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Twin Jets And The Fragility Of Etops  
User currently offlineFltAdmiralRitt From United States of America, joined Apr 2013, 37 posts, RR: 0
Posted (10 months 1 day 14 hours ago) and read 4642 times:

Over the years airliner twin jets have crossed oceans w/0 mishap with
some models gaining ETOPS 240 status. There have been a few close
calls but nothing that resulted in a water landing far from shore.
But chance is a funny thing, it has no memory, and one indicident
does preclude another. I cite as an example the two jets in the late 1960's
what went down off short shortly takeoff at LAX, within weeks of each other.

Looking at the pacific routes and how much twins utilize ETOPS. Now imagne
two water landings resulting from engine failure and consequent high casualties
within months of each other. There would be pressure to scale ETOPS
to very low minutes.

Would the public likely forget about the tragedy and
tolerate returning to higher ETOPS minutes.?
What about the capital value of all those long range twin engine aircraft?
Would Fuel prices/Passenger fear create a market for the
tri-jets again, or are they too much trouble and continue to build 4 engine jets?

25 replies: All unread, showing first 25:
 
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7344 posts, RR: 32
Reply 1, posted (10 months 1 day 13 hours ago) and read 4581 times:

Quoting FltAdmiralRitt (Thread starter):
Now imagne two water landings resulting from engine failure and consequent high casualties within months of each other. There would be pressure to scale ETOPS to very low minutes.

No there would be no public pressure to scale ETOPS back. The flying public doesn't understand the concept of ETOPS.

For an accident to even be attributable to ETOPS - one engine would have to fail. The flight would have to divert to an ETOPS alternative airport. Then after a certain amount of time - at least an hour, more likely two hours - the second engine would have to fail from a completely different cause.

The Air Transat flight was not an ETOPS failure because ALL the engines quit working at the same time from the same cause. That can happen to a four engine jet as often as it happens to a twin.

Quoting FltAdmiralRitt (Thread starter):
Would the public likely forget about the tragedy and tolerate returning to higher ETOPS minutes.?

The flying public would not tolerate a cutback on twin-jet availability by tighter ETOPS. The cancellation of flights due to tighter ETOPS would cause much more disagreement and public outcry than a couple crashes, no matter what the casualty count.

Quoting FltAdmiralRitt (Thread starter):
Would Fuel prices/Passenger fear create a market for thebtri-jets again, or are they too much trouble and continue to build 4 engine jets?

No. Passenger fear is a non-factor.

There will always be quad jets until the technology changes significantly. For some routes, some frequencies and some markets - a quad works better. Especially the VLA market.


User currently offlineRoseflyer From United States of America, joined Feb 2004, 9375 posts, RR: 52
Reply 2, posted (10 months 1 day 12 hours ago) and read 4545 times:

ETOPS programs are derived from statistics and engineering analysis. It is not based on opinions and anecdotal evidence.

If we saw multiple dual engine failures on twins, I would expect further review of the ETOPS requirements being implemented, but not an elimination of the program or drastic downgrade in ETOPS ratings for existing fleets. I’d expect an engineering review of what caused those crashes and new requirements to be put into the ETOPS program to prevent them from happening.

ETOPS programs have evolved over time. Not only has the diversion time restriction gone up, but additional requirements have been included in ETOPS programs. ETOPS is also not exclusively for twin engine aircraft now. Some requirements are required for all (including 4 engine) airplanes such as fire suppresion and increased fuel reserves to accommodate for decompression.

Crashes in general do not lead to drastic changes in the FARs that regulate airline operations. Usually a crash will have a number of recommendations and some will change design. The British Airways 777 crash changed the heat exchangers in the fuel system, the Air France A330 crash resulted in changes to the pitot static system, the TWA 800 747 crash resulted in strict fuel tank ignition requirements, the Turkish 737 crash in Amsterdam resulted in Radio Altimeter changes. In general, such crashes would lead to design changes, and potentially to a revision of the FARs to introduce new requirements, but they aren’t going to scrap ETOPS or downgrade the existing fleet. The safety analysis process used to certify an airplane always can use improvement, but it is an extremely robust process. I don’t see public opinion outweighing engineering expertise. 3 and 4 engine airplanes aren't coming back out of fear of loss of ETOPS.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineFltAdmiralRitt From United States of America, joined Apr 2013, 37 posts, RR: 0
Reply 3, posted (10 months 18 hours ago) and read 4198 times:

Maybe the public doens't know about ETOPS now, but after an ocean landing
You can be sure that the MEDIA will make sure the public MISUNDERSTANDS IT.
Don't underestimate the power of hyperbole.

On a side note, I think some of the more seasoned transpacific fliers know that a
mid ocean ditch is giant crapshoot, On a rough ocean you can be pretty certain
of a break up, and high casualties. Many must think all that talk about water landing
equipment/proceedures is a sedative for the extra nervous types.


User currently offlineRoseflyer From United States of America, joined Feb 2004, 9375 posts, RR: 52
Reply 4, posted (10 months 15 hours ago) and read 4121 times:

Quoting FltAdmiralRitt (Reply 3):
Many must think all that talk about water landing
equipment/proceedures is a sedative for the extra nervous types.

There have been two high profile water landings where everyone survived in the last few years with the US Airways crash in New York and the Lion Air crash in Bali. The Ethiopian crash in the ocean was surviveable, even though the airplane broke up. It has certainly been proven that water landings are surviveable. Now I agree a water landing in the ocean in bad weather may be worse and getting everyone into a raft with a sinking plane may not be possible, but the water landing procedures are not just sedatives for the nervous types.

I don't think there is much belief that 2 engine airplanes overwater are less safe than 4 engine planes are. Nowadays, diversions are rarely caused by engine shutdowns. They are caused by many factors.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7344 posts, RR: 32
Reply 5, posted (10 months 12 hours ago) and read 4044 times:

Quoting Roseflyer (Reply 4):
agree a water landing in the ocean in bad weather may be worse and getting everyone into a raft with a sinking plane may not be possible,

On Octoboer 26, 1978 - a US Navy P-3 was forced to ditch is stormy weather about 800 miles from Adak and Shemya.

The pilots set the plane down in 25 foot swells with a runaway prop and fire visible around the engine.

10 of the 15 people on board survived.

It was a very bad scenario.

http://www.vpnavy.com/vp9586.html


User currently offlinetimz From United States of America, joined Sep 1999, 6704 posts, RR: 7
Reply 6, posted (10 months 11 hours ago) and read 4006 times:

Quoting rfields5421 (Reply 1):
Passenger fear is a non-factor.

I guess you mean it doesn't exist. That'll continue to be true as long as twins stay in the air.


User currently offline7BOEING7 From United States of America, joined Oct 2012, 1301 posts, RR: 8
Reply 7, posted (10 months 10 hours ago) and read 3993 times:

Quoting FltAdmiralRitt (Reply 3):
Maybe the public doens't know about ETOPS now, but after an ocean landing
You can be sure that the MEDIA will make sure the public MISUNDERSTANDS IT.
Don't underestimate the power of hyperbole.

On a side note, I think some of the more seasoned transpacific fliers know that a
mid ocean ditch is giant crapshoot, On a rough ocean you can be pretty certain
of a break up, and high casualties. Many must think all that talk about water landing
equipment/proceedures is a sedative for the extra nervous types.

Any time you lose all your engines (2 or 4) it's a crapshoot whether it be over land or water. Not everybody will be as lucky as the Air Canada 767, Air Transat 330 or British Airways 777 passengers -- which if they were 4 engine airplanes would have had 4 engines out . Was there a public outcry to halt all two engine ETOPS flights -- NO! Your average passenger doesn't care until maybe 3 or 4 all fall out of the sky in a very short time frame -- then they'll quit flying, period.

I'll take my chances with a two engine airplane under an ETOPS maintenance program that flies over water over a two engine airplane not under an ETOPS maintenance program flying over land. Waters mostly flat. For 99.999% of the passengers that get on an airplane, crashing is not on their mind be it over water or land.

Since you have no credentials, I don't know why i'm wasting my time with this ridiculous thread.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 24061 posts, RR: 23
Reply 8, posted (10 months 10 hours ago) and read 3973 times:

Quoting Roseflyer (Reply 2):
ETOPS is also not exclusively for twin engine aircraft now. Some requirements are required for all (including 4 engine) airplanes such as fire suppresion and increased fuel reserves to accommodate for decompression.

The FAA changed its definition of ETOPS to simply "Extended Operations" in 2007 for those reasons.


User currently offlineBoeingGuy From United States of America, joined Dec 2010, 2878 posts, RR: 7
Reply 9, posted (10 months 9 hours ago) and read 3946 times:

Quoting FltAdmiralRitt (Thread starter):
I cite as an example the two jets in the late 1960's
what went down off short shortly takeoff at LAX, within weeks of each other.

Actually they crashed 5 days apart in 1969 and one of them crashed on approach, not takeoff. It was an SK DC-8 and UA 727. The 727 accident is what led to the mandate for Standby batteries and independently powered Standby Instruments.

Quoting rfields5421 (Reply 1):
For an accident to even be attributable to ETOPS - one engine would have to fail. The flight would have to divert to an ETOPS alternative airport. Then after a certain amount of time - at least an hour, more likely two hours - the second engine would have to fail from a completely different cause.

Yeah, and almost any scenario you could devise for an ETOPS accident could just as easily happen to a 3-4 engine jet. When was the last time both engines on a twin failed for something that would have failed all engines on a 4 engine airplane? Never.

I agree this is not a productive thread anymore. The OP asked a valid question and it was answered. ETOPS flying is safe. There has never ever been an accident that was caused by ETOPS for a twin engine airplane, that wasn't attributed to a totally unrelated cause.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 10, posted (10 months 8 hours ago) and read 3930 times:

Quoting FltAdmiralRitt (Thread starter):
But chance is a funny thing, it has no memory, and one indicident
does preclude another. I cite as an example the two jets in the late 1960's
what went down off short shortly takeoff at LAX, within weeks of each other.

"Chance" is a bad way to put it since ETOPS "non-accident rates" are not pure statistics. It's not like the dice are thrown every time an ETOPS flight operates. Thus in this case "chance" does indeed have memory. If one crash happened there would be a thorough review of procedures (just like with any crash). Thus the chances of that particular incident happening again decrease.

ETOPS has been around for nigh on forty years now without one single fatality. One or two crashes would not invalidate the entire system.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineMax Q From United States of America, joined May 2001, 4059 posts, RR: 19
Reply 11, posted (10 months 5 hours ago) and read 3881 times:

If you go down in the North Atlantic in winter the chances of survival are minimal.



Have any of you seen the massive seas of this ocean at its worst ?



forget it.



The best contribution to safety is a competent Pilot.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 12, posted (10 months 4 hours ago) and read 3857 times:

Quoting Max Q (Reply 11):
If you go down in the North Atlantic in winter the chances of survival are minimal.

Certainly, and the unpalatable survival chances of a mid-ocean ditching (or mid-Polar-Icecap "landing") are why the regs are so stringent on ETOPS. If a dual unrelated engine failure simply led to a glide to the nearest usable runway, the regs would be far less tough.

I'm not an expert on this kind of risk analysis but AFAIK the assumption is that the chances of a ditching due to dual unrelated engine failure, while possible, is so unlikely that the risk incurred while operating under ETOPS is still acceptable. Looking at CS25, "Adequate Safety Margin" forces manufacturers and operators to prove such an incident is "extremely remote", defined as 1 in 10 000 000 to 1 in 1 000 000 000 chance and described as "Unlikely to occur during the life of a fleet but still possible". This is the same probability given to "Hitting an obstacle in the Net Take-Off Path".

So yes, if a plane goes down in the mid-Atlantic everyone aboard will likely die regardless of the success or not of the ditching, but the risk of a ditching is so vanishingly remote the outcome of such is ignored.


I'd venture the risk of a plane going down due to a birdstrike, a microburst or a mid-air collision is higher than any risk posed by ETOPS, and yet those are somehow seen as acceptable risks.

Quoting FltAdmiralRitt (Thread starter):
FltAdmiralRitt

Kzinti reference? Big grin

[Edited 2013-06-20 00:36:47]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinetravelavnut From Netherlands, joined May 2010, 1535 posts, RR: 7
Reply 13, posted (10 months 3 hours ago) and read 3836 times:

Ow no, not this again...... Got the feeling the OP just recently learned about ETOPS.

Quoting FltAdmiralRitt (Reply 3):
Don't underestimate the power of hyperbole.

And don't underestimate how quickly people forget news and events nowadays.

Quoting FltAdmiralRitt (Reply 3):
On a side note, I think some of the more seasoned transpacific fliers know that a
mid ocean ditch is giant crapshoot,

Luckily, partly because of ETOPS, that doesn't seem to happen anymore.

Quoting 7BOEING7 (Reply 7):
I don't know why i'm wasting my time with this ridiculous thread.

You're quite right, bye bye   

[Edited 2013-06-20 00:46:43]


Live From Amsterdam!
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9375 posts, RR: 52
Reply 14, posted (9 months 4 weeks 1 day 19 hours ago) and read 3704 times:

Quoting Starlionblue (Reply 12):
I'm not an expert on this kind of risk analysis but AFAIK the assumption is that the chances of a ditching due to dual unrelated engine failure, while possible, is so unlikely that the risk incurred while operating under ETOPS is still acceptable. Looking at CS25, "Adequate Safety Margin" forces manufacturers and operators to prove such an incident is "extremely remote", defined as 1 in 10 000 000 to 1 in 1 000 000 000 chance and described as "Unlikely to occur during the life of a fleet but still possible". This is the same probability given to "Hitting an obstacle in the Net Take-Off Path".

FAR 25.1309 has 4 different categories of failure (Minor, Major, Hazardous and Catastrophic) and different reliability rates based on the type of failure. Dual engine failure on an ETOPS flight would usually fit in the Catastrophic category (just like loss of directional control, uncontrolled flight into terrain, etc). For the purpose of reliability requirements it is treated as an unsurviveable event and therefore required to have a probability below 1 in 1 Billion. If you are ever curious, here’s the AC describing the FAR: http://www.faa.gov/regulations_polic...ument.information/documentID/22680



If you have never designed an airplane part before, let the real designers do the work!
User currently onlinenomadd22 From United States of America, joined Feb 2008, 1761 posts, RR: 0
Reply 15, posted (9 months 4 weeks 1 day 16 hours ago) and read 3632 times:

I'm sure USCG maintenance standards weren't exactly airliner class, but I've personally been on a C-130 that lost two engines an hour apart for unrelated reasons. I'd probably be a little nervous on a one engine airliner four hours out.


Andy Goetsch
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 16, posted (9 months 4 weeks 1 day 12 hours ago) and read 3556 times:

Quoting nomadd22 (Reply 15):
I'm sure USCG maintenance standards weren't exactly airliner class, but I've personally been on a C-130 that lost two engines an hour apart for unrelated reasons. I'd probably be a little nervous on a one engine airliner four hours out.

Apart from the maintenance, the C-130 and its engines were never designed for ETOPS operations. A 777, for example, was designed for ETOPS from the time it was just a twinkle in the eyes of the Boeing engineers.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinePPVRA From Brazil, joined Nov 2004, 8868 posts, RR: 40
Reply 17, posted (9 months 4 weeks 17 hours ago) and read 3393 times:

Quoting FltAdmiralRitt (Thread starter):
I cite as an example the two jets in the late 1960's
what went down off short shortly takeoff at LAX, within weeks of each other.

Was it an ETOPS failure event if they occurred right next to the airport?



"If goods do not cross borders, soldiers will" - Frederic Bastiat
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1301 posts, RR: 8
Reply 18, posted (9 months 4 weeks 10 hours ago) and read 3285 times:

Quoting PPVRA (Reply 17):
Was it an ETOPS failure event if they occurred right next to the airport?

There was no ETOPS back then but if a 777 used for ETOPS had an engine failure shortly after takeoff it would be looked at as an ETOPS event for that engine depending on the cause.


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7344 posts, RR: 32
Reply 19, posted (9 months 3 weeks 6 days 7 hours ago) and read 3051 times:

Quoting PPVRA (Reply 17):
Was it an ETOPS failure event if they occurred right next to the airport?

No.

An ETOPS failure would only be if the aircraft was unable to reach safety within the allowed single engine operational range/ time.

The contention of folks who say ETOPS for twin jets are unnecessarily risking passengers / crew lives is that the distance/ time the jets are allowed to fly from 'safety' airports is excessive.

The contention is that a three hour flight time on one engine (ETOPS 180) increases the chance of a second engine failure over a two hour flight time (ETOPS 120).

The contention of ETOPS requlators and the airlines is that 180 minutes is a safe operating margin, and even up to 240 minutes is a safe single engine operating margin.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 20, posted (9 months 3 weeks 6 days 4 hours ago) and read 3014 times:

Quoting rfields5421 (Reply 19):
The contention of ETOPS requlators and the airlines is that 180 minutes is a safe operating margin, and even up to 240 minutes is a safe single engine operating margin.

Air New Zealand is going for ETOPS330. Worst case of 5½ hours on one engine.

http://www.flightglobal.com/news/art...7-300ers-with-330min-etops-365992/



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3423 posts, RR: 67
Reply 21, posted (9 months 3 weeks 5 days 18 hours ago) and read 2909 times:

Quoting rfields5421 (Reply 19):
An ETOPS failure would only be if the aircraft was unable to reach safety within the allowed single engine operational range/ time.

For ETOPS statistical purposes, failures are entered into the database if they occur anywhere in the flight profile.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineBoeingGuy From United States of America, joined Dec 2010, 2878 posts, RR: 7
Reply 22, posted (9 months 3 weeks 4 days 15 hours ago) and read 2674 times:

Quoting PPVRA (Reply 17):
Quoting FltAdmiralRitt (Thread starter):
I cite as an example the two jets in the late 1960's
what went down off short shortly takeoff at LAX, within weeks of each other.

Was it an ETOPS failure event if they occurred right next to the airport?

I think the OP was referring to how much safer air travel has become, not suggesting the LAX accidents were ETOPS related.

The SK DC-8 landed short of the runway in Santa Monica Bay due to a Navigation error; the UA 727 crashed in the bay after takeoff due to loss of electrical power to their instruments and it was foggy so they had no attitude display,

Predated ETOPS by like 20 years and no relation to ETOPS.


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7344 posts, RR: 32
Reply 23, posted (9 months 3 weeks 4 days 12 hours ago) and read 2613 times:

Quoting OldAeroGuy (Reply 21):
For ETOPS statistical purposes, failures are entered into the database if they occur anywhere in the flight profile.

Yes.

But the failure we are talking about is one in which the ETOPS specs are not sufficient to get an aircraft with an engine out to safety.

The ETOPS system doesn't fail until that occurs.


User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3423 posts, RR: 67
Reply 24, posted (9 months 3 weeks 3 days 22 hours ago) and read 2471 times:

Quoting rfields5421 (Reply 23):
But the failure we are talking about is one in which the ETOPS specs are not sufficient to get an aircraft with an engine out to safety.

The ETOPS system doesn't fail until that occurs.

But by counting a failure anywhere in the flight profile, the airframe/engine combination must have sufficient reliability for the whole flight profile. This lowers the probability of critical failures during the ETOPS phase of flight.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlinecornutt From United States of America, joined Jan 2013, 338 posts, RR: 1
Reply 25, posted (9 months 3 weeks 2 days 7 hours ago) and read 2243 times:

Quoting rfields5421 (Reply 19):
The contention is that a three hour flight time on one engine (ETOPS 180) increases the chance of a second engine failure over a two hour flight time (ETOPS 120).

You can calculate the probability of an engine failure occurring within a certain amount of flight time. Yes, in general, the longer you fly the more exposure you have to that fault. However, if you can make everything robust enough so that the standard for the probability of a catastrophic failure is met even with the longer exposure period, then it doesn't matter. That's what ETOPS is all about... re-evaluating which failures are considered catastrophic assuming that an intact landing within the exposure window will always be impossible, and then designing systems and procedures to meet the probability standard.


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