Aerodrome Capacity Calculation
There are a lot of variables to factor in to your calculation to come up with a figure for your aerodrome capacity. If we assume, for the sake of simplicity, a fairly conservative final approach "spacing" of 5nm and an average speed over the final 5nm of 150kts, or 2.5nm per minute. You can see that in theory, with 5nm spacing, you can land 1 aircraft every 2 minutes or 30 aircraft in 1 hour. Assuming you depart as many aircraft, then your capacity is 60 movements per hour. So that's your very basic calculation. However, very few aerodromes manage to achieve this rate because of any number of variables.
Now the variables depending on your aerodrome - Runway occupancy time, number of rapid exit taxiways, traffic mix (heavy/medium/small) i.e. wake vortex considerations, number of aircraft stands, turn-around time, taxiway configuration, weather, controller ability etc. The list is inexhaustible.
Personal experience at many airports around the world leads me to say that if you are moving 40 aircraft an hour (20 arrivals and 20 departures) every hour then you will be doing pretty well.
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