Legal Requirements

According to Annex I of EU Regulation 390/2013 - Performance Scheme for Air Navigation Services and Network Functions, the second EU-wide safety key performance indicator shall be the percentage of application of the severity classification of Risk Analysis Tool to allow harmonised reporting of severity assessment of separation minima infringements, Runway Incursions and ATM specific technical events.

Furthermore, paragraph 5.1.6 of ESARR2 - Reporting and Assessment of Safety Occurrences in ATM requires that “the severity of each occurrence is determined, the risk posed by each such occurrence classified and the results recorded”. Risk assessment shall include, in addition to the determination of the severity, the likelihood of recurrence of such incidents and their most probable consequences.

Severity Classification Scheme

The severity classification scheme of occurrences according to the severity of their effect on the safe operations of aircraft and on occupants has been defined in Attachment A to ESARR2.

The severity of an accident is to be expressed according to:

• the level of damage to the aircraft (ICAO Annex 13 identifies 4 levels: destroyed, substantially destroyed, slightly damaged and no damage);
• the type and number of injuries (ICAO Annex 13 identifies three levels of injuries: fatal, serious and minor/none).

The classification scheme for incidents is illustrated in the Table below. It consists of categories of severity for the risk that existed and for the frequency of their occurrence. These are combined as a classification matrix whose columns correspond to the frequency categories and rows correspond to the severity categories.

The severity classification scheme for incidents considers the actual frequency of each of these occurrences to enable national organisations to determine the level of effort to be placed into the assessment of the occurrence as well as to potentially support the development of trends in safety.

Accident & Incident Severity Definitions

The classification scheme specifies six severity categories for ATM related occurrences impacting the safe operations of the aircraft: accident, serious incidents, major incidents, significant incidents, no effect and risk not determined. The definitions for each are provided in the table below.

Accident & Incident Frequency Definitions

The severity classification scheme specifies five qualitative frequency categories. It is recommended that each State initiate the development of quantitative boundaries, which would take into account national traffic volumes and specific operating conditions of the national ATM system (and related sub-systems). The qualitative frequencies are defined in Table below.

Risk Analysis Tool

The Risk Analysis Tool (RAT) has been developed by EUROCONTROL to support assessment of risk induced by incidents. It has evolved over time to be a sophisticated yet simple mechanism for quantifying the level of risk present in any ATM related incident.

The RAT allows the analysis of a single event in order to understand the factors involved and then place the event in context with other events. Consequently, it contains components and information that should be appropriate to score severity and risk of recurrence of safety occurrences as required by the EU Regulation 390/2013 - Performance Scheme for Air Navigation Services and Network Functions and ESARR2 – Reporting and Assessment of Safety Occurrences in ATM.

Related Articles

• Risk Analysis Tool (RAT)

Further Reading

• Risk Analysis Tool – Guidance material, draft version of January 2013