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| Engineers from Boeing, whose Chief Executive Dennis Muilenburg is pictured here, idenftified a fault with a pilot warning system on 737 MAX planes over a year before deadly crashes that left nearly 350 people dead (AFP Photo/JOHN GRESS) |
Washington (AFP) - Boeing engineers identified a fault with a pilot warning system on its 737 MAX aircraft in 2017, a year before the deadly Lion Air crash, the company said Sunday.
Boeing said
that management was unaware of the issue until the crash in Indonesia, which
killed 189 people, and the planes were not grounded until after another of the
type operated by Ethiopian Airlines went down several months later, leaving a
further 157 people dead.
According
to Boeing, a supposedly standard piece of equipment that tells pilot about
disagreements between angle of attack (AOA) indicators -- which measure the
plane's angle vis-a-vis oncoming air to warn of impending stalls -- did not in
fact activate unless an additional optional indicator was purchased by
airlines.
That left
airlines that did not buy the optional indicator -- including both Lion Air and
Ethiopian Airlines -- without the safety feature.
Faulty
angle of attack indicator information may have played a role in both of the
deadly crashes, causing the 737 MAX anti-stall system to unnecessarily activate
and push the nose down toward the ground even as pilots fought to maintain
altitude.
"In
2017, within several months after beginning 737 MAX deliveries, engineers at
Boeing identified that the 737 MAX display system software did not correctly
meet the AOA Disagree alert requirements," the aircraft manufacturer said
in a statement.
"The
software delivered to Boeing linked the AOA Disagree alert to the AOA
indicator, which is an optional feature," it said. "Accordingly, the
software activated the AOA Disagree alert only if an airline opted for the AOA
indicator."
A Boeing
review "determined that the absence of the AOA Disagree alert did not
adversely impact airplane safety or operation," concluding that "the
existing functionality was acceptable until the alert and the indicator could
be delinked in the next planned display system software update," Boeing
said.
"Senior
company leadership was not involved in the review and first became aware of
this issue in the aftermath of the Lion Air accident."
Boeing's
entire 737 MAX fleet has been grounded since shortly after the Ethiopian
Airlines crash in March, while investigators study the incidents and engineers
work on solutions.
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