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Old 21st Apr 2019, 06:20
  #4185 (permalink)  
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 57
Posts: 378
Originally Posted by robocoder View Post
I remember someone explaining that if they went with two sensors, the system would have to notify on disagreement and generate a warning, and that would need extra training and/or somehow impact the constraints under which the MAX was being designed.

I don't remember who said that and how accurate that is. Because if true, that raises the question: if the modified MCAS now accepts two inputs and self-disables on disagreement, is the no-training card already lost? With the penalty millions of certain airlines?
There is still much to discuss about the failure of the "initial" MCAS design, particularly the points made by TryingToLearn. The whole story is a very complex chain of decisions, most of which have been described in detail earlier in this thread, and sure to be covered by the accident investigation and FAA review.

The "revised" MCAS tries to satisfy both requirements, by having a complex series of validations to reduce false activation, while still maintaining the same 2.5 degree increment of nose-down trim (rather than reverting to the original 0.6 degrees). News reports suggest that expensive additional training will not be mandated by the FAA, though some airlines will choose to do so voluntarily.

By now the costs to Boeing (direct losses and share price reduction) are in the billions, not millions, so that penalty card is somewhat irrelevant.
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