There was an oil fire in a 9, in Australia, in the test cell. All the Trents have (had) the susceptibility to vibration/harmonics, and poor resistance due to coupling weakness. Too light by several kilograms...

Weight is profit lost, migrating shafts are a potential loss of life.

There's a bit more to it than that. Lighter and more efficient propulsion is not simply a question of maximising profits, it is also (IMO more importantly) a necessity if aviation is going to be able to keep up with demand in a world where oil is becoming scarcer.

Every introduction of new technology brings with it some risk, but most people are fairly sanguine about that if the long-term benefits are worth it.

I don't think I need add that none of the problems with newer engines have resulted in a fatality.

The FAA's airworthiness directive orders

(Excerpts from the AD)

"We are issuing this AD to prevent failure of the FMS resulting in one or more engine failure(s) and possible loss of the airplane."


How does one say "crapshoot" in technese?

As with the EASA AD before it (TRENT 972), the potential for loss of an aircraft is heightened....

Statistician?

Selective emphasis. The key word is "possibly" - you can have an AD which allows the aircraft to fly while being closely monitored if the chance of hull-loss is relatively remote. Compare that to the Applegate DC-10 memorandum, which stated clearly that "in most cases [this would be likely to] result in the loss of the aircraft". That is the point at which grounding until the AD is applied becomes imperative.

All transportation, from walking across the street to going into orbit, involves a degree of risk management, and everyone who takes an interest is - or at least should be - well aware of that.

Qantas dodged a shrapnel bomb, and landed successfully. The RR AD had recently been relaxed, and taken advantage of. if the plea to relax the ADhad not been granted, no explosion, by demonstration.

Risk Management? You are heating your seat.

That's a little melodramatic. If anything, the existence of the AD proves that the system has improved. Compare this to Kegworth, where the engines on the 734 were grandfathered from the 733 design despite having to handle more stress. In that case there was no AD until after the report was published, and another 734 suffered the same problem (although thankfully with no loss of life).

Your reference to certs piled on existing, are you referring to the TRENT FAMILY?

Sistering specs and expectations for a functionally different powerplant? Gads, not again?

Your reference though intended I suppose to point to an aberration, is evocative of the fallacy that caused the TRENT failure.

Scaling up thrust by scaling up dimensions is a fool's erand, as you eloquently point out, though perhaps inadvertently.

chee ahz...

There's a lot more to the differences in the RR Trent family than simply "scaling up" - there are significant design differences between them in order to suit their application better. The GP7000 series (the alternative A380 engine) was not a from-scratch design, it was developed from the GE90 and PW4000.

I'm prepared to bet that when the A380-800 series lands for the last time, there won't be a significant difference in reliability or incident between the engine types.

Engines let go sometimes, always have. Because of this, designs are refined during the time they are made. For example, the original RB211 was considered something of a nightmare in terms of reliability initially, but by the time the -535 variant was installed on the B757, they had achieved a level of reliability so good that even the Americans had to take notice.

There's a lot more to the differences in the RR Trent family than simply "scaling up" - there are significant design differences between them in order to suit their application better.

And that is why some of their certs should not have been "borrowed" from earlier designs,


:ugh:

Lyman

Which bit of GE do you work for?

A thread about three unusual failures of a GenX engine and you've dominated the last couple of pages with ill-informed mush about the alternative engine choice. Good job!

A cursory Google search doesn't seem to uncover any evidence of this - can you point me to yours?

Covered extensively in the thread, search there. Briefly, "A three spool is a three spool"

See also why the 700, with blade stator clash, contained the IPT in 'Edelweiss' ex Miami.

The 900 substituted a Stator 'platform', the IPT oversped, and the Islanders collected Titanium. same certificate....

I know, lets eliminate the variables, and model the differentials....

Oncemore....sorry, followed the bunny hole. I'll clean it up..

Actually, the failures are quite similar in nature. 100k thrust cannot be gained by inventing a brand new platform. There was more room in GE's device, but that does not exonerate them from shortcuts to the grail.

Oversimplification. If this were the case then the entire Trent series could be grandfathered from the RB211. We know this isn't the case and that each series of the Trent had to undergo most if not all of the certification tests individually.

The overriding feature of the Trent series was to minimise the requirement for variable stators - there's a nice overview here : Rolls-Royce Engines: Trent

All new and derived designs have kinks that require ironing out - this is accepted fact.

None of this is specific to the Trent series though - it's just a feature of progress in jet engine design. The "two-spool vs. three-spool" argument is a fallacy as unnecessary as the old "A vs. B" chestnut.

For example, a two-spool CF6-80 notoriously let go during a test at LAX:
FAA to Tighten Inspections on Some GE Jet Engines - Los Angeles Times

I must apologize, Dozy...

I thought for the longest time you were purposely avoiding the point made.

I am convinced you miss it on the natch...

No idea - what's "the point" as you see it?

The fact is that modern engines are statistically a hell of a lot more reliable than their forebears were when they were new...

Well, it seems the thread has morphed from the very well defined topic of discussion into a US vs UK point -counterpoint debate. Lyman, on one hand, is looking for 110% perfection on jet engines introductions. OTOH, Dozy is attempting to point out that problems with jet engines go beyond national boundaries, i.e. the RR vs GE debate, a revived but standing debate. So lets look at this.

Under Lyman theory, all aircraft would be grounded tomorrow at dawn because an unexpected event, just might be a possibility, one that doesn't meet the 110% margin of safety. Sorry, the world doesn't work that way. Next time you descend into the "grassy valley" on that winding road, worry about if your car brakes will control the descent or not. It is about the same as if a modern jet engine will perform its task or not. Despite legalistic thinking, nothing is assured to 110%.

Now Dozy brings up an interesting experience at American Airlines regarding an engine that had an unusual engine vibration as reported by the crew bringing the B-767 into LAX. The amateur test theory, as applied to your car engine experiencing the same problem, would be to back it out of the garage into your driveway, and rev it up to red line, at which point, boom! That is exactly what happened at AA. They took the aircraft to a remote area, rev'd it up to red line and boom! The correct procedure was to remove the engine from the wing and perform a look-see to find a HPT disc that had a significant crack out of the dovetail slot region after all those cycles and years. This would be a cost
reduction/elimination decision to the reduce the cost of quality that went amok at AA. The result of the amok was a loss of an airplane, not to worry, the insurance folks picked up the tab.

So lets get back to the original purpose of the thread, should any new information develop...

@TD

I hope that nothing I've said points to a tit-for-tat international debate!

All I care about is that wherever the donks come from they are designed, tested and built as well as possible...

Dozy,
Not at all! Nothing you said is a problem in my mind. All the engine folks do the best they can, always have...

So the SHA event is different !

I asked way back for any pictures since there had been a post that stated that there were some.

It's hard to afix blame without the facts

carry on