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Case 2:A 60 knot aircraft following a 60 knot aircraft. Is this the same as Case 1? Not quite, the setup is the same, three NM required separation at the FAF and down final to the threshold. When number one touches down, number two, must be 3 NM back doing one mile per minute (60 knots) which takes three minutes to touch down. If we had a steady stream of 60 knot aircraft with three minutes between arrivals our capacity drops to 20 operations per hour. A significant decrease in capacity from case one will result from a change in aircraft performance. Case 3:A 180 knot aircraft following a 60 knot aircraft. The 3 NM separation required at the threshold becomes critical. The faster aircraft, in number two position, must be positioned 15NM behind when number one at 60 Knots crosses the FAF. Six minutes later number one aircraft will touch down (six NM final at one NM per minute) and number two aircraft will be three NM behind. Having covered the 15 miles to the FAF and three NM of the final (a total of18 NM) during this same six minute period (three NMI per minute), number two will touch down one minute behind number one.Case 4:A 60 knot aircraft following a 180 knot aircraft. This time separation at the FAF is critical. Number two must be 3 NM behind when number one crosses the FAF. Two minutes later number one touches down, having covered the six NM on the final approach at three NMper minute. But number two is still one mile short of the FAF and does not touch down until seven minutes after number one. Seven minutes between arrivals is not good for capacity. Explains the controller's attitude when you arrive at a busy commercial airport in your Warrior?These scenarios assumed away many of the complexities associated with capacity calculations. To get a better understanding of the influences of the many variables which must be considered in an actual IFR situation, develop some scenarios of your own. Change the lengthof the common approach, vary the separation between aircraft to allow for wake turbulence effect and insert a wider range of airspeeds for the arriving aircraft.
5-8 The diagram and tables, which we will use for runway capacity calculations, have been developed on the basis of random arrivals of the forecast aircraft, forecast meteorological conditions and various runway configurations. Mathematical models were prepared to provide initial estimates and the data was modified and verified on the basis of empirical data. Although these tables and figures provided by FAA AC 150-5060-5 are very useful in estimating capacity of runway configurations and other airport components they cannot consider every eventuality. Meteorological Conditions Runway capacity is highest during good weather when visibility is at its best and VFR are in effect. When visibility and ceilings are below specific minimums (3 miles visibility and 1,000 foot ceiling), IFR are imposed resulting in greater separations between aircraft and longer runway occupancy times. Meteorological factors