hi Sotiris,
actually, i think its possible
I calculated the consumption rate to be 32 000lbs / hour through this:
1) Mach 0.85 at 40 000ft will be 487 Kts according to
this speed converter, 487kts being 487nm/hour.
2) Fuel capacity of the A380 is 81 890 US gallons, and according to MSFS, 1 US gallon = 6.7 lbs hence, 548 663 lbs of fuel
3) Taking the range of the A380 (8200nm) divided by its speed (not taking into account windspeed) of 487nm/hr, i arrive at 16 hours and 48 mins maximum flight time, reeeaaaallll close :]
4) fuel capacity divided by max flight time, 548 663lbs / 16.8 hours = 32 658 lbs / hr (i took 16.8 hrs to be 17 in my original calculation and rounded off to the nearest thousandth, hence i got 32 000lbs/hour)
and since my test flights got results ranging from 33 000lbs/hr to 28 000lbs/hr depending on weight, it should be possible to have a 16 hour flight
BUT, is this method of calculation reliable? i've seen many people suggesting this to those who ask about rate of fuel consumption :s