What went wrong with the 737 Max 8 ?

This Photo by Unknown Author is licensed under CC BY-SA

​Flying is reportedly a 100 times safer way to travel than driving a car. Over the past 5 months two flights involving different operators using the same Boeing 737 Max 8 aircraft crashed killing all on board. This is shockingly unexpected from an aircraft that has been in service for 3 years and for an industry which prides itself on having a great safety record.
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​How could this possibly happen?

With the 737 Max 8 aircraft grounded around the world, and accident investigations underway, Boeing executives claim the cause of these crashes was a software problem that a new upgrade would fix.
 
A modern aircraft is highly complex and operates within multiple systems where a single cause of failure is almost impossible to result in the two crashes that occurred.
There has to be more to it. And there is. 

​It began in 2010 when Airbus was adding a new more fuel-efficient aircraft, the A320neo to its highly successful A320 family. Rather than having to design and go through the certification process for a new whole new aircraft, Airbus decided they could fit newer more fuel-efficient but larger engines to the existing A320 airframe. The A320neo would behave much like other aircraft in the A320 fleet so not require any special pilot training. This would speed the time to market by reducing the amount of engineering involved, simplifying certification, and eliminating expensive pilot training.

737 wings too low to the ground
Boeing could not take the same approach as Airbus as the 737 wings being lower to the ground could not fit any larger engines. With orders lining up, Boeing decided that buyers would likely switch to Airbus if they did not find a more fuel-efficient solution soon. Engineers found a solution using the new larger engines by mounting them higher and further forward on the airframe. This had the effect of changing the aerodynamics of the aircraft. The change meant that the plane didn’t handle properly at a high angle of attack and is prone to stall at high speeds. They then used software to correct for the aerodynamics and bring behavior back in line with the older 737s.

New software system
The software, Maneuvering Characteristics Augmentation System or MCAS fixed the problem in most circumstances but it did create new problems in some situations when it made it difficult for pilots to directly control the plane without being overridden by the MCAS.

Two sensors are fitted on the Max 8 to measure the angle of attack. The MCAS relies on just one of these sensors. If this sensor malfunctions, the MCAS function would engage and attempt to achieve a safe angle of attack. Flight simulations have shown that a faulty sensor would send a plane into an unrecoverable nosedive in as little as 40 seconds.

Boeing provided a warning light that would alert the pilots if the angle of attack sensors disagreed. They then decided to make the warning light an optional extra, costing an additional $80,000 per plane. Neither the Lion Air or Ethiopian Air 737 Max8 aircraft involved in the crashes were fitted with the warning light, presumably figuring that Boeing would only sell aircraft that were basically safe to fly. Since the crashes, Boeing has reversed this decision making the warning light a standard requirement for all Max 8 aircraft.

In summary, pilots and engineers describe the 737 Max 8 as ‘a kludge’ i.e. a clumsy but temporarily effective solution to a particular problem. I wonder how much of what is now the 737 Max 8 design was anticipated and planned for using for example, failure mode effects analysis, and how much was just ‘blind faith’.
 
FAA certification
Despite the 737 Max 8 aerodynamics and flight control systems being different to older 737s, the FAA accepted that it was not a new aircraft which would involve an extensive certification process and lengthy new pilot training. This allowed Boeing to get its new planes into customer’s hands quickly. This raises questions around how far can changes be made to an existing aircraft before it is considered new - I would have thought that the MCAS alone would have pushed the Max 8 design over this threshhold. 
 
Pilots already certified to fly the 737-800 are able to fly the 737 Max 8 with just a 1-hour lesson on the iPad. Unfortunately, neither the lesson nor the flight manuals mentioned the MCAS, with many pilots saying they only learned about the system after the Lion Air crash. This led to pilots not knowing everything they needed to know about how to handle the plane.
 
Consequences
Clearly, shortcuts have been taken by Boeing and others to get the 737 Max 8 into the marketplace quickly and counter the Airbus A320neo competition. Laying blame squarely on Boeing alone ignores the fact that the manufacturer is just one party in what is a complex industry. There are many parties who by making the business decisions they did have compromised safety that led to the loss of two aircraft and the lives of 346 people in the past 5 months. Boeing alone wiped $26.6b off their market value in the two days following the second crash, and done considerable harm to their reputation and brand.
 
Given time, the problems with the 737 Max 8 will be fixed and once again be able to fly and public faith in the industry will return. We will also hear from accident investigators about what needs to be done in future to avoid such kludges, provide more effective robust certification, and improved communications and training for pilots.
 
There are lessons for all of us involved in engineering complex systems in today’s global marketplace. With new opportunities there are new risks that need to be carefully weighed up, mitigating actions planned for, and implemented as part of the introduction of new services. No matter what industry we are in, we must all learn about what went wrong with the 737 Max 8.