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Old 30th Apr 2019, 18:20
  #4642 (permalink)  
bill fly
 
Join Date: Feb 2015
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Originally Posted by rodlittle
Does anyone on this topic know about Boeings system design ? and if so can they please explain to this simple pilot why mcas was designed in the waay it was, If I understand correctly MCAS is a sub-system designsd solely to counteract the lift generated by the engine nacelles at higher than normal AOT. It does this by trimming the stab nose down meaning that if the MCAS system fails due to incorrect AOA info, unless corrected by the PF its heading for disaster.
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
This could surely have been done so that forward ie nose down column movement was not affected.
This would mean that what ever happened the aircraft would not be left with a nose down trim and would not therefore be trying to fly into the ground.
Rod,
There are about four of us on this thread who think that. So you are in good company.
Boeing has a history of faffing with stab trim to compensate feel inputs and to them I guess it came naturally.
However, a fail mode in the control feel or a separate dedicated feel box would only cause a harder pull - once - and could be trimmed out.
That is what should have been installed (says I) and even if retrofitted may well be:
- cheaper than losing public trust
- easier to explain to the world and the pilots
- a much less critical system than MCAS can become.
B
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