Boeing 737 MAX 8

Production and delivery figures fluctuate due to inventory clearing post-grounding; hull losses refer specifically to Lion Air 610 and Ethiopian 302.

In BlackBoxWiki Archive

Design Lineage and MCAS Integration

The MAX 8 is the fourth generation of the 737 family. To accommodate larger, more fuel-efficient engines, Boeing moved the nacelles forward and higher on the wing. This altered the aircraft's aerodynamic profile at high angles of attack (AoA), necessitating the Maneuvering Characteristics Augmentation System (MCAS) to provide longitudinal stability and meet certification requirements.

Sensor Redundancy and Human Factors

Initial certification allowed MCAS to activate based on input from a single AoA sensor without cross-checking the secondary sensor. In both fatal occurrences, a single point of failure led to repeated nose-down trim commands. Investigation findings highlighted that pilot reaction times to continuous uncommanded trim were slower than the assumptions used during the original safety assessment.

Return to Service and Technical Revisions

The 2020 recertification required a flight control computer (FCC) software overhaul. MCAS now requires inputs from both AoA sensors, limits its authority to a single activation per high-AoA event, and can never override the pilot's ability to pull back on the column. Enhanced pilot training on stabilizer runaway procedures is now mandatory.

Notable Accidents

• Lion Air Flight 610· 2018
  A miscalibrated AoA sensor triggered MCAS, leading to a loss of control after pilots were unable to neutralize the automatic nose-down trim.
• Ethiopian Airlines Flight 302· 2019
  Sensor failure shortly after takeoff led to MCAS activation; the crew followed initial memory items but could not manually trim the aircraft due to high aerodynamic loads.