New operational safety study of Mid-Air Collision Incidents in Terminal Control Areas and Control Zones

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A new study examines recent MAC incidents in support of improved risks management

EUROCONTROL has completed a new operational safety study. Its findings inform our continuous efforts to fine-tune our risk identification and prioritisation practices so as to keep air traffic safe.

Based on a sample of 553 mid-air collision incidents of severity A and B that occurred in airport Terminal Control Areas (TMA) and Control Zones (CTR) in EUROCONTROL member states in the interval 2014-2016, the new study examines which defences against mid-air collision incidents worked well and which ones should be prioritised for further monitoring, research and improvement.

Key findings:

  • The Air Traffic Control (ATC) Collision Avoidance barrier had a recorded efficiency of 57%.
  • The Airborne Collision Avoidance System (ACAS) Pilot Collision Avoidance barrier had a considerably higher recorded efficiency of 79%.
  • The Pilot Visual Collision Avoidance barrier performed better than anticipated, with a recorded efficiency of 65%.
  • In six of the cases, the conflict geometry helped avoid mid-air collision, meaning that the overall recorded efficiency of the manageable TMA conflict prevention and collision avoidance barriers was of 97%.
  • The effectiveness of the first barriers, namely the ATC Separation Assurance and ATC Collision Avoidance, is lower than the effectiveness of ACAS Pilot Collision Avoidance, Pilot Visual Collision Avoidance and Providence basic barriers, therefore the latter are relatively more often challenged in comparison to the en-route environment.
  • Overall, the ATC induced tactical conflicts account for 71% of the analysed incident data sample. The tactical conflict being generated by the use of inadequate ATC controlling techniques is the clearly outstanding initiator with a share of 23 % of events analysed.
  • Incidents that occurred in class D and E airspace require further analysed in a dedicated operational safety study.
  • Nearly a quarter of the incidents in the analysed data sample involves visual flight  rules (VFR) flights. VFR/IFR (Instrument Flight Rules) encounters in TMA and CTR airspaces should be monitored.
  • The analysed sample included only one event of controlled airspace excursion but with high risk potential. This type of safety incidents should also be monitored.
  • The safety criticality of events involving going-around aircraft is considerable and the risks related to encounters between low level going-around aircraft and the preceding departure should be prioritised for further operational safety study. 

Learn more in the full report