Not just crosswind, but headwind!
Picture an aircraft flying 160 kt to 4 nm. In an hour there could be 160 nm of arrivals spaced at 3 nm giving approx. 53 arrivals in an hour if spacing is accurate and no wake turbulence requirement exists. Now put in a mere 10 kt headwind component (at 2000 ft) gives a ground speed of 150 kt and only 50 arrivals. 30 kt headwind aloft would suggest fewer than 44 per hour!
Throw in variations of spacing and a few A380s an hour and you can see why they "only" achieve scheduling of forty something and hour.
A single runway operation can reduce delays in wind by reducing the (non-vortex) spacing to take account of the extra time between arrivals: nil wind and 7 nm required between arrivals to facilitate a departure you should manage 23 arrivals and 23 departures. If the wind increases the space required reduces so the same runway utilisation could be achieved in a 35 kt wind and 5.5 nm spacing.
Last edited by Dan Dare; 5th Jun 2013 at 19:06.