Qantas A380 uncontained #2 engine failure

[Dual ground]

Try forming a skin that's over 100ft long, has tapering thickness, and reducing width along it's length, accurately and repeatably. Also where are you going to get sheet metal that's over an inch thick, and what are you going to use to bend it?

Bear in mind also that the upper and lower wing skins are the top and the bottom of the fuel tanks, so the kind of accuracy attained from computer controlled machining really does make sense.

[WillDAQ]

Really, that's amazing, why machined, isn't the skin formed from sheet into the correct curvature?

It's not curvature that's the issue. The panel is 25+mm thick at one end and <5mm at the other. The only way to get that change is to machine it from a plate that starts of 25+mm thick everywhere.

[Bolli]

Original Post by letsjet:
Does RR sub out it's manufacturing of parts or do they machine everything in-house?

The final machining is done in house, but the disks come in a circular piece originally, although the NDT (non destructive testing) is contracted out to another company based in Derby.

It will be interesting on what action is taken against manufacturers of the disk metal/NDT testing contractors if it turns out to be a material flaw.

Bolli

[Misterredmist]

Forgive me if this has been raised in an earlier post , however, I seem to recall RR Derby have a "telemetry centre" - I wonder what readings , facts, figures , and real-time notifications they received on the stricken nr 2 engine ?

[Boeing Junkie]

They do, there was a programme about RR and the Trent engines on one of the UK channels not so long ago.

They know about engine problems before the airlines do.

[kwateow]

Misterredmist

I'd be surprised if Qantas don't track their engine health in real time, transmitting the parameters back home.

In any case the two flight recorders are already being read in Oz.

[Dual ground]

I'm sure that any detected engine excedence would have been transmitted via ACARS to Qantas Maintrol in Sydney. The DFDR, CVR and QAR would have been "pulled" immediately for analysis, after the aircraft was safely shutdown and secured.

[Rengineer]

Containing a failed engine disk

Quote:
that is unless you wish to armour the engine with 1inch thick titanium all over.....
That would result in more fuel consumption and green peace having a shout!

Halloween, Heathrow, and all others:
An inertial navigation gyro from the '70s, some 1kg or so of metal , 15cm disk diameter and rotating at maybe 25000 RPM, will sometimes go right through a wall if it disintegrates during gound testing (not a common failure mode in flight, thankfully). Here you're talking about a 12000 RPM turbine disk that's over ten times that size. Remember the stored energy is proportional to the square of tangential speed at the circumference, times the mass, and you get an idea of the destructive power of such a disk. No sense trying to design an aircraft to stop that once it goes off. That's why they're supposed to be designed with enough safety margin!

-- Edited on 05-Nov 15:37 CET to correct factual errors --

[fc101]

Walnut wrote:

There is a lot of talk on this thread about which airlines have the Trent 900 fitted.
I recall that R/R had a major blow up of a test engine for the Boeing 787 recently.
Is the 787 using Trents? because if it is this could lead to a problem for an ETOPs a/c

A question I asked earlier was could anyone comment on the similarities between the A380 Trent 900, the Trent 1000 in the 787 and the Trent in the Qantas 747 incident a few months back? Apart from the fact that they're all RR Trents and two occured on Qantas aircraft....

Materials? Design? Maintenance?

Anyone?

fc101
E145 Driver

[DevX]

Quote:
DevX posted about possible parallels with this uncontained Trent 1000 failure

Correct, but the report has the test facility number wrong. Only a minor detail perhaps, but it was in fact 54 test facility, not 58. The failure did indeed damage the cell, but not significantly. I have witnessed a lot worse (many years ago) with the uncontained failure of a development RB.168 Mk 202 military Spey. The disc literally bounced around the test cell and cut through fuel, pneumatic and electrical lines like a hot knife through butter, and put the facility out of action for weeks.

As I reported in my previous post, this current failure (and the ANA T1000) is not purely a material issue as most metals are liable to failure when heated to a condition above and beyond their design requirements. Unfortunately I can't spell it out as the specific details pertaining to both incidents are confidential at the moment, but hopefully the full story will emerge via 'official' sources in the not too distant future.

[forget]

An inertial navigation gyro from the '70s, some 100g or so of metal , 5cm disk diameter and rotating at maybe 16000 RPM, will sometimes go right through a brick wall if it fails.

Ridiculous statement. Of course it wouldn't.

[Cows getting bigger]

Note to self - wear body armour before sitting in front of extremely deadly DI/AI gyro.

[Sallyann1234]

An inertial navigation gyro from the '70s, some 100g or so of metal , 5cm disk diameter and rotating at maybe 16000 RPM, will sometimes go right through a brick wall if it fails.

Yes there are many accounts of the brick walls on flight decks being damaged. It was a common problem back in the 70's. For this reason the brick walls were later replaced with reinforced concrete.

[Dual ground]

@fc101

Qantas 747-400s are powered by Rolls Royce RB211 engines not Trents. This is with the exception of the 400ER's and the 3 ugly sisters (always assuming that the Ugly Sisters are still in the fleet that is) which are CF6 powered.

[Heathrow Harry]

well the circumference would be seeing speeds of circa 150 kph (41 mps)

assuming it came off at those speeds kinetic energy is about 84 joules it would certaily hurt

[Janu]

Singapore Airlines has resumed flights on its Airbus A380 aircraft.

Source: BBC News - Singapore Airlines resumes A380 flights after scare

[VinRouge]

I am sceptical about the value of fuel tank inertion, several reasons:

1. Keeping the (expelled) oxygen out requires that the wall of the fuel tank remains gas-tight... As pictures show, engine parts can blow a hole through the wall of the fuel tank. Also, pretty often in (rejected) take off and landing incidents the fuel tanks get ruptured enough for inertion to be ineffective.
2. Jet fuel isn't that flamable. It should be heated to about 50°C to be able to form an flamable (explosive) fuel-air mixture. Hotter at altitude. Keeping the fuel cool (but not BA38 freezing) would be enough to prevent a fire hazard.

I fly with FTI. Unfortunately, I have lost friends due to a lack of it.


Ypu dont have to worry once the projectile has made a hole, at that point fti has done its job. The problem comes when you get a very hot piece of metal passing through a ullage space full of kerosene and air mix. You dont have to hit the vapour point of kerosene for this to form either.

The problem isnt the vapor point of fuel, its the effect of it sloshing in the ullage space and generating a vapour that way.

If a large hot piece of metal did go through the tank, I think we have to be thankful that the tank was full. If it was half full, I guarantee this could have ben a whole load worse.

Another more prevalent issue (I raised around page 6, together with FTI) was Hydrodynamic ram, which can destroy a tank from the inside. It will be interesting to see whether any structural damage has been done as a result of the ballistic shock as the metal fragments passed through the tank.

I also wonder how long it would have taken to discount terrorism in light of recent developments if the aircraft had been a loss. Sure would have given the conspiracists something to whine about.

[WillDAQ]

Materials? Design? Maintenance?

To be honest the subtle changes between designs are going to be way beyond anything that's worth discussing here, even if Rolls were willing to divulge what is ultimately commercially sensitive information.

Yes there are many accounts of the brick walls on flight decks being damaged. It was a common problem back in the 70's. For this reason the brick walls were later replaced with reinforced concrete.

Thank goodness for the advent of kevlar-concrete composite technologies. It's what gives Boeing's their distinctive brown instrument panel don't you know.

[Rengineer]

forget, CCN, Heathrow: Gyros

OK, got my numbers about the gyro mass and size wrong - it's been a long time. And of course I should have precised: "when it disintegrates", rather than "when it fails". Obviously the normal failure modes are different - nutation, bad signals, whatever. That was not my point. The individual gyros I had in mind had failed catastrophically during ground testing, after very long storage periods and quite possibly earlier damage; and they came from a design used on UAVs, not manned aircraft.

Just a short extract from "Aircraft accident reconstruction and litigation" by Mc Cormick, Papadakis, and Asselta, though:
"When a gyro platform crashes and the case is crushed, the gyros typically disintrgrate the internal mechanisms and almost explode due to the kinetic energy of rotating steel gyros. Even though gyros ar small, they are heavy (2 to 3 pounds), and their outer diameters at 25,000 RPM are moving about 300 miles per hour.
These steel gyros will not be simply captured in place easily. It is extremely rare to have a crushed platform of this variety with the gyros still in place. In such case, the gyros are not running at the time of impact because at the high RPM, the gyros scatter mindful of an exploding hand grenade."

My point is, in any case, a turbine disk is larger and heavier again, although the rotation is slower - but if it goes off, it's hard to stop.

[Raggyman]

Using RF for wireless engine management could be implemented the following way, to avoid a few of the issues related to it being implemented.

Firstly, you could have an inactive wireless system, in that if it looses the control line or inputs from the normal inputs, the wireless system becomes live. At that stage you won't be that interested in whether or not someone could control or hack the system, because you would have to meet the condition that the normal inputs would have had to have been disabled. But you could have an overide condition within the cockpit if you so wished.

I guess in this incident it ended in a very good way, and thankfully it did, but looking at the photos it could have ended up very seriously indeed. Another thing that it shows is that having the wires in the leading edge is quiet dangerous as well, but where else are you going to put them really. I would have thought that there would have been a few sparks flying around from the severed cables, which isn't a good thing if you have a hole in your fuel tank.

Now i guess really the only other way around this particular problem would be to run fibre optics around as a backup plan down the back of the fuel tanks, well away from the leading edge and away from the engine zone. Trouble is, where ever you are sending that signal to would have to have power readily available. Who also knows whether or not that you aren't going to see one of these types of failures do something completely different to the airframe than it did in this case.