David Learmount/LONDON

Modern air traffic management methods have failed to decrease the number of near mid-air collisions incidents, according to a 10-year study of "airprox" events in UK airspace. The independent UK Airprox Board has determined, however, that the trend remains almost level, and that the risk of collision to individual aircraft is reducing.

Meanwhile Eurocontrol, which has had no access to data to assess collision risk in the rapidly restructuring continental air traffic management (ATM) environment, now promises its first report on the Europe-wide collision risk by March next year. Last week, at Eurocontrol's Brussels headquarters, member states met to review progress under the new Safety Measurement and Improvement Programme (SMIP), initiated during this year.

Eurocontrol's airprox analysis will be limited, admits the head of the organisation's safety regulation unit Peter Stastny, because collecting the data is the responsibility of individual states and the data itself remains their property. Under the SMIP, airprox data will be submitted in a standard format, but de-identification means that precise details of the event and location within the state will not be revealed. Causal factors, Stastny confirms, will be reported, and this will enable system weaknesses and error categories to be identified. But identifying "black spot" ATM sectors within a state would not be possible for Eurocontrol.

Under the Eurocontrol Convention, ATM problems within a state are its responsibility and it is up to each country whether it publishes details or not, Stastny says. Almost all choose not to do so.

The UK report, which looks at the whole of the 1990s, reveals that traffic flow handled by controllers in UK airspace during the busiest months in 1990 was less than the traffic levels handled in the quietest months of 1999. Despite the burgeoning traffic flow there is no trend showing a rise in airprox numbers, although the actual numbers of near miss incidents have not fallen either. In 1999 there were four high risk (Category A) airprox incidents involving commercial air transport aircraft, compared with one the previous year and nine in 1997, which was the worst year of the decade. The decade average for Category A incidents totals 4.3 a year.

Broken down into causes, 33 events in 1999 were attributed to controllers, 13 to "level busts" by pilots (an aircraft passing through its cleared height), and 11 to unauthorised entry into controlled airspace by general aviation or military aircraft. Airprox Board chief Gordon McRobbie says, however, that last year there were about 2.6 million air traffic movements in UK airspace.

Source: Flight International