firstfloor wrote:
Old Engineer about FO emergency actions:
We know that he began this action before the IPT blowout
No you don't. The first thing that happens, that the crew is aware of, is two nearly simultaneous loud bangs (the engine failure). No more loud bangs after that. Emergency actions begin after the failure.
Well, let me agree (now that I've re-read the 12/3 ATSB report and the 12/8 interview with Sr Chk Capt (SSC) that I cannot know for sure that the FO took any action prior to the disc leaving the A/C thru the wing. But the throttle of #2 could have been retarded to idle in response to the "engine turbine overheat" warning in the cockpit (via ECAM), as this is the procedural response to this warning. And this response, including the FO starting an independent stopwatch, could have been done prior to loss of the turbine disc.
The ATSB report places the "two, almost coincident, 'loud bangs'" at the same time as the activation of the "turbine overheat parameter" at 0201:08. The report places the "turbine disc failure" at 201:11, based on multiple indications of A/C systems failure (the cut wiring in the wing giving the significant indications, I presume). That the two bangs occurred slightly earlier would not contradict the SSC's statement. I assume the FO had the same to say.
I do not wish to say that you cannot be correct in your comment that the engine failure occurred at the "two bangs." However, I prefer to consider the possiblity that the two "almost coincident" bangs could be the result of the flame and "explosion" of a compressor stall exiting the two ends of the 20-foot long engine. Doppler effect aided by the reduced speed of sound could separate the two enough to perceived as separate explosions.
I've luckily been present at only one compressor stall, but there was the definite impression of engine explosion, causing great alarm in the cabin. (Landing approach at 9000 feet through near vicinity of thunderstorm, pitching and bobbing, in a steep approach at low power to avoid a displaced ILS threshold, BLAM, orange glow outside-- a dark afternoon at UIO from the south, downslope shortish runway, overtaken by the city on both thresholds-- in "City of Guayaquil" A320, flagship of the Equadoran fleet.) A panicked woman across the aisle asked, explosion or lightning? I said, Just lightning, don't worry.
So RR would have us believe it's only a broken oil line. For all the detail that's been given about that, the final break in the cracked fitting could have occurred in dismantling the engine. I'm still studying the question of bearing design philosophy in this engine, including choice of permissible oil temperature, which gets more interesting all the time.
As shearing is the most energy-efficient way to cut thru metal, I am not convinced that the disc fragment would have made much noise going through the wing. You can see the impression of teeth going thru the crossframe web, cut like a die-- is this the trace of the oft-mentioned bevel gear?