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The FAA was not just using the fact of the first crash in the risk analysis. This was the methodology they used: http://rgl.faa.gov/Regulatory_and_Guidance_Lib

The FAA was not just using the fact of the first crash in the risk analysis. This was the methodology they used: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/4e5ae8707164674a862579510061f96b/$FILE/PS-ANM-25-05%20TARAM%20Handbook.pdf http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.... They would have looked at the failure rate of the AoA sensor and the failure rate of the recovery procedure and the fact that there had been one fatal crash. That gave them a reasonable estimate of the risk. Based on that analysis they should have grounded the plane, but Boeing apparently convinced them that with pilot awareness of the problem that the recovery procedure would be more effective. Unfortunately that was overly optimistic.

mzs 7y ago
Indeed, here's the QRA following Lion Air Flight 610 showing projected fleet lifetime fatalities of almost 3000. https://twitter.com/davidshepardson/status/1204795320405831681 https://twitter.com/davidshepardson/status/12047953204058316...
linuxftw 7y ago
> Unfortunately that was overly optimistic. No, it was fraudulent. Boeing didn't make even the slightest attempt to identify all the potential failure modes, and it's still unclear if the plane is even safe to fly with MCAS disabled.
- deleted 7y ago
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- cameldrv 7y ago
  The plane cannot be certified without MCAS or some other stability augmentation. This is not unusual in itself, almost every jet aircraft has some kind of instability. The problem was that MCAS is not reliable and doesn’t fail safe. The fix they’re testing actually makes it less reliable, but when it fails it will disable itself instead of making a smoking hole in the ground.