Bagso the modelling was done by NATS before Geoff Hoon gave the go ahead a few years back. LHR arrivals already fly over Central London on a daily basis.
What about safety? It's a managed risk, the things our parents were OK with but we get hysterical about. The helicopter crash at Vauxhall was a media hysteria fest.
Heathrow won't be getting much more airspace. Also SIDS are not on top of each other, departures are sequenced so you get a Northbound then a straight ahead, then either a northbound or a southbound for maximum runway capacity. The key is not having two consecutive departures on the same SID or you need increased spacing. This is unlike most other UK airports where most SIDS only go south or east and occasionally west. A model to maximise departure runway use and capacity was part of the case put to the DfT at the time.
As for runway three only giving two years growth, not sure how you come to that. They need to build T6 to get real growth as T2 will see the central area maxed out again.
Last edited by Skipness One Echo; 27th Jan 2013 at 10:57.