Jet crash probe focus on wind shear

Airport wind shear detection systems may not have been working, officials say.

    Investigators say the aircraft's voice and data recorders will be sent to the US [Reuters]

    Pilot warned
    Vutichai Singhamany, a safety director at the department of civil aviation, said: "Initial assumption is that the wind shear detection system of Phuket airport was not fully operational at the time the accident occurred.

    "We checked today [Tuesday], and just found that the system didn't respond to the control tower."

    What is wind shear?

    Wind shear is a sudden change in either wind speed or direction within a short distance, causing a sudden gain or loss of lift for aircraft.

    It is generally associated with frontal weather systems, particularly thunderstorms. 

    Wind shear can be affected by the topography of the area.

    It can easily destabilise an aircraft and is one of the most challenging conditions a pilot can face.

    Wind shear poses the greatest risk to an aircraft during take-off or landing.

    A particularly dangerous form is vertical wind shear (also known as a microburst), where wind suddenly reverses from blowing upwards to a downward direction, creating a downward force on the aircraft.

    However, a senior aviation official has said the Indonesian pilot of the aircraft, who had died in the crash, was warned of the possibility of wind shear but decided to land anyway.


    "The last word the pilot said was 'landing'," Chaisak Ungsuwan, director-general of the air transport department, said on Monday.


    Kamtorn Sirikorn, a senior executive at the Aerothai air traffic control company, said two other pilots had reported wind shear conditions as they landed minutes before the One-Two-Go flight from Bangkok.


    He said: "The pilot definitely knew about the wind shear because he was on the same radio frequency as the previous two planes."


    Referring to an audio recording of air-traffic communications,  Kamtorn said: "The control tower repeated the conditions to [the pilot] and he acknowledged them just before the landing. The tape I listened to verified this."

    The accident raised questions about whether budget carriers were weighing safety concerns against the costs.

    Tom Ballantyne, an analyst with Orient Avation magazine, told Al Jazeera that there was a lot of pressure on low-cost airlines in South Asia to compete with each other.

    "There have certainly been suggestions before that there is lots of pressure on cockpit crew to get that aircraft from point A to point B, not to abort landings, to save money as it were," he said.

    'Responsible companies'

    However, budget carriers in the region transport millions of passengers every year without incident.

    Shukor Yusof, an aviation analyst with S&P equity research said: "I think by and large budget airlines are by and large very safe in South East Asia. You've got very responsible companies running those aircraft in Thailand, in Malaysia and in Singapore."


    Forensic workers say several of the dead
    have yet to be identified [Reuters]

    The aircraft's two flight data recorders were recovered on Monday and were being sent to the US for analysis.


    Officials say the results will give a clearer indication of what brought the aircraft down and, for the moment, wind shear is one of many theories.


    Airport controllers said the pilot from the doomed aircraft had tried to abort the landing moments before it hit the ground, broke up and burst into flames.


    Survivors said the aircraft briefly touched down before rising again and veering off to the left.


    Its left wing had then clipped treetops, sending the aircraft crashing into ground before colliding with an embankment alongside the runway.


    Thai police said that all 89 bodies from the crash have been recovered, although at least 13 had yet to be identified.


    Many of the people on board were holidaymakers heading to beach resorts in Phuket.


    One-Two-Go had earlier said 90 people had died in the crash, but Thai police have since revised that figure to 89.

    SOURCE: Agencies


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