Hi all,as I understand the Cruise and Flight Planning manual, I go with the planned amximum cruise altitude and expect to step climb to that FL.Well doing this for - say - an 4500 NM trip dependent on Planned Landing Weight gives the fuel amounts as depicted in the graph below. It shows, that you should fly FL 370 for PLW of 410 klbs while for PLW of 510 klbs you should proceed to 410 - if you can (did not check that) but for PLW higher that 520 klbs you should best remain on FL 310 (or even below) for the whole flight.That sounds strange to me and I wonder, what I may have missed.Thanks for any advice!http://forums.avsim.net/user_files/184491.jpg

Maybe you're missing the lower fuel flow rates at higher altitude, hard to tell what's missing without knowing your algorithm. Likewise, it could be you're missing the higher fuel flow rates at lower altitudes... can't tell.

Well, the numbers are directly from the table in the cruise and flightplanning manual.And as I understand it, they assume step climb to the given flight level (the x-axis).But I understand your answer as kind of a confirmation, that this is unexpected behaviour :-) Clemens Kuehn

We agree, your chart is an unexpected result.Based on a spreadsheet fuel planner that uses AOM chart data (see 744fuelplannerv1-1kg.zip) one should go to FL410 if projecting a PLW = 600,000 (NAM 4500). In this scenario, FlightPlan fuel at various levels are:310 210,000330 208,000350 206,000370 203,000390 201,000410 199,000...which is what you would expect.