As early as 2017, Boeing knew that the 737 MAX aircraft were being delivered with a problem in one of the key safety features.
On Sunday, Boeing released a statement about the AOA sensors that were involved in both the Lion Air accident in October last year and the Ethiopian Airlines accident in March.
In the statement, the company said its engineers had discovered the problem with an important safety indicator within months of the first 737 MAX deliveries.
The indicator, known as the angle of attack disagree alert, is supposed to warn pilots if a plane’s sensors are providing contradictory information about the direction of the plane’s nose.
The manufacturer had originally intended for the indicator to be standard on the new aircraft, as on previous generations of 737s. However, its engineers discovered that the sensor worked only with a separate, optional safety feature.
At that time, in 2017, Boeing did not consider the missing warning system crucial, so it saw no immediate need to install the system in all MAX aircraft.
The company emphasised that a standard process was followed after the discovery of the lack of a warning system, including cooperation with experts in the field. The resulting review stated that “the absence of the AOA Disagree alert did not adversely impact airplane safety or operation.”
Management and authorities
The company claims that its management, like the US aviation authorities, the FAA, were not aware of the problem until after October 29 last year, when the Lion Air aircraft crashed into the sea off Jakarta in Indonesia.
Dennis Muilenburg, chief executive officer of Boeing, told the press after the Boeing General Assembly on April 29 that the AOA alert system was not critical for obtaining key information for pilots in the cockpit.
The FAA agrees with this, but the authority nevertheless criticises Boeing for not alerting pilots and airlines about the change to the alert system.
“Timely communication from Boeing to 737 MAX users would have helped to reduce or eliminate potential confusion,” an FAA spokesman told the Reuters news agency.