rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:41 pm

Sooner787 wrote:
What is the ETOPS number required for US west coast- Hawaii flight? 180 240?


ETOPS 180, but I believe with some additions to fuel loads due to no en-route diversion airport between the west coast & Hawaii. That extra part was added when they started, even though there was less than 180 min in use elsewhere without the issue.
 
Aptivaboy
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:51 pm

I will always select a widebody over a narrowbody if the price is equal. Who doesn't like high ceilings and open space?! If you don't operate this way, you are just playing into the hands of the airline bean counters who would fly the 737 to China if they could find a way.


I hear what you're saying (and I don't totally disagree) but the comment I was replying too specifically had to do with the number of engines, not the size of the plane's interior. And no, its the public that makes flight choice arrangements, not the bean counters. Call it supply and demand, market research, the invisible hand, or whatever you want. If the public wants frequent service in a narrowbody, then they'll demand it and be willing to pay the cash for a ticket. If not, it won't happen, but not because of the bean counters and their desires, but because of consumer choice; the market will ultimately decide. One thing that ETOPS narrowbodies give the consumer over widebodies nearly always is choice - we get a lot of planes and flights to choose from, a lot of frequency, and therefore a great deal of flexibility in our travel arrangements. How is that a bad thing?
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:52 pm

JackMeahoff wrote:
jetblueguy22 wrote:
Man, there are going to be a lot of people in this thread who won't be able to fly in a decade or so. 4 engines are going the way of the dodo, specifically because they have proven to be just as safe.


There was a time when no lifeboats were needed because "statistics" proved that a certain ship was unsinkable.

LAX772LR wrote:

There has never been an ETOPS-caused fatality in the history of aviation. Ever.



Sure, but there have been a handful of very close calls.



The Titanic had lifeboats as was required. The requirement just did not fit the needs and still does not. Most Cruise ships in the US are registered in other countries so they do not have to have enough lifeboats for every passenger on board. So with your statement, don't take a cruise.
 
JayinKitsap
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:53 pm

ETOPS is a way to assess risk. The likelyhood of twin failures is so low that other risks supersede it. The requirement for extra fuel with no diversion airport reduces risk as it gives an extra half hour flight time. I am sure there are also earlier route closure if major storms are approaching HI that could affect all islands.
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:55 pm

JackMeahoff wrote:
IPFreely wrote:
george77300 wrote:
How do you plan on getting to Hawaii then. I assume 757/777 has the same twin issue for you.


He most likely believes 757/777 twins are not twins like 737's/320's are, or are somehow safer twins. It makes as much sense as thinking 737's/320's are "landing on fumes" but people can believe whatever they want. It falls in the category of superstition, not science.


I like the ocean liner analogy. Cruise ships don't cross oceans, ocean liners do. More heavily built, higher bow, fewer windows near the water line, etc. The 737 was designed to be a regional jet, not a long range transoceanic jet.

Funny how so many commentators on here seem to be praising the use of narrowbody regional jets to cross oceans. As if this is some milestone to be celebrated.

In reality 737s and A320s crossing oceans is a sad indicator of the sorry state of the aviation industry. Gone are the days of faster, higher, bigger, better.



The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.
 
Aptivaboy
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:56 pm

The Titanic had lifeboats as was required. The requirement just did not fit the needs and still does not. Most Cruise ships in the US are registered in other countries so they do not have to have enough lifeboats for every passenger on board. So with your statement, don't take a cruise.


Um, sort of. My understanding (I don't have the exact US law in front of me) is that a liner or cruise ship which calls at or operates from a US port regardless of where its flagged must have enough life boats and life rafts for all of her pax and crew. In other words, there must still be adequate flotation of some form for everyone. Does anyone know the precise law? Google isn't being my friend right now. I'm finding references but not the precise code.
 
JayinKitsap
Posts: 1334
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 7:58 pm

The 9+ years with no passenger deaths in the US. As there are 87,000 flights in the US each day your chance of being on a passenger fatality flight in the US is 1 in 270 Million. Driving to the airport is far more hazardous.
 
fishmeal
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:01 pm

Someone desperate to visit Hawaii could try to ship himself FedEx on a 3-holer...
 
Flighty
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:04 pm

Aviano789 wrote:
767333ER wrote:
What you have to ask yourself is how long this type of engine has been in service and how much use in total such as hours have been put on it. Just because one operator has had some trouble for whatever reason doesn’t mean the engine is suddenly unsafe if everyone else’s is fine still.


The History of the CFM56-2 on the DC-8-72 and CFM56-3 B373-Classic has proven to be an outstandingly reliable engine. It should be noted the variants as fitted to the -NGs and others have built on the quality of the earlier models. However, the larger CFM56 on the A340 is known to suffer from HP turbine bearing failures at around the 20,000hrs point. My concern is just that simple, what if both engines on a twin loss of oil pressure or power at mid ocean crossing?


There are probably other events more likely to kill everyone on board than that event. The incident you mention has a known probability. Probably 1 in 500 million hours or around there. Everyone on board will die; mainly from heart disease and cancer :( worry about that.
 
CallmeJB
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:13 pm

BravoOne wrote:
Your point is well taken regarding "stories" but none the less a number of 737-800's have made the PDX fuel stop enroute to SEA. It a contingency or redispatch operation probably 98% of the time. Another poster used the critical scenario plan as he norm, but in fact the loss of pressurization and two engines still running at 10,000' can be more critical than having lost one and a decompression, at 10,000. The 737NG and -8MAX hold around 46,000 lbs of fuel so there not a lot of room left over for XTRA fuel.

I think you and I are on the same page, but I just want to point out that your scenario is considered, also. I chose to highlight the 'engine failure & depressurization' scenario because the post I was replying to expressed concern that the WN PHL incident wouldn't have been accounted for, when in fact that exact scenario is accounted for.

Fuel planning for extended over water operations must model three scenarios:
1. An engine failure and subsequent drift down
2. An engine failure coinciding with a sudden decompression, continuing the flight at a low altitude on one engine
3. A sudden decompression, continuing at low altitude on two engines.

Each of these scenarios must be independently modeled based on each occurring at the most critical point specific to that scenario. In each scenario, the flight must have enough fuel to continue to the destination or divert to a suitable ETOPS alternate.

So, extended over water fuel planning is based on the worst case of the above scenarios. Every ETOPS flight, every day.
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:18 pm

JackMeahoff wrote:
Aptivaboy wrote:
Very respectfully, kind sir, I think you're being a bit over the top by saying that you'll never fly an A320 or 737 to the islands.


I will always select a widebody over a narrowbody if the price is equal. Who doesn't like high ceilings and open space?! If you don't operate this way, you are just playing into the hands of the airline bean counters who would fly the 737 to China if they could find a way.



When I'm sitting on my ass a high ceiling is not going to make that big a difference. After all the isles are narrower in coach on a 787 in 3x3x3 layout than on an A321 3x3 layout. So if I get up to stretch on either plane I have the same or less space to stretch. So that wide body jet does not really help. It's all in you mind & perception. After all they flew 707's & DC-8's for how many years on TPAC routes. Why is it so horrible to do so now.
 
BerenErchamion
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:20 pm

nine4nine wrote:
767333ER wrote:
What you have to ask yourself is how long this type of engine has been in service and how much use in total such as hours have been put on it. Just because one operator has had some trouble for whatever reason doesn’t mean the engine is suddenly unsafe if everyone else’s is fine still.


No, but given range issues due to fuel I wouldn’t feel comfortable being down an engine and flying lower altitude with higher fuel burn or even the added drag. I’d imagine any issue on a mainland-Hawaii flight to the likes of the WN issue would have resulted in a major tragedy.


You understand that ETOPS regs ensure that the plane has contingency fuel and landing plans for just such a scenario, and if it doesn't or can't carry enough fuel for that then it's not allowed to take off, right?
 
BravoOne
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:21 pm

Gents, ETOPS range is driven by fire suppression capabilities, not the number of engines whether working or not. Don't confuse the two separate limitations.
 
BerenErchamion
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:25 pm

Aviano789 wrote:
A few Sundays ago CBS 60 Minutes reported on a low cost air carrier know in the industry for its maintenance deficiencies. The reporting was supported by the FAA Obscure Mechanical Interruption Summary. The report highlighted more than 100 serious in flight mechanical incident that carrier had from January 2016 to October 2017.
My question to you: Knowing the foregoing information about this airline, would you feel comfortable buying a ticket for your self and love ones to fly over 2000 miles of open water on any of their twins?
[i]By the way although ETOPS did not exist at time Flying Tiger Flight 923, which occurred in the dark of night during a raging storm in the cold North Atlantic Ocean. Seventy six persons were aboard. Twenty eight passengers and crew (including a mother and her two children) perished, while an unbelievable 48 survived the crash and three-day storm.
[/i]


If it came out that the Coca-Cola Company had secretly included crystal meth in its formula, would you conclude from that that you should stop eating bacon?
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:29 pm

Aptivaboy wrote:
The Titanic had lifeboats as was required. The requirement just did not fit the needs and still does not. Most Cruise ships in the US are registered in other countries so they do not have to have enough lifeboats for every passenger on board. So with your statement, don't take a cruise.


Um, sort of. My understanding (I don't have the exact US law in front of me) is that a liner or cruise ship which calls at or operates from a US port regardless of where its flagged must have enough life boats and life rafts for all of her pax and crew. In other words, there must still be adequate flotation of some form for everyone. Does anyone know the precise law? Google isn't being my friend right now. I'm finding references but not the precise code.


From what I know from the past is they must have life rafts and/or enough life rafts & life vest in combination for everyone based on the flag of registration. Big difference. Aircraft must have raft capacity & vest capacity matched.

from https://www.justia.com/admiralty/cruise-ships/

Today, almost all the ocean cruise lines use passenger ships registered under flags of various foreign countries. Each ship is subject to the vessel inspection laws of the country in which it is registered. Additionally, for cruise ships that take on passengers at U.S. ports, the U.S. Coast Guard requires these ships to meet the International Convention for the Safety of Life at Sea (SOLAS). SOLAS and other international regulations strictly regulate crewing and crew competency, fire protection, firefighting and lifesaving equipment, navigation safety, watercraft integrity and stability, vessel control, safety management and environmental protection. On U.S. passenger vessels, licensed individuals and crew must comply with Coast Guard regulations setting standards for experience and training.

So no life rafts are not part of the requirements for US boarding, Only life vest.
Last edited by rbavfan on Sun Apr 29, 2018 8:35 pm, edited 1 time in total.
 
BerenErchamion
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:29 pm

BravoOne wrote:

Your point is well taken regarding "stories" but none the less a number of 737-800's have made the PDX fuel stop enroute to SEA. It a contingency or redispatch operation probably 98% of the time


Fuel loading regulations on flights between areas with plenty of diversion airports en route are a bit less strict than they are on overwater flights precisely because that possibility exists; since it doesn't, fuel loading requirements are higher on flights over water or over desolate land areas.

.The 737NG and -8MAX hold around 46,000 lbs of fuel so there not a lot of room left over for XTRA fuel.


Which means that the maximum range they can safely fly over water while meeting contingency fuel requirements is less, and airlines plan accordingly.
 
ThePinnacleKid
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:29 pm

Cubsrule wrote:
nine4nine wrote:
767333ER wrote:
What you have to ask yourself is how long this type of engine has been in service and how much use in total such as hours have been put on it. Just because one operator has had some trouble for whatever reason doesn’t mean the engine is suddenly unsafe if everyone else’s is fine still.


No, but given range issues due to fuel I wouldn’t feel comfortable being down an engine and flying lower altitude with higher fuel burn or even the added drag. I’d imagine any issue on a mainland-Hawaii flight to the likes of the WN issue would have resulted in a major tragedy.

I will never book a Hawaii flight personally on an 320/321 or 737. Have heard stories about planes arriving on fumes after stronger than expected headwinds. Couple that with an engine issue. I think it’s a disaster in the making.


How is any of what you cited different on a 757 or widebody twin from on a 737 or 320? While the larger aircraft have more range, carriers don’t fill up the tanks just for the sake of helping passengers sleep better at night. To the extent that uncontained engine failures are some sort of systemic problem (which is debatable at best), note that they generally do not occur hours into cruise.


I can comfortably answer an aspect of this part cubs... having flown the ERJ and now the 767... both can obviously bang an engine and comfortably fly on the one remaining engine... the ERJ though has a much lower SE cruising altitude than the 767... I imagine, that in this case... that may in fact be what the poster was implying as to preference to avoid 737/320 family on long ETOPS flights.... As for myself.. knowing how the 767 was designed specifically with extended overwater operations in mind, like other large twins... vs the 737 which is not.. I also would pick an old WB over the new 73's any day on the Hawaii run.... Hawaii is a true ETOPS 180 run... much more critical than flying the Atlantic for example. While a poster above is correct.. both are certified to have it all go bad at the worst spot, drop down, and keep trucking, I still would rather be on the one that was designed for the mission over the one that inherited the mission.

As to an actual operational numbers... yesterday in the 763 on a transcon run, our midpoint SE ability (nearing the rockies) had a drift down altitude of FL301 still.... we had just over 55k lbs payload and 40k fuel still on board at that point... I don't know how the 737 numbers actually stack up in a similar situation... but someone else here who has a type in that might be able to expand on that airframes capabilities.
"Sonny, did we land? or were we shot down?"
 
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JackMeahoff
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:36 pm

rbavfan wrote:


The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.



And yet for some reason the safety requirements for flying the President of the United States didn't evolve. Four engines then, four engines now. The Air Force must know something the bean counters at the airlines and their lackeys at the FAA don't. Trump can afford to lose two engines on Air Force One but I can only afford to lose one on my 737 before I go in the drink.
 
BobbyPSP
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:37 pm

rbavfan wrote:
JackMeahoff wrote:
jetblueguy22 wrote:
Man, there are going to be a lot of people in this thread who won't be able to fly in a decade or so. 4 engines are going the way of the dodo, specifically because they have proven to be just as safe.


There was a time when no lifeboats were needed because "statistics" proved that a certain ship was unsinkable.

LAX772LR wrote:

There has never been an ETOPS-caused fatality in the history of aviation. Ever.



Sure, but there have been a handful of very close calls.



The Titanic had lifeboats as was required. The requirement just did not fit the needs and still does not. Most Cruise ships in the US are registered in other countries so they do not have to have enough lifeboats for every passenger on board. So with your statement, don't take a cruise.


Wrong. Modern cruise ships have enough lifeboats for everyone on board. Do a little research
 
Jamie514
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:39 pm

I honestly came to thread from title assuming the OP would question if maybe for the next little while, the CFM in question is subject to more rigorous inspection and regulation,maybe restrict its ETOPS envelope somewhat, as has happened to specific operators or types in the past when there is a lapse that often leads to a non fatal accident. It wouldn't be unheard of after the repetitive nature of these WN incidents especially now that life has been lost.

Boy was I shocked to see that this is just another "lets bring back 4-holers-4-paranoia" threads.
 
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JackMeahoff
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:45 pm

BobbyPSP wrote:
Wrong. Modern cruise ships have enough lifeboats for everyone on board. Do a little research


I was referring to the Titanic, which was theoretically unsinkable, just like the 737 is theoretically a good ETOPS performer.
 
dwachdorf
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:46 pm

Would having 4 engines actually increase the risk of having something like a catastrophic fan blade / disk failure? Also, I’d much rather have a proven engine like the CFM56, than a Trent 1000 or PW engine that’s having issues on the A321neo.
 
CallmeJB
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:47 pm

JackMeahoff wrote:
rbavfan wrote:
The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.

And yet for some reason the safety requirements for flying the President of the United States didn't evolve. Four engines then, four engines now. The Air Force must know something the bean counters at the airlines and their lackeys at the FAA don't. Trump can afford to lose two engines on Air Force One but I can only afford to lose one on my 737 before I go in the drink.

You can afford to lose one engine on a 737 and be stuck somewhere for a few days, or rebooked on another flight.

The President can't afford to let one engine take his plane out. If something hostile happens in a country the president is visiting, they need to get out of town right now. If protestors throw rocks in one of the engines, then they will continue and takeoff with three engines.

That sort of risk analysis doesn't apply when you're flying from SEA to OGG. The 737 is fine for that task.
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:51 pm

ThePinnacleKid wrote:
Cubsrule wrote:
nine4nine wrote:

No, but given range issues due to fuel I wouldn’t feel comfortable being down an engine and flying lower altitude with higher fuel burn or even the added drag. I’d imagine any issue on a mainland-Hawaii flight to the likes of the WN issue would have resulted in a major tragedy.

I will never book a Hawaii flight personally on an 320/321 or 737. Have heard stories about planes arriving on fumes after stronger than expected headwinds. Couple that with an engine issue. I think it’s a disaster in the making.


How is any of what you cited different on a 757 or widebody twin from on a 737 or 320? While the larger aircraft have more range, carriers don’t fill up the tanks just for the sake of helping passengers sleep better at night. To the extent that uncontained engine failures are some sort of systemic problem (which is debatable at best), note that they generally do not occur hours into cruise.


I can comfortably answer an aspect of this part cubs... having flown the ERJ and now the 767... both can obviously bang an engine and comfortably fly on the one remaining engine... the ERJ though has a much lower SE cruising altitude than the 767... I imagine, that in this case... that may in fact be what the poster was implying as to preference to avoid 737/320 family on long ETOPS flights.... As for myself.. knowing how the 767 was designed specifically with extended overwater operations in mind, like other large twins... vs the 737 which is not.. I also would pick an old WB over the new 73's any day on the Hawaii run.... Hawaii is a true ETOPS 180 run... much more critical than flying the Atlantic for example. While a poster above is correct.. both are certified to have it all go bad at the worst spot, drop down, and keep trucking, I still would rather be on the one that was designed for the mission over the one that inherited the mission.

As to an actual operational numbers... yesterday in the 763 on a transcon run, our midpoint SE ability (nearing the rockies) had a drift down altitude of FL301 still.... we had just over 55k lbs payload and 40k fuel still on board at that point... I don't know how the 737 numbers actually stack up in a similar situation... but someone else here who has a type in that might be able to expand on that airframes capabilities.



The 767 was not designed specifically for ETOPS. It was designed for domestic use based on a United Airlines requirement. The ETOPS was created later after TWA started flights TATL flights to Europe. When started they had to fly a more northerly route and once engine performance meet better specs it was upgraded to allow 120 & then 180. First flights went over Canada, Greenland & Iceland to meet safety requirements at the time. This is well covered in old issues of Aviation Week & Air transport world and other magazines in the early to late 80's. TWA was the airline that pushed for it.
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 8:56 pm

JackMeahoff wrote:
rbavfan wrote:


The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.



And yet for some reason the safety requirements for flying the President of the United States didn't evolve. Four engines then, four engines now. The Air Force must know something the bean counters at the airlines and their lackeys at the FAA don't. Trump can afford to lose two engines on Air Force One but I can only afford to lose one on my 737 before I go in the drink.


The 4 engine rule for Air Force 1 goes back to early presidential aircraft regulations put in place during the prop plane era. Like most things military the requirements have not been updated, but they have been discussing it. Mostly because other countries no longer require 4 engines for their leaders to fly on. BTW the helicopters that the president uses require 2 engines to carry him. I guess based on your comment they should have 4 engines as well.
 
rbavfan
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:00 pm

JackMeahoff wrote:
BobbyPSP wrote:
Wrong. Modern cruise ships have enough lifeboats for everyone on board. Do a little research


I was referring to the Titanic, which was theoretically unsinkable, just like the 737 is theoretically a good ETOPS performer.


The 737 has proven its a good ETOPS performer. It had to prove it to get the certification. The Titanic & it's sister ship that also sank, did not prove themselves, the titanic was on it's first cruise. So it's 2 different concepts.
 
SFOtoORD
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:05 pm

Aviano789 wrote:
SFOtoORD wrote:
Now you’re just bringing up random points that aren’t at all related to your original question. You might as well start bringing up train incidents to support your point or talking about things you saw out the window.

Mods should close this thread.

I don't see you asking the Mods to close the thread (Safety margins on CFM56-5B (A320) vs CFM56-7B (737NG) similar to this one. Should I assume you support impeding free speech?


Because you seem unable to make an on-topic cohesive point in this thread.
Last edited by SFOtoORD on Sun Apr 29, 2018 9:09 pm, edited 1 time in total.
 
m007j
Posts: 103
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:07 pm

rbavfan wrote:
The Titanic had lifeboats as was required. The requirement just did not fit the needs and still does not. Most Cruise ships in the US are registered in other countries so they do not have to have enough lifeboats for every passenger on board. So with your statement, don't take a cruise.


Good heavens, this is absolutely incorrect. Every commercial ship has to operate with SOLAS standards if they are flagged in a member state, one standard of which explicitly states that there must be enough lifeboats for everyone on board. SOLAS was the response to the Titanic disaster because the public rightfully questioned White Star Line's reluctance to block the views of their precious ship in exchange for leaving over a thousand people without recourse. The real reason most cruise ships are Panamanian or Bahamian flagged? The same reason a lot of US companies register themselves in Delaware, taxes. Enjoy your next cruise!
 
BerenErchamion
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:08 pm

dwachdorf wrote:
Would having 4 engines actually increase the risk of having something like a catastrophic fan blade / disk failure? Also, I’d much rather have a proven engine like the CFM56, than a Trent 1000 or PW engine that’s having issues on the A321neo.


Yes. Whether this is enough to offset the lower likelihood of every engine failing in a contained manner depends on the specific failure rates of the engines in question, but there is such a point where that becomes the case.

Consider the case where a given engine has an uncontained, catastrophic failure rate of one every twenty hours, and a contained, non-catastrophic failure rate of one every two hours. If you mount two of those engines on a plane, you would expect a catastrophic failure of a single engine once every ten hours, and a contained failure of all engines once every four hours. If you mount three, you'd expect a catastrophic failure of a single engine once every 6 2/3 hours, and a contained failure of all engines once every eight hours. With four, it's a single catastrophic failure expected every 5 hours, and a contained all-engine failure every 16 hours. With 5, it's single catastrophic every 4 hours, and contained all-engine every 32.

If we translate this to probability of failure per hour, then:
With two engines, the probability of an uncontained failure in a given hour is 0.1, and the probability of all engines experiencing a contained failure in a given hour is 0.25, or a 35% chance of a fatal failure of some sort per hour. With three, it's 0.15 for single uncontained, and 0.125 for all uncontained, so 27.5% chance. With four, it's 0.2 for single uncontained, and 0.0625 for all uncontained, so a 26.25% chance of a failure of any sort. Finally, with five engines, it's 0.25 for single catastrophic, and 0.03125 for all uncontained, so 28.125% chance of failure every hour--so five engines is actually less safe than four.

Obviously, this is a simplified example--as you add more engines, you're probably going to be using a different type which will have different failure rates, for one, and also not all uncontained engine failure scenarios are equally fatal, but the point is that there is a point where adding more engines makes the plane less safe.
Last edited by BerenErchamion on Sun Apr 29, 2018 9:14 pm, edited 1 time in total.
 
BerenErchamion
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:08 pm

JackMeahoff wrote:
rbavfan wrote:


The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.



And yet for some reason the safety requirements for flying the President of the United States didn't evolve. Four engines then, four engines now. The Air Force must know something the bean counters at the airlines and their lackeys at the FAA don't. Trump can afford to lose two engines on Air Force One but I can only afford to lose one on my 737 before I go in the drink.


That's more about logistics and convenience than safety.
 
BravoOne
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:09 pm

BerenErchamion wrote:
BravoOne wrote:

Your point is well taken regarding "stories" but none the less a number of 737-800's have made the PDX fuel stop enroute to SEA. It a contingency or redispatch operation probably 98% of the time


Fuel loading regulations on flights between areas with plenty of diversion airports en route are a bit less strict than they are on overwater flights precisely because that possibility exists; since it doesn't, fuel loading requirements are higher on flights over water or over desolate land areas.

.The 737NG and -8MAX hold around 46,000 lbs of fuel so there not a lot of room left over for XTRA fuel.


Which means that the maximum range they can safely fly over water while meeting contingency fuel requirements is less, and airlines plan accordingly.


10% of the flying time in minutes is added to all (FAA) international flights, plus 30 minutes for international reserves, or 15 holding at the ETOPS diversion airports, plus in the case of the 737 APU fuel burn unless you have the Boeing/FAA exemption. With this in place the 737NG will occasionally make that unscheduled fuel stop. That does not mean it would land 100 miles short of he coast line, but rather it would not meet all off the criteria imposed above.

I rode in a brand new SWA Max this morning and all in all, I would have preferred a new 747-8I, but it's not going to happen)
 
BerenErchamion
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:16 pm

JackMeahoff wrote:
BobbyPSP wrote:
Wrong. Modern cruise ships have enough lifeboats for everyone on board. Do a little research


I was referring to the Titanic, which was theoretically unsinkable, just like the 737 is theoretically a good ETOPS performer.


Yes, because obviously in 1912 data gathering and analysis and the regulatory environment were just like they are today.

It's like saying that because thalidomide was a disaster, we should be skeptical of the chicken pox vaccine--despite the fact that the safety of the chicken pox vaccine benefits from a regulatory environment that was, in fact, greatly tightened and improved in response to thalidomide.
 
nine4nine
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:49 pm

ThePinnacleKid wrote:
Cubsrule wrote:
nine4nine wrote:

No, but given range issues due to fuel I wouldn’t feel comfortable being down an engine and flying lower altitude with higher fuel burn or even the added drag. I’d imagine any issue on a mainland-Hawaii flight to the likes of the WN issue would have resulted in a major tragedy.

I will never book a Hawaii flight personally on an 320/321 or 737. Have heard stories about planes arriving on fumes after stronger than expected headwinds. Couple that with an engine issue. I think it’s a disaster in the making.


How is any of what you cited different on a 757 or widebody twin from on a 737 or 320? While the larger aircraft have more range, carriers don’t fill up the tanks just for the sake of helping passengers sleep better at night. To the extent that uncontained engine failures are some sort of systemic problem (which is debatable at best), note that they generally do not occur hours into cruise.


I can comfortably answer an aspect of this part cubs... having flown the ERJ and now the 767... both can obviously bang an engine and comfortably fly on the one remaining engine... the ERJ though has a much lower SE cruising altitude than the 767... I imagine, that in this case... that may in fact be what the poster was implying as to preference to avoid 737/320 family on long ETOPS flights.... As for myself.. knowing how the 767 was designed specifically with extended overwater operations in mind, like other large twins... vs the 737 which is not.. I also would pick an old WB over the new 73's any day on the Hawaii run.... Hawaii is a true ETOPS 180 run... much more critical than flying the Atlantic for example. While a poster above is correct.. both are certified to have it all go bad at the worst spot, drop down, and keep trucking, I still would rather be on the one that was designed for the mission over the one that inherited the mission.

As to an actual operational numbers... yesterday in the 763 on a transcon run, our midpoint SE ability (nearing the rockies) had a drift down altitude of FL301 still.... we had just over 55k lbs payload and 40k fuel still on board at that point... I don't know how the 737 numbers actually stack up in a similar situation... but someone else here who has a type in that might be able to expand on that airframes capabilities.



Thank you for your input. I’m an avaiation enthusiast and not an aviation expert. It’s great to have feedback on this topic from someone who actually flies and has experiences and professional opinions rather than some arm chair expert who sits and googles stats on a monitor and puts someone down for expressing an opinion. Much appreciated. Safe flights my friend!
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JackMeahoff
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 9:53 pm

BerenErchamion wrote:
dwachdorf wrote:
Would having 4 engines actually increase the risk of having something like a catastrophic fan blade / disk failure? Also, I’d much rather have a proven engine like the CFM56, than a Trent 1000 or PW engine that’s having issues on the A321neo.


Yes. Whether this is enough to offset the lower likelihood of every engine failing in a contained manner depends on the specific failure rates of the engines in question, but there is such a point where that becomes the case.

Consider the case where a given engine has an uncontained, catastrophic failure rate of one every twenty hours, and a contained, non-catastrophic failure rate of one every two hours. If you mount two of those engines on a plane, you would expect a catastrophic failure of a single engine once every ten hours, and a contained failure of all engines once every four hours. If you mount three, you'd expect a catastrophic failure of a single engine once every 6 2/3 hours, and a contained failure of all engines once every eight hours. With four, it's a single catastrophic failure expected every 5 hours, and a contained all-engine failure every 16 hours. With 5, it's single catastrophic every 4 hours, and contained all-engine every 32.

If we translate this to probability of failure per hour, then:
With two engines, the probability of an uncontained failure in a given hour is 0.1, and the probability of all engines experiencing a contained failure in a given hour is 0.25, or a 35% chance of a fatal failure of some sort per hour. With three, it's 0.15 for single uncontained, and 0.125 for all uncontained, so 27.5% chance. With four, it's 0.2 for single uncontained, and 0.0625 for all uncontained, so a 26.25% chance of a failure of any sort. Finally, with five engines, it's 0.25 for single catastrophic, and 0.03125 for all uncontained, so 28.125% chance of failure every hour--so five engines is actually less safe than four.

Obviously, this is a simplified example--as you add more engines, you're probably going to be using a different type which will have different failure rates, for one, and also not all uncontained engine failure scenarios are equally fatal, but the point is that there is a point where adding more engines makes the plane less safe.


You are probably more likely to get struck by lightning twice in one year than die in an airplane crash caused by an uncontained engine failure. They are so rare, especially the ones that cause catastrophic damage to other systems. I don't know how you could calculate risk based on such a small number of incidents.
 
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GE90man
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 10:14 pm

MrBretz wrote:
I am pretty sure only twins fly between Hawaii and the mainland. Thus, you won’t be visiting.

I mean, he could take a boat.
 
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GE90man
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 10:20 pm

So am I right in concluding that if we strapped two more engines on a 737, you'd fly on it to Hawaii?
 
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GE90man
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 10:29 pm

JackMeahoff wrote:
LAX772LR wrote:
Why are you assuming that 4 engines would "increase the safety margin"... they don't.
There's no mathematical evidence of that, despite what you're assuming to be a common sense conclusion.


So you are saying more redundancy doesn't increase the safety margin?

What about the number of hydraulic systems on an airliner? The more, the better, right? Why is it any different with the number of engines?


Well, there's never been a situation where 4 engines have proven to actually be better than 2 in recent and less-than-recent times, especially since now engines are so reliable. Please feel free to name a situation in the last 20 years where someone said afterwards "oh drats. We could've used two extra engines in that situation"
 
cschleic
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 10:39 pm

MrBretz wrote:
I am pretty sure only twins fly between Hawaii and the mainland. Thus, you won’t be visiting.


Although it might be possible to fly four-holers going east around the globe, maybe through Asia? Or if not now, when ANA starts flying 380s to HNL.
 
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LAX772LR
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 10:48 pm

Aviano789 wrote:
I don't see you asking the Mods to close the thread (Safety margins on CFM56-5B (A320) vs CFM56-7B (737NG) similar to this one. Should I assume you support impeding free speech?

(1) the poster was correct: that was a ridiculous response in that it had nothing to do with what you were responding to
(2) you don't have any free speech rights here, this is a private forum on a private server... your speech is limited by whatever their TOS desires.


JackMeahoff wrote:
There was a time when no lifeboats were needed because "statistics" proved that a certain ship was unsinkable.

Tell us, what "statistics proved that a certain ship was unsinkable?"
...cite the publication or statistician.

Or, I can save you the time by telling you that you won't be able to; because the (ridiculous) "unsinkable" moniker came from a June 1911 article in the Belfast Morning News that labeled the ship's bulkhead separation system as rendering it "practically unsinkable"-- a journalist's opinion which evolved into the myth that's (obviously) still suckering people even today.

There was no statistical "proof" of anything there.


JackMeahoff wrote:
LAX772LR wrote:
There has never been an ETOPS-caused fatality in the history of aviation. Ever.

Sure, but there have been a handful of very close calls.

Remind us which of those "close calls" wouldn't have done the same thing to ANY aircraft regardless of engine count.


JackMeahoff wrote:
LAX772LR wrote:
Why are you assuming that 4 engines would "increase the safety margin"... they don't.
There's no mathematical evidence of that, despite what you're assuming to be a common sense conclusion.

So you are saying more redundancy doesn't increase the safety margin?
In terms of engine count beyond two? Correct, it does not.


JackMeahoff wrote:
Why is it any different with the number of engines?

Plenty of reasons, with the most prevalent being: because unlike with hydraulic lines, with so many more moving components, there's that much more that can go wrong.
Last edited by LAX772LR on Sun Apr 29, 2018 10:59 pm, edited 1 time in total.
I myself, suspect a more prosaic motive... ~Thranduil
 
Antarius
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 10:52 pm

JackMeahoff wrote:
rbavfan wrote:


The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.



And yet for some reason the safety requirements for flying the President of the United States didn't evolve. Four engines then, four engines now. The Air Force must know something the bean counters at the airlines and their lackeys at the FAA don't. Trump can afford to lose two engines on Air Force One but I can only afford to lose one on my 737 before I go in the drink.


You might be the first person who has evoked government rules to justify common sense.

That includes Democrats and Republicans alike.
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nine4nine
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:02 pm

I don’t see the CFM 56-7 issues being a concern in this topic. They are well proven and highly reliable given the media over sensationalism they have been receiving for the extremely small amount of failures.

But as I stated earlier I personally don’t feel the 738 739 and CEO320 (exception of MAX and NEO) were made with mainland-Hawaii routes in mind when they were designed and manufactured. It has nothing to do with 2 engines or 4. Those routes were added much later with those aircraft. It has to do with capabilities in an emergency and I think these planes are cutting it close as it is and I would really hate to see what happens in a real emergency in the middle of the pacific.

I know 757,767,A330 and 777 aren’t fully stocked with fuel but enough to cover the Mission plus reserves but those reserves far surpass a fully fueled 737 and have much more capability in an engine emergency and reliant on much more comfortable fuel reserves.

If an AS 738 departing SEA has to refuel in OAK before crossing the pacific due to strong headwinds then I don’t think that aircraft is cut out to run that type of route.
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A320FlyGuy
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:07 pm

nine4nine wrote:
Cubsrule wrote:
nine4nine wrote:

No, but given range issues due to fuel I wouldn’t feel comfortable being down an engine and flying lower altitude with higher fuel burn or even the added drag. I’d imagine any issue on a mainland-Hawaii flight to the likes of the WN issue would have resulted in a major tragedy.

I will never book a Hawaii flight personally on an 320/321 or 737. Have heard stories about planes arriving on fumes after stronger than expected headwinds. Couple that with an engine issue. I think it’s a disaster in the making.


How is any of what you cited different on a 757 or widebody twin from on a 737 or 320? While the larger aircraft have more range, carriers don’t fill up the tanks just for the sake of helping passengers sleep better at night. To the extent that uncontained engine failures are some sort of systemic problem (which is debatable at best), note that they generally do not occur hours into cruise.



I’m not saying they aren’t safe. Obviously they went thru the ETOPS cert process and proving runs. I’m just stating a personal preference that I prefer not to fly one of those birds halfway across the Pacific especially in an emergency scenario. I think there are more variables with aircraft that are flying missions they weren’t designed for. That’s all.


Then you are seriously going to be limiting yourself in terms of where you can travel in the future. Airlines aren't buying 747-8 and A380s - twins are the way of the future and unless the L-1011 and DC-10/MD-11 suddenly come back in vogue, you are going to be on a twin. There is a whole generation of passengers who have never flown on anything BUT a twin. The engineers at Airbus and Boeing don't simply cobble a plane together and hope for the best - the plane is designed and engineered and pushed far beyond ANYTHING it will ever experience in passenger service before it is released to the airlines. I have absolute faith in the engineering that goes into the A300/A310/A320/A330/A350 and 737/757/767/777/787. The WN1380 incident is tragic - no question. But that being said, the CFM56 has been around for a very, very long time. It has seen more service in both commercial and military applications than just about any other engine ever built. You have to compare one incident against a 40-year service record that has been, for the most part, impeccable. I think at the end of the day, the investigation will show that this was a maintenance failure on the part of WN and not a problem with the engine. Now, by comparison, look at the CF6 which has a history of blade/turbine failures that have occurred with a much higher frequency - yet it is still an airline favorite.

Airlines don't like major incidents - they are bad for business. No airline no matter how bad they may be is going to operate an engine that is of questionable reliability and quality. Nobody wants to be the next Valujet (except maybe Allegiant) and to that end - while the CFM56 is in the spotlight right now, people aren't considering the sheer number of 737s and A320s that are flying around with these engines - and that's only 2 applications. So factor in all of the military aircraft with CFM56s, the DC-8 Series 70 and the A340. It's an engine that airlines and passengers can put their confidence in. It has been for 40 years and it will continue to be. I'd be far more concerned about flying with a PW GTF slung under the wing.

Don't be afraid of ETOPS or twins - they are here to stay and will continue to be here - for now, and for the foreseeable future. Unless warp drive becomes an available option...
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Utah744
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:08 pm

Aviano789 wrote:
nine4nine wrote:
Cubsrule wrote:

Plain and simple, I don't want to find myself and love ones or for that matter any one having to deal with the Engine Stops PAX Swim (ETOPS) Scenarios. Please note there are lot of hungry JAWS between West Coast and the Hawaiian Islands.


Sharks eat seals and other mammals, which live near the mainland or islands, not in the open ocean excerpt to transit. I'm actually surprised to find such a fraidi-cat on this board. There are experts and in general well informed aviation enthusiasts on this board. Listen them. There are cruise liners that go to Hawaii, but of course they could hit an iceberg.
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A320FlyGuy
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:08 pm

nine4nine wrote:

I know 757,767,A330 and 777 aren’t fully stocked with fuel but enough to cover the Mission plus reserves but those reserves far surpass a fully fueled 737 and have much more capability in an engine emergency and reliant on much more comfortable fuel reserves.

If an AS 738 departing SEA has to refuel in OAK before crossing the pacific due to strong headwinds then I don’t think that aircraft is cut out to run that type of route.


There is a flaw in your logic here - they have higher fuel reserves BUT they are also larger aircraft with higher drag and thus, higher consumption. The numbers will work out the same in the end.

People need to let go of the "4 Engines 4 Long Haul" mentality. It was true at one time - but that time period ended around the same time the A300/A310 and 767 began flying oceanic routes. Hell, look at the Asian carriers that didn't have the ETOPS restrictions - they deployed the A300 on long overwater routes right away and...shock of shocks...people survived the flight without becoming fish food.
My other car is an A320-200
 
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Channex757
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:25 pm

BerenErchamion wrote:
JackMeahoff wrote:
rbavfan wrote:


The early models of the 737 were designed for shorter flights. However as they have evolved, like us humans did. What they could accomplish has increased with technology. Otherwise we would be waiting a week of more for your response to this. After all we did not have telephones or computer networks 500 years ago, but we had people traveling for days to send a message.



And yet for some reason the safety requirements for flying the President of the United States didn't evolve. Four engines then, four engines now. The Air Force must know something the bean counters at the airlines and their lackeys at the FAA don't. Trump can afford to lose two engines on Air Force One but I can only afford to lose one on my 737 before I go in the drink.


That's more about logistics and convenience than safety.

It's also about good old electricity.

Air Force One consumes a lot of power. Four engines allows for redundancy as well as spreading the load across four engines. The President needs to be in touch constantly with all sorts of services and losing a generator set just isn't going to work. Neither is adding additional generator sets to single engines, which could lose 50% in an engine-out scenario.

It's one reason why the 773ER works for non-nuclear Japan but not the USA.
 
stratclub
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:28 pm

JackMeahoff wrote:
There was a time when no lifeboats were needed because "statistics" proved that a certain ship was unsinkable. .


The reason that "certain ship" did not have a full complement of life boats, was not statistical is was marketing by The White Star Line selling the idea that the Titanic was unsinkable even though there were (known by them) cost cutting design features of the ship that turned the iceberg mishap deadly. The most obvious was that the transverse water tight bulkheads did not extend much higher than the water line.

"Back in the day", if there were statistics available that proved contrary to safety, most likely they would have never seen the light of day because they would have contradicted marketing goals and been a detriment to profits.
 
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JackMeahoff
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:49 pm

Aptivaboy wrote:
I will always select a widebody over a narrowbody if the price is equal. Who doesn't like high ceilings and open space?! If you don't operate this way, you are just playing into the hands of the airline bean counters who would fly the 737 to China if they could find a way.


I hear what you're saying (and I don't totally disagree) but the comment I was replying too specifically had to do with the number of engines, not the size of the plane's interior. And no, its the public that makes flight choice arrangements, not the bean counters. Call it supply and demand, market research, the invisible hand, or whatever you want. If the public wants frequent service in a narrowbody, then they'll demand it and be willing to pay the cash for a ticket.


Flying was a much more enjoyable experience 20 years ago. Even better 30 years ago. Go back 50 years and flying was like a dream. The larger, gas guzzling planes of the previous decades were faster, roomier, and had more legroom. The flight attendants were hot, and they wore skirts. Now look where we are. 737s fill the skies going to Hawaii, and who knows, maybe to Europe soon. You are charged for checking a bag, and many cases for your carry on. Not to mention food and drinks. If consumers are in control as you say, why have consumers only lost ground as time goes on?
 
barney captain
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Sun Apr 29, 2018 11:58 pm

The 737NG and -8MAX hold around 46,000 lbs of fuel so there not a lot of room left over for XTRA fuel.


Which equates to roughly 10+ hours of fuel. I'd wager tank capacity is never an issue - ATOG is. There's likely always room for more fuel, but some folks and/or their bags are getting left behind. In my entire career, I've only seen full tanks in an NG one time, and that was on a new delivery ferry flight from PAE to GEG.
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GE90man
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Mon Apr 30, 2018 12:02 am

JackMeahoff wrote:
Aptivaboy wrote:
I will always select a widebody over a narrowbody if the price is equal. Who doesn't like high ceilings and open space?! If you don't operate this way, you are just playing into the hands of the airline bean counters who would fly the 737 to China if they could find a way.


I hear what you're saying (and I don't totally disagree) but the comment I was replying too specifically had to do with the number of engines, not the size of the plane's interior. And no, its the public that makes flight choice arrangements, not the bean counters. Call it supply and demand, market research, the invisible hand, or whatever you want. If the public wants frequent service in a narrowbody, then they'll demand it and be willing to pay the cash for a ticket.


Flying was a much more enjoyable experience 20 years ago. Even better 30 years ago. Go back 50 years and flying was like a dream. The larger, gas guzzling planes of the previous decades were faster, roomier, and had more legroom. The flight attendants were hot, and they wore skirts. Now look where we are. 737s fill the skies going to Hawaii, and who knows, maybe to Europe soon. You are charged for checking a bag, and many cases for your carry on. Not to mention food and drinks. If consumers are in control as you say, why have consumers only lost ground as time goes on?


The consumer has only gained ground on lower prices. Following recent trends, it's becoming more and more obvious that the majority of travelers book their tickets based on who sells the cheapest ones. For those who don't want bare-minimum services, they can pay more.
 
Aptivaboy
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Re: Flying 2000 miles over open water in twins powered by CFM56-7

Mon Apr 30, 2018 12:14 am

Exactly. I agree that flying was a more enjoyable experience in past decades. However, it was also far more expensive. There's a reason why my Mom had to ask her parents for help paying for tickets back in the seventies and very early eighties. Oh, and people smoked like freaking chimneys inside the plane. Talk about disgusting. Well, maybe we've actually improved in some ways, as time has marched on! In the end, the market will bear what the market can bear. If the general flying public is alright with a narrowbody twin TATL (which I've done in a 757) or transpac or wherever, then it will happen.

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