The cause of the Ethiopian
Airlines 737 crash which killed 157 people has been revealed.
According to reports it is
believed the plane suffered a damaged ‘angle-of-attack’ sensor upon take-off
from a foreign object which could have been a bird.
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.
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.
The pilots were not able to
get control of the plane back, sources told ABC News.
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 told
Reuters.
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.
The investigation has now
turned towards how the MCAS system was initially disabled by pilots, in line
with part of a cockpit checklist procedure, but then appeared to start working
again before the jet plunged to the ground, sources said.
Speaking to CNN, pilot and
aviation analyst Miles O’Brien gave his take on what could have happened in the
cockpit once pilots reportedly turned off the automatic flight control system.
“They were left with a
manual wheel to try to get the nose in the proper orientation and evidently
what we are hearing is, that maybe the wheel didn’t have enough authority, that
it was too hard to move, or could not move fast enough, given the amount of
altitude they had in order to recover. So that put them in a situation where
they followed the book, and the recovery procedure was not good enough.
“The idea that they would
have this troubleshooting system, they followed the book and it wan’t good
enough, is just horrifying,” said pilot and CNN aviation analyst Miles O’Brien.
149 passengers and eight
crew members were killed when the plane went down just six minutes after
take-off.
Boeing is working to submit
an upgrade of the software to the US regulators in a couple of weeks and adding
extra training.
Boeing’s fastest-selling
737 MAX jet, with orders worth more than $500 billion at list prices, has been
grounded globally by the Federal Aviation Administration (FAA).

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