Trend Analysis of Controller-Caused Airspace Incidents in New Zealand,1994-2002

The New Zealand government takes airspace safety very seriously. The level of safety in New Zealand airspace is measured by the number of recorded airspace incidents. An airspace incident can be thought of as a failure in the chain of operations in the air traffic system when it is provided with air traffic service (ATS). Some of these incidents result in a loss of separation between aircraft, varying from slight to very serious with a significant risk of collision, known as a near collision. New Zealand's Civil Aviation Authority (CAA) identifies the causal factors for all airspace incidents with the Reason model of human error divided into three areas: active failures committed by individuals involved in the incident, local factors relating to the task and the ATS environment, and organizational factors originating in the managerial and organizational spheres of the ATS provider. On the basis of CAA's database, trends in controller-caused incidents in New Zealand airspace from 1994 through 2002 are analyzed in six categories: loss of separation, ATS coordination deficiency, near collisions, ATS clearance or instruction deficiency, ATS flight planning system deficiency, and ATS flight information deficiency. The results indicate that execution errors predominate for active failures, whereas poor concentration or lack of attention, inadequate checking, and controller workload are the dominant local factors. For the organizational factors, inadequate control and monitoring, inadequate specifications and procedures, and poor resource management dominate. These results can be used for a better understanding of controller working practices and ATS organization for enhanced airspace safety.