747-400 cheat sheet usage for V-speed and derate calcs

[downunderscouser]

hi,

I am trying to understand the 747 takeoff data cheat sheet and am somewhat unsure of it's usage.

The cheat sheet is from b747400.com, http://b747400.com/pdf/told.pdf

I understand much of the fields in the first page but on the derate and V speed table on page 2 I am unsure of the usage of the first section with the rows:

WT-->
FIELD
CLIMB
OBST

WT is obvious but I am unsure what the figures for FIELD, CLIMB and OBST represent.

Can someone give me a run down on how to make the most of this sheet?

I am using this sheet for practice on the PMDG 747-400X on FSX using real world procedures.

Thanks in advance

Andy

[MarkerInbound]

You need the runway analysis charts. You take the adjustment for the derate from the perforance numbers to see if you can use the derate. If you are climb limited, subtract the climb number and if your actual weight is under that figure, you can use the derate. You should also check the field and obst numbers because they may now have become limiting.

[downunderscouser]

anywhere online I can find those from?

[Pontius]

Without actually looking at the website (oh, come on, I can't. Really!). The figures will represent the limiting Take-off weights for that runway. You'll either be limited by field length (TORA, TODA etc), climb performance (Net Path Gradients) or obstacles (if any exist for that runway). The lower figure will then be used for working out the rest of your take-off performance figures, including derates etc.

[MarkerInbound]

You want to use real world proceedures, send lots of money to Denver for runway analysis. (Maybe Frankfurt on your side of the world.) You could work some out in a spare afternoon with an AFM, that's why the airlines use the computerized numbers.