A350 seeks 420 minute ETOPS
Thread Starter
A350 seeks 420 minute ETOPS
An article on the Wall Street Journal website states that Airbus has told customers and air-safety officials that the A350 design contemplates 420 minute approval some day.
A question for folks with engine knowledge: how does one assess the reliability of an engine operating at high power for prolonged time as required in single-engine diversions? As a former reliability guy (in semiconductors) I'm moderately uncomfortable with estimating reliability behavior in a regime far away from high-volume field experience, which we always found to be a useful backup and corrective to estimates made from accelerated testing and various forms of analysis.
A question for folks with engine knowledge: how does one assess the reliability of an engine operating at high power for prolonged time as required in single-engine diversions? As a former reliability guy (in semiconductors) I'm moderately uncomfortable with estimating reliability behavior in a regime far away from high-volume field experience, which we always found to be a useful backup and corrective to estimates made from accelerated testing and various forms of analysis.
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
archae86:
I don't have anything quantitative at hand, but worked a decade or two on an early "big" engine used in twins, trijets, and quads. No technical difference between, same engine really, but the environment and thrust used in cruise was substantially different.
In the final analysis, it was the number of flight cycles that accounted for the wear and tear on the machines. The twin generally flew the shortest legs, and thus accumulated the most flight cycles, thus generating the most shop visits.
420 minute ETOPS? Very long legs, few cycles accumulated, so I'd expect long life for the machine.
...how does one assess the reliability of an engine operating at high power for prolonged time as required in single-engine diversions? As a former reliability guy (in semiconductors) I'm moderately uncomfortable with estimating reliability behavior in a regime far away from high-volume field experience...
In the final analysis, it was the number of flight cycles that accounted for the wear and tear on the machines. The twin generally flew the shortest legs, and thus accumulated the most flight cycles, thus generating the most shop visits.
420 minute ETOPS? Very long legs, few cycles accumulated, so I'd expect long life for the machine.
Join Date: Mar 2006
Location: USA
Posts: 2,527
Likes: 0
Received 0 Likes
on
0 Posts
7 hours aloft after an engine failure in a twin? So when I have an engine failure right after departing Honolulu, I can just continue to Los Angeles. 
Why not just get rid of the whole ETOPS concept altogether then?
Why not just get rid of the whole ETOPS concept altogether then?
Join Date: Dec 2001
Location: what U.S. calls Žold EuropeŽ
Posts: 941
Likes: 0
Received 0 Likes
on
0 Posts
Would be nice if somebody could provide reliability figures for the CFM56 on the A319 and on the A340. On the A340 they run at higher power for much longer periods. I would bet the figures are better.
I guess that is exactly what would happen in the future, once all aircraft will be twins. And just like for nuclear power, everybody will be shaken up once the statistical figures proof to be right, and the unlikely but certain event will happen one day. Extremly reliable does not mean unfailable.
Why not just get rid of the whole ETOPS concept altogether then?
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,499
Likes: 0
Received 0 Likes
on
0 Posts
Would be nice if somebody could provide reliability figures for the CFM56 on the A319 and on the A340. On the A340 they run at higher power for much longer periods. I would bet the figures are better.
Let them go 420 minutes ETOPs. Its just the manufacturers selling point ! Just make the operators approval very exacting with stringent criterias. Nothing to do with ETOPs but most of us are a little shy of cargo fires, (2 or 4 engine), this far away from a suitable ETOPs alternate.
Nothing to do with ETOPs but most of us are a little shy of cargo fires, (2 or 4 engine), this far away from a suitable ETOPs alternate.
tdracer, I hear you !
In a controlled cargo fire ( ahhh). How about a cargo fire that has been extinguished with the first bottle. Then you need numerous other bottles to keep the fire suppressed while you return to your planned ETOPs alternate 420 minutes away. Of course you will have 2 engines working but ventilation shut off which may result in computers overheating. Perhaps the extra fuel planned for the 1 engine out depressurised scenario will cover you? or perhaps there is a nearer adequate airport that your ETOPs nominated one.
Either way its a boundary I wont be pushing unless the whole ETOPs/EROPs certification is updated to reflect reality rather than the theoretical.
In a controlled cargo fire ( ahhh). How about a cargo fire that has been extinguished with the first bottle. Then you need numerous other bottles to keep the fire suppressed while you return to your planned ETOPs alternate 420 minutes away. Of course you will have 2 engines working but ventilation shut off which may result in computers overheating. Perhaps the extra fuel planned for the 1 engine out depressurised scenario will cover you? or perhaps there is a nearer adequate airport that your ETOPs nominated one.
Either way its a boundary I wont be pushing unless the whole ETOPs/EROPs certification is updated to reflect reality rather than the theoretical.
Fluke
The new ETOPS rules (FAR Part 25 Appendix K in the FAA world) attempt to take all those things into account (healthy skepticism is probably justified
).
During my recurrent DER training a couple years back they went over the Appendix K rules in some detail including the 'why'. The basic admission was the engine reliability on modern engines was to the point that loosing multiple engines due to independent causes on the same flight was no longer the only, or even primary, ETOPS concern - it was now the rest of the airplane. Things like electrical systems, fire suppression, etc.
Hence the new ETOPS regulations apply regardless of the number of engines (never mind it pretty much trashes the original ETOPS definition). IIRC, the new regs are mandatory in 2015 for all Part 25 passenger airplanes (3 and 4 engine freighters are exempt - apparently their flight crews don't matter). While engine reliability is still relevant for twins, 3 and 4 engine airplanes the regulations don't have much to do with the engines.
Right now the 777 has 330 minute ETOPS, I don't work the 777 but what I'm hearing is that extending that is not technically an issue - it's just time and money - and 330 covers everything that the operators have wanted. 420 covers some theoretical Antarctic polar routes, and could potentially give Airbus some bragging rights until Boeing responded.
My personal opinion is 420 minute ETOPS is just AIRBUS way of claiming their attachments are bigger
The new ETOPS rules (FAR Part 25 Appendix K in the FAA world) attempt to take all those things into account (healthy skepticism is probably justified
).During my recurrent DER training a couple years back they went over the Appendix K rules in some detail including the 'why'. The basic admission was the engine reliability on modern engines was to the point that loosing multiple engines due to independent causes on the same flight was no longer the only, or even primary, ETOPS concern - it was now the rest of the airplane. Things like electrical systems, fire suppression, etc.
Hence the new ETOPS regulations apply regardless of the number of engines (never mind it pretty much trashes the original ETOPS definition). IIRC, the new regs are mandatory in 2015 for all Part 25 passenger airplanes (3 and 4 engine freighters are exempt - apparently their flight crews don't matter
). While engine reliability is still relevant for twins, 3 and 4 engine airplanes the regulations don't have much to do with the engines.Right now the 777 has 330 minute ETOPS, I don't work the 777 but what I'm hearing is that extending that is not technically an issue - it's just time and money - and 330 covers everything that the operators have wanted. 420 covers some theoretical Antarctic polar routes, and could potentially give Airbus some bragging rights until Boeing responded.
My personal opinion is 420 minute ETOPS is just AIRBUS way of claiming their attachments are bigger
Join Date: Jul 2000
Location: My views - Not my employer!
Posts: 1,031
Likes: 0
Received 0 Likes
on
0 Posts
SR-22 - Check this article - 50,000h on wing CFM.
Volume - I don't think there is a competition - The thrust rating on the CFM's on 737 are low compared to the A340's (check the trust rating vs aircraft in wiki)
Back to the OP - My feelings are similar to fluke and tdracer... The engines are no longer the limiting factor...
Volume - I don't think there is a competition - The thrust rating on the CFM's on 737 are low compared to the A340's (check the trust rating vs aircraft in wiki)
Back to the OP - My feelings are similar to fluke and tdracer... The engines are no longer the limiting factor...
Join Date: Mar 2007
Location: USofA
Posts: 1,235
Likes: 0
Received 0 Likes
on
0 Posts
ETOPS beyond 180
I think you will find that the limiting factor for any ETOPS beyond 180 minutes is cargo fire/smoke suppression. Engine performance is of course a consideration but the limits are established by more critical issues involving how long can I keep this darn thing airborne with a cargo fire.
Join Date: Jan 2007
Location: British
Posts: 318
Likes: 0
Received 0 Likes
on
0 Posts
What's the difference between a Tri or 4 engine aircraft cargo fire suppression system versus a twins? Are we not talking about system redundancy instead?
ETOPs doesn't mean that you'll have a happy ending with every incident, it's just a planning tool ( sic) .
ETOPs doesn't mean that you'll have a happy ending with every incident, it's just a planning tool ( sic) .
ETOPS = Extended-range Twin OPerations
DaveReid - As I noted in my previous post, effective next year all Part 25 passenger aircraft will be subject to ETOPS rules, regardless of the number of engines. To keep the acronym semi-meaningful, they are saying it stands for ExTended OPerations.
The new ETOPS rules don't apply to Freighter aircraft with more than two engines, again noted in my previous post.
DaveReid - As I noted in my previous post, effective next year all Part 25 passenger aircraft will be subject to ETOPS rules, regardless of the number of engines. To keep the acronym semi-meaningful, they are saying it stands for ExTended OPerations.
The new ETOPS rules don't apply to Freighter aircraft with more than two engines, again noted in my previous post.
Originally Posted by tdracer
My personal opinion is 420 minute ETOPS is just AIRBUS way of claiming their attachments are bigger
Probably also were the first manufacturer to have quads meeting the ETOPS regs (A340).
How does fire differentiate between a quad and a twin?
Why should a quad survive a fire a single minute longer than a twin?
And in any case of a fire either it is extinguished successfully or after twenty minutes it's game over anyway.