Reduction in Vertical Separation Above FL290

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Reduction in Vertical Separation Above FL290

29TH ANNUAL CONFERENCE, Acapulco, Mexico, 21-25 April 1990

WP No. 50

Reduction in Vertical Separation Above FL290


The 28th. Annual Conference in Frankfurt, after considering the subject of reduced separation above FL 290, referred the concept back to SC 1 for further discussion.

The principle of reducing vertical separation above FL 290 from 2000 feet to 1000 feet is one debate, while the feasibility of implementation from an operational ATC point of view is another.

ICAO, through the Review of the General Concept of Separation Panel (RGCSP) had concluded that the concept is viable and gradual Regional Implementation will lead, ultimately, to a global application.

While the requirement for air traffic controllers to participate in, or be concerned with, deliberations pertaining to aircraft equipment and track/altitude keeping accuracy’s is limited, we must be involved in the development and implementation of ATC procedures and standards which flow from these deliberations. One example would be the Required Navigational Performance Capability (RNPC) Concept, a navigational concept using area navigation capabilities, coupled with a new set of ATC procedures and reduced separation criteria. The debate concerning the aircraft track accuracy requirements that allows the development of this concept and operation within an RNPC area does not concern us nearly as much as its subsequent procedural application.

IFATCA, through its various Working Groups and Committees, actively monitors proposed changes in the areas of separation and ATC procedures and assesses the potential impact on the operational environment. One of the more significant problems today, is that of system capacity, with manpower and equipment limitations playing a large part. In this context we must be conscious of those system changes that purport to increase system capacity without addressing the overall impact on the entire ATC operational environment.

In an effort to accommodate the ‘user’ group of the air industry, based on the capabilities of airborne technologies (which are far more advanced than any ground based ATC surveillance/communications system currently in operation) there exist a number of ‘special’ airspace types, within which only aircraft that meet certain equipment specifications can operate and where ‘tailored’, or unique ATC procedures/separation standards are employed (e.g. MNPS on the North Atlantic, CMNPS in the Canadian North and Arctic control areas, and RNPC airspace – all employing procedures and standards, not only different from each other, but at times varying within each specific area, depending on the capabilities of individual aircraft). States, in developing these structured, or special use areas, with the resultant special procedures and separation criteria, have not, for the most part, addressed the impact on the ATC system(s) of aircraft operating within these areas and transitioning to a ‘conventional’ airspace configuration. It is IFATCA’s responsibility to ensure that this aspect is not ignored.

The reduction of vertical separation above FL290, to 1000 feet, will effectively double the capacity of affected airspace. IFATCA does not accept the premise that the reason for the reduction is to enable the same number of aircraft to operate in the area, but at a more optimum altitude. Due to airspace capacity problems in domestic airspace, ATC surveillance and communications limitations and current aircraft population below FL 290 (all directly impacting on the degree of safety of operations), some states have indicated an unwillingness to accept the concept of reducing the separation above FL 290 and its inevitable increase in aircraft numbers. To contemplate this reduction in one area without assessing its impact on adjacent areas severely compounds the problem from an ATC point of view.

To Conclude

ICAO, largely due to air industry’ user’ requirements, has investigated the feasibility of reducing vertical separation above FL 290, concluding, that it is viable and foresees Regional Implementation leading to Global acceptance and application.

The air traffic control system today and for the foreseeable future, is operating at , or very near to, capacity and will continue to do so until major advances are made in the areas of manpower increases and equipment development and procurement.

The problems associated with the interfacing of ‘special use’, or ‘structured’ airspace, with airspace of a more ‘conventional’ design and procedural application must be addressed and dealt with.

Some states have, due to their capacity problems below FL 290, indicated an unwillingness to accept a reduction in separation above FL 290.

Current IFATCA policy states that ATC system capacity, capable of handling any increase in air traffic resulting from a reduction in the present vertical separation minima, is a prerequisite to the introduction of reduced vertical separation.

Reduced vertical separation above FL290 cannot be introduced in any area where it will affect adjacent FIR’s/airspace boundaries not subject to such a reduction, unless and until affected States develop specific ATC procedures and/or standards, determine the equipment requirements and address any ‘human factors ( such as staffing numbers and workload implications), that will enable all ATC personnel affected to efficiently and safely handle aircraft in the transition stage, from areas where reduced vertical separation is in effect, to areas where it is not.

Last Update: September 20, 2020  

December 2, 2019   248   Jean-Francois Lepage    1990    

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