Hi barit1, thanks for the reply. I think there is merit to what you say, without doubt, these rotors are phenomenally strong. The design consideration is strictly that to which you allude, resistant to overspeed and overtemp, to a point. We do not need to look past the existing data to find failure. In fact, the failure was foretold by no less than the regulating authority, to which the engine manufacturer is entirely responsible for proof of quality. So I do not feel the need to go beyond, the failure is in front of us.
Let's assume that some combination of above limit rpm and ambient temp caused failure, fair enough?
My purpose from the outset is to frame the evidence within the data provided in the AD as enforced. If some mechanism failed the connection other than high heat, or overspeed, let's agree it is not present in the analysis? I think the metallic spatter is the product of friction stir at the arm/engine frame, as predicted by EASA. Only one quart of oil was missing, the fire was in front of the wheel, and the prediction via EASA tend to override a lingering spin up whilst the core is melting. The Drive Arm, logically was the last failure before disintegration, and the decomposition happened instantly. For the spatter to appear on the aft face of the wheel speaks against the heat migrating from its front? Yet with a shaft transiting aft, the friction can create instant molten metal, whilst the shaft retains integrity. You cite the N2 loss of rpm, I think that was a result of metal/metal from shaft, case, as predicted. I would say the shaft slowed whilst joined to the Turbine, and EEC poured extra fuel in to compensate for the reduction in power applied to the melting metal in the core.
These are informed from the AD, directly. How can N2 unwind for seconds, as a result of separation of IPT? Again, the IPT without the Drive Arm connection is a sizable herd of horses loose in the barrel. The Orbit would have to remain precisely free of obstruction for the Wheel to accelerate. The Drive Arm/IPT resemble a Bell on a bearing at the small end. If the connection is lost, the mass is not only free to wander, chaotically, but the rim of the Bell is quite distant from the bearing attach, any imbalance would instantaneously throw the entire asembly into an extreme eccentric.
I am not arguing for its own sake, but am trying to fit the results into the predictive regulation published by the engineers before the fact.
See you in JB?
take care, and thanks again, I appreciate your patience with my stubborn streak.