Originally Posted by
Water pilot
There is evidence from the voice recorder (of the second accident) that the co-pilot was unable to move the stabilizer. Now if you are convinced that the accident was the pilot's fault then you may disregard it as insufficient knowledge of how to move the backup manual wheel connected to a cable connected to the stabilizer (what year was this plane built, anyway?) but there it is. Now perhaps the definition of "primary flight control" does not include the stabilizer, but as a creature of the water rather than a dragon rider, I'd consider anything that has the ability to put the bow of the flying ship into the ground to be a "primary flight control".
You are confusing cause and effect here. It is entirely possible to fly any aircraft into a zone where some of the controls are ineffective or unresponsive (for example, a full stall). Yes, if you let the 737 (or a number of other Boeing's for that matter) get into a severe out-of-trim situation, the manual trim wheel may be difficult, if not impossible, to use without some special techniques previously discussed.
There is no evidence from the DFDR that the manual electric trim was inoperable. That is, every time the pilot made a stab trim input with the yoke switch, the stab moved as expected. The accident aircraft arrived at a severe out-of-trim state because the flying pilot did not use a sufficient amount of electric trim. When the electric trim was then cutout in this state, the manual trim was effectively unavailable.