Hi Turbine D
Here... As the stress limits begin to be exceeded, the power drive arm fails, releasing the disk and the disk is free to rotate with no control over rotational speed. As the rotational speed increases with no impediment to slow it, it bursts. That, I believe, is what happened on this engine.
I think you are missing something, and it is key to my description of the failure. Using your own description, above, when the Disk is released, it has not the time to increase in rotational velocity. None.
The very instant it is released, it wobbles wildly out of control,, no longer restrained by a symmetric join. It contacts the case, wobbles forward and aftward, and begins immediately to SLOW. It is converting what was controlled and productive rotation into chaotic and catastrophic disintegration of the IPT cave, bursting the case.This is the mechanical Bang. The second bang is the release of P30 gases into the atmosphere, possibly.
Again, once released, it goes non planar and is free to eccentrically smash everything in its path, for a VERY short time, constrained in a Titanium "Barrrel".
There is no overspeed. Out of control rotation, along with the eccentric "orbit" of the disc, shears the blades, and initiates the tri-partite decomposition of the Disc. Failure at the IPT/Drive Arm it was, as reported by Rolls.
What say you, my friend?
Last edited by Lyman; 26th Apr 2012 at 03:45.