Report on serious incident at Oslo Airport Gardermoen on 31 October 2012, aircraft proximity (AIRPROX) between LN-DYC (NAX741) and LN-NOM (NAX740), both operated by Norwegan Air Shuttle ASA

Visibility conditions were such that the tower controller could not maintain visual separation between the two aircraft. Both were climbing, one after the other. The tower air traffic controller instructed NAX741 to divert west. A mix-up of call signs occurred and led to NAX740 executing the clearance given to NAX741. The minimum horizontal distance between the aircraft was approximately 0.2 NM (370 m) whereas the vertical separation was 500 ft (152 m). It is the AIBN's view that the situation contained a real danger of collision, but once it was a fact, the situation awareness and sound assessments of the flight crews and tower controller prevented a further escalation of the conflict.

The AIBN considers established and practiced procedures to be conductive to recognizing situations and averting them before they become critical. Data from the Cockpit Voice Recorder (CVR) was not secured. CVR data is important to understand the sequence of events, and the AIBN therefore sees it as unfortunate when CVR data is not secured. The AIBN does not promote any new safety recommendation in this report, but refers to a previously issued safety recommendation (SL No 2012/06T), which has not been closed out.