Lyman,
I should have asked my question more directly. Once separated from the Power Arm, how can the Disk possibly retain stability sufficient to gain rpm? Won't it start going bs on its cramped environs?
Do you realize that if you stand in front of a turbofan engine and grasp one of the fan blades with your little finger you can, with very, very little effort at all, turn the fan over, which in turn, turns the LP compressor and the LP turbine? It is a jewel and the same is true with a triple spool engine. So when you think about that, think of what happens in the IP turbine on the Trent 900 when the disk separates from the shaft holding it. We are talking here no more than a couple of seconds. Your talking as if we are in slow motion. The turbine wheel, once the power drive arm fractured, over sped very, very quickly. The thing driving it was the highly hot compressed air that was expanding, but passing through its turbine blades, still attached to the disk. Remember the aircraft was in the climb mode. The rotational inertia for the given mass is unbelievable in this situation, The turbine wheel was driving nothing, a free turbine is a nightmare. Additionally, there was nothing in the way to stop it, it just proceeded to burst and that is what the photos of the found disk fragment depicted.
I would suggest you, once again, look at the engine cross section and note if it moved rearward, there was no substantial material to decrease it rotational speed except for the inner flow path band of the stage 1 LPT nozzle. Whether it wobbled or not is immaterial, in fact it may have gained enough rotational speed while still in place over the IP shaft, but free of the shaft to initiate the speed leading to final failure. Remember, there was little damage to the LP turbine except for the stage 1 LPT nozzle. The majority of debris went outward in a radial direction, not rearward.
Think real time, not slow motion time which is only recorded by high speed cameras.
TD