In its Sunday statement, Boeing said the software problem "did not affect the safety or operation of the aircraft."
It is not known if the lack of alarm function played a role in the crashes of Lion Air and Ethiopian Airlines Aircraft that killed 346 people. However, the alarm could not be reported that a sensor malfunctioned. In both catastrophes, preliminary investigations indicate that faulty data from an AOA sensor (AOA) triggered the aircraft's anti-aircraft software (MCAS), which tipped its nose as a "pilot" while pilots fought for control.
Boeing says his senior leadership and the Federal Aviation Administration only learned about the problem after the crash of Lion Air.
Neither the FAA nor Boeing disrupted the operation of the fleet until the Ethiopian Airlines crash in March 201
Why the Alarm Function Is Important
The AOA did not agree with the aircraft if the airline bought an additional optional feature called the AOA indicator, Boeing said.
The AOA display informs pilots if any of the AOA sensors are not working while the "disagree" alarm indicates when the sensors are disagreeing.
In 2017, after the delivery of 737 MAX began, the Boeing engineers "identified" that the 737 Max's display system software was not properly compliant with the AOA Disagree warning requirements, the statement said.
However, after reviewing, Boeing's engineers decided not to fix the problem immediately, concluding that "the existing functionality was acceptable until the warning and indicator were cleared in the next planned display system update."
Then, a week after the Lion Air crash on October 29, Boeing added a line in an FAA Airworthiness Policy stating that the mismatched light was optional , It is not clear whether Boeing has alerted its airline customers to the problem.
Boeing also called a Safety Review Board to examine whether the lack of AOA rejection on certain 737 MAX flight displays posed a security risk. The statement stated.
When the SRB confirmed Boeing, Boeing shared it with the FAA – along with the supporting SRB analysis – said the statement.
Boeing said it had issued a software update for the display system to feature the AOA alarm as standard standalone before the system MAX will return to the service. "
" When the MAX is operational again, all MAX production aircraft have an activated and operable AOA alarm "Disagree" and an optional angle of attack indicator, "the company said." All customers have previously delivered MAX aircraft the ability to enable the disagree AOA alert. "
Drew Griffin and Michelle Toh of CNN contributed to this report.