Descend speeds!
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Join Date: Jan 2008
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Descend speeds!
Since a few months we started descending with the same speeds. (290/.84..B747-400ERF). According to the chief pilot it saves fuel.
Since the 747 operates in a wide range of weights I would say the best speed to descend with would be the best lift over drag speed and varies with weight and should be optimized every time.......right???? Opinions......anyone
Thx
Since the 747 operates in a wide range of weights I would say the best speed to descend with would be the best lift over drag speed and varies with weight and should be optimized every time.......right???? Opinions......anyone
Thx
Join Date: Aug 2008
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Not 747 rated. However, perhaps your CP is in possession of more data. Max range descent speeds are often too slow in practical terms, ATC asking for higher speeds or vectoring your slower a/c out of the way resulting in thrust during descent, too low on the profile or increased track miles. A faster fixed speed sounds like a good compromise.
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While the L/D max argument carries merit the problem is that one needs to have operational practices which fit into the real world. Slowing down to 220 (L/D max-ish in the plane I fly) while everyone else is going much faster isn't going to work. I think that, realistically, the best you could do is plan for a descent at idle with a .84/290/250 (or whichever figures work best) profile until the FAF as far as saving fuel and fitting into the big picture are concerned. Even then, this still isn't an option at many busy airports.
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Hi,
This is the sort of thing which management pilots come up with to justify their positions.
I think that Boeing/Airbus put a lot of effort into fuel saving/ efficiency and publish articles on it.
I would have thought that the FMC/FMGC would take care of calculating the best econ descent speed according to weight/ wind etc and the cost index.
If your company wishes to save fuel costs relative to other operating costs, could they not simply plan with a lower cost index?
This is what our company did, till we got in the way of everyone else, then they put it up a bit .
This is the sort of thing which management pilots come up with to justify their positions.
I think that Boeing/Airbus put a lot of effort into fuel saving/ efficiency and publish articles on it.
I would have thought that the FMC/FMGC would take care of calculating the best econ descent speed according to weight/ wind etc and the cost index.
If your company wishes to save fuel costs relative to other operating costs, could they not simply plan with a lower cost index?
This is what our company did, till we got in the way of everyone else, then they put it up a bit .
