- Understanding aviation noise
- Airport environment
Depending on the orientation and strenght 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 thereby creating two different operational modes. In other words, the runway primarily 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 but minor 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. It also explains the air traffic controllers' work in order to change the airport configuration when necessary.
In the case that the airport has more than one runway (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 to reduce noise exposure. 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 direction).