Preferential Runway System (PRS)
Decision maker: Belgian Civil Aviation Authority (BCAA) and Federal Minister for Transport
The Air Navigation Service Provider (ANSP) skeyes carries out the decisions from the BCAA and the Minister for Transport.
Brussels Airport has three runways that can be used in both directions. For environmental reasons, the federal authorities have defined a Preferential Runway System (PRS). This system provides the runways to be used by skeyes according to the time of day and the day of the week when certain conditions are met.
Why is PRS not always used?
Air traffic safety is skeyes’ top priority. This is why non-preferential runways must sometimes be used. If, for example, the tailwind or crosswind becomes too strong, a runway configuration change is needed.
Weather, and in particular wind, is a major parameter in selecting a runway configuration at any airport in the world. This is done for ensuring safety of the aircraft, its passengers and the populations overflown.
When tailwind exceeds 7 knots (gusts included) or crosswind exceeds 20 knots (gusts included), aircraft can no longer take off or land on the preferential runways (25R/L) for obvious safety reasons:
- in strong easterly or north easterly winds, Air traffic controllers must then activate an alternative configuration (runways 07L/R and/or 01);
- in strong southerly winds, runway 19 will be put into service.
In all these cases, non-preferential runways are used to ensure the safety of air traffic. For air safety reasons, wind direction and intensity are the main causes of the use of non-preferential runways, but there are others: weather conditions at high altitudes, the unavailability of some runways or taxiways due to maintenance work or the intensity of air traffic.
When does skeyes initiate a runway change?
A runway change is a complex operation that takes at least 30 minutes. Air traffic controllers must redirect the flow of aircraft – both in the air and on the ground. It is therefore necessary to plan and anticipate. skeyes decisions are based on weather forecasts updated several times a day.
In addition, a runway change cannot take place during peak traffic periods: this operation would be too complex and dangerous given the saturation of traffic in the higher layers of the airspace. It is therefore possible that a runway change may occur two hours before wind conditions become truly unfavourable.
If it is necessary to switch to a configuration that allows fewer aircraft to land over the same period of time, air traffic flow management measures must be taken in advance to avoid a congestion in the air to avoid that aircraft have to remain in the sky and fly into holding patterns.
In this case, the departure of some flights could be delayed from their origin to enable the most efficient possible flow management in the approach area of Brussels Airport.
What does Preferential Runway System (PRS) look like?
Here are the different PRS configurations as defined by the Belgian Civil Aviation Authority (BCAA) and Federal Minister for Transport:
PRS configurations on weekdays
Monday-Friday (06:00-22:59)
- Departures: runway 25R
- Arrivals: runways 25L and 25R
Monday-Friday (23:00-05:59)
- Departures: runways 25R and 19
- Arrivals: runways 25L and 25R
PRS configurations during weekends
Saturday (06:00-15:59) & Sunday (16:00-22:59)
- Departures: runway 25R
- Arrivals: runways 25L and 25R
Saturday (16:00-22:59) & Sunday (06:00-15:59)
- Departures: runways 25R and 19
- Arrivals: runways 25L and 25R
PRS configurations on weekend nights (single runway operations)
Friday night (23:00-05:59)
- runway 25R
Saturday night (23:00-05:59)
- runway 25L
Sunday night (23:00-05:59)
- runway 19