CRAB, I think you are rather missing the point. The design temperature limits for rotable components within a gas turbine hot end section are critical. That is exactly why tertiary air is used within the engine to maintain a stable temperature environment within which the components will survive.
Operating the engine in conditions, such as with airways and internal pathways blocked, especially within turbine blade and hub tree components does not simply mean that the TBO is compromised. What it means is that the inherent properties of the material, proven at a design temperature range, are entirely different when operated outside that design temperature range.
With turbine blades in particular, elasticity and thus "creep" tends to be the first indications of prolonged operation beyond the designed range (and by prolonged I do not mean weeks, but several minutes).
Thus there are no methods by which TBO can be reduced, simply due to operation beyond designed temperature ranges, and the real issue here is if such operations occurred unforeseen and undetected, catastrophic failure of the hot end is the most probable result.
That is precisley why hot end temperature limits are defined in Flight Manuals down to single degrees. The criteria and acceptable operating ranges are that critical.
The temperature we measure (and view in the cockpit) bears only a limited relationship with the critical temperatures experienced in the business bits of the hot end. Thus start temperatures and operating temperatures may differ with engine speed, as this is a function of total air mass available through the engine, the majority of which is used for flame shaping and tertiary cooling. Only a fraction of the sucked in the intake is actually used for conbustion.
Blocked air passageways within a turbine engine are an extermely serious condition, thus the immediate $3.2m overhaul of all 4 of the NASA aircraft engines.
I am not an expert in this field, far from it but I do have an aerospace engineering background to draw upon. I think it is very foolish to think that these issues are not important.
Taken as a whole this very subject is the meat and two veg of the current European policy for flight within Volcanic ash/dust environments. Modern turbine engines simply cannot endure prolonged operation in certain types of particulate atmosphere especially those emanating from volcanos.
Do you really believe that the entire European Aviation Indistry is currently being compromised by regulators who simply devise policy on a whim or the back of a fag packet.
The problem with this thread, and those who post one dimensional devil may care posts is that such individuals will never have to suffer the consequences of what they post.
I am an operational NS pilot and although I can appreciate the reasons behind the extreme caution of the European Governments I will not hesitate to start flying as soon as the restrictions are lifted, cos also taken as a whole, my expertise lies in flying helicopters and not the in depth risk assessment and decision making process necessary to ensure that we can operate safely within the current volcanic conditions.
As an aside, we have had one catstrophic engine failure (in my time) on the NS. Due to an overspeed but the results were horrific and there was not much life left in the PAX or crew long before the aircraft hit the sea.
Its all very nice and dandy to feel that what we are experiencing is overkill or just plain daft. But the days of thinking there will just be a bit of a bang down the back, and no bother we've got two engines are long gone. Modern helicopter engines let go with a spectacular bang when a catastrophic failure occurs.
That is a grown-ups explanation - just for you. My reference to the blades "melting" in my earlier posts is a bit of poetic licence............but, actually the results are about the same.
I will wait until a grown up says it is OK to fly.