Lion Air Flight 610 Investigation

26 times MCAS pushed the nose down; 26 times the pilots pulled up. This 322-page investigation documents a fatal automation trap: Boeing's MCAS system relied on a single angle-of-attack sensor that was miscalibrated during maintenance. When the sensor sent erroneous data, MCAS activated repeatedly, pushing the nose down while pilots fought to climb. The system was designed to feel like natural aircraft behavior—pilots weren't told it existed. Boeing changed MCAS authority from 0.6° to 2.5° of stabilizer movement without updating the safety assessment, creating a system that could overpower human control. The investigation reveals a signaling failure: pilots received stick shaker warnings and airspeed disagreements but had no indication that MCAS was the cause. Like a neural circuit with corrupted sensor input, the aircraft couldn't distinguish real stall conditions from sensor errors. 189 people died. Boeing later redesigned MCAS to require agreement from both sensors before activation.