The remote cause of doomed Ethiopian Airlines Boeing 737 Max which killed 157 people has been revealed.
According to sources close to an investigation into the crash, a sensor had been damaged at take off either by a bird or an as yet unidentified object.
This reportedly triggered erroneous data and the activation of an anti-stall system that sent the plane down on March 10 shortly after take off from Addis Ababa.
Boeing anti-stall software on the doomed jet re-engaged and pushed the jet downwards after the pilots initially turned it off due to suspect data from an airflow sensor, two sources said.
The pilots are said to have tried to manually bring the nose of the plane back up before restoring power but they were unable to regain control – ultimately resulting in the plane crashing to the ground.
It was not immediately clear whether the crew intentionally re-deployed the MCAS system, which was designed to push the nose of the 737 MAX down to prevent a stall but which is suspected of exacerbating a different scenario linked to two recent crashes.
Boeing’s anti-stall software is at the centre of investigations into last month’s Ethiopian Airlines crash and a Lion Air accident in Indonesia in October.
No significant new technical issues have so far emerged in the Ethiopian investigation beyond those already being addressed by Boeing through updated software in the aftermath of the Lion Air crash, a person familiar with the findings
But People close to the Ethiopian investigation have said the anti-stall software – which automatically pushes the aircraft’s nose down to guard against a loss of lift – was activated by erroneous ‘angle of attack’ data from a single sensor.
Officials briefed on the matter said a key question is when did the pilots at the helm of the Ethiopian Airlines 737 MAX disengage the MCAS system and did they do it too late to regain control of the airplane.
Two people briefed on the matter said the system is not designed to resume operations unless the crew acts and the crew may have unintentionally re-engaged the system as it desperately tried to pull the plane out of its nose-down descent.
The 737 MAX planes were grounded worldwide following the Ethiopian Airlines disaster, which came five months after a Lion Air crash in Indonesia that killed 189 people.
Boeing said on Wednesday it had reprogrammed software on its 737 MAX to prevent erroneous data from triggering an anti-stall system that is facing mounting scrutiny in the wake of two deadly nose-down crashes in the past five months.