Qantas grounds A380s after Singapore emergency landing

Originally posted by C0bzz
Qantas has decided to check each engine for flaws, a process that takes 8 hours each aircraft, then if no problems are found they will likely be flying again.

That sounded too good to be true.

How can they check the engine for the flaw if they don't understand the flaw yet?

They are keeping the fleet grounded another 72 hours:

Qantas keeps A380s grounded, eyes oil leaks

the airline, Airbus and Rolls-Royce were working "working around the clock" to find the right fix for the issue.

If they aren't even sure what the right fix is yet, I'm not so sure they'll be flying again in 72 hours, but keeping them grounded must be costing a fortune so I'm sure there's lots of pressure to get them back in the air, fix or no fix?

News just in, Qantas are to ground their entire A-380 fleet for an indefinite period. Further the engine problem seems to be spreading with both SIA and Lufthansa now removing engines as well.

This is going to get very costly and Rolls Royce are more than likely going to have to pick up the tab.

LEE.

reply to post by solidshot


That seems interesting, looking at the pictures it appears the failure occurred at the first small downstream turbine after the combustion chamber. There is a Teflon labyrinth seal on the main shaft of these turbine engines to prevent oil leakage. Lufthansa techs have been replacing these Teflon seals "early" on their motors. I'm not sure what we are expected to glean from this, teflon seal manufacture is a mature technology so unless its a question of precision or something it seems obvious where the problem lies. Why not just replace the seals and get on with it? How long are we to wait, till pigs have wings?

reply to post by Bordon81
If something is causing premature wear of the seals, then replacing the seals might be a band-aid to get the planes back in the air short term, but its not a long term solution. Longer term, they would have to find out what's causing premature wear, like an imbalance perhaps, or whatever else is making the seals fail before they are expected to fail, and fix the root cause of the premature wear.

reply to post by Arbitrageur


You are right of course. We all know how the demands by the airlines for better fuel economy have led to lighter weight designs with lower friction shaft bearings. I'm pretty sure Rolls Royce is just going to issue a replacement seal with an interlace that will accommodate the higher than expected shaft run out eccentricity. Thats the kind of thinking that led to the inexpensive Compact laser Disk designs.

Its too bad some engineer hasn't come up with a system like the acoustic canceling systems available to reduce loud noise. If you could induce counter vibrations in the moving shaft that could be used to control the natural resonance of the motor. Since such a design would cause a self seeking elimination of the slop a turbine engine could be designed to tighter tolerances and perhaps even extend the performance envelope..

reply to post by Bordon81

Actually Bordon I seem to remember somebody doing that exact thing with automotive crankshafts. I cant recall who but it was at least 15-20yrs ago I heard about it.

As a side note on this, I can confirm what is now being reported in the media on this incident. The damage to the aircraft wing structure was extensive and nearly catastrophic. Green system hydraulics were badly damaged (run dry in fact), brake anti-skid system lost, partial loss of spoilers(hence the need to use all the runway upon landing), fuel pumps were failing (although the operating engines would continue to draw fuel anyway), the inboard wing tank ruptured in several places, they apparently couldn't dump fuel fully(therefore landing overweight) fire bottle's inoperative as well as a host of other sub-systems due to severed wiring. One media report was claiming that the spar was nearly hit and if it had the wing could have failed. However a colleague tells me there is apparently a photo quietly circulating in the company that shows the spar was indeed penetrated, although I have yet to see it so it may just be the old company rumor mill.

The only bright spot I can see in this is that the EHA/EBHA's appear to have done there job without any problems which proves the principle they were designed around.

It would seem that the company may not operate any of the aircraft for weeks possibly missing part or even all of the summer peak season. The amended flight schedule does not show any 380's for an indefinite period. I guess all the company risk analysts will be seeing this as a category 5 event, something I dont think any of us ever expected to see.

LEE.

reply to post by thebozeian
That's interesting, I didn't realize the damage was that catastrophic.

Singapore Airlines and Lufthansa flying the A380s with Rolls engines don't seem to be taking this as seriously as Qantas, I wonder if they are aware how serious it is. They have resumed flights except for a few planes that needed repairs, right? I found this on Singapore Airlines:

www.reuters.com...

Singapore Airlines, which was the launch airline for the A380 and operates 11 of the aircraft, initially said it would delay A380 departures, but soon cleared them.

"We have completed the engine inspections on all our A380 aircraft and did not find anything of concern," SIA spokesman Nicholas Ionides said on Monday.

Lufthansa just did a precautionary engine change:

www.flightglobal.com...

Lufthansa changed a single engine on the airframe registered D-AIMA, the first A380 delivered to the airline. The jet is just six months old having arrived in mid-May.

A spokesman for the carrier points out that the decision is "precautionary", adding that the airline has discovered "no findings" relating to the Qantas mishap.

Interesting that only one of the 3 airlines would ground their fleet, they're all using the same engines. Or are they? This is interesting:

www.newsdaily.com...

Chief Executive Alan Joyce said on Monday that its engines had a "slightly higher level of power" than those used in Singapore Airlines or Lufthansa planes, but they were certified to operate at those levels.

Does this mean the engines are the same but the full throttle setting is different? I don't really understand that statement by Chief Executive Alan Joyce so if anyone can clarify that I'd appreciate it. Does this mean for example that Singapore Airlines never quite uses full throttle on it's A380s or something? Would this be the equivalent of a "governor" on a car engine?

Latest update from Rolls here

Rolls confirmed the problem related just to its Trent 900 engine type, and was down to the failure of a "specific component" which led to an oil fire.

BBC


One of the posters above mentioned a similar problem in the auto market? i believe Ford had problems with the crankshaft seals on one of the engines some years ago? where a small "Burr" left was left on the crankshaft ate away at the crankshaft seal leading to an oil loss problem?

This media report gives a pretty accurate list of the damage done to the aircraft. There are one or two things that I am aware of that also failed or were damaged but this is probably the most comprehensive list revealed publicly so far.
News story.

Pretty good analysis of the situation by all in this thread

It will be interesting how this all shakes out

I have a little more news after talking with a colleague who is involved with the recovery effort on VH-OQA. It seems there is a real chance the aircraft may never fly again. He tells me he spoke to another colleague of ours over there in Singapore and he reports that the airbus assessment team were not very positive. Interestingly one of their main areas of concern was not the damage done to the wing i.e.. the spar, but rather over stressing done to the empennage area due to the inability to dump fuel out of the THS (Trimmable Horizontal Stabilizer). As you may by now know the aircraft landed overweight due to an inability to carry out a full fuel dump so when she finally set down this put a large stress on the tail area. The damage to the wing area is of course a major concern as well and coupled together may see the hull written off. There have been pictures that are now circulating on the web which show a hole in the spar big enough for a man to crawl through! As well as one photo that showed part of the fuel gallery completely severed.

As a side note I have noticed that the number of affected engines has steadily risen over the last few days and last night a figure of 80 affected powerplants was being mentioned which is basically all those in service. At least they now know what the issue is and have a fix designed.

LEE.

Originally posted by thebozeian
As a side note I have noticed that the number of affected engines has steadily risen over the last few days and last night a figure of 80 affected powerplants was being mentioned which is basically all those in service. At least they now know what the issue is and have a fix designed.

Thanks for the update, have you got a link to more info about the fix?

Even a plane that isn't landing overweight could put stresses on the aircraft if the wind is gusting intermittently which may cause a rough touchdown, right? So if the plane lands overweight but touches down smoothly would the stresses really be any greater than a rough landing at normal weight?

It never occurred to me from looking at those photos that they might have to trash the entire airframe, that's amazing.

Originally posted by thebozeian
There have been pictures that are now circulating on the web which show a hole in the spar big enough for a man to crawl through!

Indeed. We've had some interesting speculation regarding what would have happened if the disc had wiped out a spar cap, rather than the web.

Originally posted by thebozeian
As well as one photo that showed part of the fuel gallery completely severed.

As I understand it, a forward pipe was completely severed - its purpose I cannot confirm at this time. However, this should not have affected the dump gallery, which is located at the trailing edge of the wing.

Originally posted by kilcoo316
Indeed. We've had some interesting speculation regarding what would have happened if the disc had wiped out a spar cap, rather than the web.

Hi Kilcoo nice to see you, yeah quite a few of us here have had that (and whole bunch of others) thought as well. Just a few inches of change in trajectory would have seen it possibly slice through at least part of the web and one of the spar caps, the result probably would have been,... well, a great deal worse.

Originally posted by kilcoo316
As I understand it, a forward pipe was completely severed - its purpose I cannot confirm at this time. However, this should not have affected the dump gallery, which is located at the trailing edge of the wing.

I must confess I dont at this stage know exactly which line(s) was severed either. However I believe the problem with the fuel dump had more to do with the severed wiring looms than the galleries. Im unfortunately busy with overnight 737 phase checks the next couple of days(nights) but I will try and have a look at the 380 AMM if I have some time and get a schematic, maybe the FIM might help explain the problem? I'll have a go and see what I can deduce.

On a related note, Qantas is returning the A-380 to service this weekend (27/11/10) but initially only one aircraft till it gets joined by a sister ship in a few days. Until further notice there will be NO flights across the Pacific, period, only London will be served. In fact any flight that requires full takeoff thrust is banned until further notice, this is a voluntary measure by the airline and not an AD, also full thrust will still be available for emergencies at the Captains discretion. One good thing is that assessments of the damage to OQA are now a little more positive and in the words of the CEO the aircraft will be returned to service in the medium term (whatever that means?).

LEE.

Air safety investigators in Australia say they have identified a serious manufacturing fault with some engines fitted to Airbus A380 passenger jets. A misaligned component of the Rolls-Royce Trent 900 engine used on a Qantas A380 which exploded last month thinned the wall of an oil pipe. This caused "fatigue cracking", which prompted leakage and ultimately a fire. Rolls-Royce said the Australian findings were "consistent with what we have said before".

BBC

More bad news for Rolls? Would this mean that the current engines already in circulation will all have to be scrapped and are unrepairable?

Originally posted by Arbitrageur
reply to post by Bordon81

 

If something is causing premature wear of the seals, then replacing the seals might be a band-aid to get the planes back in the air short term, but its not a long term solution. Longer term, they would have to find out what's causing premature wear, like an imbalance perhaps, or whatever else is making the seals fail before they are expected to fail, and fix the root cause of the premature wear.

As someone pointed out earlier the sooting leading back from the LP Bypass outlet (an area that normally has no hot combustion) is evidence of a surge or backfire.

Normally a backfire is caused by excess fuel in the HP combustion area, however in the case of this incident the solution is not a band aid.

The cause was correctly identified as failed oil seals allowing oil to pool in the HP combustion area. Hot oil will eventually explode which is what happened on the day pushing hot gasses forward at supersonic speed. This cracked the fan discs which flew centifugally off the turbine.

Fixing the seals is not a band aid and will prevent the issue repeating so long as the issue causing seal failure is correctly fixed.

Part of the problem with Rolls Royce negines is unlike other big fans they have been designed in a modular manner so that segments of the engine discs can be removed without taking the entire engine off. Whilst this is great for fast maintenance it also permits errors in bolting it all back together. This modular approach itself may be the underlying cause why seals failed.

In other words, it may ultimately be unfixable without redesigning the entire engine.

Originally posted by sy.gunson
Fixing the seals is not a band aid and will prevent the issue repeating so long as the issue causing seal failure is correctly fixed.

Yes That makes sense if the issue causing seal failure has been identified and correctly fixed, has it? You seem to be suggesting a complete redesign might fix it?

Also, I'm trying to reconcile the "seal failure" with the explanation solidshot just posted, saying "A misaligned component of the Rolls-Royce Trent 900 engine used on a Qantas A380 which exploded last month thinned the wall of an oil pipe. This caused "fatigue cracking", which prompted leakage and ultimately a fire." I'm more familiar with car engines than jet engines, but that description doesn't sound like a seal failure to me, is it? The way it's written makes it sound like the failure occurred in an area other than the seal, but I'm no expert and would appreciate any correction by the experts here.

The issue seems to me that these engines were intended to be modular. Whole banks of fan discs could be removed from the engine without the need to remove an entire engine from the aircraft. A replacement module could be re-inserted.

We are talking about a turbine spinning at high speeds and temperatures. Getting realignment of the new module perfect in the field is guaranteed to fail every now and then. Also if you've ever done car maintenance removiving a tightly wedged part from somewhere if there is a seal or interface with another part, the seal or interface is going to suffer physical damage.

It has emerged in the past 24 hours that the part was most likely a small segment of pipe with a flange around it's circumference half of which has broken off, with the remainder of the flange thinned by wear.

What I am saying is that if the engine was not modular in design then this part would be more permanent and the risks would not exist.

The big selling point of RR engines is their ease of maintenance. A redesign designing out the modularity of engine segments might be the mechanical solution.

Originally posted by sy.gunson
Also if you've ever done car maintenance removiving a tightly wedged part from somewhere if there is a seal or interface with another part, the seal or interface is going to suffer physical damage.

Very true, I never tried to re-use any seals in this scenario, I always replaced them.

It has emerged in the past 24 hours that the part was most likely a small segment of pipe with a flange around it's circumference half of which has broken off, with the remainder of the flange thinned by wear.

What I am saying is that if the engine was not modular in design then this part would be more permanent and the risks would not exist.

Thanks for the clarification, that part makes sense even in light of the emergence of the stress fracture failure.

Seeing as how the other customers for the A380 (like UAE) don't use the Rolls Royce engines at all, I wonder if just switching to the non-Rolls Royce engines like the Engine Alliance GP7200 would be a better alternative than a redesigned engine. For one thing, it must take a long time to redesign an engine, test it, etc.

And there must be a reason the UAE chose the Engine Alliance GP7200 engines instead of the Rolls Royce engines, so I wonder how the maintenance on those compares? Are they less modular and more robust as you suggest an improved Rolls Royce design might be?

www.emirates.com...

It's a very difficult proposition to re-engine an aircraft. Cammacorp did so with the DC-8 but had to redesign the engine pylons and have these certified at huge expense.

Also the electical and fuel supply systems may need reconfiguration. It would be cheaper to render the modular exchange of turbine sections unlawful and require total engine overhauls in lieu of removing modules.

That would happen if the Trent 900 lost certification for module exchange as an approved maintenance proceedure. This would change the economics for any airline using these engines and could kill future sales.

I believe singapore airlines may also use the same engines.

They are permitted to fly at present with frequent borescope inspections for seal wear. An oil leak during flight is less likely to be dangerous than oil pooling whilst an aircraft is standing at the gate. provided no oil has pooled whislt at the gate for a turnaround any subsequent oil will blow through the engine and be combusted. It would also be noticed by temperature fluctuations in the EGT readings and the aircraft's computer would produce an alert upon landing of an abnormal reading.

Many modern airliners have electronic monitoring of systems stright through to maintenance bases. Often this information is transmitted automatically during flight.