Hi Terra,
It does help thanks, I was not aware of that SL.
It explains the thermal matching difference between the two types of rods and the improved mach trim schedule on the 4/500’s, which is presumably better again on the NG’s.
But surely the big issue here is achieving a “predictable pitch upset during the in–flight hydraulic power–on to power–off transition” (Boeings terminology), ie reducing the out of trim condition that you have in the event of a total hydraulic failure.
Leaving aside the oh-my-god scenario above, getting an old aluminium rod 737-300 through an elevator power off test is almost impossible because the limits are so tight. Yet the newer aircraft with titanium rods always do much better and they give us broader tolerances. It all seems the wrong way around.
On a practical level, I would have thought that 1.5 turns was neither here nor there and not worthy of a re-fly and 15 turns would be excessive to the point of uncontrollability but this can be a pass. Go figure???
S&L