If It’s Boeing, I’m not Going.
In 1967, the first Boeing 737 came off the production lines in Seattle, Washington. In the fifty-four years since that date, over ten thousand 737s have been produced, making it one of the most ubiquitous aircraft in the whole world. Then, in October 2018, disaster struck. Lion Air flight 610, a brand-new Boeing 737, lost control and nosedived directly into the Java sea. In the ensuing investigations, it was found that Boeing had installed a faulty computer system in their new 737-Max series airplanes: the MCAS. Nevertheless, airlines and governments dismissed the incident as an avoidable accident, and Boeing 737s with MCAS continued to fly—until the almost-identical crash of Ethiopian Airlines flight 302 on March 10, 2019. After that, all affected 737-Max series airplanes were grounded, and the ban was only recently lifted in December of 2020.
How could an airplane with an outstanding safety record, and lifetime service of fifty years, suddenly fall to a simple computer error? Unexpectedly, the answer is quite simple: an engineering failure, caused by hasty slap-on solutions, and lack of redundancy.
Boeing 737-Max series jetliners were designed in the early 2010s as the chief competitor to the new Airbus A320neo, a new and improved version of the classic Airbus A320, with more efficient engines. In order to keep their edge on the market, Boeing then proceeded to modify the existing Boeing 737 platform with new engines to provide competitive performance and fuel economy. Rather than redesign the wings to accommodate the new engines, Boeing mounted the engines further forward on the wings, as shown:
This placement of the newer, more powerful engines, could lead to the aircraft drifting upward and stalling in certain specialized conditions. In order to prevent this situation, Boeing installed the MCAS, a computer which would automatically sense if the craft was in danger of stalling, and tip it back into a normal position. This worked fine most of the time, but was poorly designed to depend on a single sensor. When this sensor failed on Lion Air flight 610, and later on Ethiopian Airlines Flight 302, the pilots were unable to regain control, and the airplanes crashed, killing all on board. Between the two flights, 346 people died.
This brings another fatal flaw of the MCAS to light: its ability to override pilot control. Coupled with the dependency on only one of the two sensors that could be used for the task, this relegated all lives on board to the electrical output of a single sensor. In other words, Boeing had made a massive engineering mistake: lack of redundancy. This same problem caused the Morandi Bridge failure in 2018, which killed 39 people and left Italy lacking a critical roadway.
But before assigning all the blame to an MCAS system, another part of the story must be considered: why did the MCAS system even exist in the first place? Because Boeing added new engines to the existing 737 frames, with minimal modifications. This slapped-on modification to an airplane that wasn’t originally designed to hold the new engines ultimately caused the change in air handling that necessitated the installation of MCAS. Boeing could have avoided the crashes, following investigations, aircraft groundings, and multi-million-dollar losses by properly redesigning the 737’s wings to accommodate the larger engines.
As the second anniversary of the Ethiopian Airlines flight 302 crash approaches, Boeing 737-Max airplanes take to the skies once again, this time with a redesigned MCAS programmed to depend on two sensors, and never to override the pilot’s control. So the 737-Max series is now safe to ride, and will likely go on to lead the industry in passenger flight. But the 737-Max cruises the skies as a startling reminder of the fallibility of machines—and the humans who create them. To the people left behind after 346 deaths, the line will certainly not be “If it’s not Boeing, I’m not going.”
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