Fuel Effeciency----

[B787E]

Hi All

I am currently working on a project which looks into comparing different a/c types flying to the same route. What would be the best way to calculate the fuel effeciency and find the most fuel effecient a/c type on that particular route.

I have been supplied with the data below as per each flight.

FBF 7400---fuel before flight
FUL 14365----fuel uplift
UT LITRES---units
SG 0.787---specific gravity
FOD 18000---fuel on dep
FOA 10400----fuel on arrival
PBO 6901---planned burn off
BLF 6.25-----blocks off
TF 6.32-----take off time
LNT 7.55---landing time
BLN 8.05---blocks on
PAT 1.22----planned air time
ZFW 107254---zero fuel weight

Please can you kindly advise me on the best way.

[Intruder]

What is your definition of fuel efficiency?

What is your payload?

Generally, you need fuel burned, payload, and distance.

[kwateow]

You have been supplied a lot of irrelevant and confusing data.

As Intruder said, what matters is how much fuel is used to carry a certain payload over a certain distance.

Normally the smallest plane which can fit in the target payload will win. Forget the 787 if you have 100 pax.

"Fuel Efficiency" is a notion dear to marketeers but not something which is easily measured in the industry.

[B787E]

Hi,

First of All, many thanks for your reply....

I would think that the best way to calculate it would be to work out the fuel burned and divide it by the zero fuel weight (Is the payload = to the zero fuel weight of the a/c or the total fuel on burned is included?).

Thus for this instance it would be:

18000(FOD)-10400(FOA) = 7600 LITRES OF FUEL BURNED.

7600/107254(ZFW) = 0.071 Litres of Fuel Burned per kg of weight.

[kwateow]

I'm not going to explain every step, but you need to think of this from a commercial, not technical, point of view.

Your suggestion would show a structurally very heavy aircraft (high OWE) as being efficient, even if it carried a small payload.

As we said, you need to know the payload. You need to junk the irrelevant info (the times..) and request what you really want. If they won't give you the payload then ask for the OWE and deduce it.

It looks like an A310 size plane, so guessing the data should not be so difficult. Happy hunting!

P.S. be careful not to confuse litres and kg.

[captjns]

What type of aircraft... C-152 or B747-400? What is are enroute winds, temps. shear, trop? CG also plays a big roll too.

[Intruder]

I would think that the best way to calculate it would be to work out the fuel burned and divide it by the zero fuel weight (Is the payload = to the zero fuel weight of the a/c or the total fuel on burned is included?).
Given the data you have, and the most common definition of efficiency -- (fuel burned) / (payload * distance) [kg/tonne-km or kg/passenger-km] -- the answer is NO on both counts.

First, to get fuel burned, you need fuel on board at startup AT THE ORIGIN and fuel on board at shutdown AT THE DESTINATION ("block fuel"). Fuel uplift will NOT give you an accurate figure, since it is a function of the fuel remaining after the PREVIOUS flight and the fuel required for the current flight.

Zero fuel weight includes the weight of the airplane AND the payload. Payload is the ONLY thing that "counts" in the commercial world.

[B787E]

You are correct it is an A310..

Does this value sound about right for the Airbus A310-325
83,100 kg.

[B787E]

So Then....

If the value is true in this case of 83,100kg. Then my payload should be =

(zfw)107254-83100 = 24,154 kg as the payload.

Does this seem about right?

[kwateow]

Looks good.

[B787E]

Thanks

I appreciate your input.

Does 32,700 kg sound reasonable for a 737-300.

[kwateow]

Hi. 32.7t is not heavy but is still reasonable.