When an airspace sector needs to be closed or has limitations placed on operations within it due to an inability to provide air traffic management services, the ANSP managing the airspace can implement temporary contingency procedures. Given the potentially high costs of such disruptions to normal aviation operations, as well as potential safety risks, the plans should be designed to minimise the total impact.
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TIBA Contingency Procedures
These contingency procedures, otherwise known as Traffic Information Broadcasts by Aircraft (TIBA) Procedures, are only implemented when necessary and only as a temporary measure, according to ICAO Annex 11. The Annex also states that in the absence of air traffic management services, the procedures provide for reports and relevant supplementary information of an advisory nature to be transmitted by pilots for the information of pilots of other aircraft in the vicinity.
Relying on pilots in flight to advise each other on aircraft operations in and around the affected airspace can be a safety risk, especially on busy routes. It also increases the general workload for pilots. It is for these reasons that many airlines flight plan on contingency routes to avoid these areas.
This can cost the airlines extra in fuel, as well the costs of passenger delays and cancellations. Airlines have occasionally sought reparations from the ANSP for the non-delivery of air traffic management services. There is, therefore, a lot of pressure on ANSPs to avoid and mitigate the need for TIBAs.
Managing disrupted airspace service
The most common trigger for a sudden, unexpected inability to provide air traffic management services is staffing problems or equipment failure. An ANSP’s contingency plan will have usually been prepared based upon historical understanding of traffic patterns, aircraft numbers and airspace risk profiles.
The plan will also contain optional flight paths that can be used by aircraft to avoid the affected airspace known as Contingency Routes. A contingency plan is normally set in motion by a nominated manager tasked with the operational oversight, recording of all activities, notifying affected airlines, monitoring of all flights, and managing the transition back to normal services after the event.
Fast-time Simulation advantage
Because of the risks and costs involved, contingency planning that minimises total impact on aircraft operations must be a priority. Using Fast-Time Simulation (FTS), it is possible to develop collision risk models of TIBA airspace and to evaluate the effect of contingency flight paths on surrounding ATC sectors.
Being able to forecast the effect of TIBA airspace in general, and on ATC workload specifically, can enable timely operational risk mitigation in these contingency situations. FTS is an extremely useful and cost-effective tool that can assist ANSPs to understand and mitigate the impact of TIBA procedures.
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