wiggy, spot on...........thanks
Contingency minimum on the A340 is 700kg.......enough for 5, maybe 6 minutes.
Ok, maybe I exaggerated a bit. Its not typical, but I have seen it several times and is 5 or 6 minutes not less than 5.
Another interesting point is that there is more of a problem on short flights due to lower contingency and there is less time to take fuel conservation steps en-route.