“The sensor's role in engaging MCAS will put more scrutiny on whether Boeing was too reliant on a single device to trigger an important change in the jetliner's trajectory. ”

That’s not even a question anymore, in my mind.

One sensor fails, and the plane starts to dive. It’s not truly a “single point of failure only because the pilot theoretically still has — for the next 40 seconds — a chance to push the trim override button and save the day. A simple task, but all I can say is, “this is not the level of safety we are accustomed to.” Not when there could have been a dual sensor input, a disagree indicator, pilot training, and software changes that considered altitude and repetition.

I would say someone was asleep at the wheel, but that’s putting too much on the shoulders of one nameless person. A whole group of people were asleep at the wheel, because collaboration and oversight are the essential ingredients to maintain the umbrella of airworthiness.

There is an alarm notification for just about everything else, probably one that sounds when the co-pilot farts.

MCAS was a sloppy hack to deal with the fact that the MAX's engines wouldn't fit under the wings and had to be mounted too far forward. Boeing didn't want to go through the hassle of recertifying the 737 so MCAS was supposed to go in under the radar to make the MAX "feel" like an old-school regular 737 to its pilots. Letting those pilots know about the sloppy hack that was making it look that way would have given away the game and might have gotten the FAA's attention, making them wonder if perhaps a recertification should be called for. So they told as few people as possible and made it as invisible as possible. And that's why when it failed, nobody knew what to do about it.

This one will go into the book of engineering disasters.

Engineering is all about minimizing costs and increasing performance, but the process has to be entirely transparent.

Unfortunately managers who are not engineers, or are no longer thinking like engineers, cloud the process and cut corners in the hopes of short term gain.

In this modern world even simple things like cell phone chargers and baby powder can turn deadly. Aircraft manufacturers especially ought to know better.

Could it have just been a bottom line decision? The bean counters decided it was worth the risk to not add/fix safety features like the old Ford Pinto case? "Ultimately, the pilot will keep the plane from diving," they said.

If that's so, then clearly the cost of that upgrade was nowhere near that.

$80k savings ($40k x 2) ... 346 dead people.

The lawsuits are going to cost way more than that.

1. Frog in boiling water. I read articles that 0.6 degrees was the original maximum that the MCAS system was intended for. They ended up needing or using 2.5 degrees. The risk is greatly increased.
2. Timing. By the time they figured out the problem was a little bigger, they were running out of time in development. That is an area where delays would have been hugely costly. So not to save the cost of indicators or some software, but perhaps there would be a lot of pressure to not impact a production or certification schedule unless it was absolutely necessary. And who could be sure how necessary it was, when there was a button to override?
3. Oversight by outsiders. The FAA would normally perform the most important quality control and oversight function — judging the overall safety of the design at each step of the process, paying attention to redundant systems, criticality, risk factors, training, maintainability, human factors and so forth. They had staff that were educated, experienced, organized and professional — and though they were friendly to the airlines and manufacturers, they were not pushovers. Now, maybe, they are understaffed, and have been disempowered over time. But as outsiders, they would walk in with fresh eyes, reviewing all critical aspects.
4. Commonality as a goal. This is not only reflected in trying to avoid a whole separate training program (taking up the time of 21 crews of pilots per plane each making $300 or $400K per year for extra training in simulators) but in the usefulness of planes across markets...being able to substitute planes or use pilots wherever they are located at the end of the day.. But commonality is also a safety / human factors goal — pilot interface is important — so if the buttons don’t exist in the similar 737NG planes, pilots may not want to add them in the MAX because it makes the interface not common, and creates potential confusion.