TD: " 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."
That is my point. I think from Edelweiss, and evidence at LPT#1, there was no time for the debris to blow aft. It exited out the opening created by the departing blades, followed immediately by the three main, and hundreds of minor, bits of the disintegrated wheel. If we consider that the wheel, to gain rpm, needed time on shaft (or, 'false bearing'), then debris would have exited back through the LPT proper, making a proper mess. As the wheel was blown instantly back against the Stator vanes platform, the IP blades were shorn, and blew out the case, co-planar with rotational orbit. This is what happened to Edelweiss; in that case, the IPT remained attached (though 'fractured', circumferentially).
Consider, the IPT is not attached to the shaft, per se, and a loss of the drive arm leaves a discrepancy bore diameter/shaft of many centimeters. The bearing is ad hoc, and unable to support rotation. The IPT orbit is instantly eccentric, and the disintegration is likewise instantaneous. It is the relatively undamaged condition of the LP turbine that gives this away; all debris blew out simultaneous loss of drive arm, imho. Similarly, the IPT blades were lost instantly, nothing remained to transmit the gas flow into additional rotation. This is Edelweiss, redux, save IPT loss out the case. Only in Edelweiss, the fracture of the drive arm was not complete, and the wheel was luckily retained.
I know you are convinced of oversped wheel; without blades, and time, I cannot agree. 7000 rpm is well sufficient to blow up the IP system. Is there a conclusion in the report? The initial used the word "may" re: overspeed.
add; [B][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. /B]
Yes, again, my point. Even two seconds would have seen a substantial flow of debris out the tail pipe. Radial exit of virtually all the debris drives my conclusion that the disintegration/exit was instantaneous, not lingering.
For N2 to spool down whilst the IPT was spinning up for seconds, and there is light damage to aft rotational mass, is a reach, imo. What is more likely is a damage trail suggested by the actual AD on this engine. Aft drift of the IP shaft, metal/metal contact, superheated Drive arm, and disintegration, causing aircraft damage and parts on the ground, endangering people below. The AD was written with climb out in mind, hence the reference to population underneath. The 380 serves airports in populated regions, and catastrophic failure puts those below it at risk.
The source of the wear on the rigid coupling is published, and the damage pursuant is also. Drifted shaft, and oil fire are two results of the cause of the AD in the first place. Loss of oil is reported on many a/c, along with oil pressure problems, and preceding incidents.
If the cause of the problem was overspeed, fine; it is not necessary to the explosion, however, and that is my point. I don't see evidence of any kind that isolates this uncontained failure from one predicted by the regulator. For some reason, it has become necessary to propose a new, and unrelated anomaly. Why is that? (Rhetorical). The oil pipe problem was not new, it was not unrelated, and it is not logical to separate the "Oil Fire" from the AD. The wear was caused by vibration of the the Rotating Mass. imho
Thanks
Last edited by Lyman; 29th Apr 2012 at 17:34.