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Boeing knew of 737 MAX safety system glitch year before deadly crash
WASHINGTON, May 6, 2019 (BSS/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.
BSS/AFP/MSY/0813 hrs