At a high-level briefing at the Federal Aviation Administration on March 28, officials revealed "black box" data from Ethiopian Airlines Flight 302 indicated that the Boeing 737 MAX's flight software had activated an anti-stall feature that pushed the nose of the plane down just moments after take-off. The preliminary finding officially links Boeing's Maneuvering Characteristics Augmentation System (MCAS) to a second crash within a five month period. The finding was based on data provided to FAA officials by Ethiopian investigators.
MCAS was partly blamed for the crash of a Lion Air 737 MAX off Indonesia last October. The software, intended to adjust the aircraft's handling because of aerodynamic changes caused by the 737 MAX's larger turbofan engines and their proximity to the wing, was designed to take input from one of two angle of attack (AOA) sensors on the aircraft's nose to determine if the aircraft was in danger of stalling. Faulty sensor data caused the MCAS systems on both the Lion Air and Ethiopian Airlines flights to react as if the aircraft was entering a stall and to push the nose of the aircraft down to gain airspeed.
On March 27, acting FAA Administrator Daniel Ewell told the Senate Commerce, Science, and Transportation Committee's aviation subcommittee that there had been no flight tests of the 737 MAX prior to its certification to determine how pilots would react in the event of an MCAS malfunction. He said that a panel of pilots had reviewed the software in a simulator and determined no additional training was required for 737-rated pilots to fly the 737 MAX.