Qatar B773 over Atlantic on Dec 4th 2016, turbulence causes 4 injuries

Last Update: April 9, 2020 / 15:58:26 GMT/Zulu time

Bookmark this article

Photo of Qatar Airways A7-BAN, Boeing 777-300 — Qatar Airways A7-BAN, Boeing 777-300 (Photo credit: kitmasterbloke / Flickr / License: CC by)

Incident Facts

Date of incident
Dec 4, 2016

Classification
Accident

Cause
Turbulence

Airline
Qatar Airways

Flight number
QR-708

Departure
Washington Dulles, United States

Destination
Doha, Qatar

Aircraft Registration
A7-BAN

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

A Qatar Airways Boeing 777-300, registration A7-BAN performing flight QR-708 (Dec 3rd) from Washington Dulles,DC (USA) to Doha (Qatar) with 350 people on board, was enroute at FL310 over the Atlantic Ocean about 115nm northeast of Lajes Terceira Island (Portugal) when the crew initiated a diversion to Lajes reporting a number of injuries on board after experiencing turbulence. The aircraft entered a hold at 6000 feet to dump fuel and landed safely on Lajes' runway 15 about 35 minutes after setting course towards Lajes. Two passengers received serious injuries (one a fractured leg) in the upset, 3 minor injuries, another passenger complained about heart ache causing concerns of a possible heart attack which turned out not true however.

Radar data do not show any altitude deviation in the last 45 minutes prior to the diversion (from about 420nm westnorthwest of Lajes until leaving FL310).

Passengers reported the aircraft dropped suddenly causing passengers with seatbelts not fastened to be thrown out of their seats, for example a three year old boy was thrown across the aisle onto the lap of another passenger, other passengers hit the ceiling resulting in a number of injuries. A number of oxygen masks dropped as result of the turbulence encounter. The aircraft needs to overnight in Lajes due to crew duty time limitation.

A hospital on Terceira Island reported that three passengers were taken to the hospital, two were discharged after treatment, a third remains in hospital care.

The passengers were taken to hotels.

A replacement Boeing 777-300 registration A7-BAH has been dispatched to Lajes and is estimated to continue the flight in the morning of Dec 5th, while the occurrence aircraft is being checked for possible structural damage.

Portugals GPIAA have opened an investigation into the occurrence.

According to information The Aviation Herald received the severe turbulence lasted for four minutes.

On Dec 7th 2016 Portugal's GPIAA reported the occurrence has been rated an accident, the GPIAA is investigating the accident. The aircraft was enroute at FL310 at about position N41 W40, about 600nm west of Lajes, in instrument meteorological conditions and night conditions at a constant speed of 0.84 mach when the aircraft encountered severe turbulence. Two occupants received serious, two other occupants minor injuries, the aircraft sustained "superficial" damage to the ceiling panels.

The GPIAA reported the captain had left the cockpit for a toilet break, when first light turbulence was noticed, the first officer illuminated the fasten seat belt signs, which prompted the captain to return to the flight deck and assume control of the aircraft. The crew assessed the situation, the GPIAA wrote: "No changes in air density were detected on the weather radar to predict turbulence and the crew decided to continue on the established route." The captain observed strong winds from their right hand side, instructed cabin crew to get seated at their present positions, when severe turbulence hit the aircraft causing loose objects including passengers, who had not closed their seat belts, and cabin crew not yet being seated to be thrown through the cabin. The stick shaker activated temporarily, the aircraft encountered altitude deviations of 200 feet, the autopilot did not disconnected however, the crew disconnected autothrottle during the most severe turbulence. The turbulence lasted intermittently between 10 and 25 minutes. After the encounter the flight crew communicated with the cabin crew to find out whether there were injuries and to understand the extent of damage in the cabin. During the turbulence encounter most of the passengers had been seated with their seat belts fastened, only a few were out of their seats. At the time of the turbulence all cabin service trolley had been stowed and locked.

The GPIAA wrote: "The occurrence was most likely a case of encounter with turbulent masses of clean air." and reported the flight data recorder revealed vertical accelerations between +1.133G and -0.836G. GPIAA investigators have travelled on site for the investigation.

The GPIAA released their final report concluding the probable cause of the accident was:

The GPIAA has determined that the most likely cause for this event was encounter with severe clear air turbulence (CAT), due to strong and dry winds at high altitude.

Contributing factors were:

- The lack of precipitable moisture in the air, like clouds for instance, prevented the premature detection of unstable regions by the onboard meteorological radar.

- Some passengers got injured for not properly following the captain’s command to fasten the seat belts.

The GPIAA reported a total of 5 passengers received injuries, one a serious injury: a "major trauma passenger sustained skull skin
cuts, left hip and femur trauma, and had to remain in the hospital with the affected leg immobilized.", 4 other passengers received minor injuries. The GPIAA added: "After a medical examination, no passengers were confirmed of having had a life threatening cardiac arrest. The passenger that complained of chest pain was later diagnosed as having posttraumatic stress disorder and anxiety syndrome."

The GPIAA described the FDR data:

From the plots a rapid change in vertical acceleration can be observed, changing from -0.5 to +0.5 G in a period of 1 second, with
a 400ft drop in altitude.

Approximately 7 minutes before the event acceleration peak, a moderately turbulence can be seen on the recorded data and two more moderate turbulences after the event peak.

During the event, the aircraft recorded wind gusts from 60kt to 105kt, variating from 215° to 255°.

The autopilot remained engaged during the whole observed and recorded period. The auto-throttle was briefly disengaged, for 2 minutes, during the first moderate turbulence that followed the severe turbulence event.

After the severe turbulence event, the selected Mach speed was reduced from 0.84 to 0.82, with oscillation of the actual speed being recorded trough out the event.

During the event peak, vertical acceleration the aircraft pitch changed from 0° to 4°, with oscillations of about 2° during the previous seconds before the event.

A change of heading from 110 to 080, with a 10° roll to the left, was also recorded just after the event, followed by two more 15° rolls to the right setting the aircraft to heading 120°.

During the turbulence encounter, quick thrust lever changes could be seen, with correspondent N1 changes by both engines, as well as control inputs to the flight controls. At this moment, both the auto-throttle and autopilot systems were active and engaged.

The GPIAA analysed:

Though being very difficult to predict accurately where and when clear turbulence may occur, the received pre-flight weather information showed
that moderate to severe turbulence was to be expected while crossing the Atlantic at latitude 40°N, and between longitudes 40°W and 20°W, from flight levels 290 to 400.

The investigation determined that the crew performed its duty adequately and the recordings contained no additional relevant contributory facts to this event.

The test out of both weather radar computer concluded that none of the units recorded any faults at or near the time of the turbulence encounter that would have inhibited their operation.

...

Clear Air Turbulences (CAT) occurs when strong and dry wind drafts are encountered in flight.