Manual on how VNAV computes descent
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Manual on how VNAV computes descent
Hi all,
Just for my curiosity I'm looking for a detailed explaination on how VNAV computes the descent profile, like a step-by-step, I tried to find on the net but nothing. Do you have any link to a similar document?
Just for my curiosity I'm looking for a detailed explaination on how VNAV computes the descent profile, like a step-by-step, I tried to find on the net but nothing. Do you have any link to a similar document?
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I was looking for the B737, but I'm trying to understand deeply how a computer plans a descent path and which/how considers variables, so any aircraft would be welcomed...
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Bill Bulfer's FMC guide should give you as detailed description as you could find:
Boeing 737 FMC Users Guide
Boeing 737 FMC Users Guide
By whatever PFM it uses, it's not very good at it. You always need to know a few gates and see when it is off on its own not making sense. Three times table is your best friend!
. I just wanted to understand in dept how it really works.
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That doesn't work on high-traffic STARS. Case in point: Freedom Three STAR into KDCA from the west:
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One very important thing to remember; no 2 VITR.
VNAV does not update actual winds during descent. It has computed a descent profile with what you told it to expect, or from actual TOD wind reducing an unknown algo' to zero at ground. It needs monitoring and some help; at times.
2nd most important thing to remember is it needs monitoring at all times.
3rd most......same as 2nd!!
There in lies the most oft heard ????? from cadets. Sadly 3x anything, too often, requires a japanese brain to find an answer.
VNAV does not update actual winds during descent. It has computed a descent profile with what you told it to expect, or from actual TOD wind reducing an unknown algo' to zero at ground. It needs monitoring and some help; at times.
2nd most important thing to remember is it needs monitoring at all times.
3rd most......same as 2nd!!
There in lies the most oft heard ????? from cadets. Sadly 3x anything, too often, requires a japanese brain to find an answer.
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With a state-of-the-art VNAV FMS, if the pilot or the procedures places unacceptable constraints on VNAV, the FMS should provide a warning, and perhaps even a disconnect from VNAV.
