Black box hints at similar cause of Boeing air disasters
Black box data from a doomed Ethiopian Airlines flight suggests the crash was caused by a faulty sensor that erroneously activated an automated system on the Boeing 737 Max, a series of similar events suspected in the Indonesian disaster involving the same jet last year.
Data from the angle-of-attack sensor incorrectly activated the computer-controlled system, according to three people who have been briefed on the contents of the black box in Ethiopia. The system, known as MCAS, is believed to have pushed the nose of the plane down, leading to an irrecoverable nosedive that killed all 157 people aboard.
The black box contains information on dozens of systems aboard the plane.
The black boxes on both planes survived the crashes, allowing investigators to begin piecing together what caused the disasters.
Both investigations are continuing, and no final determinations have been made.
The new connections between the two crashes adds to the pressure on Boeing, which faces scrutiny over the design and certification of the plane. Boeing played a major role in approving the 737 Max, as regulators delegated significant responsibility and oversight to the manufacturer.
The design and certification of the plane is the subject of multiple government inquiries. The Justice Department is investigating the plane’s development, while the Transportation Department’s inspector general is looking into the certification process. The inspector general has issued a subpoena to at least one former Boeing engineer for documents related to the 737 Max, according to a person familiar with the investigation.
MCAS was originally designed to activate based on data from a single angle-of-attack sensor, which measures the level of the jet’s nose relative to oncoming air. Air-safety experts, as well as former employees at Boeing and the supplier that made the sensor, have expressed concern that system had this single point of failure, a rarity in aviation.
In a tacit acknowledgment that the initial design was flawed, Boeing unveiled a software update this week that would make the system rely on both sensors, instead of just one. If the two sensors disagree by a certain amount, MCAS will not engage.