JFZ90 wrote:
Obviously a metal disc doesn't burn under fire like a piece of string, but its mechnical strength can still be significantly changed - even at modest temps well under melting point to the point where it is no longer strong enough to spin at its normal speed of say 7000rpm.
I don't question that, but I have this question: for a material built to withstand the temps and pressures of air that has combusted under pressure at about 1300-1400 deg C, (those numbers from the RR video linked a few pages back) how does one surmise that the material fails when subjected to burning lube oil, (which I think burns at a lower temp than jet fuel )?. From all of the explanations, I am left with the oil fire weakening something else (not quite sure what) which then led to turbine wheel doing X (contact with stator/fixed part) leading to failure.
The other explanation, that oil consumed in an oil fire does not return via scavenge to lube system and eventually lube system is starved, temps rise, and something fails, a something which then leads to turbine wheel/disc failure.
Am I following correctly?
Panzer John:
A wonderful effort by the crew.I wonder why they took so long to disembark the passegers, esp as the No1 engine was still running. And as for using only one exit as they wanted to headcount, did they think they may have lost someone?. I know its a big plane, but?
Mach 2.7
"The passengers commenced disembarking from the aircraft via the No 2 main deck forward door about 55 minutes after the aircraft touched down. The last passengers and cabin crew disembarked the aircraft about 1 hour later."
Meaning 1hr and 55min after touch down ?
Initially, the most likely answer was that they'd wish to shut down the engine, then disembark pax. As each means to shut the engine down didn't produce a secured engine, the worry that they still have pax on board and an uncontrollable engine (and an aircraft fuel system not responding as desired) on their hands, the crew (IMO correctly) decided to get the pax off in the safest and orderly manner possible. The head count rule and strict control reflect legal and regulatory requirements that one keep track of passengers who board, and who disembark, on a one for one basis. If that slightly slowed down disembarkation, they were prepared to speed it up IF Necessary. Speeding up did not become necessary. Controlled and deliberate.
Looks like a good call to me.
Turbine D (Post # 1620)
I would also suspect the IP turbine blade rotor slid aft contacting the LPT stage 1 nozzle ring and then burst due to overspeed as it was no longer coupled to the IP compressor. If you look carefully at the engine being removed from the pylon, you can see the gap (missing casing that held the LP stage one nozzle ring. (and more, some great posts, thanks!)
(More Turbine D)
AD 2010-0008 R1
This AD requires inspection of the IP shaft coupling splines and, depending on the results, requires further repetitive inspections or corrective actions.
Could the spline wear and potential vibrations cause the initiation of the stub pipe fracture? In other words, are there multiple events taking place that lead to the engine failure in a different location (IPT) instead of LPT) as postulated in the AD?
bearfoil:
The possible starvation of oil can create a dynamic wear, over time; it is this wear the EASA wanted a firm grip upon. The splines were allowed a loss of "crest" down to .5mm from 2.65 new. The TRENT is a fire breather, add some hydrocarbons, it is thrilled. The oil fire did not directly affect the thrust values, imo. The oil fire burned up the lubrication, very bad. The ramp up of N2 to 98 when 88 was selected across the wings, may have been coincident with Shaft Coupling loss.
Your estimate, or a summary of a report out at present?
Old Engineer:
Buckling is a difficult concept to explain--
Thanks for that post. Made some things about wing design more clear to me (and recalled what I learned about skyscraper design/three d lattice work, as I read up on NIST conclusions after 9-11).
PBL:
Thanks for the link to your commentary on providing accurate information to the public.
It seems to me that the flap track damage (not the "major damage" as the manufacturer put it) lies outside of even the 15° region. Since all damage is supposed to be covered by the assumptions, this led to my wondering if the acceptable-means-of-compliance guidance would be revisited.
Ricochet? Isn't one somewhat at the mercy of probability and distribution once the catastrophic failure occurs and the various bits, each in his own departure angle, accelerates away from where it is supposed to be ... which is still on the engine?