Qantas ground A-380's

According to the above, a turbine disk was found on the ground. If a full disk was found, that would indicate a shaft integrity problem and that's really nasty. When a shaft lets go the turbine can overspeed and burst, or it can shed blades and then exit the case. Either way you can't hope to contain that much energy. In one of the articles they said there is a shaft spline wear issue on these engines. The aircraft has 8,000 hours on it, and based on the engine cycle count the engine probably has less than 6,000 hours on it. For a turbine that's a premature failure for sure.

Usually, if you burst a disk you get the disk coming out in three or four pieces and it cuts the engine in half pretty much. If the disk comes out in one piece you get something like we saw here, a single segment of the case opened up. When I first saw the damage I thought that the disk just shed blades, because the damage wasn't all the way around the case, and stuff came out in several directions. Loss of a shaft is really rare and a big engineering issue. One classic way this can happen is that you can get an oil leak and get a fire that heats up the shaft and causes a failure, or you can have a mechanical issue with the deisgn. Either way it's not a good thing.

We had a amazing thing happen during a failure on a JT-11 (engine in the SR-71) in Florida during an outdoor engine test. The engine blew up on the stand and at the bottom right under the engine was a turbine disk with blades that were smeared with tar. They couldn't figure out why the blades had that junk on them, but it was in the right place pretty much and they just went along with the failure analysis. A couple of days later somebody noticed a set of two inch long curved marks, about an inch apart, going up a wall of the next test stand control building. This was odd, because the marks were on a wall away from the failed engine and from that point you couldn't even see the test stand where the failure occurred. Then they found a divot in the parking lot just in line with that. What they figured happened was that the disk came out of the engine and hit the strongback above the engine. That meant it had backspin when it shot away from the test stand, went OVER the next test stand, hit the parking lot with backspin, shot back toward the stand that it went over, climbed the wall and shot up into the air, and ended up back under the engine that it came out of. Imagine a hot disk weighing 50 or more pounds, with a temperature of about 1,000 degrees F, spinning at 12,000 rpm flying across a parking lot. If it would have hit someone it would have killed them for sure. Lots of energy in a loose disk!

 

FYI for folks reading Solofast's analysis (which is very good):

The segment above was about an American 767 that had a catastrophic failure during a ground run in 2008. The VLAC (A380) motor failed in flight. I'm not sure if Quantas/RR will have the ability/luck to find the pieces that departed the aircraft as I think (and I may well be wrong) that it happened in flight over water.

 

I was referring to the Av Herald article where they said the following:

Residents on the ground in Batam reported hearing a bang like an explosion before the debris came down onto a main road just south of the city center of Batam. The occurrence had even sparked rumours the airplane may have crashed.

Some of the debris including a turbine disk struck through the walls of a house on the ground in Batam.

They had shots of people recovering the cowling from the engine, but disks are a lot harder to find since they are heavy and often bury themselves when they fall. If the disk or pieces of it hit a house, as noted in the article they will have them and that will make it a lot easier to figure out what failed...

 

Apologies Solofast: I thought it was a reference to the 767 disk quote above!

 

Classic disk burst, broke into three pieces. Question now will be if it failed from material low cycle fatigue or did it break from overspeed. Could be hard to tell if they don't find more parts.

 

Just wondering... would it be wise to run different types of engines on the same plane?

For instance... run R.R. engines on 1 and 4, while running G.E. engines on 2 and 3? I remember in another thread someone saying that if you suck up sand it can cause failures in the engines and a R.R. variant will run long enough to let you land the plane while a G.E. engine will shut down automatically to prevent engine damage. At least this way you have two engines that'll continue in some manner. Or if you have systemic/design failures in the engines, then chances are you'll always have two engines working.

All the best,
Andrew.

 

Looks like you might have nailed this one. Qantas now mentioning oil being where it shouldn't be.

 

That wasn't rocket science, it's a very common issue. Oil leaks out into a cavity and then burns and the shaft gets hot and fails, which lets the turbine overspeed because there isn't a load on it, which causes the big noise and then silence. It's one of those "for want of a nail" stories.


The other thing that can happen is you can get a fire inside a bearing compartment if a seal goes bad and hot gasses get into the compartment. That appears to be what happened to the RR engine on the 787 that blew up on the test stand recently.

Qantas appears to be being very cautious and that's probably warranted.

 

Uneducated public perception might still be one of "Quantas doesn't maintain its planes"... do you think there will be some sort of recourse by Quantas against Rolls-Royce?

All the best,
Andrew.

 

The most scary part to me is loss of FADEC to #1. That has got to be addressed. I don't know if they pulled the fire handle or not for #1, but leaving it running to be shut down with foam doesn't sound good. Also, they were leaking hydro by the gallon, the spoilers didn't deploy fully on squatting. That's got to be looked at too. This sounds more systemic than just a burst rotor disk that was uncontained.

 

Most applications aren't "plug and play". While the mounts are the same, most engines have their own control systems and interfaces, so, while when you buy the airplane you can specify what engine you want, you don't generally change that once the aircraft is built. There are some newer airplanes where the interface is specified by the airframer, and perhaps you could do what you suggest, but there would be FAA cert issues with it. Example being procedures for specific engine issues that would be different for each engine, pilot training and know which engine is in which position, so it really wouldn't be practical.

The engine companies would also hate that because once you buy the airplane they want you hooked on their spare parts business for the life of the airplane and they will do anything they can to try to keep the other guys off of an airframe and protect their cash stream.

 

The engines in question are close to new. There shouldn't be any maintenance required at this point in their life. I don't see this as having anything to do with maintenance, and I think that point will likely get made over time. The more caution they exhibit now, (and especially when compared to other airlines) the better they look.

There is a huge amount of language in airline engine contracts that covers things like fuel burn guaranties, engine life, performance degradation, scheduled maintenance costs, and lots of other things that keep lawyers eating well for a long time. It is all part of buying the engine, which may or may not (and more usually is not) be part of the airplane contract. That is, most airlines buy the engines outside of the airplane purchase and supply them to the airfamer for installation. This means that in most cases the contract is between the airline and the engine maker, which is why I am sure Airbus is very happy they aren't in the middle of this.

With any new engine program some of the initial buyers may get guarantees that state "if your airplane is grounded due to an engine problem with our new unproven engine we will pay". That would not be unexpected. The engine companies have to do that to get the initial sales and make the risk acceptable for early customers. Later, when the engine is proven, those kinds of things go away. I would not be more surprised if RR didn't end up paying big money to Qantas. RR stock has fallen something like 15% since the middle of last week and they have been mum on any effects on the bottom line, but with something of that value parked and not making money, the costs can get big pretty fast.

 

+1

It does appear that there are a bunch of issues that seem to have popped up as a result of this failure. Call me old fashioned, but IMHO modern subsystem control systems need to be fail safe. The FAA doesn't requrire that at all, they only have to go to three levels of redundency, and that cleary isn't sufficient. It seems that the more systems and advanced computer controls that we install, the less we look into what the FMEA (Failure Modes and Effects Analysis) says can happen, and we really don't understand what bad things can (or eventually will) go wrong.

Don't know if Boeing is any better, but I pray it is because I avoid Airbus airplanes like the plague.

 

When the 727 was being designed, the hydraulics group considered 4 hyd. systems. The failure analysis guys figured that the probability of a failure went up with more than three systems and that the greater the number of systems the lower the reliability.
It appears that Rolls has a serious problem.

 

Gota love those old Boeing Aircraft. Every electrical component and all the hyrolics can fail and you can still fly. With essential power you even have basic indicators in the cockpit. Try that in an Airbus.

 

Bob- Lots of analyses on number of systems, engines, etc that provide the best reliability/suvivability. Answer nearly always comes out the fewer the systems/engines, the higher the reliability. But, if failures can be controlled so they are non-catastrophic, the survivability increases with an increase in number of engines and sometimes systems. Very tricky analyses used frequently for ETOPs aircraft.

The odds of a failure are higher on a 4 engine aircraft than a twin, but survivability is higher on a 4 engine aircraft if the failure is non-catastrophic. The RR engines are pushing the envelope on non-catastrophic.

Taz
terry Phillips

 

Yeah. That's what I said....I think.
Switchesoff

 

I didn't know any of that - thanks. I had previously assumed engines were more easily interchangeable as they essentially hang outside of the aircraft.

Well, I suspected maintenance issues weren't the cause as I'm somewhat interested in things that move (cars, etc), but I wasn't sure. I can think about it, talk to people like you who know what's really going on, and appreciate that Qantas are being very cautious and responsible about this - but not everyone will do that.

Take someone more like my wife... she'll look at the headlines and see that Qantas had an incident on their big plane, found similar developing problems on their other big planes after they were 'forced' to ground them, and then had a Boeing suffer an engine problem too. She won't ask why there were problems, she'll just know that Qantas has had engine problems not strictly related to one type of aircraft, and, given her terror with anything to do with flying anyway, will absolutely refuse to fly with them.

It's not just the down-time of the aircraft, it's the negative perception amongst the "partially informed" demographics of the flying, ticket-paying public that will affect future bookings even when all those planes are fixed and back up in the air. It's completely not the fault of Qantas, but I can't help but think that they'll end up paying a price for it anyway - despite compensation for the aircrafts' down time coming their way from Rolls-Royce.

All the best,
Andrew.

 

Maybe you would be happier flying on a Tupolev or Illyushin?

 

No, but I may be crazy, but I'm not stupid. However, as the saying goes, If it's not Boeing, I'm not going...

Airbus aircraft have known structual defects (the tail), and a flight control system that doesn't have (in my PROFESSIONAL opinion) sufficient backup programming for me to consider it safe (the incident with Air France over the Atlantic is just one example of this, and some of the things that happened after the disk blew on the 380 are additional confirmation of this).

Having conducted FAA certification of software, I understand what is to ME accceptable software practice and what isn't, and I'll give you a hint, I'm more picky than the FAA. I only know enough about the software practices that Airbus has used in their aircraft and understand how critical that is to the safety of their aircraft that I won't fly in them.

I'm sure that ten of thousands of flights will be conducted without incident, but I don't trust my life to statistics. I don't play Russian roulette either, and wouldn't want to even if the odds were a million to one if I don't have to. Like I said, I may be crazy, but I'm not stupid. I am sure that this is much like sausage, if you saw it being made you wouldn't eat it, but that's just how I feel.

At some point you have to draw the line, but if more people were a bit more discerning about what aircraft they flew on, as opposed to looking to save $15 on a ticket, perhaps there would be more market pressure on the airframers like Airbus to make aircraft safer and that would be a good thing.