dilan12345
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How to calculate how much fuel an A320 needs for the whole flight.

Wed Mar 08, 2017 8:22 pm

Hi there, I am interested to know how to calculate how much fuel a aircraft such as an A320 needs to have for a specific distance. For e.g. If the distance is 163miles=141.643nm. I am working on a project and want to see how much fuel is used for a domestic flight within the UK, but I dont know what the take off weight should be as I do not know how much fuel should be used. The time it takes should be around 1hour. Any help is appreciate.

Thanks
 
Woodreau
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Wed Mar 08, 2017 9:01 pm

Fuel burn really depends on how much payload is on board and what altitude, the lighter the plane, the less fuel is required to fly the same distance compared to a heavier plane.
But generally, a 320 burns somewhere between 5000-5800lbs/hr.

My airline does not dispatch any aircraft with less than 10,000lbs. So for a 1 hour flight the fuel required for the 1 hour flight plus fuel reserve will mostly likely be less than 10,000lbs, so it will be dispatched with 10,000lbs of fuel. (example flight between Las Vegas to San Diego or Los Angeles)
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Starlionblue
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Thu Mar 09, 2017 1:22 am

Fuel consists of:
- Taxi fuel. Normally a fixed number, but can vary at some airports e.g. LHR.
- Trip fuel. Including departure and arrival maneuvering, i.e. SID and STAR.
- Contingency. For a short distances usually 5% of trip fuel.
- Mandatory fuel. Added to satisfy a constraint, either a requirement like Rec Extra + Alternate + Mandatory must be at least equal to Reserve OR due to fuel required in case of a given emergency from an enroute critical point exceeding the normal calculated load.
- Alternate fuel. From the missed approach point at destination to landing at the alternate.
- Reserve. 30 minutes at holding speed at 1500ft above alternate aerodrome level, based on the weight on arrival at alternate.
- Rec Extra. Not legally required but added if dispatch has information about probable delays or the like.

There are many online tools: http://fuelplanner.com/index.php
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zeke
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Thu Mar 09, 2017 5:05 pm

The A320 FCOM has a table in it used for gross error checks of flight plans.

If you want to calculate it from first principles you actually work backwards.

Hold 1500 ft over alternate airport
Missed apprpach
Approach
Fuel to alternate
Missed approach
Approach
Descent fuel
Cruise fuel
Climb fuel
Takeoff fuel
Contingency fuel
Taxi fuel

At each step you know how heavy the aircraft is and you add the fuel from the previous segment to build up the total fuel required.
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dilan12345
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Thu Mar 09, 2017 6:35 pm

Woodreau wrote:
Fuel burn really depends on how much payload is on board and what altitude, the lighter the plane, the less fuel is required to fly the same distance compared to a heavier plane.
But generally, a 320 burns somewhere between 5000-5800lbs/hr.

My airline does not dispatch any aircraft with less than 10,000lbs. So for a 1 hour flight the fuel required for the 1 hour flight plus fuel reserve will mostly likely be less than 10,000lbs, so it will be dispatched with 10,000lbs of fuel. (example flight between Las Vegas to San Diego or Los Angeles)


I've come across this https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft

If you scroll down it tells you roughly how much fuel is burnt per km for a variety of aircrafts and a variety of ranges. How accurate would you say this is to use?
 
Flighty
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Thu Mar 09, 2017 7:28 pm

Generally an A320 will burn around 900 gallons per hour in dispatch. In rougher terms than above, I can say there is a climb component and a cruise component. Every flight has near identical taxi/climb, so the first hour has a defined fuel burn quantity. For longer flights you add to the cruise time.

So your function would be 1000 gal per departure/landing, which every flight has, plus 750 gal per hour of cruise time. Or something like that.
 
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longhauler
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Fri Mar 10, 2017 2:28 pm

Just out of interest, I pulled out a flight plan for one of our flights from YOW to YYZ. This is 197 nms, great circle, with a flight plan distance of 214 nms. The weight of 144 passengers is accounted for, out of 146 seats, flying time is 43 minutes.

Burn to YYZ from YOW is 1900 Kgs.
Reserve (30 minutes as required by CARS) is 1100 Kgs.
Contingency fuel (5 minutes, added by airline policy) is 200 Kgs.
Alternate is YHM, fuel is 600 Kgs.
Taxi fuel is increased to 500 Kgs, to reflect de-icing in YOW. Normally it is 200 Kgs.
Additional 500 Kgs is added for "ATC" fuel, to reflect possible delays in YYZ.

Total dispatch fuel is 4800 Kgs.

However ... actual legal minimum fuel at take-off would be 3700 Kgs. (Burn, Reserve, Cont and Alternate)

BTW, this is an A320-200 with -A engines.
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greg85
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Fri Mar 10, 2017 4:43 pm

5 and a bit tonnes will do for London to Glasgow or Edinburgh. You'll probably burn between 2 and a half and 3 depending on all the variables.
 
dilan12345
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Fri Mar 10, 2017 5:32 pm

longhauler wrote:
Just out of interest, I pulled out a flight plan for one of our flights from YOW to YYZ. This is 197 nms, great circle, with a flight plan distance of 214 nms. The weight of 144 passengers is accounted for, out of 146 seats, flying time is 43 minutes.

Burn to YYZ from YOW is 1900 Kgs.
Reserve (30 minutes as required by CARS) is 1100 Kgs.
Contingency fuel (5 minutes, added by airline policy) is 200 Kgs.
Alternate is YHM, fuel is 600 Kgs.
Taxi fuel is increased to 500 Kgs, to reflect de-icing in YOW. Normally it is 200 Kgs.
Additional 500 Kgs is added for "ATC" fuel, to reflect possible delays in YYZ.

Total dispatch fuel is 4800 Kgs.

However ... actual legal minimum fuel at take-off would be 3700 Kgs. (Burn, Reserve, Cont and Alternate)

BTW, this is an A320-200 with -A engines.


Thanks for this information. My question is, how are these numbers decided? Do you know how they are calculated for each specific flight?
 
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zeke
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Fri Mar 10, 2017 5:56 pm

There is a blue book, performance book produced by the manufacturer that either the airline or the flight planning company will have made as computer model for the aircraft type. It all is related to weight, see this chart how much fuel is required to hold for 30 minutes at 50 tonnes would be 1210 kg (this is for a 737).

Image

The reserve fuel is 30 minutes at 1500 ft at the alternate, finishing at the ZFW. Add that 1210 kg of reserve fuel to ZFW gives you the weight the aircraft ended the previous segment, and it is just an iterative process from there all the way back to when the aircraft was parked at the gate for departure. Each segment the aircraft gets heavier, and that results in extra fuel burnt just to carry that weight of fuel.

Image
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dilan12345
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Fri Mar 10, 2017 6:12 pm

https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft --how accurate would you guys say this link is then? it gives the kg of fuel burnt per km, and doesnt seem to match some of the numbers I have heard before
 
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longhauler
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Fri Mar 10, 2017 8:57 pm

dilan12345 wrote:
Thanks for this information. My question is, how are these numbers decided? Do you know how they are calculated for each specific flight?

Most airlines use very advanced flight planning software. The Flight Dispatcher compiles the operational flight plan, of which a large part is the Fuel Plan. The fuel estimates are very very accurate, as actual and forecast winds are used as well as each particular aircraft in the fleet has "fuel factors" as a comparison to ideal fuel consumption. As a result, by the time the parking brake is set at the destination gate, fuel use is usually with a few kilos of the estimate!!

Notwithstanding, after the flight plan and winds are uploaded into the FMGC of the aircraft, a comparison is made ... just in case.

Also, to add to the estimation, each city pair fuel use as a comparison to the fuel plan is plotted and recorded. So factors like day of the week and time of day are also taken into account. It has become a very exact science.

For example, the numbers I quoted above would be different for the flight an hour later, also an A320-200. And those would be different from the next flight, etc. They wouldn't differ by much, but it would certainly show that more than just "gut feeling" is put into the planning!
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BawliBooch
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Sat Mar 11, 2017 7:15 am

Maybe not an international practice, but some airlines have minimum fuel on departure criteria - I think 5 tons or so for A320 family.
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CXfirst
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Sat Mar 11, 2017 2:40 pm

Have a look at this, if you are interested in how things are calculated by hand.

https://publicapps.caa.co.uk/docs/33/CAP697.pdf

This is the data booklet that question from the ATPL Flight Planning exam is taken from in the UK. It isn't based on the A320, but rather a generic aircraft.

From page 18, you have the detailed medium range jet fuel planning section. There are instructions on how to use the tables, but I won't blame you for not understanding completely. Starts with en route climb, and then goes into the cruise burn (page 25 and beyond). It has different figures for different altitudes.

The gist of it is to choose a given altitude at a cruise configuration, and choose your aircraft weight. Find out how many Still Air Miles you will fly (SAM), Go to your weight, find the nautical mile figure, subtract how many miles you will fly, find the new corresponding nautical mile figure, and that will be your new weight. The weight difference is the fuel burn.

In reality, these figures are computerized now, and things are calculated backwards. The above method requires a starting weight, which requires some amount of fuel (which you haven't actually calculated the amount for yet).

The tables give a good indication on how fuel burn differs at different altitudes and at different aircraft weights.

-CXfirst
 
dilan12345
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Mon Mar 13, 2017 9:35 pm

longhauler wrote:
Just out of interest, I pulled out a flight plan for one of our flights from YOW to YYZ. This is 197 nms, great circle, with a flight plan distance of 214 nms. The weight of 144 passengers is accounted for, out of 146 seats, flying time is 43 minutes.

Burn to YYZ from YOW is 1900 Kgs.
Reserve (30 minutes as required by CARS) is 1100 Kgs.
Contingency fuel (5 minutes, added by airline policy) is 200 Kgs.
Alternate is YHM, fuel is 600 Kgs.
Taxi fuel is increased to 500 Kgs, to reflect de-icing in YOW. Normally it is 200 Kgs.
Additional 500 Kgs is added for "ATC" fuel, to reflect possible delays in YYZ.

Total dispatch fuel is 4800 Kgs.

However ... actual legal minimum fuel at take-off would be 3700 Kgs. (Burn, Reserve, Cont and Alternate)

BTW, this is an A320-200 with -A engines.


Do you happen to have a picture of the flight plan on the actual piece of paper or a print screen, just so I can use it as a reference in dissertation please?

Dilan
 
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longhauler
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Mon Mar 13, 2017 10:17 pm

dilan12345 wrote:
Do you happen to have a picture of the flight plan on the actual piece of paper or a print screen, just so I can use it as a reference in dissertation please?
Dilan

I wish I could, but as this is proprietary information from a flight planning computer, I can't give anything other than what can be garnered in the public domain. As I fly for a large corporation, I work under a very strict code of conduct with regard to social media.

I am guessing, one could hire one of the flight planning companies on line, but it's likely very expensive.

For the record ... the Operational Flight Plan in this case, is 26 pages long!
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
VS11
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Re: How to calculate how much fuel an A320 needs for the whole flight.

Wed Mar 15, 2017 3:18 am

dilan12345 wrote:

Do you happen to have a picture of the flight plan on the actual piece of paper or a print screen, just so I can use it as a reference in dissertation please?

Dilan


You can use this website to generate a flight plan: https://skyvector.com/

It probably will not be the exact plan longhauler used but you can use the logic/steps to recalculate based on the plan you end up.

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