Johnomaha From United States of America, joined Aug 2005, 2 posts, RR: 0 Posted (8 years 3 months 3 weeks 3 days 8 hours ago) and read 2225 times:
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?
TripleDelta From Croatia, joined Jul 2004, 1083 posts, RR: 7 Reply 1, posted (8 years 3 months 3 weeks 3 days 8 hours ago) and read 2215 times:
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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.
Johnomaha From United States of America, joined Aug 2005, 2 posts, RR: 0 Reply 2, posted (8 years 3 months 3 weeks 3 days 8 hours ago) and read 2213 times:
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 From United States of America, joined Feb 2005, 2254 posts, RR: 16 Reply 3, posted (8 years 3 months 3 weeks 3 days 7 hours ago) and read 2212 times:
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.
Sabenaboy From Belgium, joined Feb 2001, 187 posts, RR: 2 Reply 4, posted (8 years 3 months 3 weeks 3 days 7 hours ago) and read 2208 times:
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.