Study into near-miss in January 2001 convinces investigators that ICAO needs to clarify pilot instruction standards

Japanese air accident investigators want international regulations revised to give orders from airborne collision avoidance systems (ACAS) precedence over those from air traffic control (ATC). It follows a probe into a Japan Airlines (JAL) air miss in January last year which has strong parallels to the collision over southern Germany on 1 July.

The incident involved a JAL Boeing 747-400 which continued an ATC cleared descent despite a climb instruction from ACAS, while a conflicting JAL McDonnell Douglas DC-10-40 followed an ACAS command to descend. The two aircraft came within 10m (33ft) of each other, with a collision averted when the DC-10 pilot saw what was happening and pulled up, while the 747 crew pushed its aircraft into a steeper dive. Japanese investigators blame controller confusion and a conflict between ATC orders and the ACAS resolution advisory (RA) instructions. They also criticise incomplete pilot training.

When Japanese investigators meet International Civil Aviation Organisation officials in Montreal this month they say they will urge ICAO to clarify RA standards.

The Japanese report to ICAO says: "Pilots should comply with an RA when pilots receive simultaneously an instruction to manoeuvre from ATC and an RA, and they conflict." They want standard operating procedures (SOP) for response to RAs put into operations manuals and to make it standard for pilots to inform ATC they have followed an RA before returning to their cleared height or flight path.

Investigators concluded an instruction issued to the wrong aircraft by a busy trainee controller set up the chain of events. In addition, the ATC conflict alert system failed to warn controllers. Investigators attribute this to the system's inability to account for the effect on separation when aircraft are turning. After the incident JAL changed its SOP to make ACAS RAs take precedence over ATC instructions.

Source: Flight International