- Understanding aviation noise
- Airport environment
Depending on the orientation and intensity of the wind, it is necessary to have an alternative airport configuration in which aircraft use flight paths that are not as common but well-known and normal. Usually, in airports with one runway or two parallel runways, alternative configuration involves switching the roles of the runways. In other words, the one used for take-offs is used for landings and vice versa. These tracks are not for emergencies (which sometimes exist) or unexpected situations – they are normal flight paths with significant use (1% - 30%).
The airport combines three main factors (safety, environmental and capacity) to establish a preferred configuration and one or more non-preferred configuration. These configurations can be different for different time slots, for example, night-time periods.
In this video of Heathrow Airport, airport configurations are presented. Also, it explains the air traffic controllers' work in order to change the airport configuration when necessary.
In the case that the airport has more runways (or when the runways cross each other), the airport has different normal configuration possibilities. They are established by taking into account different factors: safety, environment and capacity. Here is the Minneapolis example which includes four runways.
Another four runways example is the Madrid-Barajas Airport. It uses four runways during the daytime – two of them for landing and two for take-off in two different configurations – North (preferred) and South (non-preferred).
During the night-time, the airport's capacity is restricted because of the noise. Two runways, which are placed far from the populated areas, are enough to cope with the traffic. One runway is used for landing and one for take-offs, and each of them can be used in two possible configurations (depending on the current wind).