#controlzzzz<3

One of the biggest stories this year was the Boeing MAX 737 crashes and the recent revelations regarding the flaws in the onboard automated control system which contributed to the accidents. As these stories broke, there was a significant amount of concern regarding the culture of the airplane manufacturing industry-- specifically within the industry giant Boeing-- and the trustworthiness of aircraft that we often get on without a second thought. Talk about the relevance of control theory in everyday life!

I was interested in digging into exactly how this MCAS control system was designed to work and the specific flaw that lead to the horrible crashes of Lion Air 610 in October 2018 and Ethiopian Air 302 in March 2019. On an initial dive, I came across a news article published this month by Forbes, which discusses an MIT Professor’s evaluation of the FAA estimate of 15 MAX crashes over the next 30 to 45 years. According to Professor Arnold Barnett-- a statistics professor at MIT who has written extensively about the MAX crisis-- this estimate is about 24 times too low by his calculations. This is a shocking assertion, especially given the number of missteps already made by the Federal Aviation Administration (FAA) over the course of the MAX crisis: when the Lion Air crash occurred, the FAA did not ground the MAX fleet immediately. Instead, it issued a reminder to pilots regarding how to handle the misfiring flight control system. Unfortunately for the passengers of the Ethiopian Air flight, this correction procedure is not always successful in overriding the misfiring flight control system, and only after this second crash did the FAA ground the MAX 737 fleet indefinitely. As of yet, those planes are still not back in the air-- to the benefit of everyone. Somewhat ironically, in the case of the MAX 737, the much-touted factoid that it’s significantly more dangerous to get in a car than to get in an airplane is not quite as drastic-- flying in a MAX 737 begins to approach the risk levels of driving a car. 

So what is the MCAS system that is at the crux of these tragedies? MCAS stands for the Maneuvering Characteristics Augmentation System (MCAS) flight control system, which was designed to “enhance the pitch stability of the 737 MAX” airplane after changes to the physical structure of the aircraft changed the way the plane flies relative to previous 737 models (Boeing, 2019; “NYT: The Daily,” 2019). Essentially the software was designed to compensate for these physical changes in aircraft design to ensure it handled in a familiar way for pilots who were accommodated to the 737 model. Specifically, MCAS was “designed to activate in manual flight, with the airplane’s flaps up, at an elevated Angle of Attack” (Boeing, 2019). However, in flight, the sensors of the MCAS system malfunctioned, essentially tricking onboard computers into interpreting the angle of the jetliner plane’s nose to be too high. In response, the MCAS system compensated by pushing the nose of the plane downwards. Despite multiple attempts on the part of the pilots to bring the nose of the plane back up, the MCAS system continued to push the nose of the plane down. Ultimately, it was too late for the plant to pull away from the ground, and the plane crashed at nearly the speed of sound. 

Why is it always the sensors?

What’s shocking to me is that the MCAS system was reliant only upon a single sensor. How could engineers at Boeing have thought this was cool? What about redundancy??? That was a complete oversight that I would be confident any of my fellow Chemical Engineers at Columbia would have spotted before the planes took off-- after all, the redundant pump heuristic was drummed into us this semester in Senior Design, and in the end, there isn’t really a difference between a back-up pump for a cooling jacket system on a reactor in a chemical plant and an extra sensor for a flight control system in an airplane. 

In addition to the massive engineering oversight made in the design of the MCAS, there was significant oversight on the part of the FAA in regulating and monitoring the quality of the aircraft coming out of Boeing. In fact, the FAA had delegated quite a lot of the safety checks over to the process engineers at Boeing-- not sure how they thought that was going to pan out, given the fact that these leaders are under pressure from their own bosses, and at the end of the day, Boeing is business looking to make a profit (“NYT: The Daily,” 2019). In any case, there was a massive ethical violation of Boeing engineers in the case of the Boeing MAX 737 and perhaps other models-- they were knowingly putting faulty parts into planes, endangering passengers and neglecting their responsibility as engineers to uphold a certain moral and professional standard. In the end, Boeing is only setting a slap on the wrist for the violation regarding to the use of faulty parts on 133 737 planes-- this week, a $3.9 million fine was imposed on Boeing by the FAA. Given that a Boeing 737 costs just under 90 million dollars, I don’t see how the FAA thinks this fine is a considerable censure. Whatever, they’re obviously clueless. 

On the “un-grounding” front for the Boeing 737 fleet, it’s not looking too good-- while Boeing has been maintaining that it hopes to have planes back in the air in December and pressuring the FAA to make this happen, the FAA has been pushing back and is refusing to speed up the recertification process of the 737 fleet. Good on the FAA-- I don’t think they could have afforded another gigantuan mistake like the last 15…

All in all, it’s astonishing how consistent the presence of this crisis has been in the news headlines. Pretty much since the revelations regarding the MCAS system failure broke, there has been constant coverage of the grounding, correction of the control system in question, and recertification of the fleet. I’m interested to see how Boeing plans to go about gaining back the trust of passengers and the market-- unfortunately, given the size of their market share, there is often no choice but to fly on a Boeing plane.

Reflecting on this controls flop, I’m pretty astonished that it occurred. The fact that a faulty sensor had not been identified is scary, but what’s even more striking is that a redundant sensor had not been installed to provide alternate input for the MCAS control system. I would have thought this would have been a given. The significance and scope of control systems cannot be underestimated in today’s world. 

References

https://www.npr.org/2019/12/12/787646809/faa-chief-pushes-back-on-boeing-pressure-to-return-737-max-jets-to-service

https://thehill.com/policy/transportation/aviation/473481-faa-proposes-fining-boeing-39-million-for-installing-defective

 https://www.forbes.com/sites/petercohan/2019/12/13/mit-professor-says-faa-estimate-of-15-catastrophic-boeing-max-crashes-is-way-too-low/#20c53c6f5ce8

https://www.wsj.com/articles/the-four-second-catastrophe-how-boeing-doomed-the-737-max-11565966629