(CNN)A
new statement from Boeing indicates that the aerospace manufacturer
knew about a problem with the 737 Max aircraft well before the deadly
October 2018 Lion Air crash, but decided not to do anything about it.
Boeing previously acknowledged that an alert system that was supposed to be a standard feature in the fleet "was not operable on all airplanes."
But a statement
released Sunday describes a troubling timeline that shows how long some
at the company were aware of the problem before finally deciding to
act.
In its statement Sunday, Boeing maintained that the software issue "did not adversely impact airplane safety or operation."
It's
not known if the lack of the alert function played a role in the
crashes of Lion Air and Ethiopian Airlines planes, which killed 346
people. But the disagree alert could have notified pilots that a sensor
was malfunctioning. In both disasters, preliminary investigations
suggest faulty data from a malfunctioning angle of attack (AOA) sensor
triggered the aircraft's anti-stall software, known as MCAS, which
pitched down the nose of the planes as pilots struggled for control.
Boeing
says its senior leadership and the Federal Aviation Administration did
not know about the issue until after the Lion Air crash.
Neither
the FAA or Boeing interfered with the fleet's operations until the
Ethiopian Airlines crash in March 2019. The Trump administration
grounded all 737 Max jets worldwide, creating financial and logistical
problems for three major US airlines, while Boeing continues working to
fix the problem.
Why the alert function is important
The
AOA disagree alert only worked on an aircraft if the airline had
purchased an additional, optional feature, known as the AOA indicator,
Boeing said.
The AOA indicator
lets pilots know if one of the AOA sensors is not working, while the
disagree alert shows if the sensors contradict each other.
Boeing
contends the alert function was not necessary for the safe operation of
the airplane. But former Boeing engineers and aviation analysts interviewed by CNN
criticized Boeing's original software design for relying on data from a
single AOA sensor, claiming that those devices are vulnerable to
defects.
Boeing also did not flight test what would happen to the MCAS system if the single AOA sensor failed, CNN previously reported.
In
2017, after 737 MAX deliveries began, Boeing engineers "identified"
that the 737 Max display system software did not correctly meet the AOA
Disagree alert requirements, the statement reads.
Yet,
after a review, Boeing's engineers decided not to immediately correct
the problem, concluding that "the existing functionality was acceptable
until the alert and the indicator could be delinked in the next planned
display system software update."
The response
Then,
one week after the Lion Air crash on October 29, Boeing added a line in
an FAA airworthiness directive that said the disagree light was
optional. It's not clear if Boeing alerted its airline customers to the
issue.
Boeing also convened a
Safety Review Board to consider whether the absence of the AOA Disagree
alert from certain 737 MAX flight displays presented a safety issue, the
statement said.
When the SRB
confirmed Boeing's conclusion, Boeing shared it -- along with supporting
SRB analysis -- with the FAA, the statement said.
Boeing
said it is issuing a display system software update "to implement the
AOA Disagree alert as a standard, standalone feature before the MAX
returns to service."
"When the MAX
returns to service, all MAX production aircraft will have an activated
and operable AOA Disagree alert and an optional angle of attack
indicator," the company said. "All customers with previously delivered
MAX airplanes will have the ability to activate the AOA Disagree alert."
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