Event Description
On 29 December 2020, between 22:38 and 23:15 UTC, the AIRCON 2100 automated air traffic control system experienced a malfunction. The Situation Data Display (SDD) screens in the Central, Moron, Gobi, and Eastern sectors of the Area Control Center lost aircraft symbols. The symbols appeared frozen, jumped to different locations, or disappeared entirely, rendering radar-based control impossible. The shift supervisor (ENU) informed the duty engineer of the alternating loss of symbols at 22:38 UTC. At 22:40 UTC, the ENU transitioned all sectors to procedural control. The sectors had been combined earlier at 22:00 UTC, with Moron and Central sectors merged, and Gobi and Eastern sectors merged; they were separated again at 22:57 UTC. At 23:12 UTC, the automation engineer notified the ENU that the system had returned to normal. After verifying the SDD displays, the ENU resumed radar control at 23:15 UTC. A recorded ATM log confirmed the unstable behavior of aircraft symbols during the period. The procedural control operation maintained safe separation, as noted in an inspector's report (No. 866/20).
System Background
The AIRCON 2100 system is an integrated air traffic surveillance management system that receives and processes ASTERIX data from radar and ADS-B ground stations. It includes servers such as RDCU, FDP, SDP, NTP, and multiple workstations (CMD, FDD, SDD, DRF). The system was commissioned on 23 August 2012, initially with three Indra IRS-20MPS secondary radar stations located at Altanbulag (Tov), Khengerteg (Khovsgol), and Bor-Ondor (Khentii). Two Thales RSM-970S stations were added on 14 November 2013 at Ikh-Olgii (Sukhbaatar) and Bayanteeg (Umnogovi). Two more Indra IRS-20MPS-2NA stations were added on 10 September 2015 at Bombogor (Bayankhongor) and Saikhandulaan (Dornogovi). The system supports up to 8 radar sources, 30 ADS-B sources, and 500 simultaneous tracks.
History of Modifications and Failures
Several modifications were made to the system: addition of SDD-7 and SDD-8 workstations in 2010, flight plan changes in 2012, SDD-9 to SDD-12 in 2014, OLDI/AIDC software in 2016, connection of 13 ADS-B ground stations in 2016, a system upgrade in November 2017, and addition of SDD-13 and SDD-14 in 2019, along with a software update in 2019. These changes were coordinated with the manufacturer, Indra Sistemas S.A.
Failure records from 2017 to 2020 show: 42 failures in 2017, 39 in 2018, 30 in 2019, and 23 in 2020. The 2020 failures included 11 software faults, 6 hardware faults, 3 due to external equipment, 2 OLDI interruptions, and 1 NTP-1/DRF-2 malfunction.
Investigation Findings
The investigation reviewed reports from the Air Traffic Services Department (forms MKh-03A No. 12/17 and 12/18). The shift supervisor's actions were documented. At the time of the malfunction, a total of 11 aircraft were under control: 4 in Moron, 2 in Central, 3 in Gobi, and 2 in Eastern sectors. The procedural control operation from 22:40 to 23:15 UTC was conducted without loss of separation. The system returned to normal operation at 23:12 UTC, and radar control resumed at 23:15 UTC.