mm43
Thank you for helping me posting the list files.
This list shows no self made additions, itīs just data derived from the ATSB Preliminary Report. The time scale starts where the oil pressure starts to drop below the level of the previous trace in Fig. A3. It is also the moment that rise of oil temperature is recorded.
The time frame ends 8 sec. after the breakup occured. The engine is dead but oil status, though starting to drop in all 3 lines is still within certification parameters.
Remarkable is also the period between 02:01:06 and 02:01:09, where first the N2 line drops to zero in half a second followed by N1 shortly after 02:01:06 but obviously ahead or at the same moment the IPT disk vandalized the engine.
Apparently the front end of the engine was already dead while the HP part still ran at 98 % of its max. perm. N3. So there must be still fuel being pumped into the combustion chamber. There is mentioned in the report that the fuel flow was cut back automatically when these high rpm where achieved.
What I left out in the time scale is the timing of some warnings that became switched on and subsequently displayed in the cockpit. That is
02:01:06:30 - OVERHT Engine 2 turbine overheat - ON
02:01:07:30 - Captain Master Caution - ON
02:01:11 - Pylon Overheat Engine 2 - ON
It is very clear by this that - as stated in the crew interviews - the first real reactions by the crew came after the two reported "loud bangs". Subsequent actions than were worked down according the procedures layed down for such cases.
Now to the different possible developments as they have been discussed in this thread.
1. The preliminary version (ATSB / RR)
> oil tube rupture > oil spills into the cavern formed by the supporting structure > oil becomes ignited by the surrounding heat > oil fire weakens the structural integrity of the IPT disk ( because its closer to that cavern than the HPT disk)> circumferential diskfailer at the drive arm> migration of the disk backward into the structure of the LPT thus destroying this and disintegrating due to overstress
What Proīs and what Conīs ?
Pro - Oil fire can start in that cavern , outside the bearing chamber, weaken
the disk with subsequent consequences
Con - An rupture / break of an oil tube that size involved will fill that cavern,
no oil backflow into the sampling scavenge
- an rupture that dimension will show a) in drop of oilpressure and b) in
steady dropping quantity
- break of oil tube means no sufficient lubrication to the 2 roller bearings
in that chamber, causing damage and destruction of the bearings
- N3 went to the permissable topspeed, N2 turbine rpm likely went to
overspeed - both not very likely with corrupted or damaged bearings
the Forum derived version
> inside the central ball bearing chamber a component started to deteriorate
> strong vibrations of HP shaft developed > IP shaft "decoupled"> heat of
compromised parts ignited an oilfire that corrupted the seals> subsequent
blowout of hot gases that were at higher pressure values foreward ! > migration of the IPT disk rearward > overspeed in few seconds > contact to IPT structure anddesintegration of the disk> oilspill by instantly broken oil tube, start of an oilfire with recorded oil fire remains on the disk
Pro - heavy vibration in HP part, mild in LP and IP
- obviously the oil system worked beyond breakup of disk within
certification parameters
- heavyest fire damage on the cowling is visible foreward of the gap
caused by the disk break up
- solid thrust drop of N1 and N2 with in 3,5 sec - N2 stops in 0,5 sec. and
N1 is down in just 3,5 sec !! about 5 sec prior disk break up
- oil soot on the LP shaft at about the position of ball bearing nr.2,
means gap, leak or fracture of the surrounding IP-shaft
- no oil soot at the position of the roller bearings for IP and HP rear
support
- previous repair of foreward bearing because of spalling (only outer race
???)
Con - no known as primary cause reported cases for the ball bearing chamber
in previous Trent 3 - shaft models
- spline coupling wasnīt a problem before
I stop here, but I think the final report of this incident may have some additions.
Probably also towards another candidate of trouble, the bevelgear drive that has its delivering ring mounted ahead and leaning against the HPC ball bearing.
Just an idea that has caught my attention!
Another item too - no one untill now has said where excactly that demolished and broken oiltube - shown in picture - was mounted - at the rear roller bearing chamber or at the foreward ball bearing chamber ??
Lots of questions, many ideas and much assumption! Okay, RR and the ATSB could overcome that by releasing some more pictures from the interior and /or plainly say what the ongoing investigations have revealed so far.
My opinion is : Knowing is Safety - Not knowing is Unsafe
Jo