Boeing says it knew about aircraft issue with 737 Max jets a year before deadly crashes
Boeing has admitted its engineers discovered an issue with the 737 Max aircraft in 2017 – a year before the aircraft was involved in two deadly crashes – but took no action.
In a detailed statement, the world’s largest aerospace company said an angle of attack (AOA) disagree alert, an alarm that tells pilots when two sensors report conflicting data, was inadvertently made an optional extra instead of a standard feature in some aircraft.
The US Federal Aviation Administration (FAA) said Boeing did not inform it of the software issue until November 2018 – a month after the Lion Air crash – but that it was a “low risk” issue.
The plane’s flight angle has been identified as a factor in both 737 Max disasters. Boeing has said that in both crashes, erroneous AOA data was fed to the Manoeuvring Characteristics Augmentation System (MCAS), the aircraft's anti-stall system which has come under scrutiny in recent months.
All 737 Max planes were grounded in March after an Ethiopian Airlines flight crashed, killing 157 people. In October last year, a Lion Air flight crashed and killed 189 people.
There were 387 of the aircraft worldwide when the fleet was grounded.
“In 2017, within several months after beginning 737 MAX deliveries, engineers at Boeing identified that the 737 MAX display system did not correctly meet the AOA disagree alert requirements,” Boeing said, adding it asked its experts to review the issue. “That review… determined that the absence of the AOA Disagree alert did not adversely impact airplane safety or operation.” They concluded the issue could be fixed in the next software update
The aircraft’s two angle of attack sensors, the statement said, provide “supplemental information only” and are not considered safety feature.
Boeing added that senior company leadership was “not involved” in the review, and didn’t become aware of the issue until after the Lion Air accident.