Boeing on Sunday said that a key alert system linked to faulty sensors was sold as an optional feature on Boeing 737 MAX planes.
Boeing has taken heat in recent months, following the crash of Lion Air Flight JT610 and Ethiopian Airlines Flight ET302, which both featured Boeing 737 MAX planes. Investigators have linked the crashes to a sensor called the angle of attack (AOA), which delivered faulty readings and triggered a mechanism on the MAX planes to automatically push the nose of the plane downwards, causing them to plummet.
Issues with the AOA sensor had reportedly been flagged to the Federal Aviation Authority over 200 times, and it was noted that the sensors had the potential to “cause problems” on planes which relied solely on the data from the single sensor, like the 737 MAX.
In a statement on Tuesday, Boeing said that it included a mechanism called the AOA disagree alert system, which was designed to show discrepancies in the AOA reading, as a standard feature on its 737 planes. But once it started deliveries on the updated 737 MAX planes, the AOA disagree alert was being sold as an optional feature.
“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 company said.
But the company said that AOA indicator and AOA disagree alert were not crucial safety requirements to the 737 MAX, and that there were other indicators which identified the plane’s speed, altitude, and engine performance which should have allowed flight crews to safely operate the aircraft.
“Neither the angle of attack indicator nor the AOA Disagree alert are necessary for the safe operation of the airplane,” Boeing said. “They provide supplemental information only, and have never been considered safety features on commercial jet transport airplanes.”
Boeing also admitted that they waited a year to tell airlines and regulators about discrepancies with the now-optional alert, insisting that it did not pose a safety risk.
Boeing’s CEO Dennis Muilenburg has previously said pilots in the Ethiopian Airlines crash did not “completely” follow emergency procedures, though the company has admitted that the AOA sensor malfunctioned during both incidents.