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Airspace and Procedure Design

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Article Information
Category: Level Bust Level Bust
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

Description

The proper planning and design of routes, holding patterns, airspace structure and ATC sectorisation in both terminal and en-route airspace can be effective in reducing the likelihood of level bust incidents. The converse is also true: poorly designed airspace can create situations where a level bust incident is more likely to occur within an air traffic management (ATM) system.

In an ideal world, airspace design would make it possible for arriving, departing and en-route flights to operate so that they did not have to cross one another, or climb and descend through each other’s levels. Furthermore, approach and take-off flight paths would be free of obstacles. Unfortunately, however, this “ideal” design environment is seldom possible, which means that airspace designers need to take steps to reduce the likelihood of level busts in the above circumstances.

Effects

While not actually causing them, poorly designed airspace can increase the risk of loss of separation, level bust, and Controlled Flight Into Terrain (CFIT).

Defences

Airspace and procedure design should follow the principles laid down in ICAO Doc 8168 (PANS-OPS) and Doc 4444 (PANS-ATM). PANS-OPS provides criteria for the design of instrument approach, holding and departure procedures. PANS-OPS provisions also cover en-route procedures where obstacle clearance is a consideration. PANS-ATM provides procedures for air navigation services, whose basic tenets form the basis of airspace design.

EUROCONTROL Manual for Airspace Planning provides guidance material for airspace design and PANS-OPS Procedure design. This is supplemented by Guidance Material for the design of Terminal Procedures for Area Navigation (DME, GNSS, Baro-VNAV and RNP RNAV).

Typical Scenarios

  • A standard instrument departure (SID) requires pilots to level at an intermediate altitude until passing a specified point. The pilot fails to stop at this intermediate altitude and loses separation with an aircraft above.
  • A SID is based on an off-airfield DME. The pilot does not notice this and becomes confused when the DME range decreases rather than increases.
  • A non-precision approach begins at a fix defined by bearing and distance from a radio facility. The pilot has difficulty flying to this fix and descends the aircraft outside the calculated safety zone.

Contributory Factors

  • The extent of the navigation, communication and surveillance infrastructure;
  • Terrain surrounding the aerodrome;
  • Proximity of other aerodromes and other airspace structures;

Solutions

  • The introduction of airspace procedures and design should be planned. This implies identifying and addressing all relevant stakeholder interests; carrying out an impact assessment; and carrying out a safety assessment. This also implies the introduction of changes in an organised manner which reduces the likelihood of design solutions creating operational difficulties for either pilots or ATCOs.
  • Changes introduced to existing terminal area procedures as well as SIDs and STARs should be properly validated, prior to implementation.
  • Sufficient time should be allowed in the planning process to allow for necessary ATCO and pilot training.
  • When RNAV terminal area procedures are designed (excluding the final approach and missed approach segment), procedures should be designed using P-RNAV criteria in accordance with guidance material published by EUROCONTROL.
  • Make use of procedure-design tools.

Further Reading

ICAO Documentation:

  • Doc 8168 (PANS-OPS);
  • Doc 4444 (PANS-ATM);

EUROCONTROL Guidance material

EUROCONTROL Level Bust Toolkit