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Separation Management and Separation Standards

Specific Challenge: Keeping aircraft separated from each other is one of the core functions of ATM. In the SESAR concept, ground automation supports air traffic controllers in their task to provide separation management. Separation management starts by strategically limiting the density of potential separation conflicts (i.e. limiting complexity), but is ultimately ensured tactically by keeping aircraft separated at or above defined separation minima. The use of accurate and timely trajectory information in support of automation tools allows more effective strategic separation management; however the separation standards themselves, which ultimately limit capacity, remain unchanged.

The exploratory research challenge is to define potential new separation standards and separation management techniques that will allow aircraft to be more closely spaced. Any newly proposed separation scheme needs to be assessed against the risk of collisions and the probability of disruptive wake vortex encounters.

Scope: Exploratory Research projects should investigate the overall principle of separation management in ATM and propose innovative and adapted separation schemes, both in terms of the definition of separation minima and the mechanism for assuring separation. Collision and wake-encounter risk assessments should be done in support of any proposed changes to the minima, though it should be noted this subject is not addressing collision avoidance itself. Assessments should also be made investigating the risk of infringement of any revised minima where aircraft are now spaced more closely together. Specific areas for investigation could include the following:

The use of Time-Based Separation (TBS) on final approach has already been validated in SESAR. In headwind conditions TBS are lower than Distance Based Separation (DBS) thus maintaining capacity that would otherwise be reduced. At higher altitudes, winds are usually stronger, which may result in a bigger difference between TBS and DBS than in final approach. Exploratory research projects may analyse the potential use and benefits of TBS in environments other than final approach.

The speed at which aircraft fly in the TMA is usually slower than en-route. Minimum Radar Separation (MRS) is usually 3NM in the TMA and 5NM in en-route environments, however, this difference is not directly related to the speed at which aircraft fly (i.e. the 5NM minimum is applied in en-route regardless of aircraft speed). The principle of discriminating between aircraft flying at different speeds, in order to investigate if new speed-based separation minima would be safe for aircraft that fly slower could be assessed. Unlike TBS, these newly-defined speed-based minima would be applicable under all wind conditions.

Separation minima currently in use are defined either as a lateral or as a vertical minimum. Exploratory research projects may investigate the possibility of defining separation minima that combine lateral and vertical minima. Combined separation minima would specify lateral and vertical separation minima that are individually below the existing vertical and lateral minima, but when attained simultaneously still achieve safe separation between aircraft (e.g. 1 NM and 500 feet).

Historically radar surveillance performance was the basis for the definition of separation minima. New surveillance technologies may enable a revision of such minima based on surveillance performance. Exploratory research projects may look into the possibility to define lower separation minima based on the actual surveillance performance which could be achieved through any combination of radar, ADS-B and Wide-Area Multilateration

The concept of Performance Based Navigation (PBN) brings with it the capability of clearly defined and predictable navigation performance. Projects may investigate the contribution that PBN and the associated navigation applications, specifications and technologies could make to the revision of separation minima.

Expected impact:

Reduced separation minima will allow for an increase of airspace capacity, which is one of the key objectives of SESAR.

Type of action: SESAR2020 Research and Innovation Action (RIA)

Further conditions related to this topic are provided in the Technical Specification of the Call.