preliminary report from the safety board has just been published. Could you live with this assessment by two informed followers of this incident?
Misjudged the risk? Judgement of risk is at best an estimate of uncertainty; there are are always misjudgments because there are no facts, only estimates and forecasts. All risks events are in the future; there are no facts about the future. The facts are in the past. All judgments are made in the context of uncertainty.
A better question is about failure modes: what failure modes did Boeing model/analyze; did they appreciate the effect of multiple and cumulative effects? It's reasonable and customary to evaluate the safety of something as complex as the battery -- a system that mixes chemistry, electronics, and flight safety -- with the Failure Mode and Criticality Analysis method (FMECA).
[Note: the FMECA link is to the DoD's ACQuipedia site, launched in 2012, that is the defense Aquisition equivalent to Wikipedia: In the DoD's blurb, we learn: "ACQuipedia serves as an online encyclopedia of common defense acquisition topics. Each topic is identified as an article; each article contains a definition, a brief narrative that provides context, and includes links to the most pertinent policy, guidance, tools, practices, and training, that further augment understanding and expand depth"]
NASA pioneered FMECA in the Apollo program when it was evident that probability risk analysis (PRA) was not going to get them there. (NASA originally called it FMEA)
Why FMECA? In complex systems with a lot of parts, it's not unusual that the expected value of failure is so high as to be meaningless. Thus, the alternative is to model the failures and trace their effects through networks and trees that represent failure effects and interactions. Each failure mode has its own PRA, but n a sense, we have to substitute weighted judgments for expected value. They are not the same. (If you don't understand this point, catch up by reading "Thinking, Fast and Slow" by Daniel Kahneman)
Drew and Mouawad continue with a review of the preliminary report. We learn that
To be fair:
Fortunately, for all of us who fly:
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