RetiredF4....
1.) they know the cause already, but there is no quick solution at hand/approved by FAA and therefore there is no need to tell anybody...
Almost certainly. And known cause is what caused the feverish replacement scheme. Buy time, hope for a fix.....with the blessing of the FAA.
Certainly "Flight Test" with people inside...
While Rolls R/Rs Intermediate shafts, the danger lurked..(QF32)
For all intents, a DENDRITE is an inadvertant "Fusible LINK"