Additional fuel x fuel burn
Thread Starter
Joined: May 2004
Posts: 15
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From: sunny side up
Additional fuel x fuel burn
Gentlemen,
I have a question for B 777 pilots. If you choose to carry on extra fuel, is there any rule of thumb to calculate how much fuel you burn for this "additional weight"?
regards,
CortaVento
I have a question for B 777 pilots. If you choose to carry on extra fuel, is there any rule of thumb to calculate how much fuel you burn for this "additional weight"?
regards,
CortaVento
Joined: Sep 1999
Posts: 25
Likes: 0
From: Earth
4% is a good WAG. I've seen things range around 3-4% for a variety of Boeings & Airbus equip.
Really depends on how much fuel and how far. As the 2nd factor to compute, is a possible lower FL profile (2000' lower, etc).
Marc
Really depends on how much fuel and how far. As the 2nd factor to compute, is a possible lower FL profile (2000' lower, etc).
Marc
Joined: Jun 2004
Posts: 1,843
Likes: 0
From: Australia
Assuming that you're already operating the B777, why not take a look at the "Fuel adjustment per 1000 Kg change in Zero Fuel Weight" print-out on the Computerised Flight Plan. Divide that by the number of hours flight time, and you have a pretty good adjustment per 1000 Kg per Hour.
Hope that that helps.
Old Smokey
Hope that that helps.
Old Smokey
Joined: Jun 2004
Posts: 1,843
Likes: 0
From: Australia
CortaVento,
Further to my previous suggestion, some actual figures for a 5:30 flight just completed -
Additional fuel per 1000 Kg ZFW increase = 227 Kg
That's 4.3% per 1000 Kg per hour, pretty close to the earlier 4% suggestions.
Bear in mind that that's for a B777-200 with RR Trent 892 engines, it will vary for the B777-300 and for other engines. Bear in mind too, that the flight I just operated was a positioning flight at just 206.3 Tonnes TOW, and will obviously be higher at more typical operating weights, or on shorter sectors where Climb fuel forms a much larger proportion of the overall burn. (The opposite for longer sectors).
Also, for info, the adjustment for a 1000 Kg DECREASE in ZFW was 199 Kg, i.e. -3.75% / Tonne / Hour. All of which approximates to 4% "Ball Park".
Regards,
Old Smokey
Further to my previous suggestion, some actual figures for a 5:30 flight just completed -
Additional fuel per 1000 Kg ZFW increase = 227 Kg
That's 4.3% per 1000 Kg per hour, pretty close to the earlier 4% suggestions.
Bear in mind that that's for a B777-200 with RR Trent 892 engines, it will vary for the B777-300 and for other engines. Bear in mind too, that the flight I just operated was a positioning flight at just 206.3 Tonnes TOW, and will obviously be higher at more typical operating weights, or on shorter sectors where Climb fuel forms a much larger proportion of the overall burn. (The opposite for longer sectors).
Also, for info, the adjustment for a 1000 Kg DECREASE in ZFW was 199 Kg, i.e. -3.75% / Tonne / Hour. All of which approximates to 4% "Ball Park".
Regards,
Old Smokey
