%MAC's effect on Fuelflow

[PiperChauffeur]

When I did dispatch, I was advised to optimize the trim for most favorable fuelflow (eg 24.5% for KLM 737-400, although it probably dosn't have a mesurable effect on very short flts).
Now, in ATPL training, my instructer tells me that they (767 drivers) don't take that into account, its not in their AFMs. I would think, especially on longhaul AC, that the trim shold have a rather big effect on fuelflow.
Does anyone know how large the effect is??

rgds
PC

[quid]

I don't remember just what the figures were, but a few years ago we made a policy that all a/c should be loaded in the aft 20% of the trim range. I seem to remember savings of about 3% or so. Very signifigant if your fuel bill is many millions each year.

Makes little difference on short hauls, and I don't think the a/c type would have a major bearing. All a/c fly by the rules of aerodynamics.