Departure
Toronto, Canada

Destination
Istanbul, Turkey

Aircraft Registration
TC-JJJ

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

A THY Turkish Airlines Boeing 777-300, registration TC-JJJ performing flight TK-18 from Toronto,ON (Canada) to Istanbul (Turkey) with 280 people on board, was enroute at FL350 about 70nm northeast of Keflavik (Iceland) when the aircraft encountered severe turbulence causing an uncontrolled descent of 8000 feet with a maximum rate of descent of 17100 fpm resulting in injuries to two passengers and 5 cabin crew. After checks and consultations with dispatch the crew decided to continue to Istanbul where the aircraft landed without further incident.

On May 9th 2025 Iceland's RNSA released their final report concluding the probable causes of the occurrence were:

SIA‐Iceland found the following to be the causes of the serious incident:

- An encounter with severe turbulence.

- Breakdown in Crew Resource Management.

- Loss of Situational Awareness.

Contributing factors

SIA‐Iceland found the following to be contributing factors to the serious incident:

- SIGMET for high‐altitude severe mountain waves had not been issued prior to the incident.

- The Captain (PM) did not follow procedure by using the phrase “I have control” (used by the flight operator), when he tried to take over the controls.

- Inappropriate control inputs during the aircraft upset.

- The autothrottle remained engaged and speedbrakes remained deployed during
the aircraft upset.

The RNSF summarized the sequence of events:

At 08:09 UTC, when at FL350 north of the glacier Langjökull in Iceland, the aircraft encountered severe turbulence.

There were three pilots on the flight crew, two Captains and a First Officer, because the length of the flight required a relief pilot (augmented flight crew). One of the Captains, who was also the Commander of the flight, was resting and not on the flight deck when the aircraft encountered the turbulence. The Captain, occupying the leftseat, wasthe Pilot Monitoring (PM) and the First Officer was the Pilot Flying (PF).

According to the flight crew, they were flying along their planned route in Reykjavik CTA3 when the airplane encountered severe turbulence. The flight crew had expected light turbulence in this area and had therefore turned the seatbeltsign ON, about 10 min before encountering the severe turbulence.

The turbulence encounter resulted in an aircraft upset condition, with an extremely low pitch angle and high rate of descent. The flight crew struggled to control the lateral and vertical path simultaneously and the aircraft lost close to 8000 ft of altitude in approximately one minute, with the highest rate of descent of 17,100 feet per minute.

The airspeed increased beyond the airspeed limit. This occurred regardless of the flight crew‘s effort to keep the airspeed within its limit. During the upset, multiple stick shaker activations occurred. The aircraft’s lowest altitude was FL273.

The flight crew regained control of the aircraft and then maintained FL280, still in light turbulence, for a short time and then started climbing. They scanned the instruments for any anomalies within the aircraft systems.

At 08:13, the aircraft re‐encountered turbulence.

When the turbulence conditions had improved and conditions permitted, the Commander of the flight re‐entered the flight deck. The Commander sat down in the observer’s seat and at 08:15 communicated with ATC, where the following PAN‐PAN message was transmitted:

“Reykjavik Turkish 18Alpha – PAN‐PAN, PAN‐PAN, PAN‐PAN, severe turbulence, we cannot maintain level, descending 290 now passing 300.”

The Commander then replaced the Captain in the left seat and took over as the Pilot Flying.

After that the flight crew talked to the cabin chief to inquire about any damage and injuries in the cabin. No one was seriously injured, although a few passengers and cabin crew members had incurred minor injuries and were under the supervision of a medical doctor, travelling as a passenger on the flight. After discussing the possibility of diverting the flight to either Glasgow Airport (EGPF) or Copenhagen Airport (EKCH) as well as consulting with IOCC2F1F, the decision was made to continue the flight to Istanbul Airport (LTFM), where a request for ambulances for the injured was made to ATC.