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.
This was discussed somewhere in the thousands of preceding posts. I think we've reached the point (probably long past it really) where there's nothing more to really be said until new information is released from the investigating authorities.
Basically (if I recall correctly) the elevator feel doesn't operate in a continuously variable fashion relative to AoA. Also the elevator feel system does not have enough authority to maintain the linear stick force called for by certification reqirements. Finally, EFS operates during the stall, stick shaker active, etc. while MCAS (or its effect on stick feel) is needed prior to the stall.