But in an airport with accurate weather reporting, are you going to use tailwind data for ZERO wind conditions, and contaminated runway data for a dry runway?
Well, not
deliberately but I have, many times, set up for a tailwind or contaminated departure to find that the said tailwind or contaminant is not present when I get there. In that case I'm perfectly happy to go 'as is' because I'm pretty sure my aircraft performance will be better than planned in all respects. If that's OK, then I don't see a problem with using that data all the time if it gives you better figures (assuming the data is correct, of course). I don't think any safety margins are being eroded; if fact it would seem to be the opposite. If you can fit another bit of freight on to make more money for your company by using this technique, then I'm sure they'd be all for it.
Those last couple of sentences were part tongue-in-cheek, before anyone gets overly righteous.
Seriously, I can't see why the takeoff data using
a tailwind should give better weights but equally, if it's valid, I don't see why (in safety terms) it shouldn't be used for calm conditions. SOPs permitting, of course...