The Boeing 737 MAX remains an updated version of the 737NG, developed in response to the demand for more modern aircraft like the Airbus A320neo. This update was initiated as a response to a significant order from American Airlines for 100 planes before the official announcement of the 737 MAX. The 737 MAX series includes several updated features, such as new CFM LEAP-1B engines, winglets, and an updated flight deck. However, it was also equipped with the Maneuvering Characteristics Augmentation System (MCAS), which is linked to the crashes of Lion Air JT610 and Ethiopian Airlines ET302.
"The 737 MAX still has MCAS, but it's not the same as before," stated Boeing, emphasizing changes made to the system. The original MCAS system responded to high angles of attack due to new engine configurations by adjusting the stabilizer trim to counter pitch-up movements, ensuring minimal new training requirements for pilots. Initial reliance on a single Angle of Attack sensor and virtually unlimited authority led to repeated unintended activations, contributing to the tragic accidents involving JT610 and ET302. With redesigns, the system now relies on data from both AOA sensors, reducing authority and enabling system deactivation when sensor data significantly differs.
Pilots initially were not informed about MCAS, which aimed to maintain similarities with earlier 737 models. Following the two crashes and investigations, it was revealed that many pilots experienced unexpected downward pitches. Boeing clarified, "Boeing has reiterated that it is not an anti-stall system, but rather a flight control system intended to provide specific flight characteristics." However, flight crews of both crashed flights faced sudden and forceful MCAS activations amid challenging flight conditions.