Maintenance Lapse Identified as Initial Problem Leading to Lion Air Crash
Crash investigators have concluded preliminarily that
improper calibration of an airspeed (AoA?) sensor during maintenance touched off the sequence of events that led to October’s fatal Lion Air jetliner crash in Indonesia, according to people familiar with the details.
The conclusion is subject to further analysis, these people said, but it is the firmest indication so far that a suspected maintenance lapse was the initial misstep that ended with the months-old
Boeing Co. 737 MAX aircraft plunging into the Java Sea, killing all 189 people on board.
Two days before Lion Air Flight 610’s early morning takeoff from Jakarta on Oct. 29, according to these people, mechanics installed but failed to properly calibrate a replacement airspeed sensor called an angle-of-attack indicator.
Based on information downloaded from the flight-data recorder, last month’s interim report revealed a constant 20-degree difference between signals from the angle-of attack sensor on the captain’s side—which had been replaced—and those from the co-pilot’s-side sensor.
Until now, the precise cause of the improper signals from the captain’s-side sensor hasn’t been clear.
People closely tracking the probe said that after U.S. air-safety experts re-enacted the tasks of installing, calibrating and verifying operation of the sensor, they deemed current maintenance instructions appropriate.
https://www.wsj.com/articles/mainten...39204?mod=e2tw