Design Trade Offs

The airspace design process is an interminable process of trade-offs! For example, if the runway usage at an airport is over 75% use of one runway, it is general practice to make maximum efficiency design for that 75% and with controllers accepting to have to work a little harder for 25% of the time when the airspace design is not as easy to operate.  Often, this kind of trade-off has to do with where entry points are placed into the airspace.  In airports where the same amount of traffic arrives from every entry point, it is usually reasonably straightforward to create a mirror design.  But when 80% of the traffic enters the terminal from one direction (typically, this happens in terminal areas at Europe’s geographic periphery), a switch of runways to the less favourable directly invariably results in controllers having to work harder often because there are more cross overs and the crossing points cannot be as ideally designed.  Sometimes the lateral placement of routes will be traded-off (put in a less favourable place) so as to ensure a better vertical profile. These decisions and discussions rely completely on a sound team approach and the involvement of the right stakeholders in the design of routes, holds and sectors.