Flying

[alpha]

This kind of sounds like my mother (without the references to carbon emissions) . . .

http://www.dailymail.co.uk/news/worl...-boarding.html

[BigguyZ]

Wow, that's just rediculous. Do they actually mean to say that the minor change in weight (in comparison, overall) will make a significant reduction in fuel?

Though it does remind me of my brother's hypothesis that only filling your car with a quarter tank at a time will save money, since it's less fuel to carry. Yet still, I think this is silly.

[cabinetman]

Maybe they will make it more convenient while going through security to have receptacles right there. One tray for metal objects, one tray for shoes, one tray for bladder contents.
.

[BobSch]

This kind of sounds like my mother (without the references to carbon emissions) . . .

http://www.dailymail.co.uk/news/worl...-boarding.html

I had to check twice to make sure that wasn't from The Onion!

Maybe they'll start offering a cheaper ticket at the restroom door. Sort of a no-s..t fare.

[cgallery]

Maybe passengers should be required to take a diuretic and a laxative the day before the flight.

[cabinetman]

Maybe passengers should be required to take a diuretic and a laxative the day before the flight.

Might as well make your next flight a colonoscopic one.
.

[LCHIEN]

First of all, here's some assumptions and facts:
ANA and JAL operate in Japan, much of their operations are short haul (domestic within Japan), high capacity. They used to operate special 747s outfitted with smaller seats to accomodate 450-550 Japanese with smaller body sizes than their american counterparts.
The maximim take off weight of a 747 is around 730,000-800,000 lbs
Human bladder size is listed in the article as 15 oz, but a check of the web http://hypertextbook.com/facts/2001/DanielShaw.shtml shows that humans have strong urges to go at around 7-8 oz and someone with 15 oz of urine is probably doing a serious dance to avoid having an accident. I'm going to assume that people don't board a plane with a strong urge to go and the average bladder contents is closer to 4-6 oz.

So a full 747-100SR with 500 people with average bladders with 4-6 Oz being asked to go before boarding will save on the average 5 oz of urine x 500 or 2500 oz is 74000 cm3. using the density of water, Roughly equivalent to 74 kg or 163 lbs. I'll round it up because urine will be slightly denser than pure water, lets call it 175 lbs.

So we are saving 175 lbs on a TOW of 730,000 lbs. Thats a savings of 0.024 percent.
Realistically, taking 1% off the weight of an airplane doesn't return 1% savings in fuel, it returns less than that because the airplane drag in the air is unchanged and a significant part of the energy is just pushing that shape thru the air.

How much does fuel cost? Lets guess as an upper bound that the cost per passsenger goes 100% to cover fuel... a $200 ticket and 500 pax would give $100,000 revenue, no profit for salaries or debt service or anything else...
if we saved 0.024% in fuel which is unrealistically the same as the weight savings, then the airline would save $24 per flight.

More realistically the fuel cost being half the revenue, and the fuel savings as a percent being less than half the weight savings, then the total savings per trip would be no more than $6 for a fully loaded 747.


I have a suggestion for the airlines: Why don't they get rid of that totally useless cart with the duty free sales items - watches, jewelry, toys, electronics - that they carry on every transatlantic/transpacific/international flight - that thing must weigh 100 pounds and 98% of it gets flown back and forth 50 times before its sold. If you did the economics of what it cost in pound-air-miles transportation for each item I'll bet they're losing $50 on each item. Not to mention the additional 100 pounds of in-flight-shopping catalogs in every seat that never goes away.

[Wood_workur]

Though it does remind me of my brother's hypothesis that only filling your car with a quarter tank at a time will save money, since it's less fuel to carry. Yet still, I think this is silly.

It does save slight fuel, but probably not as much as if you were to fill up when its coldest out (early morning) because the gas is sold by volume, and when its coldest you will est the most amount of fuel per dollar.

And I bet if you are doing highway only driving that will cost you fuel economy in having to stop to refuel more often.


But back on topic, even if the savings are only a mere $6 per flight, I think it is a win-win, because the passengers get better facilities to use and then the airline can turn the plane around faster because cleaning will not take as long.

[Mr__Bill]

I'm thinking that if everyone goes on the ground (that doesn't sound right does it?) then the airline can dump the waste water less often and save on manpower and dumping charges. That could be a real saving in money but I don't see a carbon saving there at all.

Bill,

[Uncle Cracker]

Wow... I wonder if their cost models have factored in the excess wear and tear on the toilet equipment?

I guess you really can't spell "anal" without ANA.

[woodturner]

It does save slight fuel, but probably not as much as if you were to fill up when its coldest out (early morning) because the gas is sold by volume, and when its coldest you will est the most amount of fuel per dollar.

Gas (and aviation fuel) pumps adjust volume for temperature - so you get the same amount of gas when it is 30F or 90F. So it doesn't matter when you buy your gas, you get the same volume adjusted for temperature and pressure.

As a practical matter, underground storage tanks also don't very much in temperature - the ground stays around 55F, maybe varies 5F over the course of a year, so the adjustments the pumps have to make are minimal.

[Wood_workur]

Gas (and aviation fuel) pumps adjust volume for temperature - so you get the same amount of gas when it is 30F or 90F. So it doesn't matter when you buy your gas, you get the same volume adjusted for temperature and pressure.

As a practical matter, underground storage tanks also don't very much in temperature - the ground stays around 55F, maybe varies 5F over the course of a year, so the adjustments the pumps have to make are minimal.

I have read that many don't. I guess the lack of change in temperature would explain why. How far under ground is the gasoline stored?

[woodturner]

I have read that many don't. I guess the lack of change in temperature would explain why. How far under ground is the gasoline stored?

I guess I should qualify my comment - in the states where I have lived, the regulations require the pumps to adjust for temperature and pressure - but that may not be the case in every state.


The tanks are buried at least below the frost line. Not positive about the actual depth, but it seems like around here they are buried around 10 feet deep. Once you get below the frost line, the ground temperature is relatively stable year round (which is why geothermal heat pumps can work - you have a huge 50F or so mass from which to draw cool from or deposit excess heat)

[cabinetman]

It does save slight fuel, but probably not as much as if you were to fill up when its coldest out (early morning) because the gas is sold by volume, and when its coldest you will est the most amount of fuel per dollar.

And I bet if you are doing highway only driving that will cost you fuel economy in having to stop to refuel more often.

Your assessment is correct. Here is an explanation.
And, one more.
.

[woodturner]

Your assessment is correct.

No, it really doesn't make any difference, even though a few old, inaccurate, and unscientific articles making false claims can be found on the internet.

The second article says they pumped gas into a can, THEN measured temperature of the gas. Not surprisingly, they measure close to air temperature - since the gas is now in that environment. That is not a valid way to measure gasoline temperature in the tank or pump. A better way would be to put the thermometer in the stream of gas as you fill the can. That's one method the state inspector use to check the pump. They also pump one gallon into a temperature controlled and pressure stabilized vessel to accurately measure one gallon.

Here is a more reputable link dispelling the myths and adding that the cost difference would be insignificant anyway. That, and due to the "thermos bottle" effects of the storage tanks, the gas temperature is likely not lower in the morning anyway. This article is also a bit dated now - a lot of states now require ATC
http://www.snopes.com/inboxer/household/gastips.asp