Norwegian 787 blows a donk in FCO
 

The RR engines (Rotating Rubbish...) have several restrictions on them. Many of them are cycle limited, and some versions have been restricted to ETOPS 138 instead of 180. I am sure this will place further restrictions on those junk engines. Rolls Royce and Boeing, not a great combination these days...

Can you elaborate? There are about 5 different issues with those engines and I'm curious if you know what was updated on it. Thanks.

I guess in the strive for efficiency that reliability has taken a hit. The alternate engine has issues too pushing current technology to the limits, the GE90 on the 777 still has regular BUG failures after 25 years, as for the MAX and now A320NEO with their stab AFCS faults, the A350 computer resets every so many days, it all reminds me of working the L1011 Tristar in the 1990's. I am afraid it looks like we are now in an industry relying on backups rather than designing safety and reliability in to the airframes and engines in the first place. I think they call it safety risk assessment.

I actually laughed out loud when I read that.

Exactly. I'm not sure why Boeing went all-electric on the 787. I can see arguments for the cabin air supply, but taking 250kW from the IP turbine, rectifying it, and inverting it once again to drive the CACs surely outweighs the simple benefit of taking bleed air directly from the compressor.

The air quality seems no better (very dry) since Boeing updated the CAC schedules to minimise surging.

Likewise with the electric brakes - they seem bulkier than their hydraulic equivalents and more prone to failure.

Pros? Well, I'm a big fan of the dual engine start.

Actually, the Trent 7000 on the A330-800 and -900 is derived from the Trent 1000-TEN on the 787 and the Trent XWB 84 on the A350 both of which are substantially different to the Trent 1000-A/B/C and, while not immune to some of the same issues, is likely to be far less affected.

A lot of folk deriding the engine without knowing what actually happened to cause it! Was it caused by FOD or a bird strike or a mechanical failure?

Well of course many like to sound knowledgeable by citing history. I just can't recall a similar event (dumped turbine blade pieces) on the B787, but I'm sure somebody will throw out something.

The engine pairs don't necessarily have the same hours. There's currently a restriction on fitting two engines (of the type affected by the known problems) with more than a certain number of cycles on the same aircraft. This is for exactly the reason you are concerned about.

I'd guess from one of their older fleet and swapped for the new one. So one older and one new on each aircraft until enough new ones available to swap out all the older ones maybe.

I believe bleed air has to be cooled before entering the cabin, which under some conditions could condense some of the water content out resulting in the low humidity experienced (building air conditioning plants will cool air below the target and then warm it back up to ensure it isn't too humid). I'm guessing the 787 cabin compressors don't heat the air so much, so perhaps lose less moisture this way? But I can't imagine them carrying a tank of water to actively humidify the air?

You're correct with regards to the Dreamliner but there has been at least one rather thorough independent test of air quality and relative humidity performed by Carlo Giaconia using an A319 flying a variety of short haul routes. His paper is here.

787s have humidifiers for flight deck and crew rest air. Something like that is being done on the A350 and 777X as well, with humidification of first and business as on option. For the most part, the cabin experience is the same.
The colder the air, the less moisture it can hold, so if you cool air with nonzero relative humidity, the resulting air will have a higher relative humidity, which is why air conditioners have dehumidifiers. If you warm air, the result has a lower relative humidity. If the air outside is -40, heating it to room temperature is going to create a very dry environment that sucks the water out of you. This has nothing to do with bleed air or electrically heated.

There's also the claim when the 380 and 787 were entering service that they're pressurized to 6000 feet, while previous gen ac are pressurized to 8000. I'll leave it to someone else to say how often their Cabin Alt climbs to 8000.

Hasn't the claim been the humidity could be set higher because of the CFRP fuselage? Like less corrosion risk or similar?

Given the issues with the Trent I'm surprised this has not caused more of a stir.

Was this a mechanical failure of the engine, a precautionary shutdown, or was there an external cause?

Perhaps it was an ingested small UAS (aka drone) so a drone strike/mid-air collision, not a bird strike.

It's not 'set' higher - as Dinger noted there simply isn't much moisture in the outside air at 35k - compressing it and heating it doesn't change that regardless of how you do it.
What they were able to do on the 787 - that hadn't been done previously - was have humidifiers to improve the humidity of the passenger (and crew) air. The carbon fiber construction meant there is no corrosion risk associated with that, but the ability to add humidifiers for passenger comfort has always been there - just seldom used.
It's up to the operator as to if they bother to service the humidifiers with water between flights...

BTW, for all the problems the Trent 1000 has been having, the current generation of engines is still an order of magnitude more reliable than what was available 40 years ago. Back then, people thought a shutdown every 10,000 hours was just fine, today a shutdown every 100,000 hours is cause for concern.

787 Humidity
 

Zonal driers in the crown area stops the moisture from condensing out, it is then recirculated back into the cabin to keep the humidity level above 15%.

At least, thats the theory.

Back to exploding engines....

6000 foot cabin at what cruising altitude in a B787?

I think people are getting caught up in Boeing spin here, our 30 year old 757s regularly cruise along at 6000 feet cabin altitude but our 737s sit at 8000 at the same level. Both use standard engine bleed as far as I'm aware

Once again association does not equal causation.

Big pieces typically equate to loose larger bits which often stem from the cooler parts in a turbine. I was under the impression that the earlier publizied problem was in the hot part of the turbine.So I remain neutral in picking a cause out of a news item.

I'm surprised how little factual information has been released about this incident, especially given the history of problems with the Trent on the 787. The only photo of the affected engine I could find had a large advertising board placed in front of it to try to prevent photos of the damage. Normally, by this stage, we would have seen photos of the damaged engine, know the variant of the engine, the number of cycles and hours it had done, and have some idea about what part of the engine had failed, even if the cause is still to be determined.

Twitter had this amusing observation;