Gem Developer
Hello. My picture of turbine wheels has the accelerated gas passing through their chamber at the perimeter, not "through them". The gas passes through the "Blades"?
pedantic?
Blade Loss, timing.
The incipient failure I think was the IPT migrating aft and "nesting" on the face of the stator, which severed all the wheel's Blades, and quite likely rapidly. While an Oil fire is hot, and may have caused some shaft and wheel distortion problems, the heat produced in a mating of two wheels with a dramatic difference in RPM may suggest alarming Heat also. The heat signature on the IPT rotor, which is under discussion ( as a "shape" ) , looks from my experience to be 23-25hundred degrees.
I think it's been mentioned that the first AD referenced "Oil Relief" circuits that needed inspection for clogging vanes, that could over-pressure the bearing race, and cause a fire. (Coking and Carbon, as above). In addition, as GD reports, the drag on the wheel "could force" the turbine wheel aft. After losing blades, and opening its well to Stall, a reversal in airflow would force the IPT forward, Bladeless, to allow Combustion products to blow into the LP well, then out the Thrust Stator, depositing the telltale "Soot" on the nacelle. The forward migration followed by a reversal to aftward, could produce some impressive loads on the shaft, from elliptical stress (unbalanced). These reversals, depending on number, (if any), would hasten the failure at the interface with Shaft two.
It starts to come into view where the little bits had the energy to "shot Peen" the IPT.
bear
Last edited by bearfoil; 11th Nov 2010 at 17:13.