Sponsor Message:
Civil Aviation Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
QF A380 SIN-SYD Engine Failure - Part 7  
User currently offlinemoderators From United States of America, joined Apr 2004, 513 posts, RR: 0
Posted (3 years 9 months 1 week 2 days 5 hours ago) and read 20386 times:
AIRLINERS.NET CREW
FORUM MODERATOR

This is a continuation thread from part 6 which can be found here: QF A380 SIN-SYD Engine Failure - Part 6


Enjoy the airliners.net forums!  


The Forum Moderators


Please use moderators@airliners.net to contact us.
38 replies: All unread, showing first 25:
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 1, posted (3 years 9 months 1 week 2 days 5 hours ago) and read 20392 times:

These quotes all refer back to Part 6 (see link in Reply 1):

Quoting thegeek (Reply 240):
So it is a pretty minor reason to have the EPR mode at all, then? Is it more responsive in that mode or something like that?

In addition to what Zeke said (reply 247), EPR is less sensitive to engine degradation than N1. In other words, the same EPR will give you closer to the same thrust on two different engines than the same N1. There is an N1 trim built into engines to take care of this at the initial calibration, but the difference between N1 and actual thrust moves more as the engine ages than EPR. TPR, which RR brought out recently, is a temperature-corrected EPR that's supposed to be even more stable over the engines' life.

Quoting Tristarsteve (Reply 241):
Can we be clear that on an airliner you do not transfer fuel between tanks in flight.
The A330/340/380 and B744 can transfer fuel from the stab tank fwd, but I have never met any airliner where you can transfer fuel between wing tanks.

Not being able to do tank-to-tank transfer is generally only true of modern Boeing (Puget Sound heritage) twins. The 737/757/767/777 can't do it, but most of the other Boeing's can, most Airbuses can. I'm not sure about the Bombardier/Embraer crowd..

Tom.


User currently offlineKlaus From Germany, joined Jul 2001, 21461 posts, RR: 53
Reply 2, posted (3 years 9 months 1 week 2 days 4 hours ago) and read 20241 times:

Quoting tdscanuck (Reply 1):
The 737/757/767/777 can't do it, but most of the other Boeing's can

"most" being the 747 and ...?


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 3, posted (3 years 9 months 1 week 2 days 2 hours ago) and read 19989 times:

Quoting Klaus (Reply 2):
"most" being the 747 and ...?

707, 727, 787, KC-767, DC-8, DC-10, MD-11...

I think the DC-9/MD-80/MD-90/717 can as well, but I'm not positive.

Tom.


User currently offlineKlaus From Germany, joined Jul 2001, 21461 posts, RR: 53
Reply 4, posted (3 years 9 months 1 week 2 days 2 hours ago) and read 19979 times:

Quoting tdscanuck (Reply 3):
I think the DC-9/MD-80/MD-90/717 can as well, but I'm not positive.

Ah, okay. That widens the selection, if not much by currently available models...


User currently offlineFerpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 5, posted (3 years 9 months 1 week 1 day 23 hours ago) and read 19747 times:

The explanation of the C mod insistence by QF is here:

Flightglobla today;
"Qantas Airways is modifying or replacing 16 of its Rolls-Royce Trent 900 engines due to a secondary oil leak besides the stub pipe fault, identified last week as the cause behind the Qantas A380 uncontained engine failure on 4 November.

These engines have oil sediment in the high pressure (HP)/intermediate pressure (IP) turbine, a Qantas spokesman says, unable to specify the exact area affected. The engines do not have a stub pipe fault, he says.

The only stub pipe [fault] we have found is on [an] aircraft awaiting delivery," the spokesman says. On 8 November, the Australian Transport Safety Bureau said three Trent 900s, including one on an A380 to be delivered to Qantas, were found with the stub pipe defect. The defect has been identified as the cause behind an oil leak and fire which resulted in the uncontained engine failure on the Qantas A380."


So the A and possibly B mods leaked a bit of oil from the rear bearing box (which is not un-normal for these constructions (pneumatic knife-edge or carbon contact, don't know which they used)) and it might be what C mod should improve. The oil leek was probably deemed non dangerous by RR and on can guess they felt relieved when they discovered the faulty pipe/fatigue crack, otherwise their judgment could be proven wrong. Well time will tell if this is indeed what happened.



Non French in France
User currently offlineFerpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 6, posted (3 years 9 months 1 week 1 day 16 hours ago) and read 18817 times:

They probably used a pneumatic knifeedge/labyrinth seal, here the principle for it:



The oil lubed bearings are in the inner box: Bleed air is keeping the outer box under overpressure thereby forcing any oil that enters the knife-edge labyrinth back into the inner box.

Such bearing boxes can leak a bit of oil out the outer labyrinth depending on how much bleed air is spent on the design.

[Edited 2010-12-12 22:25:10]


Non French in France
User currently offlineFerpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 7, posted (3 years 9 months 1 week 1 day 15 hours ago) and read 18776 times:

An finally a picture of IIRC a Trent 800 showing where the bearings are:

Trent 800 bearing and shafts


The bearings in questions are the double bearings to the right.



Non French in France
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5457 posts, RR: 30
Reply 8, posted (3 years 9 months 1 week 1 day 13 hours ago) and read 18213 times:

Quoting Ferpe (Reply 7):

Very interesting cutaway....thanks.



What the...?
User currently offlinezeke From Hong Kong, joined Dec 2006, 9097 posts, RR: 75
Reply 9, posted (3 years 9 months 1 week 1 day 12 hours ago) and read 17901 times:

Quoting JoeCanuck (Reply 8):
Very interesting cutaway....thanks.

The Trent 800 is on the 777, not A380.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5457 posts, RR: 30
Reply 10, posted (3 years 9 months 1 week 1 day 12 hours ago) and read 17849 times:

Quoting zeke (Reply 9):

That doesn't make it a less interesting cutaway.



What the...?
User currently offlineFerpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 11, posted (3 years 9 months 1 week 1 day 11 hours ago) and read 17662 times:

IIRC all the RB211s except the XWB are very similar (the XWB has a 2 stage IPT), therefore the cutaway is also applicable for the 900 on a principle level.


Non French in France
User currently onlineTristarsteve From Sweden, joined Nov 2005, 4007 posts, RR: 34
Reply 12, posted (3 years 9 months 1 week 1 day 10 hours ago) and read 17409 times:

Quoting Ferpe (Reply 7):
An finally a picture of IIRC a Trent 800 showing where the bearings are:

The cutaway features counter rotating shafts, which was first introduced by RR on the Trent 900.
I believe this cutaway is an A380 Trent 900 engine


User currently offlineJambrain From United Kingdom, joined Sep 2008, 251 posts, RR: 0
Reply 13, posted (3 years 9 months 1 week 1 day 10 hours ago) and read 17345 times:

Quoting Ferpe (Reply 7):
Trent 800

Not if it's got counter-rotation

That's a T900
http://www.abload.de/image.php?img=trent900u6cu.jpg#

This is an T800

http://fromtheflightdeck.com/MEL/PPRune/Trent800.jpg

The giveaways include the sweep on the IGVs and the turbine casing angle.



Jambrain
User currently onlineTristarsteve From Sweden, joined Nov 2005, 4007 posts, RR: 34
Reply 14, posted (3 years 9 months 1 week 1 day 10 hours ago) and read 17320 times:

Quoting tdscanuck (Reply 1):
Not being able to do tank-to-tank transfer is generally only true of modern Boeing (Puget Sound heritage) twins. The 737/757/767/777 can't do it, but most of the other Boeing's can, most Airbuses can

I think I will stop posting in here, there is always someone who knows more  

When this question about fuel transfer started, it was asked about correcting the balance of the aircraft when you had a leak in a tank. The A320/330/340 and B747 all have reserve or outer tanks that transfer BOTH SIDES together into the nearby wing tanks. Ever tried to get one outer tank on an Airbus to transfer. I have tried on A320 and I can't do it with CB pulling.
Even then transferring outer to inner, which the pilot can do on easily on an A330, and with much difficulty on an A320 will not correct the lateral balance very much.

So far I have only seen evidence that a B747-200 can do tank to tank transfer, what else can, that will affect the lateral balance?

p.s. as Tristar steve, I must say you could not do it on a Tristar. The Tristar fuel computor was called the Flight Engineer!


User currently offlineKlaus From Germany, joined Jul 2001, 21461 posts, RR: 53
Reply 15, posted (3 years 9 months 1 week 1 day 8 hours ago) and read 16789 times:

In the illustrations, which are the thrust bearings?

I would have expected the ones directly at the fan, but "radial loads only" roller bearings wouldn't seem to be a good choice for that. What's the design there?


User currently offlineSEPilot From United States of America, joined Dec 2006, 6907 posts, RR: 46
Reply 16, posted (3 years 9 months 1 week 1 day 8 hours ago) and read 16655 times:

Quoting Klaus (Reply 15):
In the illustrations, which are the thrust bearings?

The ball bearings are the thrust bearings. Since there would be substantial thermal growth in the shafts that would not necessarily exist in the support structure, it is necessary to have one bearing bear all the thrust loads and the other be radial only. Ball bearings can handle considerable thrust if properly designed and sized.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlinezeke From Hong Kong, joined Dec 2006, 9097 posts, RR: 75
Reply 17, posted (3 years 9 months 1 week 1 day 7 hours ago) and read 16480 times:

Quoting Tristarsteve (Reply 12):
The cutaway features counter rotating shafts, which was first introduced by RR on the Trent 900.

Rolls-Royce Pegasus to make the Harrier easier to hover, about 50 years ago now when they first ran.

Quoting Tristarsteve (Reply 12):
I believe this cutaway is an A380 Trent 900 engine

Closer look I agree, the number of LP turbines is the other clue. Trent 1000 (and GEnx) are also counter-rotatng. The Trent 1000 however has a 6 stage LPT. I didnt look at the counter rotating clue before, just the other stages, which are the same on the Trent 800 and 900 (Fan, 8 IPC, 6 HPC, 1 HPT, 1 IPT, 5 LPT) and the photo title.

Quoting Tristarsteve (Reply 14):
So far I have only seen evidence that a B747-200 can do tank to tank transfer, what else can, that will affect the lateral balance?

A380, transferres to the outers after takeoff for load alleviation.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently onlineTristarsteve From Sweden, joined Nov 2005, 4007 posts, RR: 34
Reply 18, posted (3 years 9 months 1 week 1 day 7 hours ago) and read 16405 times:

Quoting zeke (Reply 17):
Quoting Tristarsteve (Reply 14):
So far I have only seen evidence that a B747-200 can do tank to tank transfer, what else can, that will affect the lateral balance?

A380, transferres to the outers after takeoff for load alleviation.

Yes, but again you can only do both sides at the same time. The fuel computor will not allow you to transfer in one wing only to correct lateral balance problems. All two crew aircraft seem to be the same. One sided transfer only allowed with a Flt Eng to control it.


User currently offlineKlaus From Germany, joined Jul 2001, 21461 posts, RR: 53
Reply 19, posted (3 years 9 months 1 week 1 day 7 hours ago) and read 16319 times:

Quoting SEPilot (Reply 16):
The ball bearings are the thrust bearings. Since there would be substantial thermal growth in the shafts that would not necessarily exist in the support structure, it is necessary to have one bearing bear all the thrust loads and the other be radial only.

Sounds logical... but that would mean the intershaft bearing between LP and IP shafts near the generator drive would be the one carrying the entire fan thrust, would it not?

I guess all three spools are supposed to meet there near the structural center of the engine and at the main pylon interface. There's probably not much of a choice given the circumstances, but it still looks a bit strange that the main thrust would be transferred indirectly through the IP shaft instead of directly to the fixed structure.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 20, posted (3 years 9 months 1 week 1 day 7 hours ago) and read 16232 times:

Quoting Tristarsteve (Reply 14):
So far I have only seen evidence that a B747-200 can do tank to tank transfer, what else can, that will affect the lateral balance?

Sorry, I see what you're getting at now...the only one of modern vintage that I know of that can do that is a 787, explicitly to correct a lateral balance, but it's a flight-crew commanded function not an automatic one.

Quoting Klaus (Reply 19):
Sounds logical... but that would mean the intershaft bearing between LP and IP shafts near the generator drive would be the one carrying the entire fan thrust, would it not?

I thing the thrust load is carried by the most forward bearing (between the LP shaft and the fan support structure. There's no appreciable thrust on any of the other spools, and the LP shaft itself runs in tension between it's thrust bearing and the turbines, so having the bearing close to the fan would lower the overall weight of the shafts.

Tom.


User currently offlinezeke From Hong Kong, joined Dec 2006, 9097 posts, RR: 75
Reply 21, posted (3 years 9 months 1 week 1 day 7 hours ago) and read 16224 times:

Quoting Tristarsteve (Reply 18):
The fuel computor will not allow you to transfer in one wing only to correct lateral balance problems.

It does that automatically with the forward transfer, the tanks with the least amount of fuel get the fuel first.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineSEPilot From United States of America, joined Dec 2006, 6907 posts, RR: 46
Reply 22, posted (3 years 9 months 1 week 1 day 6 hours ago) and read 16177 times:

Quoting Klaus (Reply 19):
Sounds logical... but that would mean the intershaft bearing between LP and IP shafts near the generator drive would be the one carrying the entire fan thrust, would it not?

The thrust bearing for the LP stage, which drives the fan, appears to be at the very rear of the engine. It is unclear what supports it, but it is not the other shafts. The load is transferred directly to the case.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently onlineTristarsteve From Sweden, joined Nov 2005, 4007 posts, RR: 34
Reply 23, posted (3 years 9 months 1 week 1 day 6 hours ago) and read 16037 times:

Quoting tdscanuck (Reply 20):
I thing the thrust load is carried by the most forward bearing (between the LP shaft and the fan support structure. There's no appreciable thrust on any of the other spools
Quoting SEPilot (Reply 22):
The thrust bearing for the LP stage, which drives the fan, appears to be at the very rear of the engine.

You can only carry thrust loads on ball bearings.

Look at the bottom of the diagram and it says
Roller bearing x5 radial loads only.

Think about it, how can you transfer thrust through a roller bearing? All you do is try and push it apart.


User currently offlineFerpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 24, posted (3 years 9 months 1 week 1 day 6 hours ago) and read 15878 times:

Well it actually sais in the schema below the cutaway which bearings carry the axial and radial loads, the centre 3 ball bearings   . The are placed in the centre to have minimal axial play appear on the radial load ball bearings as the casing and shafts expands and contracts with temperature and forces.

The thrust bearings only carry a fraction of the thrust, the engine is balanced by the pressure forces of the compressor and turbine vertical discs vs. the casings vertical surfaces to only have a small part of the thrust taken by these bearings. Imagine the bearings taking among them 72k lbf   , that would be quite a load and they would not last long!

The pressure forces thus injects the loads aerodynamically into the casing at different points of the engine to distribute the stresses. This is done this way in all jet engines.



Non French in France
25 Post contains images Ferpe : While we are at it, here a principle sketch of an oil system of a RB211/Trent (not sure which one but once again they are all very similar). One can c
26 SEPilot : You can carry thrust on tapered roller bearings, but not straight. You can also carry it on plain bearings, or roller thrust bearings. On closer exam
27 WingedMigrator : That makes sense for a turbojet, but this is a turbofan. What reacts the thrust produced by the fan, other than these bearings?
28 traindoc : Was the QF A380 even using maximum thrust when the engine disintegrated? I thought that I read somewhere that it was only at 87% max thrust at the tim
29 tdscanuck : Some of it is picked up by aerodynamic pressure on the fan duct and nozzle, but the vast majority is carried by the fan bearing(s). They weren't at m
30 Post contains images PM : Sounds about right. I remember leaning out of my bedroom window forty years ago and watching operational GR1s coming and going.
31 Ferpe : @WingeMigrator The fan is balanced via the LP shaft by the LPT and the cavities before and aft of the LPT coned centre structure (look at the cutaway
32 Post contains links 747classic : 72.000 lbs T/O thrust ? According the Type Certificate of the Trent 900 series : Max. Continuous Thrust is 71.850 lbs for ALL Trent 900 variants. Max
33 litz : That's the first time I've seen it confirmed in print that additional faulty stub pipes have been found ... That's a big, huge, expensive "oops" ... -
34 okie : For this we are going to call it 72K but that a side the concept that now RR is saying that the turbine is only good for 75 take-offs at the 72K rati
35 N14AZ : Finally MSN 047 has left TLS and QF will have one additional A 380, QF A 380 Nr. 7
36 gokmengs : Hey guys felt like the thread needed a bump, also aside from the very technical and informative discussion, does anyone know the status of the aircraf
37 Post contains links JoeCanuck : More 380's are re-entering Qantas service; QF A380 SIN-SYD Engine Failure - Part 7 (by moderators Dec 12 2010 in Civil Aviation)
38 PM : From today's ATWonline: "Qantas is believed to be closer to restarting Airbus A380 service on the Los Angeles to Sydney and Melbourne routes after reg
Top Of Page
Forum Index

This topic is archived and can not be replied to any more.

Printer friendly format

Similar topics:More similar topics...
QF 78 SIN - PER Engine Fire posted Fri May 16 2008 06:54:18 by Flyerau
Likelihood Of Getting The A380 SIN-SYD This Novemb posted Fri Oct 12 2007 02:32:22 by Windowplease
QF A380 First Flight SYD-SIN-LHR Today 16JAN! posted Thu Jan 15 2009 20:02:58 by AlitaliaDC10
QF A380 Emergency At SYD Yet Again posted Wed Mar 31 2010 02:44:45 by KLXA380
QF A380 Passengers Stranded For 26 Hours In SYD? posted Mon Oct 12 2009 23:19:17 by Springbok747
QF A380 SYD-MEL-ANTARCTICA-MEL-SYD On NYE posted Fri Sep 11 2009 00:53:11 by Tayser
SQ SIN-SYD A380 Service Begins Oct 28th posted Wed Sep 12 2007 12:58:28 by Pilot21
QF 744 Returns To LAX With Engine Failure. posted Thu May 3 2007 11:00:37 by Jafa39
First SQ A380 Flight: SIN-SYD In Dec 06 posted Wed Aug 2 2006 01:02:55 by RedChili
First A380 Route - SQ SIN-SYD In December posted Tue Jun 6 2006 12:59:56 by ClassicLover