Rick Liu

Cannon Editor-in-Chief

In 2011, American Airlines signed a massive $38 billion order for the next generation A320neo with Airbus. Having lost a longtime customer, Boeing had a major dilemma on its hands. The company was working on a replacement aircraft to its Boeing 737 at the time, but the threat of even more customers defecting to the A320neo changed its decision making. After three generations, dating back to 1966, Boeing decided to design a fourth generation Boeing 737, named the Boeing 737 MAX, with brand new engines in order to compete with the newer Airbus plane in terms of fuel efficiency. 


Nothing appeared particularly out of the ordinary until the Lion Air crash on October 29, 2018. Almost two weeks after the crash, speculation immediately turned to the MCAS system Boeing implemented on its plane. 


The MCAS system was a software fix for changes in the engine that led to increased fuel economy, but also changed the way the plane flew in the air. The 4th generation plane had larger engines, which meant that the engines had to be shifted forward and higher on the wing than previous generations in order to provide sufficient ground clearance. However, this created different aerodynamic handling characteristics which could cause stalls to occur more often. MCAS was designed to fix that problem by taking over some control of the plane in order to prevent stalls. While this level of automation is not unprecedented since similar electronic handling existed in the previous generation 737 and A320, MCAS was more aggressive in “correcting” the plane’s handling, and was activated more often than other anti-stall measures. 


While many in the industry pointed to MCAS, many others questioned the safety record of the airline. Lion Air had a questionable history of safety, and was previously banned from flying to the European Union and the United States until 2016. It was not until the Ethiopian Airlines crash on March 10, 2019 where it seemed that the fault was clearly on the aircraft.


Even before the March 2019 crash, it was clear that a brand new aircraft crashing, especially with a new design that incorporated all of the latest innovations in the aircraft industry, meant that there was a high likelihood that this was not a fluke. Media outlets such as the New York Times and aviation analysts such as Leeham Group pointed out that the MCAS system was a likely cause in the aircraft undergoing a sharp and sudden descent. 


Moreover, Boeing did not disclose the presence of the system to pilots in its manual, or the steps needed to dis-engage it. As a new feature, that only existed on the 4th generation 737, engineers at Boeing should have held “paramount the safety, health, and welfare of the public” as stated in the National Society of Professional Engineers in the United States. Many other professional engineering institutions have a similar clause, including the Professional Engineers of Ontario. 


Not specific to engineering, the practice of informed consent also applies, where pilots should have had the right to know that the plane, even when auto-pilot was off, would suddenly take over the operation of the aircraft much more than existing “fly-by-wire” automation systems found in other aircrafts. 


However, it was purely an economic decision by Boeing to not disclose the existence of the system. In advertising the plane to airlines, Boeing emphasized the plane’s commonality with the previous three generations. This was done so that airlines with large existing fleets of 737s did not face enormous expenses of re-stocking parts, training mechanics, and especially re-training pilots to fly the new plane. This trade-off clearly showed that engineers at Boeing prioritized economics over the safety of the public in not disclosing this feature to pilots.


After the October crash, Boeing did disclose the existence of the system to pilots and ways to dis-engage the system. However, the March crash by a reputable and reliable carrier in Ethiopian Airlines raises more questions about the engineering failures. Black box data, released in the interim report, showed that the pilots did exactly as Boeing recommended to dis-engage MCAS when it forced the nose of the airplane down. However, the system kept re-enabling and eventually pushed the aircraft to enter a steep descent. 


This brings into question the need for the system in the first place. The New York Times reported on June 1st that the original design for MCAS system was far less aggressive in its automated corrections. This was the original justification for removing any mention of MCAS from pilot training and the manual. But initial test flights and simulator runs brought up unsatisfactory maneuvering characteristics caused by the larger engines. On two occasions, engineers increased the aggressiveness and the level of control of MCAS to make the aircraft fly smoother. These actions highlight another common problem of engineering, where decisions are made in a vacuum.


Engineers at Boeing were too fixated on the maneuvering characteristics of the plane, and wanting to minimize the difference between the 737 MAX and previous generations of 737s, that they did not realize how much bigger they were making the holes in the swiss cheese theory of safety, or how increasingly reliant the plane was on MCAS over manual control. Quick fixes that Boeing is considering now to get the 737 MAX in the air, such as making MCAS less aggressive in its corrections, or making it reliant on more than one airspeed and angle sensors (as is the case currently) should have been considered earlier.


Moreover, there are further questions on how much  Boeing can safely optimize what is already a 53 year old design. Boeing focused too much on optimizing fuel burn with the larger engine and minimizing cost to itself, without considering more creative and radical approaches to lowering fuel economy. The 737’s ground clearance, by far the lowest among any modern airplane, has not changed since 1966, while Airbus in its A320, or Boeing in their 777, can easily add larger engines to improve fuel burn without shifting the positioning of the engines like on the 737, or modifying the maneuverability of the plane. 


Many students probably remember one of the very first lectures in APS100: Orientation to Engineering. In it, Professor Stickel quotes an excerpt from the book “Educating the Engineer of 2020”. The book cites a number of attributes for the engineer of 2020 that engineers at Boeing could have shown more of.  However, this “engineering in the vacuum” shows that there was not good communication, and not all stakeholders with different perspectives were engaged. Engineers did not engage their creativity in finding ways to fit larger engines (or even designing a brand new aircraft instead of rehashing a 53 year old plane). And probably the most significant error was the lack of high ethical standards and professionalism in doing their full due diligence and proper disclosure in designing the plane. 


With automation playing an increasing role in today’s society, engineers should not just be relied on for their technical and analytical skills, which machines can probably do a much better job of. Rather, it’s these skills described in the Engineer of 2020 (analytical skills, practical ingenuity, communication, business and management, leadership, high ethical standards, agility, and lifelong learning) that will truly make great engineers, and avoid engineering failures in the future.

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