When flying in the IFR system it is a seamless flow from one piece of airspace to the other thanks to ATC, fuel calculations are all calculated on our flight plans but it's our responsibility to do a gross error check to keep the computer honest, so if the flight plan says Flight Time 0+57, on the A320 I expect to see a Fuel Burn of 2679 thereabouts (47 KGS x 57 min). Fuel burn with gear down is in my memory but all other figures must be looked up in the FCOM.
D.L.