(p. A18) . . . , Boeing engineers created the automated anti-stall system, called MCAS, that pushed the jet’s nose down if it was lifting too high. The software was intended to operate in the background so that the Max flew just like its predecessor. Boeing didn’t mention the system in its training materials for the Max.
Boeing also designed the system to rely on a single sensor — a rarity in aviation, where redundancy is common. Several former Boeing engineers who were not directly involved in the system’s design said their colleagues most likely opted for such an approach since relying on two sensors could still create issues. If one of two sensors malfunctioned, the system could struggle to know which was right.
Airbus addressed this potential problem on some of its planes by installing three or more such sensors. Former Max engineers, including one who worked on the sensors, said adding a third sensor to the Max was a nonstarter. Previous 737s, they said, had used two and managers wanted to limit changes.
“They wanted to A, save money and B, to minimize the certification and flight-test costs,” said Mike Renzelmann, an engineer who worked on the Max’s flight controls. “Any changes are going to require recertification.” Mr. Renzelmann was not involved in discussions about the sensors.
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(Note: the online version of the story has the date , and has the title “Boeing’s 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals.”)