PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
Old 13th Dec 2019, 20:04
  #4462 (permalink)  
MechEngr
 
Join Date: Oct 2019
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Originally Posted by Takwis
David P. Davies' solution to a slight pitch up into a stall in the 707 used only the elevator, not the much larger horizontal stab, and the solution was safe, effective, and benign. The MAX uses the stab, and trims forward for up to 10 seconds at a shot. That's at least an order of magnitude, maybe two, larger trim input than Davies'. I refuse to believe that a correction that large is "only feel."
The 10 second time limit is for when a pilot ignores the increasing angle of attack and increasing control force and continues to pull the wheel farther back, It's not a full-shot on every excursion. A pilot should take the hint and stop pulling all the way to stall unless they are really dedicated to it because that mountain isn't budging or a plane has ignored the Tower and started to taxi across the active runway.

The accident aircraft problem was the AoA system failed and provided ridiculously large values and the pilots were unknowingly provoking it further. Had the AoA system been accurate, none of this would be happening today.

Which leaves the question - is the greater blame for an instrument that generates false information or for a user of that data, like the stick-shaker and MCAS and airspeed and the pilots, which believes it? Unfortunately the aviation industry has long accepted that some planes will generate false AoA data and pilots will be forced to go through checklists to realize it's a false alarm.
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