Southwest B737 near Oakland on Dec 1st 2011, turbulence injures three cabin crew

Last Update: October 30, 2013 / 17:36:33 GMT/Zulu time

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Incident Facts

Date of incident
Dec 1, 2011

Classification
Accident

Flight number
WN-1489

Aircraft Registration
N261WN

Aircraft Type
Boeing 737-700

ICAO Type Designator
B737

Airport ICAO Code
KOAK

A Southwest Airlines Boeing 737-700, registration N261WN performing flight WN-1489 from Albuquerque,NM to Oakland,CA (USA) with 95 passengers and 5 crew, was on approach to Oakland descending through about 14,000 feet when the aircraft encountered turbulence lasting for about 10 seconds causing injuries to all three cabin crew. The crew continued for a safe landing on Oakland's runway 29 about 10 minutes later. Two cabin crew were taken to hospital, the third was treated at the airport but did not require hospitalization.

The NTSB reported on Dec 17th 2011, that the aircraft was descending from FL400 through FL300 when the aircraft encountered turbulence while overflying Yosemite National Park. All three flight attendants were working in the galleys at that time, the flight attendant in the forward galley was thrown up and down, side to side with her feet leaving the floor, she was able to hold on a counter and secure herself into the forward jumpseat and didn't need to be taken to a hospital. The two flight attendants working in the aft galley were thrown around the aft galley and struck their heads and backs. Both were able to eventually secure themselves into their respective jumpseats, however both needed to be taken to hospital. One flight attendant was diagnosed with a serious injury (compression fracture of his vertebrae), the other with a minor injury.

On Oct 30th 2013 the NTSB released their final report concluding the probable cause was:

The flight crew’s flight into known severe turbulence associated with mountain wave activity

The NTSB reported that the seatbelt signs were on at the time of the turbulence encounter. The FMC computed significantly increased windspeeds at FL300 compared to FL400. At FL300, about 10 seconds after the aircraft had levelled off, the aircraft encountered a speed increase from 0.760 to 0.865 mach associated with according pitch changes and yaw and began to encounter vertical fluctuations that culminated in maxima of -0.18G and +3.52G vertical acceleration within a period of 13 seconds.

Flight dispatch had planned that flight to enter the accident area at FL260 due to known turbulence activity associated with mountain wave activity.

At the time of turbulence encounter all three flight attendants were not seated. The flight crew could not recall whether they had instructed cabin crew to take seats before entering the known zone of turbulence. The flight had been generally turbulent, flight attendants had been seated several times during the flight.

At the accident area there were no visual indications of possible turbulence (e.g. cloud), visual meteorologic conditions prevailed.



Metars:
KOAK 020653Z 03015KT 10SM SCT200 16/M08 A3005 RMK AO2 SLP175 T01611083 $
KOAK 020553Z 35012KT 10SM FEW200 17/M08 A3006 RMK AO2 SLP179 T01671083 10194 20161 58005 $
KOAK 020453Z 34011KT 10SM FEW200 17/M08 A3006 RMK AO2 SLP180 T01671083 $
KOAK 020353Z 32008KT 10SM CLR 16/M07 A3009 RMK AO2 SLP188 T01611072 $
KOAK 020253Z 31009KT 10SM CLR 17/M08 A3008 RMK AO2 SLP185 T01721083 55001 $
KOAK 020153Z 33004KT 10SM CLR 18/M08 A3007 RMK AO2 SLP184 T01781083 $
KOAK 020053Z 34013G17KT 10SM FEW200 19/M09 A3007 RMK AO2 SLP181 T01891089 $
Aircraft Registration Data
Registration mark
N261WN
Country of Registration
United States
Date of Registration
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TCDS Ident. No.
Manufacturer
BOEING
Aircraft Model / Type
737-7H4
Number of Seats
ICAO Aircraft Type
B737
Year of Manufacture
Serial Number
Aircraft Address / Mode S Code (HEX)
Engine Count
Engine Manufacturer
Engine Model
Engine Type
Pounds of Thrust
Main Owner
gcj kepjqbfeqpnggdcnfdkbchqfAiqAqeqmkmegimemldnqkqempplmkiqfdmdkpqnfmc lckbecnmAqlfh Subscribe to unlock
Incident Facts

Date of incident
Dec 1, 2011

Classification
Accident

Flight number
WN-1489

Aircraft Registration
N261WN

Aircraft Type
Boeing 737-700

ICAO Type Designator
B737

Airport ICAO Code
KOAK

This article is published under license from Avherald.com. © of text by Avherald.com.
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