Fuel Efficiency

[Ozcrew70]

Hi All,

I'm posting hoping to get some advice / assistance from people a lot smarter than I am regarding a project I'm undertaking related to Optimisation of potable water upload and its effect on possible fuel savings.

I will firstly apologise if the information I provide is in any way incorrect or inadequate. I work as Cabin Crew and certainly do not claim to be anything remotely close to an expert related to this area. In short I was just hoping to get some assistance / advice from here to see whether completing and submitting the project is a worthwhile exercise of not. Hence the reason I post here seeking assistance.

Effectively I have reviewed a large number of our flights and feel my current company has the opportunity to safely reduce carried potable water and thus weight / fuel requirements.

Relevant Flight Information:

1. 28 flights per week / Long Haul (for average sake say 14 hours per flight).

2. B777 aircraft.

3. Fuel cost (for conversion below - 0.82 per litre).

H20 related Information:

The recommendation that will be made based on the collected data is that effectively 288L of potable water per flight can be safely removed.

What I was hoping to obtain some assistance on is obtaining some figures on:

1. An idea of how much fuel (L) could potentially be saved per annum by reducing each flight by 288L.

2. A (rough) monetary figure that could potentially be saved on fuel based on this weight reduction & at a purchase price of 0.82 per litre.

3. How many ??? (pounds) of C02 emissions could result.

Many thanks in advance to anyone who can possibly provide any advice - its greatly appreciated.

Cheers

[OVC008]

Hey Oz,

You may be wanting to talk with some dispatcher guy.

It wont be an easy calculation unless we have the manuals of the aircraft, to calculate the fuel burn.

On the other hand, you can try to find on the web something like a flight planner, where you can put an average weight, and calculate for the same flight, less 288 kg, or say, less 188, if that's where you're trying to go.

Good luck.

[toffeez]

You would save approx 0.1% of fuel burn.

Your company can tell you the average fuel burn on a 14h sector.

The cost calculation is then child's play.

120000 to 150000 p.a. saving wouldn't surprise me.

[Jet Man]

Go and ask your pilots.

The delta burn on those sectors is usually about 450kg for every 1000kg loaded.

Therefore the fuel saving per sector would be approx 130kg which is 160 litres.

Is the 0.82 you mention the purchase price or the SG of the fuel.

[airbus_driver319]

My company reduced water uplift for exactly this reason, it works for us.

[bigduke6]

You will save fuel weight of at least 25% of the weight of the water not being carried on longhaul (on B744, I would think B777 and A380 would be similar). Use weigh, not liters/volume.

From flight plan: SYD-PVG (10:08 flight time) saving of 29.6% of the weight not carried.

Longer flight of 14:14 hours shows 39.6%

[Ozcrew70]

Hi All,

Firstly thank you to each of you for taking the time to comment and giving me (some) direction.

Just some further information that may or may not be relevant to any of you who may be able to contribute some more or anyone else reading.

1. The aircraft is a 777 300ER.

2. As mentioned I undertook a "snapshot" review of 56 flights which equates to 2 weeks worth on sectors between AUS-LAX (Hence the average-ish 14hr flight time based on departures / return to the 3 major east coast cities). My thought (hope) was to project these figures over a full year of flights.

3. As mentioned the main aspect being studied is potable water which (on average) we depart with 1288L and land with in excess of 600L on average. The recommendation to be presented is to (conservatively) reduce this to a (rounded figure) of 1000L at departure. ie. so effectively LOSE 300L (288) per sector.

4. The aircraft is configured over 3 cabins and accommodates 361 guests. The average guest numbers over the 56 flights studied was 300.

5. Re fuel cost - my apologies I originally cited 0.82/litre. This should be 0.86AUD/litre which is a nominal figure for the month of may.

Again guys if any one has any further "rough" ideas (not looking for exact $$ figures here) on how much this is likely to save per flight / week / year - any info would be appreciated.

[Ozcrew70]

Jetman,

Just to clarify - as such......

160L fuel x 0.86AUD/ litre = $138 per sector saved.

28 flights a week --> 1456 per year x $138

Equals an annual saving of slightly over $200K ($200928).

[toffeez]

A good rule of thumb which is valid for pax jets of most sizes and efficiency levels is Z% change in aircraft weight translates into 0.9 x Z% change in fuel burn.

I still think 160 litres saved is a bit too high in this case.

[Jet Man]

Maybe toffeez.

I was only taking the information straight from the flight plans we use on those sectors!

[TSIO540]

How much water will you need to continue to the destination if due to a tech diversion you end up in a port without potable water?

[woodja51]

.. many operators reduce water carried..have you also looked at removing the duty free carts...that is also an area ( for cabin crew) weight can be saved. especially out of Australia where you can leave it at DFS...
also to ease calculations look at the price of fuel per tonne.. all plans have a delta burn per delta tonne of ZFW - at current prices it is 835 USD per tonne of fuel. so if you carried 300 kg less water you would save about 250 dollars per sector. maybe. .. but would your company also reduce the fuel surcharge the same percentage?? I expect not. it makes it hard to justify fuel surcharges I if you find ways to save it.. food for thought only - every tonne of fuel you save also saves four tonnes of co2 emissions as well.
😄

[Ozcrew70]

Thanks again all for your comments and assistance.

Woodja - we don't carry duty free but take on board your suggestions of other potential removal options.

TSIO - my "theory" (Which may be naïve) is that between AUS-LAX the options for a diversion are relatively limited and indeed all would seem likely to have potable water available? (Feel free to correct me on this).

[misd-agin]

Checked fuel burns. Approx. 2.5% additional fuel burn per hour for each additional pound carried.

Example = 10 hr flight. You'd burn 25% of the additional weight in fuel.
288L is approx. 90 gallons. Eight lbs per gallon = 720 lbs.
25% of 720 lbs = 180 lbs.
180 lbs x $0.45(approx. fuel cost per pound) = $81.

[Linktrained]

Misd-agin

That 2.5% per hour extra fuel burn for extra weight is very close to the 3% which applied on a B707-320, with its less efficient engines. And airframe ?
LT