Turbine D
Have you taken into account the AD amendment which lowered the amount of metal left on the Splines necessary for continued on wing? The original AD requirement was for an off wing strip if any single Spline showed wear of 2mm or more. Later the requirement was relaxed to require an average only of not more than 2mm for all the Splines taken as an aggregate.
Obviously, an average of 2mm wear for all the Splines would allow for some splines to have worn a good deal in excess of the 2mm previously allowed. At certain aspects of Load and Strain, this joint can be bearing several thousand pounds on Two Splines alone. One gets the magnitude of accelerated wear (per cycle) when the damage is expressed in this way. No argument why EASA was demanding borescope of the Splines at every third Landing. Likewise, even with the inspection, seriously rated Thrust and Loading METO.
Now to me, I "get" the "Oil Fire". I understand the willingness of some to claim the new (post uncontained event) AD absolves the Operators of application of sanctions re: the original (and still in force) AD's. To my knowledge the Splines AD's are still in force. If this is so, the manufacturer may be performing retro fits of the internals that caused the Splines to wear so quickly, and replacing "Oil Pipes" at the same time. I am unfamiliar of the Regulatory process that allows an operator/manufacturer to ignore prior and "unrelated" AD's simply because they are honoring new ones?? Can you help with this??
Add: The vibration problem is well known, yet seems to have escaped comment here, will you be the one to elaborate?
Also, the drive gear for the gearbox, Fuel Pump is fixed to the IP Shaft, is there possibility of some loss of metal when the IP Shaft migrates aft?
I take your point re: the Blades/Vanes miss and would like to point out that the friction/clash w/o blade clash would occur at the Drive Arm Return "corner" verse the Stator. If aft migration of the Wheel/Drive Arm was gradual, one can entertain the heat that must have been generated. Lost (molten) metal from the Stator/Drive Arm interface would explain the "splattering" molten metal on the Aft face of the Disc. It is this metal/metal contact I believe the AD references as possibly causing uncontained failure with damage to airframe and humans on the ground. It is for this reason among others that I believe the engine failure was caused not by Fire (forward of the IPT) but heat and damage Aft of it. I don't believe there was time for the Oil Fire to have soaked the IPT from one side, when the Drive Arm failure is not only demonstrable here, but also in two prior events.
Last edited by bearfoil; 24th December 2010 at 22:38.