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 of providing separation management. Separation management starts by strategically limiting the density of potential separation conflicts (i.e. limiting traffic density and traffic complexity), but is ultimately ensured tactically by keeping aircraft separated at or above the pre-defined separation minima. The tactical separation minima are defined for each surveillance environment, and are essentially the same as they were decades ago.
With reference to the SJU Annual Work Programme 2016, this topic covers Section 3.5.4, sub Work area 1.2 topic a).
The exploratory research challenge is to hypothesize and test a set of conditions in which lower tactical separation standards may be safe within the current surveillance environment. Any newly proposed separation scheme needs to be assessed against the risk of collisions and the probability of disruptive wake vortex encounters.
This is an applications-oriented research topic. Proposals submitted for this topic should clearly formulate a hypothesis that tactical separation minima can be reduced below current minima under a specific and clearly defined set of conditions without safety being degraded, and explain what their rationale is.
Even though this topic is not addressing collision avoidance, it is expected that a collision-risk assessment must be conducted whenever a reduction of separation minima is considered. It is also expected that wake-encounter risk assessments be carried out in support of any proposed reduction to the minima. Project proposals should explain whether they will conduct the wake-encounter risk assessment, the collision risk assessment, or both, explain the rationale for their proposed approach and describe the methodology that they will use for collecting input data and for conducting the analysis. The proposal must also explain the validation techniques they plan to use in their research. It is expected that the validation techniques include any of the validation techniques that are commonly used for concepts at low Technology Readiness Levels (TRL), including expert groups, and model based validations. Innovative validation approaches may also be proposed. The objective of the project will be to either confirm or reject their hypothesis.
The following is a non-exhaustive list of potential areas for research:
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 larger difference between TBS and DBS than in final approach. Exploratory research projects may analyse the potential benefits of defining TBS minima in environments other than final approach. Research into the use of TBS may include the definition of speed-based minima (i.e. separation minima as a function of aircraft speed), potentially considering the higher resistance to wake vortex of slower propeller-powered aircraft.
Current tactical separation minima 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 are as safe as current minima (e.g. in an environmment where aircrafts are currently separated 5NM laterally or 1.000 ft. vertically, separate them X NM laterally and Y feet vertically, with X less than NM and Y less than 1.000 ft.).
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 (e.g. by reducing applicable minima when two aircraft are known to be established on tracks that they will conform to as per a specific
Applications-oriented projects in this topic are expected to contribute to the body of knowledge in the field of how separation minima can be reduced without compromising safety. The reduction of separation minima will allow for an increase of airspace capacity, which is one of the key objectives of the SESAR programme.