Root Cause Analysis of B737 MAX accidents Lion Air Flight 610 and Ethiopian Airlines Flight 302

1. Why did the aircraft crash? The Maneuvering Characteristics Augmentation System (MCAS) repeatedly activated, forcing the aircraft into an unrecoverable dive.
2. Why did MCAS activate? MCAS was triggered by erroneous data from a faulty Angle of Attack (AoA) sensor, which indicated the aircraft was at a high angle of attack (nose-up position), even though it wasn’t.
3. Why was the sensor data erroneous? The AoA sensor failed, likely due to mechanical damage or miscalibration, providing incorrect information to the flight control systems.
4. Why did MCAS rely solely on one AoA sensor? Boeing designed MCAS to rely on data from a single sensor, without incorporating redundant systems to cross-check the accuracy of the sensor input.
5. Why was redundancy not included in the MCAS design? The MCAS was intended to be a minor augmentation system, so Boeing did not classify it as a critical system that required redundancy, underestimating the risks associated with single-point failure.
6. Why did Boeing underestimate the risk of single-point failure? The system's safety assessment did not fully account for the catastrophic consequences of an MCAS failure, particularly in the context of sensor failure. Boeing’s assessment assumed that pilots could respond quickly to any malfunctions.
7. Why were pilots unable to effectively respond to the MCAS activation? Pilots were not properly trained on how to recognize and respond to MCAS activation. Boeing downplayed the system’s impact and did not provide detailed MCAS-specific training in the 737 MAX flight manual or simulator training.
8. Why was MCAS training not included in pilot manuals? Boeing chose not to emphasize MCAS in training to avoid costly simulator-based sessions and to position the 737 MAX as similar to previous 737 models, reducing the need for pilot retraining and expediting certification.
9. Why was MCAS not thoroughly reviewed during certification? Boeing and the FAA’s certification process had become increasingly self-regulatory, with Boeing having significant autonomy in approving and evaluating the system’s safety. This led to gaps in oversight and a lack of independent scrutiny of the system.
10. Why did the certification process fail to catch these issues? Regulatory pressure to quickly certify the 737 MAX (in response to competition from Airbus) and Boeing’s emphasis on minimizing operational disruptions for airlines led to compromises in the rigor of the certification process and safety assessments.

The root causes of the Boeing 737 MAX accidents were a combination of technical failures (faulty sensor, lack of redundancy), design flaws (single-sensor MCAS reliance), inadequate pilot training, and systemic issues in the regulatory and certification process. These factors collectively created an environment where small failures cascaded into catastrophic outcomes.

Article is generated with the help of AI and edited based on experience.