Wednesday 09 / July / 2025
Los Angeles: Boeing engineers discovered a fault in the 737 MAX pilot warning system in 2017, a year before the Lion Air crash that killed 189 people, according to a statement released by the company.
According to Boeing, "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 software delivered to Boeing linked the AOA Disagree alert to the AOA indicator, which is an optional feature on the MAX and the NG. Accordingly, the software activated the AOA Disagree alert only if an airline opted for the AOA indicator."
According to Boeing, a supposedly standard piece of equipment that tells pilot about disagreements between angle of attack (AOA) indicators did not in fact activate unless an additional optional indicator was purchased by airlines. Those that did not purchase the optional indicator were without the safety feature.
Boeing said that management was unaware of the issue until the crash in Indonesia.
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.
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.
