Jeju B738 at Seoul on Dec 4th 2011, flock of birds, both engines operating at severe vibrations

Last Update: March 14, 2013 / 18:31:38 GMT/Zulu time

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Incident Facts

Date of incident
Dec 4, 2011

Classification
Report

Airline
Jeju Air

Flight number
7C-101

Aircraft Registration
HL7796

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

A Jeju Air Boeing 737-800, registration HL7796 performing flight 7C-101 from Seoul Gimpo to Jeju (South Korea) with 160 people on board, had departed Gimpo Airport's runway 32R in good visibility (8000 meters) and twilight at 07:03L (22:03Z Dec 3rd) and was climbing through 193 feet AGL when the aircraft flew through a flock of mallards with both engines (CFM56) ingestings birds and receiving serious damage resulting in severe vibrations of both engines and partial loss of thrust from both engines. The crew managed to continue the climb and attempted to connect the autopilot at 500 feet AGL, autopilot and autothrust disengaged at 600 feet AGL however. The crew attempted to gradually reduce engine thrust slightly which helped to stabilise the engines and reduce the vibrations. Burning smell developed in cabin and cockpit, the crew declared Mayday and declined the controllers instruction to climb to 4000 feet. The crew managed to climb the aircraft to 2000 feet, accelerating the aircraft and retracting the flaps in the process, thereafter the crew climbed the aircraft further reaching a maximum of 3200 feet with the thrust available and requested a wide pattern to return to Gimpo. The aircraft intercepted the localizer of runway 32L at about 15nm out and landed safely on runway 32L about 25 minutes after becoming airborne.

South Korea's Accident and Railway Accident Investigation Board (ARAIB) released their final report in Korean concluding the probable causes of the serious incident were:

- The flock of migratory birds was not detected so that takeoff was not delayed. After the aircraft became airborne the crew had no possibility to avoid the birds.

- Gimpo Airport has no effective system to detect movements of migratory birds

The ARAIB reported that Gimpo Airport has a wildlife control program, which includes the use of bird scare devices and bird patrols responsible to detect movements of birds and scare them away. Gimpo Airport however is surrounded by 13km of agricultural land including rivers and streams, which highly attract migratory and resident birds including birds of prey. The bird patrols would need to rely on naked eye observations to detect birds moving in the area, then report those bird movements to the tower prompting the controllers, who could then delay departures or arrivals as necessary. The measures around Gimpo Airport to reduce attractivity and scare birds away are being implemented however have not yet been able to calm the "tidal wave".

Prior to the departure of HL7796 no bird activity had been reported.

The captain (62, ATPL, 15,465 hours total, 12,281 hours on type) was pilot flying, the first officer (33, CPL, 1,060 hours total, 810 hours on type) was pilot monitoring for the sector. At the time of the departure the visibility was about 8000 meters, there were few clouds at 3000 feet, temperature was 0 degrees C and variable winds at 2 knots, morning twilight prevailed. The airport's ATIS broadcast the message "Flock of birds in the vicinity of the airport, use caution when landing or departing". The flight crew was aware of that broadcast prior to departure.

After the crew had declared Mayday shortly after becoming airborne a runway inspection on runway 32R was dispatched which recovered a number of mallards (wild ducks) from the intersection of the runway with taxiway E1 about 2800 meters/9200 feet down the runway.

The ARAIB analysed that a bird detection and warning system (bird radar) would be necessary at Gimpo Airport.

The use of firearms and cannons to scare the birds have proven not effective. Other measures are showing effect but have not been able to control the situation.

As of current the birds are being detected by bird patrols moving through the area, looking out for birds with their naked eyes and reporting such movements to the tower via radio. This proves however to be very limited due to inability of bird patrols to scan the whole area (range, angle limitations) and detect multiple bird movements at once.

The ARAIB analysed very positively of the pilot performance stating that every judgement and action, including the gradual reduction of engine thrust, was appropriate but stopped short of commending the crew for returning the aircraft to a safe landing.

The ARAIB issued two safety recommendations to South Korea's Minstry of Transport with the focus to develop and introduce technical systems to detect and warn of bird activity as well as take measures to reduce the attractivity of the "green belt" to birds around the aerodrome and another safety recommendation to the Korean Airport Operator to introduce state of the art technology to detect and warn of bird activity.
Incident Facts

Date of incident
Dec 4, 2011

Classification
Report

Airline
Jeju Air

Flight number
7C-101

Aircraft Registration
HL7796

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

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