It's actually more to do with having much higher requirements in terms of minimum visibility and cloud base than other airfields due to the steep nature of the approach. Your average normal approach requires about 5-600m visibility but LCY requires 1000-1300m , you also need to be able to see sufficient about 2-300ft higher up . So it doesn't need to be that bad to be unable to make an approach. When the visibility and cloud base drop to ear the minimums LCY impose a flow rate of arrivals which can be really really low (2 or 3 an hour) at which point many airlines cancel because the delays become pretty large. ( I've seen 4hr slot delays!)
Last edited by towser; 21st Nov 2012 at 12:13.