CREDOS : Crosswind-Reduced Separations for Departure Operations

Air Traffic Management research suggested that reducing wake turbulence separation minima – while maintaining levels of safety – could address one of the major challenges facing airport capacity today.  CREDOS* took the research efforts world-wide by uniting European and US wake vortex research.

In reply to the rising numbers of flights and issues of how to deal with the increased traffic and delays that this may cause, in 2006 the EUROCONTROL Experimental Centre (EEC) launched CREDOS, a research Project of the 6th Framework Programme of the European Commission (in cooperation with 11 partners including universities, national research centres and industry partners). Thanks to EUROCONTROL’s memorandum of cooperation with the Federal Aviation Authority (FAA), the latter together with the National Aeronautics and Space Administration (NASA) of the United States could be part of this European Research Project. A major first in those days!


“The CREDOS project was at its time, unique, in that it united European and US wake vortex research efforts. One of the major outcomes was the first world-wide statistically meaningful data collection of vortices shed by heavy aircraft after lift-off”, adds Marie-Thérèse Meloni, the Project Leader of CREDOS.

The research was based on the minimal separation required between aircraft during landing or taking-off. This separation is vital due to wake vortex turbulence – a dangerous air-flow phenomenon. CREDOS’s aim was to study crosswind–reduced separation for departure operations and possibly update the rules, first set in the 1970s, on how large this separation should be, taking into consideration a wider range of factors such as wake vortex behaviour and meteorological conditions.

Emphasis is to be put on the fact that CREDOS is not expected to add strategic capacity in terms of scheduled slots. The major benefits are to be achieved when a single segregated runway is used for departing traffic and during peak periods or when queuing creates delays of departing traffic at the runway. An actual change in the declared runway capacity may be published only if a longer period of stable crosswind conditions is forecast.


The CREDOS end-user portal is still a highly appreciated tool to understand the impact of wake vortices for Pilots and Air Traffic Controllers.”

CREDOS ended in 2009, giving way to other projects such as:

  • RECAT-EU, which safely increases airport capacity by redefining wake turbulence categories and their associated separation minima;
  • Pair-Wise Separation, which developed a static separation matrix of distance and time for both arrivals and departures;
  • Dynamic Pair-Wise Separation, which allows for the dynamic adjustment of aircraft spacing, using wake turbulence measurement, real-time weather conditions and data from air and ground systems;
  • Time Based Separation, which developed new methods for separating arriving aircraft by time instead of applying distance separations in strong headwind conditions;
  • Weather Dependant Separation, which optimises aircraft spacing by taking into account all meteorological conditions (crosswinds, headwinds, turbulence and temperature) and wake vortex behaviour.

* CREDOS: Crosswind-Reduced Separations for Departure Operations