What happened
On the evening of 22 April 2012, a serious loss of separation occurred approximately 5nm west of Dubai International Airport involving two commercial flights. The first aircraft, an Airbus A320-214 operated by Air Arabia (registration A6-ABS), was climbing from Sharjah toward Istanbul. Simultaneously, a Boeing B737-800 operated by Fly Dubai (registration A6-FDK) was climbing from Dubai toward Doha.
As both aircraft were being managed by Dubai Departure Air Traffic Control, a breakdown in separation occurred at approximately 21:01:45 local time. The situation escalated quickly, leading the onboard collision avoidance systems to intervene. The crew of the B737-800 received a TCAS Resolution Advisory (RA) to climb at 21:02:41, followed by the A320-214 crew receiving an RA to descend roughly nine seconds later. Both flight crews executed the necessary evasive maneuvers to avoid a collision, and no injuries or aircraft damage were reported.
The investigation
The GCAA AAIS investigation examined the sequence of instructions provided by Dubai Departure ATC, the functionality of the aircraft's TCAS systems, and the operational status of radar alert systems. Investigators reviewed flight data recorder information and radar snapshots to reconstruct the conflict. The inquiry also looked into the awareness of newer ACAS II version 7.1 capabilities among UAE operators and air traffic controllers, as well as the operational status of the Short Term Conflict Alert (STCA) system at Dubai ATC.
Findings
- The primary cause of the near-miss was the loss of minimum vertical and lateral separation between the two aircraft.
- The STCA/MSAW (Minimum Safe Altitude Warning) unit at Dubai ATC was not operational due to issues with the Flight Refuelling Radar system software.
- While both aircraft were equipped with the required ACAS II version 7.0, there was a lack of standardized guidance regarding the transition to version 7.1.
- There was a lack of updated training for both pilots and air traffic controllers regarding the specific behaviors of the newer ACAS II version 7.1, such as the "Level off, level off" command.
- The GCAA had not yet issued specific guidelines to UAE operators regarding the preferred ACAS II version for the region.
Safety action
- The GCAA was advised to provide clear guidelines regarding the minimum ACAS II version required for aircraft operating within the UAE FIR.
- Recommendations were made to ensure all UAE Civil ATC units utilize safety-related radar alerts and warnings.
- The GCAA was urged to issue an Air Navigation Service Information Notice (ANSIN) to ensure air traffic controllers include awareness of ACAS II version 7.1 capabilities and limitations in their training syllabus.