If the TA is 5000' then the first available level is FL55 but could be FL60, but dependent on pressure. It would be unlikely for an atco to use 55 because after that it will be 65, 75, etc. and then to get back to normal levels you would have to use 90, 100 etc, so somewhere you will lose 500'. So std operating would be TA 5000' QNH 1000 hpa or below lowest FL70, QNH above 1000 hpa, lowest FL60. Technically if all a/c are on the same pressure setting either QFE, QNH, 1013, then separation would be easier unfortunately we have to use different pressure settings due aerodrome elevation (QFE, for GA and RAF), terrain and obstacle clearance (QNH) and FL for everyone who is safe from terrain. So wherever you are there are calculations to be done. (normally by the computer)
76mike, what was the qnh at the time. If the atco said 6000' i would question it, as the first descent to an altitude you must be given the qnh, its in the book. Also where were you at the time the descent was given, as I remember all the departure SID's go to FL60, and if you were on the transition downwind abeam the field FL70 is adequate for a 3 deg glide path descent profile (continuous, or as near as)
Last edited by ILS 119.5; 27th Feb 2013 at 12:36.