HKG return, nope nothing to do with RR on that one, other tech issue unrelated

Earlier this week VS had 2 787s parked up outside their LHR hangar. One with no engines and the other with just one. I assume they are getting sufficiently compensated by RR.

Doesn't this issue go back a couple of months to some issues with ANA aircraft? I seem to remember RR discovered an issue with premature wear or something and began a programme of engine inspections/replacements. I think a couple of the LHR based VS planes were taken out of circulation for a while recently because of this.

Just to be clear, the .02 shutdown rate is for 180 minute ETOPS - longer ETOPS have correspondingly better shutdown rate requirements. However 180 is important because as I mentioned earlier 180 ETOPS will get you anywhere in the world (although may require less than optimal routing).
No first hand knowledge here but I suspect Kelvin is right and this is the same issue that ANA had. As I understood it - the ANA issue was related to corrosion of the turbine blade. At the high temperatures that turbines operate at, many materials corrode that don't corrode at lower temps - and some of the contaminates and impurities in the air and fuel act as catalysts at high temperatures.
The engine companies try to prevent this with various coatings - I suspect whatever coatings Rolls is using on the Trent 1000 are not working as well as they'd planned...

I think I have said this before but is it possible that the industry has gone a step too far with respect to technology and big airframes/powerplants?

Chris, that's a rather open ended and imprecise question. What do you mean by a "step too far" given the size and power of, for example, the engines on the A380.

I am very interested in these recent reliability events in terms of terms of ETOPS certification process. I'm wondering if a crack (pun not intended) has been found in the certification methodology that has been implemented.

To obtain ETOPS certification, a new model aircraft must conduct a mandated number of hours of operation of the engine type without shutdown required, during the certification period. However, no consideration is given or mandated based on engine wear (number of hours of operation) vs probability of failure.

To maintain a specific ETOPS certification, i.e. ETOPS 75-370, requires that the service history of aircraft using the engine type demonstrate an IFSD (in flight shut down) rate due of less than the specific rate: e.g. 0.01% per 1000 hours for ETOPS 180.

Herein lies the problem. The IFSD rate is averaged across all engines of the certified type, regardless of operational hours. It does not take in the scenario where newer engines are extremely reliable and older engines have a dramatic drop in the reliability rate.

If separate samples were taken by say every 1000 hours of engine life, with the ETOPS rating concurrent with the average IFSD within each 1000 hour period, then I would feel comfortable, but this isn't the methodology used. The high reliability of newer engines (higher at the moment for the B787 as a newer model) can mask the effective unreliability of high operational hour engines.

ETOPS/EDTO certification is part of the equation, but an Airlines approval comes from the regulator.

Regardless of what becomes of the 789's certification, individual regulators might start knocking them back to 180 or less until the Engine issues are resolved.

Yes, it's a 330 min EDTO approval on the B 789. I'm sure the necessary internal and regulatory risk assessments have taken place with prudent outcomes.

Your presumptions are not valid.

Overall (millions of hours) there is such a thing as a bath tub rate high during the learning process of what's near perfect and what doesn't work as expected. These kind of problems get high attention and only after enough hours are ETOPs considered. Then there is the mature rate where wear-out rates are kept track of in scheduled maintenance. In the end the rate often goes up when the product line moves to third tier operators with less diligence.

Meanwhile as I said in my earlier post, this problem, as described so far, is a common cause risk aggravated by a much faster and less defined wear-out rate that has little bearing on the ETOPS data assumptions. As such, day to day inspection results predict the liklihood of any two engines on the same aircraft failing in the same flight.

The fleet mix needs to address this by combinations of engines in and out of the new and changing maintenance schedule. Hence the available engine resource problem until enough "fixed" engines are available to match route structure.

ETOPs is not a protector when you are dealing with dual engine common cause failures since it only assesses the very small probabilities of independent failures

We used to plan to avoid engines on a twin being of similar life since O/H; of course this did incur extra non essential engine changes, hence costs, I wonder if this is still a practice?

Disagree. Auckland-Buenos Aires would not be practical. I think you'd struggle with Perth-Joberg too, for example.

Only one of the two events was a shutdown in terms of EDTO stats.

It's more the pushing of the limits of efficiency.

Hence the difference between impractical and impossible. With (only) 180 minute ETOPS, those routes are impractical. With less than 180 minute ETOPS those routes are impossible...

Yea, assuming all alternates are available, 240 will get you reasonably direct routing between AKL and EZE. 180 will require a dog leg to the North to keep range on the Islands (NCRG/NTAA) before SCIP.

Beyond 240 is good for more southerly routing if the winds are favorable or an Alternate isn't available.

More like have we surpassed practical limits in terms of thrust and airframe design.

Chris2303 mentioned:

No, that stage was reached in 1943 as reported here:

https://en.wikipedia.org/wiki/Junkers_Jumo_004

Jumo -:- thrust -:- weight
109-004B -:- 8.83 kN (1,984 lbf) -:- 745 kg (1,642 lb) 8,700 rpm


https://en.wikipedia.org/wiki/Willia...Specifications
Dry weight: less than 300 lb (140 kg)
Maximum thrust: max takeoff thrust 1500 lbf

Testimonials - Company - Williams International
The Williams FJ44-3AP engines ... and 5,000 hours between overhauls.

Thank god we realised when to stop in 1943 or goodness knows what might have happened?

tdracer,
I also suspect the alloy being used for the turbine blades may be more prone to corrosion than perhaps other alloys required by other engine manufacturers. In other words, if the coating deteriorates, the bare alloy needs to provide a margin for a period of time in terms of strength and corrosion resistance.

Not sure about GE having fewer problems than RR. Icing problems in the descent.....high vibration on start etc. That said the oil problems which have always haunted the Trent and its predecessor seem to be rearing their head again.

They aren't that powerful. 747 had 60,000 lbs out of various engines...the 380 max is 72k.