[apachelongbow]

Originally Posted by nkishore_007

Are you sure about this? If a new wide body aircraft provides 40% savings than another relatively similar one in the aviation industry, Boeing would have killed their own product the day it was released.
This figure of yours caught my eye, and I started checking online only to find that the cost per seat per nautical mile is marginally high in 747-8 (link).

Of course, an airlines can go in for this kind of setup (458 seats in a 777ER). OMG was my first reaction when I read this. They should put up a disclaimer to have all 468 passengers who are ~5 ft or less to board the flight.
Don't they have some regulations to counter such money making measures? FAA has jurisdiction only in USA. Darn!

Aviation is a high risk low return business all over the world. Forget 11$/mile companies will chase 11 cents/mile in order to improve margins, the reason being in a good year, one can expect 2% returns on an average.
It is not just about the fuel costs, the other major cost is maintenance, engines, landing gear, tyres, other components costs a lot of money and regular inspections, checks and replacements need to be carried out per number of landings, hours of usage etc. This means a four engine plane will always cost more than a twin even if fuel costs are the same for both.
Plus other costs like increased turn around time due to cleaning, catering uplift etc.

[Jeroen]

Originally Posted by nkishore_007

Don't they have some regulations to counter such money making measures? FAA has jurisdiction only in USA. Darn!

The FAA mandate is only concerned about safety, not passenger comfort as such.

Jeroen

[nkishore_007]

Originally Posted by cooldude1988765

My first international flight was in a 747-400 owned and operated by Air India.
That one flight made me decide never to fly in a 747 ever again.
Absolutely dismal leg room in economy. My knees were literally at my chin when the passenger in front of me reclined their seat.

You can blame the airlines, not the aircraft.

Originally Posted by apachelongbow

It is not just about the fuel costs, the other major cost is maintenance, engines, landing gear, tyres, other components costs a lot of money and regular inspections, checks and replacements need to be carried out per number of landings, hours of usage etc. This means a four engine plane will always cost more than a twin even if fuel costs are the same for both.
Plus other costs like increased turn around time due to cleaning, catering uplift etc.

Agreed to some extent! But I was referring only to the 40% fuel saving figures.
I would say that the general tendency is to target the wrong factors when it comes to cost. Of course, a twin engine costs less than a quad, needs less maintenance, etc. Nowadays pilots can maneuver the pane to safety even if one of the engines goes out of operation. But I would like to believe that a 4 engine plane provides extra probability of making a safe emergency landing than a 2 engine one. My opinion though.
An unfortunate incident (to the extent of hull loss) is going to be even bigger worry for the Airlines. Malaysian lost two aircraft (of course not because of technical issues) but it did get them to the brink of bankruptcy. Good that it is the official Malay Govt Carrier.

Originally Posted by Jeroen

The FAA mandate is only concerned about safety, not passenger comfort as such.

Jeroen

Right. A 458 seater which is not a B747 or A380, is a tremendous safety hazard in terms of evacuation. Don't you agree?

[Jeroen]

Originally Posted by nkishore_007

Right. A 458 seater which is not a B747 or A380, is a tremendous safety hazard in terms of evacuation. Don't you agree?

Evacuation is exactly something that is very strictly controlled, simulated an tested as per FAA standards. There are very strict regulations, specifications and procedures pertaining to evacuation.

So a carrier and or a plane manufacturing can cram as many seats he or she would like into a plane, but they would still need to adhere and prove in simulations to meet to the respective FAA standards regarding evacuation.

Again, evacuation is safety, not comfort.

Jeroen

[apachelongbow]

Originally Posted by nkishore_007

Agreed to some extent! But I was referring only to the 40% fuel saving figures.
I would say that the general tendency is to target the wrong factors when it comes to cost. Of course, a twin engine costs less than a quad, needs less maintenance, etc. Nowadays pilots can maneuver the pane to safety even if one of the engines goes out of operation. But I would like to believe that a 4 engine plane provides extra probability of making a safe emergency landing than a 2 engine one. My opinion though.


Right. A 458 seater which is not a B747 or A380, is a tremendous safety hazard in terms of evacuation. Don't you agree?

No, a twin engined jet is as safe or safer than an antiquated 4 engine plane. That is the reason EDTO operations are permitted with twin jets with even 180 mins range. Also that argument of 4 engines being safe was valid when engine power was not good enough, to ensure 1 engine could hold a airplane in air long enough to make a safe landing, today's jet can take off, cruise and land with one engine, without much trouble, if needed.

Evacuation of a plane is dependent on number of seats and exits not engines. It depends entirely on the number of safety exits and slides, how can they be related to whether the airplane has x number of engines?

[Jeroen]

To add:

From the FAA:

The FAA may require airplane manufacturers to perform full-scale evacuation demonstrations in order to acquire type certification for new airplanes, and also for derivative models of currently certificated airplanes when the cabin configuration is unique or when a significant number of passenger seats have been added. A full-scale demonstration is a simulated emergency evacuation in which a full complement of passengers deplane through half of the required emergency exits, under dark-of-night conditions (14 CFR 25.803). A trained crew directs the evacuation, and the passengers are required to meet certain age/gender specifications (14 CFR Part 25, Appendix J).In order for manufacturers to pass the full-scale demonstrations, all passengers and crew must evacuate the aircraft and be on the ground in 90 seconds or less.

Note, the evacuation requirement is 90 seconds, type of plane, number of engines, colour of the plane, carrier, number of seats, none are relevant. Whichever (commerical) plane flying under FAA jurisdiciton needs to be designed and needs to be demonstrated to take less than 90 second to evacuate.

The reliability of modern commercial aircraft is such that the ETOPS limit gets pushed out all the time. From Wikipedia:

Effective February 15, 2007, the FAA ruled that US-registered twin-engined airplane operators can fly more than 180-minute ETOPS to the design limit of the aircraft. In October 2014 EASA certified the Airbus to 370-minute ETOPS, while Boeing is planning to certify its 787 to 330-minute ETOPS.
In November 2009, the became the first aircraft to receive ETOPS–240 approval, which has since been offered by Airbus as an option. On December 12, 2011, Boeing received type-design approval from the U.S. for up to 330-minute extended operations for its 777 fleet. This certification applies to the 777-200LR, 777-300ER, 777F and 777-200ER equipped with engines.
On May 28, 2014, the Boeing 787 Dreamliner received its ETOPS-330 certificate from the FAA.

I could be wrong, but I dont think a single incident or accident has ever occured as part of ETOPS operation.

Jeroen

[sriramr9]

Originally Posted by Stratos

Unfortunately, the 747-8i and -8f could never do what their predecessor, the 747-400 did. The increased wingspan being one of the problems. Whereas the 747 can almost land and depart at most major airports of the world, the 747-8 requires Code-F runways and taxiways that can accommodate its big wingspan. The A380 faces similar problems too. This can be a major hurdle as most airports are not willing to invest in modifying their taxiways or runways just for the sake of one of two models of quads.

Long Haul/ ultra long haul carriers like Lufthansa, Emirates and Singapore Airlines, BA should be supporting the quads for more than a decade or two from now, seeing the order list they have made.

Lufthansa for sure will be closely be associated with their -8 Quads as they were involved in the development of -8's and launch customers for the passenger version.

One note to end here, Boeing had this double decker idea 40 years back but did not materialize and they started working to compete against with DC -10 and tristar with the outcome of a 747 SP version.

They also stopped competing with the Concorde program to make supersonic airplanes and instead focused in bettering their latest offering and that decision was vital as many companies fate were tied to the success of the 747 program.

[sagarpadaki]

Originally Posted by nkishore_007

Are you sure about this? If a new wide body aircraft provides 40% savings than another relatively similar one in the aviation industry, Boeing would have killed their own product the day it was released.
This figure of yours caught my eye, and I started checking online only to find that the cost per seat per nautical mile is marginally high in 747-8 (link).

Nevertheless,
747-200 production ended in 1991.
747- 400 took over from -300, and the last passenger version was delivered in 2005.
Courtesy: Wiki
Hence, 747-8 is what the aviation industry "could" look forward to, if they want to replace their aging -400 with an advanced version of it's own. Some kind of trade off ? I don't know how that works in Aviation industry.

Sorry there was a calculation mistake from my side. I compared the fuel capacity of 747-8 with the 777-300ER and the difference comes to approx 25%.

However the 747 carries that much extra passengers to make up for the extra fuel it guzzles. So the cost per seat metric makes more sense rather than the outright fuel consumption.

However the running cost of a 747 over a period of say 10 years will be considerably more than 777. This also adds to be burden of costs

[Jeroen]

If anybody is interested in how to operate and fly the 747-400 you might consider having a look here:

http://aerowinx.com

Don't think of it as a sort of souped up Microsoft Aircraft Simulator. This is as near to a professional desktop simulator as you can get. The level of detailed operation and accurate system interaction is uncanny. You can actually pull individual circuit breaker and the various system will behave completely identical as in real life. and has got an excellent forum. Ive been a member for more then a decade and Have come to known many of the members, quite a few are (retired) 747-400 pilots or work in various aviation related engineering jobs.

Only thing, its not cheap. But I still think it is incredible value for money.

Jeroen

[nkishore_007]

I guess the discussion would or could go back to why quads came into place.

Probably, we don't needs quads anymore, or maybe we do.
Probably, the jumbos (B747/A380/A340) do need a quad setup by design, maybe they don't.
Probably, GE/RR/... will come up with even better engines, so that only twins can be fitted in the jumbos.

Interesting discussion indeed! Always gears up your knowledge.

Why do we say twins are safer than quads? Because there is no record of anything disastrous that has happened for a ETOPS specified fly path? Or it has been tried and tested by aviation industry flying a plane on a single engine (in a controlled environment & by a highly skilled test pilot)? Or Quads have more complexity and more parts which can fail? (Btw, I love flying in a B777/787/A333.)

I read this in an article online in favor of quads:

"
These include the ability to continue to their destination after an engine failure, better take-off performance in hot and high conditions, and the freedom to overfly remote areas free from extended range twin-engine operations (ETOPS) limitations.
"

Originally Posted by Jeroen

Again, evacuation is safety, not comfort.

Jeroen

Absolutely. I guess there is a confusion on when I stated "regulations" and on what context. Probably, because I put that statement immediately after the 458 seater 777 news. My bad! We are talking the same thing, but from different directions.

Originally Posted by apachelongbow

No, a twin engined jet is as safe or safer than an antiquated 4 engine plane. That is the reason EDTO operations are permitted with twin jets with even 180 mins range. Also that argument of 4 engines being safe was valid when engine power was not good enough, to ensure 1 engine could hold a airplane in air long enough to make a safe landing, today's jet can take off, cruise and land with one engine, without much trouble, if needed.

Evacuation of a plane is dependent on number of seats and exits not engines. It depends entirely on the number of safety exits and slides, how can they be related to whether the airplane has x number of engines?

Thank you. I know statistics do not prove that a quad is more safer than a twin (not sure if there exists a report on the other way round). I pray that there would never be a situation when both engines fail to deliver. But this is where my statement comes from. Worse case is to get rid of quads in years to come, only to have unfortunate incident/s forcing it back in action.

Evacuation: You are bang on target. But we are talking two different aspects of safety here, not to be mixed.
Engines (of course!) do not decide evacuation time, neither did I state it did!

Originally Posted by Jeroen

To add:

From the FAA:

Whichever (commerical) plane flying under FAA jurisdiciton needs to be designed and needs to be demonstrated to take less than 90 second to evacuate.

The reliability of modern commercial aircraft is such that the ETOPS limit gets pushed out all the time. From Wikipedia:

I could be wrong, but I dont think a single incident or accident has ever occured as part of ETOPS operation.

Jeroen

I am not sure about the jurisdiction of FAA. Do they cover whole of NA, or just USA? Or do they cover all airline aircraft which fly within and in or out of USA?

A cramped aircraft will take more time to evacuate. When disaster strikes, the situation is unforgiving!

I interpret ETOPS as means to make sure that you minimize the risks in case one engine fails to deliver.
Personally, I am not in favor of the increasing the duration limit within ETOPS directive only because there had not been any registered incidents, or one engine has the capacity to fly this or that many miles. No news is definitely not good news here!

Originally Posted by sagarpadaki

However the running cost of a 747 over a period of say 10 years will be considerably more than 777. This also adds to be burden of costs

Probably yes, but a twin engine flight maintenance requires more attention than a quad. Why? The first thing that comes to my mind is 2 is less than 4. Second, the twin guzzles more (per unit time) and produces more power (hence more wear & tear).

[Jeroen]

Originally Posted by nkishore_007

I guess the discussion would or could go back to why quads came into place.

You might want to refer to this thread where some of this was discussed before:

http://www.team-bhp.com/forum/techni...ml#post3466548

Very simply put, when four engine planes were introduced, aviation and jet engine technology was less mature and you simply needed four engines to get a big plane that would cary a lot of passengers and fly long distances into the air. A two engine plane simply could not hack it.

Aviation and jet engine technology has come a long way since. For all intents and purposes these days the what's safer 2 or 4 engines has lots its practical relevance.

Originally Posted by nkishore_007

Why do we say twins are safer than quads? Because there is no record of anything disastrous that has happened for a ETOPS specified fly path? Or it has been tried and tested by aviation industry flying a plane on a single engine (in a controlled environment & by a highly skilled test pilot)? Or Quads have more complexity and more parts which can fail? (Btw, I love flying in a B777/787/A333.)

I don't think anybody suggested that twins are safer than quads. As stated before, from a practical point of view, these days either is incredible safe. In theory, see my earlier thread, we can calculate the statistical difference between the two, but that has no practical meaning anymore.

All pilots flying a multi engine plane are trained to handle engine out scenario's. You don't need to be highly skilled test pilot. Every pilot who is rated multi engine knows how to do it.

The ETOPS regulations and subsequent increase in maximum times have come as a result of rigorous design testing, simulation, actual testing and of course all data collected of ten of millions of miles of ETOP operations

Originally Posted by nkishore_007

I am not sure about the jurisdiction of FAA. Do they cover whole of NA, or just USA? Or do they cover all airline aircraft which fly within and in or out of USA?

USA Only, It has the authority to regulate and oversee all aspects of American civil aviation and American civil airspace.

Originally Posted by nkishore_007

A cramped aircraft will take more time to evacuate. When disaster strikes, the situation is unforgiving!

See my previous answers. The aircraft manufacturer needs to design it in such a way passenger and crew can be evacuated and on the ground in less than 90 seconds. So that means more doors, escape chutes etc as the number of seats/passengers increase

Originally Posted by nkishore_007

I interpret ETOPS as means to make sure that you minimize the risks in case one engine fails to deliver.
Personally, I am not in favor of the increasing the duration limit within ETOPS directive only because there had not been any registered incidents, or one engine has the capacity to fly this or that many miles. No news is definitely not good news here!
.

See the above answer. There is quite a bit more science and methods too how ETOPS limits get pushed out. No news is definitely one type of validation of the design criteria. The number of miles flows under ETOPS is absolutely staggering, so it is definitely a statistically very significant factor that things work. You need to look at some other factors as well. And you can't extrapolate from it to higher duration limits. But as making a statistically very significant case that the ETOPS criteria are reliable and statistically extremely significant can't be denied.

Problem is we tend to approach these sort of issues, understandably, from a gut type of feeling. Unfortunately, on these matters it is down to science, mathematics and statics that hold the truth.

Jeroen

[hangover]

It's a bit more than just cost per mile.

Take a new outfit say, FirstWings. They somehow get permission for 4 slots at a busy airport like Heathrow. Using 2 B-737's and 2 Airbus 320's business is good.

Now the CEO wants to expand. So they reduce legroom by 2 inches and pack more seats in each plane. On the accountants advise they add another seat in each row. Now each plane carries 250-300 skinny passengers.

Tickets are cheap and so FirstWingers passengers don't complain.

That is the main reason fewer 747's are getting sold worldwide.

Now oil prices are low. The hard working CEO want to expand further. But the Heathrow guys refuse to give any more slots. Suitcases filled with green ones (curry leaves, coriander) makes no difference.

His wife, usually a quite lady suggests buying 4 Boeing 747s. The CEO laughs and talks about fuel costs of 4 engines and so on. What does she know?

CEO thinks some more and realizes he can bring in 400 - 500 passengers per flight. Then x times 4 = Plenty of €£¥$.

He quietly dumps the small planes and leases 4 B-747's cheaply.

Then he follows the same old strategy and he jams in more seats like Air Canada making each ones capacity 500 pax. A few passengers complain about fewer onboard toilets and legroom. But nobody wants diamond studded faucets for the amount they're paying.

The B747's are painted gold and blue. Seats are pink and white. All colors being his wife's favorites.

Oil prices stay low next decade. FirstWings stock rises 1000%. The world is a happy place.

The CEO now a billionaire retires to the Bahamas. Grateful shareholders gift him a civilian Fairchild A-10 warthog for island hopping.

His wife is the now the new CEO. Airbus offer their 380's at dirt cheap prices. Like when they got Air India to cancel B757 orders for A320's in 1992 or 1995.

New CEO has one look at them and deems them too ugly to match her Gucci and Prada. She pities her relatives who had to fly the worlds most spacious 410 seater Korean Air's A380 planes. Really Bharathi Aunty ought to have better sense.

Orders 100 more 747's.

And 747's rule next 20 years.

End of story.

[nkishore_007]

Can anybody throw some light how do upgrades happen in Aviation industry? What is the product lifecycle like? How long do they keep supporting, say 747 - 100 which is still in service (not sure if this variant does fly today)? Special agreements/contracts?

This could possibly explain what happens to the existing -400 jumbo fleet & fate of 747 altogether. They may be fly worthy for few more decades, but new regulations & avionics could force them to upgrade (not necessarily to -8i though).

When & where do they send one craft back to scrap? Back to the manufacturer?

I would be interested to know.

Originally Posted by Jeroen

You might want to refer to this thread where some of this was discussed before:
Aviation and jet engine technology has come a long way since. For all intents and purposes these days the what's safer 2 or 4 engines has lots its practical relevance.

Thank you. I hope to see a twin engine which can power the jumbos.

Originally Posted by Jeroen

I don't think anybody suggested that twins are safer than quads.

Well, there was a statement by one gentleman in this conversation. Plus, there are threads online where people openly state that twins are safer than quads (I would agree if they say, it equally safer, but they categorically state twins are safer. Maybe because of ETOPS and all!).

Originally Posted by Jeroen

All pilots flying a multi engine plane are trained to handle engine out scenario's. You don't need to be highly skilled test pilot. Every pilot who is rated multi engine knows how to do it.

Right. And I am grateful to them for doing what they do best, 365 days a year.

Originally Posted by hangover

.......
And 747's rule next 20 years.
End of story.

Entertaining! Thanks.

[Jeroen]

Originally Posted by nkishore_007

Can anybody throw some light how do upgrades happen in Aviation industry? What is the product lifecycle like? How long do they keep supporting, say 747 - 100 which is still in service (not sure if this variant does fly today)? Special agreements/contracts?

This could possibly explain what happens to the existing -400 jumbo fleet & fate of 747 altogether. They may be fly worthy for few more decades, but new regulations & avionics could force them to upgrade (not necessarily to -8i though).

When & where do they send one craft back to scrap? Back to the manufacturer?

.

I'm really not very familiar with this, but here are a few things I think are relevant. Other more knowledgeable members can chip in.

First of all, we need to distinguish between economic, technical and legal life time. (note, all based on my limited undestanding how things work under the FAA, might be different in different countries)

Economic is pretty simple. As planes get older, they do require more maintenance, tend to get less fuel efficient to newer versions etc. In essence, very similar to say cars, or trucks. Even though the plane is in perfect technical condition, it might just not be viable to operate it economically. Better to get the newer/latest version so to speak.

Every plane within the jurisdiction of the FAA needs, amongst others, an airworthiness certificate. It's issued by the FAA. Getting such a certificate starts from the very early conception of designing a new plane.

From a technical point of view, planes get designed and certified for a specific lifetime, expressed in amongst others, number of cycles. I.e. take off and landings. Especially on commercial planes with a pressurised hull, number of cycles is a very important parameter. After so many cycles, you need major inspection, possible replacments of structural parts etc. But at some point in time the airframe is just, technically, used up. And it will be permanently grounded (its airworthiness certificate will be pulled permanently) and usually scrapped.

The same is true for the engines. For instance on the little single engine planes I fly, it is stipulated how often the engines requires a complete overhaul. Say every 1500 hours. Also, how often you can do the overhaul, say 2 times. After that the engine needs replacing. In said example this engine would need to replaced after 4500 hours.

All planes in the USA are certified by the FAA. During the design phase the manufacturer needs to comply with a whole bunch of design critiria and the FAA actually validates a lot of the manufactures assumptions, calculations. Then there is a whole bunch of actual testing, again dictated by the FAA that needs to be done. On all components, and on the whole plane. From static testing on the ground, to actual flight testing.

So for an airplane to become certified, is a very lengthy, elaborate, precise very detailled process, all dictated and supervised by FAA. The maintenance procedures and schedules are also part of the FAA jurisdiction.

Legally speaking an aircraft might be grounded permanently as well. I.e. it losed it's airworthiness certificate. This could be the case if it has suffered from such failures that it can not be repaired to meet FAA requirements.

If an aircraft loosed it's so called airworthiness certificate permanently, i.e. it can not be repaired to a state where it meets FAA requirements, it will be scrapped. Parts might be salvaged of course and sold on in the second hand market

If operating an aircraft is not economically viable the carrier is very likely to try and find a buyer. Lots of older planes can still be operated economically in other countries, with lower cost, lower aviation standards etc. If they cant find a buyer, again the only option would be to scrap it.

There is one alternative to scrapping. You might have heard of these so called boneyards in the USA. Planes that are still technically airworthy, or can be made airworthy again quickly/cheaply, are stored in for instance the Arizona dessert. Its a cheap way to quickly get rid of excess capacity in a fleet, but when needed, it can be quickly made operational again. So that is an economic consideration, but more on total volume of aircrafts required.

The US airforce is one of the big players that mothball thousands of planes!

I am not sure how things work in India. Do the Indian aviation authorities accept the FAA, (or their European counterparts) certifications? Or are all planes certified under a specific Indian regime?

Hope this helps a bit.

Jeroen

[gthang]

Ahh the Jumbo.

Once as a schoolkid, took a flight as a solo passenger on the upper deck!! One of those small things in life one never forgets.

Very informative thread with a lot of info from aviation buffs.

I understood that Emissions also played a part in phasing out of aircraft models?

Wonder how much a role that played, and which otherwise successful aircraft it affected.

Cheers.