Lemonbreath:
I think your two scenarios are wrong, leading you to ask the wrong question in the wrong way. You have to learn to read/listen/watch, three times, sometimes, to really understand what’s being said. If it doesn’t ring true listen again, and see if you are missing something btwn. the lines (i.e. read btwn. the lines).
They said that the cable had a failure/design strength of about 600lbs. (632#) and that it broke at about 900lbs., at a quick disconnect joint in the cable. These results were from a lab test after that accident. In fact, the cable did not break, the quick disconnect came apart. They also implied that it was hard to imagine that a pilot could possibly apply 600lbs. to the cable, so there was a significant FoS in that respect. He is pushing on the top (handle) of the throttle lever, which then has a pivot pin at the bottom of the lever and assuming the cable is connected an inch or two above the pivot pin. Maybe the pilot can apply 40-60lbs. to the top of the lever, and that arc of travel is maybe 8 or 10". The statics of the problem (free body diagrams, etc. etc.) are that the cable connection would move through a couple inch arc, but with a potential tension force of (6, 8, 10 multiplier, times)(40-60lb. pilot force, on the handle), maybe approaching the 600lb. ult. cable cap’y. Once the pilot has the throttle lever fully extended, with his straight arm behind it (holding it extended), he can probably hold more than the 40-60-lbs. I suggested above. Furthermore, at that point the throttle lever is probably starting to be in an over centered position, giving it some added mechanical holding and force advantage.
Then they said that the second pulling force was applied by the plane’s own mech. system (safety system), in particular connected to (interacting with) the thrust reverser on the copilots side, which was acting up. The trust reverser kept deploying, which caused the safety system to automatically pull the throttle lever back under these conditions, this was all unbeknownst to the pilots at the moment; and the copilot would push the throttle forward again. All he knew at that instant was that they needed power to gain altitude. Full thrust, with the trust reverser deployed on the copilot’s side, would cause the plane to roll and dive to the right (copilot’s side).
You said.... “ Cable A with a joint midway is fixed to a static point. Cable B with joint midway is pulled from both ends. Cable B is more likeley to break. In both cases one end can apply a max force that can not be exceeded (this would be the pilot end).
--“fixed to a static point”, not true at all.
--“Cable B is more likeley to break”, they didn’t say that.
--“In both cases one end can apply a max force that can not be exceeded”, they didn’t say that either.
--Your use of the phrase ‘fixed joint, static point’ is pretty misleading. In fact, you have not characterized the test you watched at all well. The test had nothing to do with pulling from both ends causing the cable force/stress to be higher. They were pulling from both ends during the first phase of the test, to 600lbs., too.
Your question should have been, something like.... can the polit with the throttle lever fully extended, hold more than the 900lbs. it took to break the quick disconnect? And, the answer to that is yes, apparently. Can the safety system apply that much force (900#) to the throttle cable to draw it back to idle position; apparently, yes. We would have to know much more about these interconnected systems to make a more meaningful judgement about all the details. But, I don’t find my above explanation too hard to imagine, it fits what I think I heard.
