Boeing Company (BA)

[Porgie Tirebiter]

That's what it seems to be coming down to. A split between airspeed indicators had been written up four times prior to the accident flight.

Prior to the next to last leg the airplane flew, maintenance replaced one of the AOA sensors. On the next flight the crew experienced the same problem the crew on the fatal flight was going to experience. They properly executed the runaway pitch procedure (which is identical on the Classic, NG, and MAX series) and completed the flight. That crew wrote up a 20 degree split between the AOA systems. Maintenance drained the pitot-static systems and returned the aircraft to service without addressing the AOA issue.

Apparently the crew flying the fatal flight experienced the same anomalies as on that previous flight, but wrestled with the system rather than kill it by executing the runaway pitch procedure.

So it's beginning to look like the issue that actually caused the accident was induced by maintenance not properly calibrating the AOA system after the sensor replacement, followed by maintenance failing to fix the proper issue after it was written up on the plane's next to last flight, followed by the accident crew not reacting properly when they experienced an issue they should have known might happen if a proper 'pass-down' system was in place.

In simple terms: This looks like a Lion Air issue.