TurbineD
Thanks for the comprehensive explanation, I am always open to learn more!
I think what all our efforts to clarify the sequence of events hampers is the shortage of reliable information and pictures. A closeup picture of the rear - roller bearing chamber and drive arm residues, or a similar picture from the central ball bearing chamber and LP / IP / HP shaft situation may probably give us the information we now more or less are guessing at.
I also think that the findings of ATSB, stating break of an oil tube and oilfire near the IPT disk are doubtless correct. They have had the pieces in their hands, we have only seen pictures.
Yet, the question must be allowed to ask: what, where and when started the oil fire ? Was it really the pimary cause - the oil fire - or secondary to the extend that it had no influence on the drive arms break up ??
I have a problem to become convinced that the oil fire did it, seen the total time elapsed since take off, the obvious scarce space in front, looking FTA, of the IPT disk and underneath towards the drive arm and the total mass of that disk. Therecovered part - about 1/3 was an estimate - weights about 70 Kg, times 3 makes a total of roughly 210 - 220 Kg or 450 - 500 lbs. I canīt see how that big chunk of metal can be heated beyond desighn limits under the circumstances prevailing.
One other hint that might point to a different cause I have found checking through these graphs added to the ATSB preliminary report, Fig. A2 and Fig. A3. The latter is the one that shows the recording og oil related data. There is that faint drop in pressure - total of about 5 Psi - starting at the same time the oil temperature raise. Oil pressure remains the entire final second above minimum oil pressure requirement - taken from the Certification Form, it even hikes momentarily before disk break up, drops, comes back before final drop. Oil temperature raises steady and falls after break up. The steady rise of oil temperature indicates to my understanding an constant heating in progress.
Meanwhile and untill several seconds after breakup the measured oil quantity remains level.
My conclusion, the final break of the repeatedly mentioned oil tube occured either seconds before, at or immediatly after the breakup. Oil will have become ignited by the hot parts of the engine or the hot engine gases beeing blown into that cavity on break up.
Could be that I am wrong with this entire theory but I thought there a lot indications that I canīt be that far off.