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? |
Which aircraft? C172 or PA28?
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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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Originally Posted by FlyingStone
(Post 9786232)
Which aircraft? C172 or PA28?
Curtiss Jenny. |
Bill Bulfer's FMC guide should give you as detailed description as you could find:
Boeing 737 FMC Users Guide |
PFM, I believe.
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I think it has something to do with triangles.
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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!
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Thank you all!
Of course I know, 3x table is always there to backup :). I just wanted to understand in dept how it really works. |
It's kind of like SPICA fuel injection on older Alfa Romeos. It works, but nobody is real clear on how.
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1 Attachment(s)
Originally Posted by mustafagander
(Post 9787069)
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!
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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. |
Originally Posted by RAT 5
(Post 9788362)
One very important thing to remember; no 2 VITR.
VNAV does not update actual winds during descent. 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. |
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