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Yes, if the alternative is even less safe. This is important when the alternative might be driving, as driving is orders of magnitude more dangerous. Safety mea

Yes, if the alternative is even less safe. This is important when the alternative might be driving, as driving is orders of magnitude more dangerous. Safety measures that annoy people too much can end up with a net loss of life because of this. If there are other airliners that can be put into service to take up the slack, though, they’re very unlikely to be more dangerous.

Skunkleton 8y ago
I doubt that enters into the FAA's calculus here. It is more likely that there is not enough information to show that the plane is unsafe (a sample size of 2 is not statistically significant). The FAA has already approved this design, and to say that there is a design flaw would cast a shadow on their own approval process, and by extension their authority. Of course, over the last 10 years or so the FAA has delegated much of the approval process to the corporations themselves. Perhaps the system really is rotten?
- mikeash 8y ago
  No, it doesn’t enter into this decision because there are other planes that can step in, and grounding this type won’t encourage more driving. That was just an example of how safety measures can potentially backfire. The FAA absolutely does consider this in general. For example, this is a major reason they don’t require child safety seats: their analysis is that the extra expense would shift some travel to cars and ultimately kill more kids than it saves. https://www.faa.gov/news/press_releases/news_story.cfm?contentKey=1966 https://www.faa.gov/news/press_releases/news_story.cfm?conte... As for two crashes not being significant, I don’t buy it. Against such a low background rate (2017 recorded zero fatalities across all jet airliners of all types, for example), two crashes of the same type in a few months is huge. Six years ago, two non-fatal battery fires aboard 787s was enough for the FAA to ground the type until a fix could be made. In hindsight, that seems to have been the correct action. This 787 Max problem appears to be far more severe.
  - js2 8y ago
    If I had to hazard a guess at the logic behind not grounding the Max it’s something like this: We believe there may be an MCAS issue due to the preliminary Lion investigation but we haven’t seen it in our fleet and our pilots are confident they are prepared for it anyway. We don’t yet have enough data to draw any conclusion on the Ethiopian crash and so we’re currently treating it as an independent incident and a single incident doesn’t warrant grounding the plane. Would I personally feel safer on a new Southwest Max or on an older Southwest 737? I don’t know. Statistically, there have been no 737 Max crashes in the US.
mehrdadn 8y ago
I think it's a fallacy that people compares chances of death/injury like a computer would. Things like being in control of your own fate matter too.
- mikeash 8y ago
  People in general do not, but agencies like the FAA absolutely do, and that’s what I’m talking about.
jsharf 8y ago
By the way, the difference between the safety factors of driving and flying are not quite so straightforward. This is one of my favorite charts, which shows that per-mile, flying is safer, but per-journey, driving is safer (which makes some sense, since flying journeys are much longer, but 80% of accidents happen in the 5 minutes during takeoff/landing, so really in some sense, takeoff and landing are more dangerous than driving to work). https://en.wikipedia.org/wiki/Aviation_safety#Transport_comparisons https://en.wikipedia.org/wiki/Aviation_safety#Transport_comp... Also, note the final entry in that table: Space Shuttle. Per-kilometer, it's hardly that much more dangerous than driving. But per Journey....
- mikeash 8y ago
  Those numbers are for the UK in the 1990s. Commercial aviation is much safer today. The fatality rate per journey for US airlines over the last ten years is approximately 0.14 per billion journeys, several hundred times better than the number from your link. (Roughly 700 million journeys per year on average, one fatality during that period.) Cars have gotten safer too, but not nearly as much.
  - rootusrootus 8y ago
    Is there a point at which the statistics are too muddy to be useful? We have had 1 fatality in the last ten years, but in the last 10 years, 1 month, and 1 day we have had 51 fatalities.
    - mikeash 8y ago
      Definitely! If you take the fatalities for the last ten years and convert that to a risk estimate, the result will have gigantic error bars. We can be confident that the real risk is greater than zero, and it's pretty clear that it's small, but the exact number is pretty much impossible to know. The farther back you look, the less noise you get in your data, but you also incorporate data that's less and less relevant to the current environment. Ten years seems like a decent cutoff, although it is a cutoff that happens to have had a wild swing recently. My original point still stands if you want to take the data back a bit further: even if you include Colgan, the resulting number is way below the 117 per billion listed on that Wikipedia page.
js2 8y ago
So the argument is to ground the Max because there is a known MCAS issue and have people fly on proven older equipment. But Southwest hasn’t seen the MCAS issue in its fleet and its own pilots union feels its prepared to handle an MCAS issue should it occur. Could the reasoning be the Max is believed to be safer with US pilots at the helm than flying on the older equipment the Max is replacing? If the argument is that this is just about dollars and inconvenience to the airline, what would a 737 Max crash, now, cost Southwest in law suits and reputation? Maybe SWA is weighing this against the likelihood of another flight 1380 type incident.
- mikeash 8y ago
  The rationale could be that it’s still safer with a pilot who knows what to do. Given how safe other aircraft are, it seems unlikely. As for financial damages, it’s human nature to underestimate risks that have a large cost to mitigate. Even if grounding the Max is more cost effective, I wouldn’t be confident in them reaching that conclusion.
- LeifCarrotson 8y ago
  There's an additional confounding factor: Now that this has happened not just once but twice, causing hundreds of deaths, every pilot on the planet is acutely aware of this issue. Instead of Boeing publishing information about the systems and requiring pilots to receive training in the new models, the pilots themselves have essentially come up with their own pilot training course, and used the tragedies plastered across global news as the change notification system.

Skunkleton 8y ago

I doubt that enters into the FAA's calculus here. It is more likely that there is not enough information to show that the plane is unsafe (a sample size of 2 is not statistically significant). The FAA has already approved this design, and to say that there is a design flaw would cast a shadow on their own approval process, and by extension their authority. Of course, over the last 10 years or so the FAA has delegated much of the approval process to the corporations themselves. Perhaps the system really is rotten?

mikeash 8y ago
No, it doesn’t enter into this decision because there are other planes that can step in, and grounding this type won’t encourage more driving. That was just an example of how safety measures can potentially backfire. The FAA absolutely does consider this in general. For example, this is a major reason they don’t require child safety seats: their analysis is that the extra expense would shift some travel to cars and ultimately kill more kids than it saves. https://www.faa.gov/news/press_releases/news_story.cfm?contentKey=1966 https://www.faa.gov/news/press_releases/news_story.cfm?conte... As for two crashes not being significant, I don’t buy it. Against such a low background rate (2017 recorded zero fatalities across all jet airliners of all types, for example), two crashes of the same type in a few months is huge. Six years ago, two non-fatal battery fires aboard 787s was enough for the FAA to ground the type until a fix could be made. In hindsight, that seems to have been the correct action. This 787 Max problem appears to be far more severe.
- js2 8y ago
  If I had to hazard a guess at the logic behind not grounding the Max it’s something like this: We believe there may be an MCAS issue due to the preliminary Lion investigation but we haven’t seen it in our fleet and our pilots are confident they are prepared for it anyway. We don’t yet have enough data to draw any conclusion on the Ethiopian crash and so we’re currently treating it as an independent incident and a single incident doesn’t warrant grounding the plane. Would I personally feel safer on a new Southwest Max or on an older Southwest 737? I don’t know. Statistically, there have been no 737 Max crashes in the US.

mehrdadn 8y ago

I think it's a fallacy that people compares chances of death/injury like a computer would. Things like being in control of your own fate matter too.

mikeash 8y ago
People in general do not, but agencies like the FAA absolutely do, and that’s what I’m talking about.

jsharf 8y ago

By the way, the difference between the safety factors of driving and flying are not quite so straightforward. This is one of my favorite charts, which shows that per-mile, flying is safer, but per-journey, driving is safer (which makes some sense, since flying journeys are much longer, but 80% of accidents happen in the 5 minutes during takeoff/landing, so really in some sense, takeoff and landing are more dangerous than driving to work). https://en.wikipedia.org/wiki/Aviation_safety#Transport_comparisons https://en.wikipedia.org/wiki/Aviation_safety#Transport_comp... Also, note the final entry in that table: Space Shuttle. Per-kilometer, it's hardly that much more dangerous than driving. But per Journey....

mikeash 8y ago
Those numbers are for the UK in the 1990s. Commercial aviation is much safer today. The fatality rate per journey for US airlines over the last ten years is approximately 0.14 per billion journeys, several hundred times better than the number from your link. (Roughly 700 million journeys per year on average, one fatality during that period.) Cars have gotten safer too, but not nearly as much.
- rootusrootus 8y ago
  Is there a point at which the statistics are too muddy to be useful? We have had 1 fatality in the last ten years, but in the last 10 years, 1 month, and 1 day we have had 51 fatalities.
  - mikeash 8y ago
    Definitely! If you take the fatalities for the last ten years and convert that to a risk estimate, the result will have gigantic error bars. We can be confident that the real risk is greater than zero, and it's pretty clear that it's small, but the exact number is pretty much impossible to know. The farther back you look, the less noise you get in your data, but you also incorporate data that's less and less relevant to the current environment. Ten years seems like a decent cutoff, although it is a cutoff that happens to have had a wild swing recently. My original point still stands if you want to take the data back a bit further: even if you include Colgan, the resulting number is way below the 117 per billion listed on that Wikipedia page.

js2 8y ago

So the argument is to ground the Max because there is a known MCAS issue and have people fly on proven older equipment. But Southwest hasn’t seen the MCAS issue in its fleet and its own pilots union feels its prepared to handle an MCAS issue should it occur. Could the reasoning be the Max is believed to be safer with US pilots at the helm than flying on the older equipment the Max is replacing? If the argument is that this is just about dollars and inconvenience to the airline, what would a 737 Max crash, now, cost Southwest in law suits and reputation? Maybe SWA is weighing this against the likelihood of another flight 1380 type incident.

mikeash 8y ago
The rationale could be that it’s still safer with a pilot who knows what to do. Given how safe other aircraft are, it seems unlikely. As for financial damages, it’s human nature to underestimate risks that have a large cost to mitigate. Even if grounding the Max is more cost effective, I wouldn’t be confident in them reaching that conclusion.
LeifCarrotson 8y ago
There's an additional confounding factor: Now that this has happened not just once but twice, causing hundreds of deaths, every pilot on the planet is acutely aware of this issue. Instead of Boeing publishing information about the systems and requiring pilots to receive training in the new models, the pilots themselves have essentially come up with their own pilot training course, and used the tragedies plastered across global news as the change notification system.