johnomaha
Posts: 2
Joined: Mon Aug 29, 2005 3:38 am

Flight Plans And Fuel Forecasts

Mon Aug 29, 2005 3:49 am

Can anyone tell me how accurate airlines flight plans are in terms of fuel forecast at each waypoint and at destination? Is it right on or is it less/more.
Also, do airline pilots step climb according to the FMC or do they step climb according to the flight plan given to them from dispatch?

Thanks.

John
Omaha, NE
 
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TripleDelta
Crew
Posts: 1020
Joined: Sat Jul 17, 2004 4:13 pm

RE: Flight Plans And Fuel Forecasts

Mon Aug 29, 2005 4:30 am

Quoting Johnomaha (Thread starter):
Also, do airline pilots step climb according to the FMC or do they step climb according to the flight plan given to them from dispatch?

If I understood your question correctly, pilots step climb according to instructions received from ATC. In some cases, especially in smaller FIRs, ATC may give the a/c a level which will clear it from some future conflicting traffic, or stop its climb if there's traffic nearby - and, if possible, give the a/c the requested level once it is clear of traffic. Generally, the allocated level is dependent on traffic - if there's no traffic, and the FIR dimensions allow it, the a/c may be given only a few steps to speed things up.

Step climbs also depend on FIR sector boundaries. In Croatia for example, lower airspace ends at FL285 - therefore the a/c has to level out at FL280, switch to upper airspace frequency and be given further climb clearance there. Sometimes the two controllers can coordinate things out to allow the a/c an uninterrupted climb, but in heavy traffic this is the procedure most used.
No plane, no gain.
 
johnomaha
Posts: 2
Joined: Mon Aug 29, 2005 3:38 am

RE: Flight Plans And Fuel Forecasts

Mon Aug 29, 2005 4:37 am

I guess what I was wanting to know is information on the step climbs for heavy aircraft such as the 747-400. Do the pilots step climb to the optimal level using FMC information or do they go by the flight plan from dispatch.
 
CosmicCruiser
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Joined: Tue Feb 22, 2005 3:01 am

RE: Flight Plans And Fuel Forecasts

Mon Aug 29, 2005 4:54 am

First most of our fuel predictions are very accurate and most often within a couple hundred pounds.

For your second question..There is no real definitive answer. Most step climbs on the flight plan will be for wind and fuel burn considerations. A pilot may wish to try a different alt. if the winds are worse than forcasted or turbulence, wx, etc.

I think that's what you were looking for.
 
Sabenaboy
Posts: 183
Joined: Tue Feb 20, 2001 5:31 pm

RE: Flight Plans And Fuel Forecasts

Mon Aug 29, 2005 5:07 am

Hi,

Our flightplans are very accurate indeed. It's remarkable to see how the wind forecast aloft is spot on. The fuelprediction on our flightplan is very reliable. What stepclimbs are concerned: there we trust our FMC. He calculates the optimum FL, taking in account the temperatures aloft and the actual weight of the aircraft. The actual ZFW (zero fuel weight) can sometimes differ significantly from the ZFW that the flightplan was made for.
Therefore the step climbs in the flightplan can't always be trusted.

Regards,
Sabenaboy

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