There are times when the wind can be critical and the only information available is that which is reported via the tower. In this aircraft a 5 kt TW can equate to a 12 tonne or more difference in take off weight from a given runway. That is a lot of pax or freight. Of course, as has been pointed out, the lighter winds can vary considerably along the length of the runway or even at a given point over a period of time ie. From pushback to TO roll. A prudent operator will always factor in the worst case ie. If the wind is reported as Light and variable at 5 kts then TO performance would be calculated as a 5 kt tailwind. The only redeeming feature here is that the winds used in the TO tables are based on 150% of the reported tailwind. So if a table is entered with a 5 knot tailwind then the weight, or distance extracted will be for an actual 7.5 kts tailwind. This gives a small margin of safety. I imagine curvature of the earth would come into an A343's takeoff performance wouldn't it? :) Those 4 hair dryers aren't up to much.CheersSteve

Hit the nail on the head Steve. Whne the winds are reported as calm in the A343, beware!!! He does say he prfers tropical takeoffs, where the earth is more curved.PS I always call it the plane with 5 APU's, but i guess 4 hair dryers and an APU works too.Paul