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klm617
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Twins vs. quads and international over water routings.

Sun May 21, 2017 12:38 pm

While I understand that twins are less expensive to operate than tri jets or quads has the ETOPs rules that they are required to abide by adding more flight time to their international over water routing because of there requirement to be so many mile from the nearest suitable airport incase of an engine out emergency and if that is the case what is the time saved on a routing flown by a 747, A340 verses a 767 or A330.
the truth does matter, guys. too bad it's often quite subjective. the truth is beyond the mere facts and figures. it's beyond good and bad, right and wrong...
 
CplKlinger
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 1:00 pm

I can't speak to specifics, but the difference is obviously small enough that airlines are good with it. If it was too long they'd still be flying quads. To be up front about it, no airline worth their salt is going to make a choice that compromises safety. So if it's just as safe to use a twin and it costs less over time, they're going to use the twin, because they get the same safety level with more profit.
 
sadiqutp
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 1:02 pm

klm617 wrote:
While I understand that twins are less expensive to operate than tri jets or quads has the ETOPs rules that they are required to abide by adding more flight time to their international over water routing because of there requirement to be so many mile from the nearest suitable airport incase of an engine out emergency and if that is the case what is the time saved on a routing flown by a 747, A340 verses a 767 or A330.

A comprehensive answer to your question is well put in this video
https://www.youtube.com/watch?v=HSxSgbNQi-g&t=473s
 
chiki
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 1:06 pm

if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin
 
n757kw
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 1:14 pm

From the uninformed passenger view. I have been flying to ICN regularly since 2001. The flight time varies from 14-15 hours. I have flown the route in a B747-400, B777-200ER, B777-300ER, A380-800, B747-8I. The routings may vary but the overall flight time is about the same across the aircraft.

N757KW
"What we've got here, is failure to communicate." from Cool Hand Luke
 
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PatrickZ80
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 1:16 pm

chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


Not true. A twin can fly on one engine perfectly safe, the only stage they really need two engines is on take-off. Once in the air you could theoretically switch one engine off and continue to your destination on the other engine. Of course that's not done because it's better to have two engines performing on half power than one on full power, but it's possible.

In the past there were times when you needed at least three engines for long overwater routings, but those days are long gone. Engine reliability and performance has improved so much that a third engine isn't needed anymore.
 
mmo
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 1:28 pm

chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin



Care to back that statement up with some facts? Your statement is absolutely false and pretty uninformed.
If we weren't all crazy we'd all go insane!
 
george77300
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 2:40 pm

chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


The A350 can fly for I believe 370 minutes, (Over 6hrs) on one engine and this is way more than enough to land safely on. Your argument is completely floored.
 
klm617
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 2:55 pm

sadiqutp wrote:
klm617 wrote:
While I understand that twins are less expensive to operate than tri jets or quads has the ETOPs rules that they are required to abide by adding more flight time to their international over water routing because of there requirement to be so many mile from the nearest suitable airport incase of an engine out emergency and if that is the case what is the time saved on a routing flown by a 747, A340 verses a 767 or A330.

A comprehensive answer to your question is well put in this video
https://www.youtube.com/watch?v=HSxSgbNQi-g&t=473s


Thank you for sharing this with the current technology the planes really can fly the shortest routing even with 2 engines.
the truth does matter, guys. too bad it's often quite subjective. the truth is beyond the mere facts and figures. it's beyond good and bad, right and wrong...
 
FlyHappy
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 3:05 pm

george77300 wrote:
chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


The A350 can fly for I believe 370 minutes, (Over 6hrs) on one engine and this is way more than enough to land safely on. Your argument is completely floored.


Hey before we all pile on, it's only fair to point out that long range ETOPS a/c like A350/777/787 have lengthy ratings, not any particularly "ability". Look, most of these modern planes could still complete a long haul mission (given degraded aerodynamics/range) on 1 engine - BUT, a 1 engine situation is still an *emergency*, redundancy is lost, and the plane is required to land at first opportunity (and for very, very good reason). It cannot be denied that twins enter this state with a single engine loss, while tri's and quads do not.

I personally have no trepidation crossing oceans on twins, but despite the infinitesimally small probability that anyone will suffer a fluke 2 engine out scenario, flying thru invisible ash clouds (for example) is also a crazy fluke. Flukes can happen, and in those crazy situations, there may arise a scenario when more than 2 engines would have been preferable.
 
BravoOne
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 4:05 pm

You need to understand that this one vs. two engines is not the limiting issue when you go beyond 180 or 207 minutes rather is the capability of the cargo fire suppression system to go out to 330 minutes without further problems. When you look at an ETOPS compliant flight plan you will typically see the different scenarios.

1. Decompression with 2 engines running (Think cargo door failure)
2. Decompression with 1 engine running (think catastrophic engine failure)
3. Pressurized with 2 engines running (Think one of the engines just rolled back and flamed out, descend to FL230)

Of these three scenarios one of them becomes the "Critical Fuel Scenario" and that become the limiting factor for the ETP vs ETP area of operations. Depending on model of aircraft either scenario 1 or scenario 2 can be the most critical. The difference between 1 and 2 can be quite small regarding the required fuel. A number of additional factors are thrown in for good measure as well and to numerous to go over here. Both scenarios 1 & 2 are computed for flying to the designated alternate at 10,000, while scenario 3 is based upon single engine cruise computed at a one engine out diversion speed, usually something around 330 to 380kts TAS. The higher the speed the bigger the circles are that define your ETOPS Area of Operations. Going across the North Atlantic you will typically have three circles all of which overlap thus giving you a constant diversion plan or diversion escape route. A typical NAT routing would EINN, BIKF, CYQX airports designated as ETOPS Alternates, weather permitting.

The Quads and Tris do not use the same flight planning ETP selection process. Typically they will use a 2 engine out ETP and if hey loose just, keep on going, although we know how that works out sometimes after the BA incident from KLA to EGLL several years ago.
 
BG777300ER
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 5:42 pm

FlyHappy wrote:
george77300 wrote:
chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


The A350 can fly for I believe 370 minutes, (Over 6hrs) on one engine and this is way more than enough to land safely on. Your argument is completely floored.


Hey before we all pile on, it's only fair to point out that long range ETOPS a/c like A350/777/787 have lengthy ratings, not any particularly "ability". Look, most of these modern planes could still complete a long haul mission (given degraded aerodynamics/range) on 1 engine - BUT, a 1 engine situation is still an *emergency*, redundancy is lost, and the plane is required to land at first opportunity (and for very, very good reason). It cannot be denied that twins enter this state with a single engine loss, while tri's and quads do not.

I personally have no trepidation crossing oceans on twins, but despite the infinitesimally small probability that anyone will suffer a fluke 2 engine out scenario, flying thru invisible ash clouds (for example) is also a crazy fluke. Flukes can happen, and in those crazy situations, there may arise a scenario when more than 2 engines would have been preferable.



Thank you. I think this summarizes it all. ETOPS is no guarantee/ability or some magical thing. It's purely based on statistics and more stringent maintenance. I honestly think any ETOPS ratings above 120 are BS. 6 hours on one engine. Who would want to do that? Even pilots would sweat on that...anyone who says they wouldn't is full of BS. It all comes down to the balance of risk vs profit. Yes, engines are much more efficient today. No matter how you look at it, 2/2 engines going out will always have a greater probability than 4/4...although the probability of either is minuscule. A lot of people's blind love for airplanes on this forum really doesn't let them see the facts clearly.

Will I fly a twin over the Pacific? --- Sure
Would I pick a quad over a twin if the ticket price was the same? --- Sure

Its all about $$, to consumers, to airlines, to the FAA.
 
BravoOne
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 6:39 pm

You sort of contradicted yourself there." Any ETOPS beyond 120 minutes is BS" and "Will I fly a twin over the Pacific? --- Sure" so which is going to be The fact there will be little if any quad flying on the Pacific in the next few years other than freighters.

I'm not familiar with the A350 but there are damn few city pairs that would require that kind of range if any, and once again these limitation are fire suppression driven after 180 minutes.

Not sure how you figure this a $$$ issue to the FAA?
 
BravoOne
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 8:03 pm

No airliner shuts down an engine once at cruise for any reason other than a failure. You MIGHT be thinking of the US Navy P3 that will shut down an engine to increase their low level loiter time while looking for subs, but that is a completely different animal. The pure crap that shows on web sites like this will never cease to amaze me. Is there no common sense left in the aviation community anymore?
FWIW, if you loose and engine at your cruise altitude, you will need to descend to a lower altitude to maintain level flight. Something in the range of 10,000' is most likely. So if you had leveled off at FL350 and the number two engine flamed out, the first thing that will happen is you need to turn off track as you are going to start down and if you are heavy as you would be with fuel at the beginning of the crossing you're probably going to lose 10,000+ feet before you can level off. There are bunch of other procedures that will need to addressed before you can either divert to another airport, or return to your point of origin for a landing. We can save those for another discussion.
 
george77300
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 8:54 pm

BG777300ER wrote:
FlyHappy wrote:
george77300 wrote:

The A350 can fly for I believe 370 minutes, (Over 6hrs) on one engine and this is way more than enough to land safely on. Your argument is completely floored.


Hey before we all pile on, it's only fair to point out that long range ETOPS a/c like A350/777/787 have lengthy ratings, not any particularly "ability". Look, most of these modern planes could still complete a long haul mission (given degraded aerodynamics/range) on 1 engine - BUT, a 1 engine situation is still an *emergency*, redundancy is lost, and the plane is required to land at first opportunity (and for very, very good reason). It cannot be denied that twins enter this state with a single engine loss, while tri's and quads do not.

I personally have no trepidation crossing oceans on twins, but despite the infinitesimally small probability that anyone will suffer a fluke 2 engine out scenario, flying thru invisible ash clouds (for example) is also a crazy fluke. Flukes can happen, and in those crazy situations, there may arise a scenario when more than 2 engines would have been preferable.



Thank you. I think this summarizes it all. ETOPS is no guarantee/ability or some magical thing. It's purely based on statistics and more stringent maintenance. I honestly think any ETOPS ratings above 120 are BS. 6 hours on one engine. Who would want to do that? Even pilots would sweat on that...anyone who says they wouldn't is full of BS. It all comes down to the balance of risk vs profit. Yes, engines are much more efficient today. No matter how you look at it, 2/2 engines going out will always have a greater probability than 4/4...although the probability of either is minuscule. A lot of people's blind love for airplanes on this forum really doesn't let them see the facts clearly.

Will I fly a twin over the Pacific? --- Sure
Would I pick a quad over a twin if the ticket price was the same? --- Sure

Its all about $$, to consumers, to airlines, to the FAA.


I respect your point of view but a twin flying on 1 engine and a quad flying on 3 are both somewhat equally safe as a quad can't fly on 2 engines anyway. (Granted the decent rate will be slower than dual failure on a twin.) But either way you have to land very soon and both will have the same outcome. So imho I really am not bothered in a twin/quad oversea flights
 
sharles
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 8:58 pm

I would actually say that recently there have been multiple incidents that show the advantages of two engine planes.
QF32, BA2276, SQ368, AA383 are all examples of why you want less engines on your plane (lower probability of catastrophic engine failure that damages other systems).
 
BG777300ER
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 9:28 pm

BravoOne wrote:
You sort of contradicted yourself there." Any ETOPS beyond 120 minutes is BS" and "Will I fly a twin over the Pacific? --- Sure" so which is going to be The fact there will be little if any quad flying on the Pacific in the next few years other than freighters.

I'm not familiar with the A350 but there are damn few city pairs that would require that kind of range if any, and once again these limitation are fire suppression driven after 180 minutes.

Not sure how you figure this a $$$ issue to the FAA?


Haha, appreciate constructive criticism. I live in the real world, and realize ETOPS is not going away. That is fine with me. I just think continually jacking up the times is not right. There needs to be a balance. The reason I say 120 is, you mostly are flying on one engine for only 60 min, then the second 60 min is descent (engine almost idle). I think that is the max and best of both worlds. I can tell you, I do NOT want to be a passenger on an A350 flying on one engine over the Pacific for their 6 hours and 10 min ETOPS. No. No.and No. ANYONE who tells you they would be comfortable with that is full of it, or they just don't value their life enough. If I want to play with my life, I'll go skydiving and go out having fun...not in a metal tube over the lonely Pacific with people screaming and praying around me.

I do believe the FAA gets lobbied and influenced by airlines, but that's another topic for another day.

To summarize, I am cool with ETOPS, but the ETOPS they are giving out these days are a result of anything and everything done to phase out 4 engine airplanes in favor of economics = more money in airlines' pockets, and people in DC.
 
BG777300ER
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 9:32 pm

sharles wrote:
I would actually say that recently there have been multiple incidents that show the advantages of two engine planes.
QF32, BA2276, SQ368, AA383 are all examples of why you want less engines on your plane (lower probability of catastrophic engine failure that damages other systems).


Very, very valid point as well.
 
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Starlionblue
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Re: Twins vs. quads and international over water routings.

Sun May 21, 2017 11:50 pm

chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


As mentioned, we can fly perfecly well on one engine. Twins also tend to perform better than quads on all engines.

george77300 wrote:
chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


The A350 can fly for I believe 370 minutes, (Over 6hrs) on one engine and this is way more than enough to land safely on. Your argument is completely floored.


Just to be clear, it's not like the other engine just quits after 6 hours or whatever time period. ;) The engine will keep running until it runs out of fuel, unless it also encounters a rather catastrophic event, just as it would on any normal flight.

The EDTO range number is based on statistical engineering analysis, given the design of the engine and other systems, maintenance standards and flight crew training. The certifying authority gives permission for operations a certain number of minutes from a diversion airport, judging that the possibility of an engine failing is lower than a certain value. Another operator may have certification for a higher or lower number of EDTO range minutes, despite using the exact same engine and airframe.

My point is that the engine doesn't know how many minutes of running by itself it is certified for. :D


FlyHappy wrote:
george77300 wrote:
chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


The A350 can fly for I believe 370 minutes, (Over 6hrs) on one engine and this is way more than enough to land safely on. Your argument is completely floored.


Hey before we all pile on, it's only fair to point out that long range ETOPS a/c like A350/777/787 have lengthy ratings, not any particularly "ability". Look, most of these modern planes could still complete a long haul mission (given degraded aerodynamics/range) on 1 engine - BUT, a 1 engine situation is still an *emergency*, redundancy is lost, and the plane is required to land at first opportunity (and for very, very good reason). It cannot be denied that twins enter this state with a single engine loss, while tri's and quads do not.

I personally have no trepidation crossing oceans on twins, but despite the infinitesimally small probability that anyone will suffer a fluke 2 engine out scenario, flying thru invisible ash clouds (for example) is also a crazy fluke. Flukes can happen, and in those crazy situations, there may arise a scenario when more than 2 engines would have been preferable.


You are right that there are scenarios where more than 2 engines are preferable, but they are very rare.

There are other failures and errors more likely than dual unrelated engine failure, and we accept those daily. (Runway incursion and pressurization failure just to name two things.) We can't try to avoid every astronomically unlikely scenario. If we did so we'd never get off the ground.


PatrickZ80 wrote:
chiki wrote:
if you lose an engine like the recent A380 you thank God that you are in a quad vs a twin


Not true. A twin can fly on one engine perfectly safe, the only stage they really need two engines is on take-off. Once in the air you could theoretically switch one engine off and continue to your destination on the other engine. Of course that's not done because it's better to have two engines performing on half power than one on full power, but it's possible.

In the past there were times when you needed at least three engines for long overwater routings, but those days are long gone. Engine reliability and performance has improved so much that a third engine isn't needed anymore.


Well, no. We can't get to the destination on one engine, at least with current fuel loads, because we'd never reach our performance targets. We'd be cruising way lower and have asymmetric drag.

Engines aren't on half power in the cruise. More like 85-90%.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
TigerFlyer
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 12:11 am

Under current FAA regs, quads are also subject to ETOPs. According to this Boeing press release, the 747-8 is certified to ETOPs 330. http://boeing.mediaroom.com/2015-03-18- ... nute-ETOPS

I am equally comfortable flying a quad or a twin overwater. The risks of things likely to bring down a modern airliner over water apply relatively equally to twins and quads. Fire. Major systems failure. Volcanic ash.

Flying has inherent risks that cannot be eleminated entirely. But the odds of a second engine giving up on a 1-in-million probability over the next five hours seem acceptable. Passengers and pilots may experience some "pucker factor" for the duration. But it is unquestionably an acceptable risk.

That said, whether flying a twin or quad, it seems to me to make sense to plan a flight with the most available diversion options. For mechanical as well as medical reasons. If an optimal flight path puts you in the middle of the Atlantic, but an alternate route adds 10 minutes and keeps you in easy diversion range of Iceland, Greenland and Gander, why not play it safe.

You can't fly Sydney-Santiago without crossing a lot of open water, but I'm willing to take the risk, twin or quad, vs flying half way around the planet out of the way.
 
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Starlionblue
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 12:29 am

TigerFlyer wrote:
Under current FAA regs, quads are also subject to ETOPs. According to this Boeing press release, the 747-8 is certified to ETOPs 330. http://boeing.mediaroom.com/2015-03-18- ... nute-ETOPS

I am equally comfortable flying a quad or a twin overwater. The risks of things likely to bring down a modern airliner over water apply relatively equally to twins and quads. Fire. Major systems failure. Volcanic ash.

Flying has inherent risks that cannot be eleminated entirely. But the odds of a second engine giving up on a 1-in-million probability over the next five hours seem acceptable. Passengers and pilots may experience some "pucker factor" for the duration. But it is unquestionably an acceptable risk.

That said, whether flying a twin or quad, it seems to me to make sense to plan a flight with the most available diversion options. For mechanical as well as medical reasons. If an optimal flight path puts you in the middle of the Atlantic, but an alternate route adds 10 minutes and keeps you in easy diversion range of Iceland, Greenland and Gander, why not play it safe.

You can't fly Sydney-Santiago without crossing a lot of open water, but I'm willing to take the risk, twin or quad, vs flying half way around the planet out of the way.


AFAIK, most jurisdictions now regulate EDTO irrespective of number of engines. That is, an aircraft is not exempt from EDTO regs because you have more than two engines. Different models and different operators just have different EDTO range figures.

Like it or not, flight planning is not optimized for maximum diversion options, but for most efficient routing. Any legal routing will have the aircraft within legal range of a designated diversion airport at all times. In my aircraft, 10 minutes is literally around a ton of fuel. That's a lot of money to be spending on an infinitesimal increase in safety.

In any case, diversions are much more likely for an in flight medical emergency than for a mechanical issue.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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OneSexyL1011
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 7:37 am

On what planet is being on 1 engine in a twin as safe as being on 3 engines in a quad? None.

ETOPS isn't any kind of capability that the aircraft can magically do. Stop applying 120, 138,180, 207...etc to any aircraft as being "perfectly capable" of flying on a single engine. The ETOPS minutes rating is directly related to a signature on a piece of paper based on hypotheticals and conjecture of statistical data. Magically its "fully capable to fly 300 minutes!"

Its not like the aircraft has some magical ability to fly in a non-emergency scenario on one engine for 2-6 hours and all is well and safe. In the case of the level of risk in relation to the number of engines, the quad (or tri) will always statistically be safer than the twin. A single engine out scenario in a twin is an immediate land at the nearest suitable airport in point in time (Non-ETOPS or in ETOPS) and is treated as an extreme emergency. You have lost 50% of your redundancies and performance capabilities. A quad can only be at most 25% and depending on the engine, ZERO % redundancies lost.

Lost an engine in a quad? Meh maybe we can keep going maybe we should divert. We'll see, oh and where's my coffee?. Engine out in a twin? Holy *** we need to land.

The only reason why twins are flying these extreme ETOPS routes is $$$. Just because engines fail less often today doesn't make a 1 engine out scenario on a twin any less unsafe and dangerous.
Last edited by OneSexyL1011 on Mon May 22, 2017 7:53 am, edited 1 time in total.
 
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77west
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 7:53 am

OneSexyL1011 wrote:
You people are a piece of work.

On what planet is being on 1 engine in a twin as safe as being on 3 engines in a quad? None.

ETOPS isn't any kind of capability that the aircraft can magically do. Stop applying 120, 138,180, 207...etc to any aircraft as being "perfectly capable" of flying on a single engine. The ETOPS minutes rating is directly related to statistical reliability of the engines and fire suppression of the aircraft.

Its not like the aircraft has some magical ability to fly in a non-emergency scenario on one engine for 2-6 hours and all is well and safe. In the case of the level of risk in relation to the number of engines, the quad (or tri) will always statistically be safer than the twin. A single engine out scenario in a twin is an immediate land at the nearest suitable airport in point in time9Non-ETOPS or in ETOPS) and is treated as an extreme emergency. You have lost 50% of your redundancies. A quad can only be at most 25% and depending on the engine, ZERO % redundancies lost.

Lost an engine in a quad? Meh maybe we can keep going maybe we should divert. We'll see. Engine out in a twin? Holy *** we need to land.

The only reason why twins are flying these extreme ETOPS routes is $$$. Thats it.


Going back to a comment of mine on a previous thread of this nature - in the history of twin-engine flight, there is no example of an incident or crash involving a twin-engine commercial airliner that would otherwise not have had the same outcome, regardless of the number of engines. The Air Transat A330 that always comes up - fuel leak and fuel system mismanagement by crew. Air Canada 767 - ran out of fuel. 4 engines stop turning just as quickly as 2 with no fuel. BA9 - oh wait that was a quad jet.

Losing one motor in a twin is not "holy **** we must land!" it is simply "divert to the nearest suitable airport". You have not lost 50% of your redundancy as the APU will be started providing a source of air and electrical power, and hydraulics. A fire in the cargo hold, however, is definitely a "holy **** we must land!" moment, and would be so on a twin, tri or quad, or even the AN225 with 6 engines.
77West - AW109S - BE90 - JS31 - B1900 - Q300 - ATR72 - DC9-30 - MD80 - B733 - A320 - B738 - A300-B4 - B773 - B77W
 
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OneSexyL1011
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 7:54 am

77west wrote:
OneSexyL1011 wrote:
You people are a piece of work.

On what planet is being on 1 engine in a twin as safe as being on 3 engines in a quad? None.

ETOPS isn't any kind of capability that the aircraft can magically do. Stop applying 120, 138,180, 207...etc to any aircraft as being "perfectly capable" of flying on a single engine. The ETOPS minutes rating is directly related to statistical reliability of the engines and fire suppression of the aircraft.

Its not like the aircraft has some magical ability to fly in a non-emergency scenario on one engine for 2-6 hours and all is well and safe. In the case of the level of risk in relation to the number of engines, the quad (or tri) will always statistically be safer than the twin. A single engine out scenario in a twin is an immediate land at the nearest suitable airport in point in time9Non-ETOPS or in ETOPS) and is treated as an extreme emergency. You have lost 50% of your redundancies. A quad can only be at most 25% and depending on the engine, ZERO % redundancies lost.

Lost an engine in a quad? Meh maybe we can keep going maybe we should divert. We'll see. Engine out in a twin? Holy *** we need to land.

The only reason why twins are flying these extreme ETOPS routes is $$$. Thats it.


Going back to a comment of mine on a previous thread of this nature - in the history of twin-engine flight, there is no example of an incident or crash involving a twin-engine commercial airliner that would otherwise not have had the same outcome, regardless of the number of engines. The Air Transat A330 that always comes up - fuel leak and fuel system mismanagement by crew. Air Canada 767 - ran out of fuel. 4 engines stop turning just as quickly as 2 with no fuel. BA9 - oh wait that was a quad jet.

Losing one motor in a twin is not "holy **** we must land!" it is simply "divert to the nearest suitable airport". You have not lost 50% of your redundancy as the APU will be started providing a source of air and electrical power, and hydraulics. A fire in the cargo hold, however, is definitely a "holy **** we must land!" moment, and would be so on a twin, tri or quad, or even the AN225 with 6 engines.


Cool. Ill tell my co pilots this next time we run though 1EO scenarios in sim over the middle of the Pacific.

They'll need a good laugh.
 
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 8:20 am

OneSexyL1011 wrote:
On what planet is being on 1 engine in a twin as safe as being on 3 engines in a quad? None.

ETOPS isn't any kind of capability that the aircraft can magically do. Stop applying 120, 138,180, 207...etc to any aircraft as being "perfectly capable" of flying on a single engine. The ETOPS minutes rating is directly related to a signature on a piece of paper based on hypotheticals and conjecture of statistical data. Magically its "fully capable to fly 300 minutes!"

Its not like the aircraft has some magical ability to fly in a non-emergency scenario on one engine for 2-6 hours and all is well and safe. In the case of the level of risk in relation to the number of engines, the quad (or tri) will always statistically be safer than the twin. A single engine out scenario in a twin is an immediate land at the nearest suitable airport in point in time (Non-ETOPS or in ETOPS) and is treated as an extreme emergency. You have lost 50% of your redundancies and performance capabilities. A quad can only be at most 25% and depending on the engine, ZERO % redundancies lost.

Lost an engine in a quad? Meh maybe we can keep going maybe we should divert. We'll see, oh and where's my coffee?. Engine out in a twin? Holy *** we need to land.

The only reason why twins are flying these extreme ETOPS routes is $$$. Just because engines fail less often today doesn't make a 1 engine out scenario on a twin any less unsafe and dangerous.


Of course an engine out in a twin is "land ASAP". You've lost half your thrust and losing the other half would be bad Feng Shui. However as an emergency it is less extreme than uncontrollable smoke or a cargo fire. The aircraft is stable and the pilots aren't diving for the ground like they would be for uncontrollable smoke. You'd typically enter a hold and prepare for the approach for a not insignificant amount of time. You'd definitely keep going to an airport. If you had uncontrollable smoke far from an airport you'd seriously consider a ditching or a forced landing.

Regarding lost redundancies, in a modern design you still get all your systems. Full hydraulics, all necessary electric (perhaps shedding commercial), autoflight including autoland, all the instruments, even on the one remaining engine.
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 8:39 am

george77300 wrote:
BG777300ER wrote:
FlyHappy wrote:

Hey before we all pile on, it's only fair to point out that long range ETOPS a/c like A350/777/787 have lengthy ratings, not any particularly "ability". Look, most of these modern planes could still complete a long haul mission (given degraded aerodynamics/range) on 1 engine - BUT, a 1 engine situation is still an *emergency*, redundancy is lost, and the plane is required to land at first opportunity (and for very, very good reason). It cannot be denied that twins enter this state with a single engine loss, while tri's and quads do not.

I personally have no trepidation crossing oceans on twins, but despite the infinitesimally small probability that anyone will suffer a fluke 2 engine out scenario, flying thru invisible ash clouds (for example) is also a crazy fluke. Flukes can happen, and in those crazy situations, there may arise a scenario when more than 2 engines would have been preferable.



Thank you. I think this summarizes it all. ETOPS is no guarantee/ability or some magical thing. It's purely based on statistics and more stringent maintenance. I honestly think any ETOPS ratings above 120 are BS. 6 hours on one engine. Who would want to do that? Even pilots would sweat on that...anyone who says they wouldn't is full of BS. It all comes down to the balance of risk vs profit. Yes, engines are much more efficient today. No matter how you look at it, 2/2 engines going out will always have a greater probability than 4/4...although the probability of either is minuscule. A lot of people's blind love for airplanes on this forum really doesn't let them see the facts clearly.

Will I fly a twin over the Pacific? --- Sure
Would I pick a quad over a twin if the ticket price was the same? --- Sure

Its all about $$, to consumers, to airlines, to the FAA.


I respect your point of view but a twin flying on 1 engine and a quad flying on 3 are both somewhat equally safe as a quad can't fly on 2 engines anyway. (Granted the decent rate will be slower than dual failure on a twin.) But either way you have to land very soon and both will have the same outcome. So imho I really am not bothered in a twin/quad oversea flights


Well that's simply not true. The 3 quads I've flown will all happily fly around in level flight at a sensible altitude with 2 failed.
 
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 9:06 am

OneSexyL1011 wrote:
77west wrote:
OneSexyL1011 wrote:
You people are a piece of work.

On what planet is being on 1 engine in a twin as safe as being on 3 engines in a quad? None.

ETOPS isn't any kind of capability that the aircraft can magically do. Stop applying 120, 138,180, 207...etc to any aircraft as being "perfectly capable" of flying on a single engine. The ETOPS minutes rating is directly related to statistical reliability of the engines and fire suppression of the aircraft.

Its not like the aircraft has some magical ability to fly in a non-emergency scenario on one engine for 2-6 hours and all is well and safe. In the case of the level of risk in relation to the number of engines, the quad (or tri) will always statistically be safer than the twin. A single engine out scenario in a twin is an immediate land at the nearest suitable airport in point in time9Non-ETOPS or in ETOPS) and is treated as an extreme emergency. You have lost 50% of your redundancies. A quad can only be at most 25% and depending on the engine, ZERO % redundancies lost.

Lost an engine in a quad? Meh maybe we can keep going maybe we should divert. We'll see. Engine out in a twin? Holy *** we need to land.

The only reason why twins are flying these extreme ETOPS routes is $$$. Thats it.


Going back to a comment of mine on a previous thread of this nature - in the history of twin-engine flight, there is no example of an incident or crash involving a twin-engine commercial airliner that would otherwise not have had the same outcome, regardless of the number of engines. The Air Transat A330 that always comes up - fuel leak and fuel system mismanagement by crew. Air Canada 767 - ran out of fuel. 4 engines stop turning just as quickly as 2 with no fuel. BA9 - oh wait that was a quad jet.

Losing one motor in a twin is not "holy **** we must land!" it is simply "divert to the nearest suitable airport". You have not lost 50% of your redundancy as the APU will be started providing a source of air and electrical power, and hydraulics. A fire in the cargo hold, however, is definitely a "holy **** we must land!" moment, and would be so on a twin, tri or quad, or even the AN225 with 6 engines.


Cool. Ill tell my co pilots this next time we run though 1EO scenarios in sim over the middle of the Pacific.

They'll need a good laugh.


If your airlines pilots have time to laugh at my comments while you are practising a one-engine inoperative pacific diversion, remind me not to fly with you. I am not saying it is a trivial matter, but there are many more situations that would constitute a "land NOW even in the sea" situation than losing one engine on a twin. I worry about batteries / other flammables in pax luggage far more than losing an engine. And many pilots I know agree with that...

I will concur that a forced no engine landing, possibly at night, in the middle of an ocean, is not a situation I want to be in, as pax or crew. I just dont see the quad/tri vs twin argument as having any bearing on this. As I said... that would otherwise not have had the same outcome, regardless of the number of engines.
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 9:27 am

BG777300ER wrote:
BravoOne wrote:
You sort of contradicted yourself there." Any ETOPS beyond 120 minutes is BS" and "Will I fly a twin over the Pacific? --- Sure" so which is going to be The fact there will be little if any quad flying on the Pacific in the next few years other than freighters.

I'm not familiar with the A350 but there are damn few city pairs that would require that kind of range if any, and once again these limitation are fire suppression driven after 180 minutes.

Not sure how you figure this a $$$ issue to the FAA?


Haha, appreciate constructive criticism. I live in the real world, and realize ETOPS is not going away. That is fine with me. I just think continually jacking up the times is not right. There needs to be a balance. The reason I say 120 is, you mostly are flying on one engine for only 60 min, then the second 60 min is descent (engine almost idle). I think that is the max and best of both worlds. I can tell you, I do NOT want to be a passenger on an A350 flying on one engine over the Pacific for their 6 hours and 10 min ETOPS. No. No.and No. ANYONE who tells you they would be comfortable with that is full of it, or they just don't value their life enough. If I want to play with my life, I'll go skydiving and go out having fun...not in a metal tube over the lonely Pacific with people screaming and praying around me.

I do believe the FAA gets lobbied and influenced by airlines, but that's another topic for another day.

To summarize, I am cool with ETOPS, but the ETOPS they are giving out these days are a result of anything and everything done to phase out 4 engine airplanes in favor of economics = more money in airlines' pockets, and people in DC.



You obviously don't get and also may have failed both math, and geography. Where do you come up with this stuff?
 
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 9:51 am

The other issue with these arguments is it is not all about the sea; I would be just as worried having to make an emergency landing on say South Africa - Europe over the "lonely" African deep equatorial region. No form of transport is 100% safe. I would gladly fly a twin over any ocean, barren continent or to the moon, if the airline and airframe meets all the regulatory EDTO/ETOPS requirements. There is some evidence that ETOPS twins are actually safer, by virtue of being held to higher operational standards than tri or quad (This difference is being reduced with EDTO)
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 9:51 am

BG777300ER wrote:
I just think continually jacking up the times is not right. There needs to be a balance. The reason I say 120 is, you mostly are flying on one engine for only 60 min, then the second 60 min is descent (engine almost idle). I think that is the max and best of both worlds. I can tell you, I do NOT want to be a passenger on an A350 flying on one engine over the Pacific for their 6 hours and 10 min ETOPS. No. No.and No. ANYONE who tells you they would be comfortable with that is full of it, or they just don't value their life enough. If I want to play with my life, I'll go skydiving and go out having fun...not in a metal tube over the lonely Pacific with people screaming and praying around me.

I do believe the FAA gets lobbied and influenced by airlines, but that's another topic for another day.

To summarize, I am cool with ETOPS, but the ETOPS they are giving out these days are a result of anything and everything done to phase out 4 engine airplanes in favor of economics = more money in airlines' pockets, and people in DC.


EDTO diversion times aren't just arbitrarily being increased. For every increase, there has to be analysis every time demonstrating that the probability of a failure is at or below a stated level. That stated level doesn't change. The difference is that ability of aircraft (and operators) to meet the level is increasing given new designs as they designed with EDTO in mind from the ground up. For example on the 350, with an engine out you still have all the hydraulics. That wasn't the case on the 330.

It's not so much about the engines, which are ridiculously reliable already, but about systems and fire suppression capability. Those have been improving steadily.

(Also, 60 minutes in descent? That's about twice as long as you'd normally need.)
Last edited by Starlionblue on Mon May 22, 2017 9:56 am, edited 3 times in total.
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 9:55 am

Starlionblue wrote:
BG777300ER wrote:
I just think continually jacking up the times is not right. There needs to be a balance. The reason I say 120 is, you mostly are flying on one engine for only 60 min, then the second 60 min is descent (engine almost idle). I think that is the max and best of both worlds. I can tell you, I do NOT want to be a passenger on an A350 flying on one engine over the Pacific for their 6 hours and 10 min ETOPS. No. No.and No. ANYONE who tells you they would be comfortable with that is full of it, or they just don't value their life enough. If I want to play with my life, I'll go skydiving and go out having fun...not in a metal tube over the lonely Pacific with people screaming and praying around me.

I do believe the FAA gets lobbied and influenced by airlines, but that's another topic for another day.

To summarize, I am cool with ETOPS, but the ETOPS they are giving out these days are a result of anything and everything done to phase out 4 engine airplanes in favor of economics = more money in airlines' pockets, and people in DC.


EDTO diversion times aren't just arbitrarily being increased. For every increase, there has to be analysis every time demonstrating that the probability of a failure is at or below a stated level. That stated level doesn't change. The ability of aircraft to meet the level is increasing given new designs as they designed with EDTO in mind from the ground up. For example on the 350, with an engine out you still get all the hydraulics. That wasn't the case on the 330.

It's not so much about the engines, which are ridiculously reliable already, but about systems and fire suppression capability. Those have been improving steadily.

(Also, 60 minutes in descent? That's about twice as long as you'd normally need.)


The systems and fire suppression - this is what it is all about these days. So you can fly with one engine offline for 20 hours? - great! - how long can you keep the raging lithium battery fuelled fire at bay in cargo position 12...? Not quite that long I think.
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 4:31 pm

77west wrote:
Starlionblue wrote:
BG777300ER wrote:
I just think continually jacking up the times is not right. There needs to be a balance. The reason I say 120 is, you mostly are flying on one engine for only 60 min, then the second 60 min is descent (engine almost idle). I think that is the max and best of both worlds. I can tell you, I do NOT want to be a passenger on an A350 flying on one engine over the Pacific for their 6 hours and 10 min ETOPS. No. No.and No. ANYONE who tells you they would be comfortable with that is full of it, or they just don't value their life enough. If I want to play with my life, I'll go skydiving and go out having fun...not in a metal tube over the lonely Pacific with people screaming and praying around me.

I do believe the FAA gets lobbied and influenced by airlines, but that's another topic for another day.

To summarize, I am cool with ETOPS, but the ETOPS they are giving out these days are a result of anything and everything done to phase out 4 engine airplanes in favor of economics = more money in airlines' pockets, and people in DC.


EDTO diversion times aren't just arbitrarily being increased. For every increase, there has to be analysis every time demonstrating that the probability of a failure is at or below a stated level. That stated level doesn't change. The ability of aircraft to meet the level is increasing given new designs as they designed with EDTO in mind from the ground up. For example on the 350, with an engine out you still get all the hydraulics. That wasn't the case on the 330.

It's not so much about the engines, which are ridiculously reliable already, but about systems and fire suppression capability. Those have been improving steadily.

(Also, 60 minutes in descent? That's about twice as long as you'd normally need.)


The systems and fire suppression - this is what it is all about these days. So you can fly with one engine offline for 20 hours? - great! - how long can you keep the raging lithium battery fuelled fire at bay in cargo position 12...? Not quite that long I think.


And your point is?
 
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Re: Twins vs. quads and international over water routings.

Mon May 22, 2017 11:50 pm

BravoOne wrote:
77west wrote:
Starlionblue wrote:

EDTO diversion times aren't just arbitrarily being increased. For every increase, there has to be analysis every time demonstrating that the probability of a failure is at or below a stated level. That stated level doesn't change. The ability of aircraft to meet the level is increasing given new designs as they designed with EDTO in mind from the ground up. For example on the 350, with an engine out you still get all the hydraulics. That wasn't the case on the 330.

It's not so much about the engines, which are ridiculously reliable already, but about systems and fire suppression capability. Those have been improving steadily.

(Also, 60 minutes in descent? That's about twice as long as you'd normally need.)


The systems and fire suppression - this is what it is all about these days. So you can fly with one engine offline for 20 hours? - great! - how long can you keep the raging lithium battery fuelled fire at bay in cargo position 12...? Not quite that long I think.


And your point is?



I think his point is that when discussing EDTO we shouldn't be worrying too much about the whole single engine scenario because that is not likely to be the biggest threat.
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Re: Twins vs. quads and international over water routings.

Tue May 23, 2017 8:59 am

Starlionblue wrote:
BravoOne wrote:
77west wrote:

The systems and fire suppression - this is what it is all about these days. So you can fly with one engine offline for 20 hours? - great! - how long can you keep the raging lithium battery fuelled fire at bay in cargo position 12...? Not quite that long I think.


And your point is?



I think his point is that when discussing EDTO we shouldn't be worrying too much about the whole single engine scenario because that is not likely to be the biggest threat.



Agreed but it's hard to wean these guys off the engine out stuff!
 
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Re: Twins vs. quads and international over water routings.

Tue May 23, 2017 10:59 am

Agreed guys - the biggest threat is certainly not the fact you only have two (very well maintained) engines. Fire, passenger issues (medical, fighting etc) are all much more probable issues. A fire on an etops / edto route really scares me, especially with more and more lithium battery devices in the hold.
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Re: Twins vs. quads and international over water routings.

Tue May 23, 2017 11:19 am

Good points. In many cases just a simple depressurization that otherwise would not be life threatening can generate the "most critical fuel scenario" for the diversion. Descending to 10,000 and flying for three hours uses up a lot of fuel. Of course this scenario is taken into account during the fight planning phase of the trip.
 
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Re: Twins vs. quads and international over water routings.

Fri May 26, 2017 8:44 pm

BG777300ER wrote:
[ I can tell you, I do NOT want to be a passenger on an A350 flying on one engine over the Pacific for their 6 hours and 10 min ETOPS. .


Don't worry, you will not be! The longest city pair EDTO is between CHC and USH at EDTO 300 min. NZ fly this at least 5x weekly on their AKL-EZE flight. Don't forget that the maintenance under EDTO is very stringent.
 
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Re: Twins vs. quads and international over water routings.

Fri May 26, 2017 9:31 pm

So true and that's why I questioned math and geography skills.LMAO at some of these the saying is falling posts.
 
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 5:01 am

PatrickZ80 wrote:
A twin can fly on one engine perfectly safe, the only stage they really need two engines is on take-off.


What if they do lose one engine on take off, i.e., at V1? Aren't twins certified to take off on one engine? I'm not talking about starting a take off roll on one engine, that would be insanity. I'm talking V1 speeds. Thanks.
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 6:36 am

BEG2IAH wrote:
What if they do lose one engine on take off, i.e., at V1? Aren't twins certified to take off on one engine? I'm not talking about starting a take off roll on one engine, that would be insanity. I'm talking V1 speeds. Thanks.


I guess so, but in that case the length or route of the flight wouldn't matter either. A take off is a take off, regardless if it's a long flight or a short hop.
 
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77west
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 6:40 am

BEG2IAH wrote:
PatrickZ80 wrote:
A twin can fly on one engine perfectly safe, the only stage they really need two engines is on take-off.


What if they do lose one engine on take off, i.e., at V1? Aren't twins certified to take off on one engine? I'm not talking about starting a take off roll on one engine, that would be insanity. I'm talking V1 speeds. Thanks.


All large twins are fully capable of taking off on one engine AFTER V1. By this speed, the rudder has enough authority to mostly counteract the yaw of a failed engine, and the airplane lifts off the runway as if nothing happened, with perhaps a slight yawing motion as it begins a (lethargic) climb.

See this 757, yes a bird strike, but demonstrates the principle:

http://www.youtube.com/watch?v=L1jZvlFmqQU
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 6:35 pm

so given B748 have ETOP330 and A350 have ETOPS370, A350 can fly further away from diversion than B748?
It's pointless to attempt winning internet debate.
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 7:09 pm

c933103 wrote:
so given B748 have ETOP330 and A350 have ETOPS370, A350 can fly further away from diversion than B748?


The longest EDTO in the world is CHC-USH and that is EDTO 300min +-. In reality both aircraft are equal except the EDTO calculation for the B748 with 4 engines is less restrictive than the A350 with two engines. The > 2 engine is allowed 180 min from both the EDTO entry and exit point whereas the 2 engine is only allowed 60 min The dispatch requirements for both are the same.
 
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 9:43 pm

sunrisevalley wrote:
c933103 wrote:
so given B748 have ETOP330 and A350 have ETOPS370, A350 can fly further away from diversion than B748?


The longest EDTO in the world is CHC-USH and that is EDTO 300min +-. In reality both aircraft are equal except the EDTO calculation for the B748 with 4 engines is less restrictive than the A350 with two engines. The > 2 engine is allowed 180 min from both the EDTO entry and exit point whereas the 2 engine is only allowed 60 min The dispatch requirements for both are the same.

How about for example between CHC and CPT?
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 10:25 pm

sunrisevalley wrote:
c933103 wrote:
so given B748 have ETOP330 and A350 have ETOPS370, A350 can fly further away from diversion than B748?


The longest EDTO in the world is CHC-USH and that is EDTO 300min +-. In reality both aircraft are equal except the EDTO calculation for the B748 with 4 engines is less restrictive than the A350 with two engines. The > 2 engine is allowed 180 min from both the EDTO entry and exit point whereas the 2 engine is only allowed 60 min The dispatch requirements for both are the same.


Please keep in mind ETOPS for quads and tris only applies to pax aircraft and not freighters.AC120-42B is your friend if you looking for FAA data.
 
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Re: Twins vs. quads and international over water routings.

Sat May 27, 2017 11:21 pm

Any flights going New Zealand - South Africa will come up against some serious restrictions over Antarctica.

Here is a theoretical 777 flight using EDTO 330 minutes:

http://www.gcmap.com/mapui?P=akl-cpt&MS=wls&DU=nm&SG=.84&SU=mach&E=330&EV=410&EU=kts

As you can see, it will take a significant detour or increase in EDTO neither of which I see happening.
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Re: Twins vs. quads and international over water routings.

Sun May 28, 2017 12:06 am

77west wrote:
Any flights going New Zealand - South Africa will come up against some serious restrictions over Antarctica.
As you can see, it will take a significant detour or increase in EDTO neither of which I see happening.


I believe the EDTO entry and exit points for this routing is GET or PER -MRU. But this is a long way off the GC track AKL-JNB/CPT The distance from this track to either GET/PER or MRU is substantial. Someone other than I might calculate what these distances might be from various waypoints on the GC track.
 
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Re: Twins vs. quads and international over water routings.

Sun May 28, 2017 2:15 pm

As a side note I believe LAN CHILIE has encountered some instances where they have used 330 minutes for occasions when Russia space junk was on a planed re-entry that in turn closed down airspace that would have otherwise been available.
 
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Re: Twins vs. quads and international over water routings.

Sun May 28, 2017 5:28 pm

sunrisevalley wrote:
I believe the EDTO entry and exit points for this routing is GET or PER -MRU. But this is a long way off the GC track AKL-JNB/CPT The distance from this track to either GET/PER or MRU is substantial. Someone other than I might calculate what these distances might be from various waypoints on the GC track.

I have taken a shot at it based on a EDTO distance of 2396nm from entry/exit points 60min (400nm) from GET and MRU on the GC track between the two The two circles intersect above the AKL-JNB GC track at S61.5 . As I understand it the GC track could not be flown but the difference is negligible. But the 77E and 787 are limited to 302 minutes so that 2396nm is too much and the track would have to be flattened somewhat.
All FWIW......
 
BravoOne
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Joined: Fri Apr 12, 2013 2:27 pm

Re: Twins vs. quads and international over water routings.

Sun May 28, 2017 6:14 pm

Having a problem posting Boeing graphic for South Polar ETOPS operations. Suggestions are welcomed.

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