SAS A343 near Copenhagen on Sep 20th 2012, turbulence injures 3 cabin crew

Last Update: December 17, 2012 / 16:58:37 GMT/Zulu time

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Photo of SAS Scandinavian Airlines OY-KBA, Airbus A340-300 — SAS Scandinavian Airlines OY-KBA, Airbus A340-300 (Photo credit: Kentaro IEMOTO@Tokyo / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Sep 20, 2012

Classification
Report

Cause
Turbulence

Airline
SAS Scandinavian Airlines

Flight number
SK-944

Departure
Chicago O'Hare, United States

Destination
Copenhagen, Denmark

Aircraft Registration
OY-KBA

Aircraft Type
Airbus A340-300

ICAO Type Designator
A343

A SAS Scandinavian Airlines Airbus A340-300, registration OY-KBA performing flight SK-944 (dep Sep 19th) from Chicago O'Hare,IL (USA) to Copenhagen (Denmark) with 209 passengers and 12 crew, was descending through about 7000 feet towards Copenhagen when the aircraft encountered brief severe turbulence at approx 12:30L (10:30Z) causing minor injuries to a flight attendant still working in the aft galley and two other flight attendants who were already seated but had not yet secured their seat belts. The aircraft continued for a safe landing on Copenhagen's runway 22L about 10 minutes later.

Denmark's Havarikommissionen (HCL) released their final report in Danish concluding the probable cause of the accident (AVH definition)/incident (ICAO definition) was:

the short notice given to cabin crew was not enough to permit all cabin crew get strapped in before the aircraft entered turbulence. According to quick access recorders the aircraft entered towering cumulo nimbus clouds with an upward airflow that caused the vertical speed of the aircraft change from 1440 feet per minute descent to 44 feet per minute climb within 3 seconds resulting in a brief vertical acceleration of +1.73G and minor injuries to three flight attendants due to the vertical acceleration. The autoflight systems, that were steering the aircraft at the time, adjusted the vertical profile of the aircraft in a way that positive vertical acceleration was maintained throughout the encounter limiting the extent of injuries.

The HCL reported the aircraft was descending through 6800 feet when the flight crew spotted an area of black clouds ahead and notified cabin crew via intercom instructing cabin crew to get seated immediately. At exactly the same time the purser told the flight crew that the cabin had been secured for landing. The purser then called the other flight attendants to instruct them to get seated and seat belts fastened. The flight, until that point, had been smooth, but the aircraft now entered a towering cumulo nimbus cloud while descending at 1440 feet per minute. A vertical updraft caught the aircraft changing the pitch angle from +0.2 degrees to +0.5 degrees and turning the 1440 feet per minute descent into a 44 feet per minute climb within 3 seconds, the pitch angle reduced again to -1.9 degrees over the next 10 seconds while the aircraft acceleration from about 280 KCAS to 289 KCAS. The vertical acceleration reached a maximum of +1.73G and a minimum of +0.84G.

The HCL reported that following landing the flight attendant working in the aft galley was taken to a hospital for treatment but discharged the same evening.

The radar images did not indicate cumulo nimbus clouds in the area of the turbulence, however, air masses were quite unstable and towering cumulo nimbus were forming with the ceiling at about 5000-7000 feet and bases between 3000 and 5000 feet, freezing level was at 5000 feet. Updraft of about 3-5 meters/second (590-950 feet per minute) are usually observed within such clouds, due to the latent heat of water vapour the speed could well have been twice that value, too.

The investigation could not determine the exact time between the call from the flight deck to have cabin crew seated and the actual turbulence encounter.