Sensor fault led to Lion Air crash
Data from the jetliner that crashed into the Java Sea last month shows the pilots fought to save the plane almost from the moment it took off, as the Boeing 737’s nose was repeatedly forced down, apparently by an automatic system receiving incorrect sensor readings.
The information from the flight data recorder, contained in a preliminary report prepared by Indonesian crash investigators and released on Wednesday, documents a fatal tug-of-war between man and machine, with the plane’s nose forced dangerously downward more than two dozen times during the 11-minute flight.
The pilots managed to pull the nose back up over and over until finally “losing control”, leaving the Lion Air Flight 610 to plummet into the ocean at 450 mph, killing all 189 people on board.
The data from the so-called black box is consistent with the theory that investigators have been most focused on: that a computerised system Boeing installed on its latest generation of 737 to prevent the plane’s nose from getting too high and causing a stall instead forced the nose down because of incorrect information it was receiving from sensors on the fuselage. In the aftermath of the crash, pilots have expressed concern that they had not been fully informed about the new Boeing system - known as the manoeuvring characteristics augmentation system, or MCAS - and how it would require them to respond differently in case of the type of emergency encountered by the Lion Air crew.
Boeing has said the proper steps for pulling out of an incorrect activation of the system were already in flight manuals, so there was no need to detail this specific system in the new 737 jet. It said the appropriate flight crew response to uncommanded trim, regardless of cause, is contained in existing procedures. NYT