A statement released by Boeing states the company was aware of the 737 MAX problem of the aircraft’s display software not correctly meeting the AOA disagree alert requirements but, took no action to resolve the issue.
It is likely the manufacturer knew that the problem existed as far back as 2017, long before the fatal crashes of a Lion Air and Ethiopian Airlines 737 MAX 8s.
Boeing said that among the primary features indicators and features for the safe aircraft operations are airspeed, attitude, altitude, vertical speed, heading and engine power settings. At elevated angles of attack, the most important features are the pilot’s stick shaker and pitch limit indicator.
“Neither the angle of attack indicator nor the AOA disagree alert are necessary for the safe operation of the airplane. They provide supplemental information only, and have never been considered safety features on commercial jet transport airplanes”, stated Boeing.
Thus, after detecting the discrepancy between the requirements and the software, Boeing followed the procedures to determine how to resolve the problem, however, the company came to the same conclusion in that “the absence of the AOA Disagree alert did not adversely impact airplane safety or operations.”
The issue was due to be fixed during the following planned system software update, without any urgency placed to initiate the update right away.
Boeing has stated that “senior company leadership was not involved in the review and first became aware of the AOA issue in the aftermath of the Lion Air accident.”
It is important to remember that the AOA disagree alert only worked on a MAX if the airline had purchased an additional, optional feature, the AOA indicator.
A Boeing statement said: “In both disasters, preliminary investigations suggest faulty data from a malfunctioning AOA sensor triggered the aircraft’s anti-stall software, the MCAS, which pitched the nose of the planes as pilots struggled for control.”
In the aftermath of the Lion Air accident, “Boeing informed the FAA that its engineers had identified the software issue in 2017 and had determined per Boeing’s standard process that the issue did not adversely impact airplane safety or operations”, the company reported.