Being a bit of an aircraft buff, I’ve looked at Boeing and their civilian and military aircraft since the 1980’s. I’ve long been well aware of Boeing’s reputation for innovation and quality. This has come into serious question, beginning in August of 1997, when Boeing merged with McDonnell Douglas. Does this have any relevance to the US automotive industry?
737 MAX
Here’s a nutshell description of the aircraft and the issue. Airbus introduced a more fuel efficient competitor for the 737, the A320 NEO. This aircraft used more efficient engines that had a higher bypass ratio and thus a larger exterior diameter. Boeing wasn’t able to simply place engines like this on their 737, as they were too big to fit. The solution? Place the engines in a position they will fit, even though it’s not in the optimal engine position!
These Should Fit Here, Right?
If the two engines are placed farther forward than the optimal position (to fit), what then? Simple. You design a system to compensate for this. This was the now-infamous MCAS (Maneuvering Characteristics Augmentation System), which consisted of hardware and software. The problem with this engine placement is that the thrust might tend to lift the nose rather than move the plane straight forward. This situation, they thought, needed to be accommodated if it were to occur.
MCAS
This system had one simple task: detect undesired nose lift and adjust the tail elevator to ‘trim this out’. This wasn’t a bad engineering decision. What were bad engineering decisions, though, were the decisions to make this a ‘stealth’ subsystem and then to make it less than robust. Boeing had agreed to compensate their customers $1M for each 737 Max they purchased if it became necessary for their customers to have their pilots recertify on the new aircraft. It should be noted that $1M is paltry when you’re talking about an aircraft like this (cost over $130M 2024). To be clear, pilots wouldn’t even be required to do simulator training, and documentation would have no reference to MCAS. Pilots of the new aircraft wouldn’t even know this system existed!
You’re Kidding, Right?
The MCAS consisted of a front-mounted angle of attack sensor, computer code to take signals from this sensor and to then control the tail elevator properly. One might think to ask “What if the angle of attack sensor fails”. The answer to this was exhibited by the Lion Air and Ethiopian Airline crashes of 2019. The two crashes caused 346 deaths. The MCAS caused the plane crashes, and the pilots didn’t even know that MCAS existed! It should be noted that Boeing engineers and test pilots were aware of this possible situation, but Boeing buried this information!
Redundancy? What’s That?
I’m not an aircraft engineer. I always thought that commercial aircraft had substantial amounts of redundancy engineered in. The answer seems to be “not so much”. There was just one angle of attack sensor, not the two that you might expect. This is simple engineering. The computer system could have processed two sensor inputs, looking for discrepancies between the two sensors, and if found, acted accordingly. What might this look like?
With two AOA sensors, both are read at a rate determined to be adequate by the engineering team. This would be at a rate that allowed the control system to recognize the pitch trends of the aircraft (pitch up or down at this rate). As an example, If both sensors indicate 0 pitch and then 100mS later one indicates 1° positive pitch and the second sensor 10°, what does this mean? Can the plane go from 0° to 10° in 100ms (1/10th of a sec.)? Again, not an aircraft engineer, but let’s say no, this isn’t possible. The controller could then disregard the second, errant, input and then perform some type of notification. With three sensors, a ‘voting scheme’ could be implemented.
Solid State?
Since this issue hit the news in 2019 and we learned more about MCAS, one question has bugged me. We now have marvelous little solid state (‘chip’) accelerometers that are in things like your phone, your Wii, and your late model car. Why not use a few of these to sense aircraft pitch? Maybe three of them in a voting configuration? I can guarantee you that modern fighter aircraft utilize these components. The answers I’ve found on the web are unsatisfactory. Consider this paper: https://ntrs.nasa.gov/api/citations/20060020184/downloads/20060020184.pdf
Not Just 737 MAX
The Boeing 787 Dreamliner has had its own issues, mostly related to its lithium-ion cobalt batteries catching fire. I’m not aware of a root-cause determination for these battery failures. Boeing did a bit of a Band-Aid fix, in enclosing the batteries in a metal box with a vent to the outside to prevent smoke in the cabin. All of this was on top of the 787 being years behind schedule.
Then, just this month (Jan. 2024):
In January 2024, the FAA grounded some 171 737 MAX 9s with a configuration similar to that of Alaska Airlines Flight 1282, which suffered a mid-flight blowout of a plug filling an unused emergency exit on January 5, 2024, causing rapid decompression of the aircraft. From Wikipedia.org.
But What About Cars
Boeing used to be a company with a reputation for quality and safety that far exceeded by far that of any domestic automaker. Regarding reputations, I think that ship has already sailed for domestic automakers. I don’t take any pleasure in making this statement, but it seems to be true. Sad.
Most reliable cars, from Caredge.com:
- 1 Lexus – 79
- 2 Toyota – 72
- 3 Mini – 71
- 4 Acura – 70
- 5 Honda – 70
- 6 Subaru – 69
- 7 Mazda – 67
- 8 Porsche – 66
- 9 BMW – 64
- 10 Kia – 61
The source of this data is Consumer Reports. No domestic brands listed.
Another 737 MAX link:
http://en.wikipedia.org/wiki/Boeing_737_MAX_groundings
787 link:
https://en.wikipedia.org/wiki/Boeing_787_Dreamliner
