Changes to prevent another mid-air collision are at the top of the agenda for Eurocontrol's "high-level European air traffic management (ATM) safety action group", which was established this month in the wake of the 1 July mid-air collision over Germany. Present standards for pilot reaction to on-board collision avoidance alerts leave room for confusion.

Objectives include deciding whether or not to make pilot response to airborne collision avoidance system (ACAS) alerts mandatory, and how best to inform air traffic control (ATC) that an ACAS resolution advisory (RA) has "intervened".

On 1 July a DHL Boeing 757 and a Bashkirian Airlines Tupolev Tu-154 collided over southern Germany despite the pilots receiving ACAS RAs that would have separated them. Following the RA to climb, the Tu-154 pilot was told twice by ATC to descend and fatally did so. Eurocontrol says it has found the latest ACAS operation - version 7 - satisfactory, so no change is needed. But the organisation says the collision has made it clear that it is not enough to have advice on how to react to an RA "in training material only". A crucial issue for the safety action group is whether standard operating procedures (SOP) should be developed and made mandatory. Operators can use their discretion in drawing up SOPs for their pilots. Eurocontrol says it intends to work with the International Civil Aviation Organisation, the Joint Aviation Authorities, pilots' and controllers' organisations and the airlines.

Meanwhile, there are two possible choices for notifying controllers that an ACAS RA has triggered. One is verbally - the pilot talks to ATC; the other would use the Mode S secondary surveillance radar (SSR) datalink to give the controller on-screen information. However, RA data is not one of the items planned at present for downlinking to ATC and there are only seven out of the 31 Eurocontrol countries that plan to have Mode S capability by 2005.

Source: Flight International