Qantas744er
Topic Author
Posts: 1189
Joined: Sat Jun 04, 2005 4:36 am

Boeing 747-400 Initial Fuel Burn?

Mon Feb 27, 2006 6:34 am

Hey, I have a question when pilots plan a flight on the plane lets say at a MTOW of 834.300 Lbs the pilots decide that at cruise the initial Flight level will be FL 340. and the fuel reserve for that initial cruise will be 19.000 pounds.
But then after hours inflight the flight level will be FL370 but then the fuel reserve will ofcourse increase, so how do the pilots not end up to take away to much fuel at the takeoff?

Cheers leo
You live and you die, by the FMA
 
User avatar
CCA
Posts: 778
Joined: Wed Oct 02, 2002 7:29 pm

RE: Boeing 747-400 Initial Fuel Burn?

Mon Feb 27, 2006 7:06 am

A very simplified explanation, depending on each airline basically computers work out how much fuel to take they know the engine fuel burn rate for each particular A/C the winds are entered and the departure, destination and alternate airfields, finally the ZFW is entered.

It's then basically worked out backwards ie the A/C is on the ground at it's alternate with 30 Min's of fuel on board at the estimated ZFW, this is a start point as the A/C is a known weight. Fuel is then added as the A/C goes backwards from the landing at the alternate backwards to the destination where a Go around was performed (5% contingency may be added to the diversion fuel) this point is also the diversion fuel requirement or reserve/alternate fuel which is then basically fixed. Fuel then continues to be added as the A/C continues backward through the descent to destination from whatever the optimum altitude is at that weight and wind, then backwards through the cruise and step climbs, and finally the climb from take off from the departure airfield, where another 5% contingency is added.

So during flight contingency fuel reduces and reserve/alternate fuel effectively remains fixed.

So now you know how much fuel you need to get there, but this fuel figure may be adjusted due to weather or change in ZFW at the Captains discretion, which there are various ways to account for the new fuel burn without getting a new flight plan.

Also it can become a fine balance between the ZFW entered resulting in a MTOW flightplan, it will be able to produce the MZFW on the information entered.

[Edited 2006-02-26 23:24:46]
P1 in A330, A340, A346, B742, B744, B748.

Who is online

Users browsing this forum: No registered users and 3 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos