24 July 2019, 00:51:36 *

Login with username, password and session length
Welcome to War and Tactics!    War and Tactics Forum is currently undergoing some modifications that might disable features you are used to. This is unabvoidable as we have to update the forum engine to a new structure that is incompatible with many of the features we had used so far. The good news: WaT will be more secure and stable, and most of the features we uninstalled will be a natural part of the new structure anyway. For the rest we will be looking for solutions. (APR 23, 2018)
   
  Home   Forum   Help ! Forum Rules ! Search Calendar Donations Login Register Chat  
Pages:  1 [2]   Go Down
  Print  
Share this topic on Del.icio.usShare this topic on DiggShare this topic on FacebookShare this topic on GoogleShare this topic on MySpaceShare this topic on RedditShare this topic on StumbleUponShare this topic on TechnoratiShare this topic on TwitterShare this topic on Yahoo
Author Topic: A-380 emergency landing!  (Read 16799 times)
Rattler
WaT Supporter

*

Offline Offline

Germany

Location: Med Island
Posts: 2268




View Profile WWW
« Reply #20 on: 11 November 2010, 22:30:35 »
ReplyReply

Indeed, with time passing more and more seems really to look like a (certain) oil line giving problems at first glance from a non-experts view.

I guess by now the point where the oil leaks originate should have been established (again, educated guessing only), so I think tose parts until re-design would be under special scrutiny, problem partially solved methinks (wheher I would release the fleet, another question, my guess woulld probably NO).

Still, as we dont know what engines have been affeced, whether there was something systematically or pure random, there still might be the thrust reverser option in play.

Rob, as you know more of that stuff than I do, how would the mechanism of having an oil fire in a void space between turbines work that leads to a turbine disc failure? What temp do they run on? Is it the shaft or the disc affected first? Gear failure and overspeed? Or lack of lubrication?

From my just basically educated perspective oil leak induced fires should be rather low temp, and hence should not (?) affect shaft or discs seriously material wise, or they even simply should end up being blown out with too little seapage to keep it alive, but maybe I have too simplistic a view on this high-tech stuff (and I trust basically what has been published so far from QF or RR).

OTOH, maybe it is just the quantity of oil leaked that might lead to unlubricated contact and consequent failure?

I am totally in the dark on that, hence a truly innocent question out of my little knowledge about ingeneering details of turbines, please bear with me on that one.

Rattler

Logged

"War does not determine who is right, war determines who is left...": The Rattler Way Of Life (thanks! to Solideo)... http://www.youtube.com/watch?v=n9v3Vyr5o2Q
Robert Hilton
Sergeant
*

Offline Offline

Netherlands

Location: Limburg
Posts: 32




View Profile
« Reply #21 on: 12 November 2010, 22:32:48 »
ReplyReply

Turbine stages (especially the HP) are usually protected with impinging cooling air blown over the blades, this is normally tapped off the compressor from the latter stages so that the temperature differential isn't too high. It is normally blown either through the turbine shaft, disc and through the blades, or around an anullar ring and through the stator blades. I couldn't see any evidence of cooling ducts in the disc in the photo.
I would imagine, looking at the disc piece that the bearing gave way first and the turbine 'followed on'.
Having said that the disc is somewhat different to what I am used to in gas turbines, alot thinner than I would expect. Mind you the number of compressor stages required have been dramatically reduced over the last two decades.


* 7097426-0-large.jpg (405.25 KB, 1356x1773 - viewed 310 times.)

* 6672832-0-large.jpg (913.67 KB, 3459x2858 - viewed 359 times.)
Logged
Rattler
WaT Supporter

*

Offline Offline

Germany

Location: Med Island
Posts: 2268




View Profile WWW
« Reply #22 on: 15 November 2010, 13:06:56 »
ReplyReply

I am now getting a better understanding (and more questions!) on how the sequence of events for this incident might look like, starting from here:

Quote
An Airbus executive said Friday that Rolls-Royce has identified a faulty bearing box as the cause of the oil leak problem implicated in the midair disintegration of an engine -snip-

Airbus Chief Operating Officer John Leahy told reporters ... that Rolls-Royce had at some point fixed the bearing box on newer versions of the massive Trent 900 engine. ... He said Rolls was now fixing it on older versions. ...
His comments did not address why Rolls-Royce had not fixed the bearing box in older versions of the engine.



Some explanations have been proposed on pprune, here what they sum up to:

http://www.pprune.org/6056506-post838.html
Quote
The bearing "race" is supplied oil by a pump. The pump is dumb, so the oil needs be regulated by scavenge through vaned galleries (manifold). If the "vane restrictors" (the installed regulators of oil flow) become clogged (coking, carbon), the bearing "box" is pressurized with oil, and the seal fails, supplying oil to "where it shouldn't be" (Joyce). It ignites, causing heat and utter failure of the oil seal. Now the bearing is metal to metal, supplying friction heat to the heat of combustion, and the shaft slows in its fixed mount as its bearings grind to a halt. If the timing of the failures is sufficient, the Shaft locks, the wheel scrubs off its splines, overspeeds, and separates from the engine in pieces whose shape shows not Blade (related) failure, but hub failure, the part of the Wheel that is the strongest, witness the perpendicular fractures of the disc.


and http://www.pprune.org/6056690-post846.html
Quote
The AD itself focuses on "restricted" restrictors. Coking and Carbon were identified. Now this might be a maintenance issue. If failure happens before scheduled work, it is not a maintenance issue, but a problem that escaped design or materials considerations, or specifying a part incorrectly. The important part of the first AD relates to the "return line"

This return line(s) had installed restrictors to control oil flow. These restrictors evidently pack up with combustion and heat byproducts that further restrict the flow of lubricating oil. If the flow "back" stops, the pump continues to supply oil, and the bearing compartment may fill with oil, to overwhelm the seals.

Whether this is what caused the oil fire and loss of IPT is not at all shown, but whether a cynic or an innocent, it provides a very convenient explanation for the entire kerfuffel.



Last, as the ATSB is following a rather different (better, methinks!) information policy like many other institutions, you can follow the ongoing investigation with frequent updates at their web page:

http://www.atsb.gov.au/newsroom/news-items/qantas-airbus-a380-singapore.aspx

Rattler
Logged

"War does not determine who is right, war determines who is left...": The Rattler Way Of Life (thanks! to Solideo)... http://www.youtube.com/watch?v=n9v3Vyr5o2Q
Robert Hilton
Sergeant
*

Offline Offline

Netherlands

Location: Limburg
Posts: 32




View Profile
« Reply #23 on: 15 November 2010, 20:53:54 »
ReplyReply

So in effect the scavange side if the bearing box was blocked by debris causing the oil level to increase and overwhelm the labyrinth seal which then dumped too much oil onto the hot side of the turbine. Fire ensues and the turbine ultimately fails. Interesting development, again, luckily not a major disc problem.
Logged
Koen
Poster

****

Offline Offline

Belgium

Location: Belgium
Posts: 4247




View Profile
« Reply #24 on: 15 November 2010, 21:13:45 »
ReplyReply

I read in the newspapers:

all technicians on the production line for the new 380's have been shifted to the repairlines to ensure the operational life of the current fleet of 39 A380's.
This also indicates that the productionnumber of 20 new 380's this year will not be reached.

Both RR and Airbus have predicted profitmarges for 2010.
Logged
Rattler
WaT Supporter

*

Offline Offline

Germany

Location: Med Island
Posts: 2268




View Profile WWW
« Reply #25 on: 15 November 2010, 23:21:27 »
ReplyReply

So in effect the scavange side if the bearing box was blocked by debris causing the oil level to increase and overwhelm the labyrinth seal which then dumped too much oil onto the hot side of the turbine. Fire ensues and the turbine ultimately fails. Interesting development, again, luckily not a major disc problem.

Indeed.

Here the patent claims for the US by RR for this special bearing box, interesting read: At start it is well explained what the difference of old-art sealing and the new-art system is which allows to keep the pressure inside the bearing box half that (max) of the turbine comsbustion side (and which could have failed because of the scavenge line restrictors becoming clogged somehow).

Also gives a graphic explanation of what consequences an oil spill will have.

http://www.freepatentsonline.com/6516618.pdf

@ Koen: In those things I would not trust news papers inherently too much, they do the same what we here do, research the net and experts and then try to formulate their understanding of things, which must not always co-incide with reality as the journos themselves are not experts.

Rattler
Logged

"War does not determine who is right, war determines who is left...": The Rattler Way Of Life (thanks! to Solideo)... http://www.youtube.com/watch?v=n9v3Vyr5o2Q
Rattler
WaT Supporter

*

Offline Offline

Germany

Location: Med Island
Posts: 2268




View Profile WWW
« Reply #26 on: 14 February 2011, 00:11:51 »
ReplyReply

Update: RR has payed the damage created to Quantas for the grounding of their fleet:

Quote
ritish aircraft engine maker Rolls-Royce has disclosed that it paid out more than $80 million after the failure of one of its engines on a Qantas jet.

The Qantas fleet of A380 superjumbo jets was grounded for several weeks, at a considerable cost to the airline, after an engine exploded in mid-air in November last year.


Read more here...

Rattler
Logged

"War does not determine who is right, war determines who is left...": The Rattler Way Of Life (thanks! to Solideo)... http://www.youtube.com/watch?v=n9v3Vyr5o2Q
Pages:  1 [2]   Go Up
  Print  
 
Jump to:  

Unique Hits: 25680835 | Sitemap
Powered by MySQL Powered by PHP Powered by SMF 1.1.16 | SMF © 2011, Simple Machines
TinyPortal v0.9.8 © Bloc
Valid XHTML 1.0! Valid CSS!


Google visited last this page 16 October 2018, 02:29:16