TCAS Alert Avoids Mid-Air Collision Near Jönköping

Casualties unknown • Serious incident involving the aircraft PH-DCI and SE-MDC north-east of Jönköping, SE

Two aircraft narrowly avoided a collision in Swedish airspace after an air traffic controller failed to detect a conflict between a climbing Jetstream and an ATR 72.

What happened

On 20 June 2012, a serious separation infringement occurred in the airspace northeast of Jönköping, Sweden. An ATR 72, registration SE-MDC, was operating a commercial flight from Bromma to Ängelholm at Flight Level 140. Simultaneously, a Jetstream Series 3 200, registration PH-DCI, was climbing from Flight Level 60 to 150 on a route toward Bromma.

As the two aircraft converged, the vertical separation dropped to just 300 feet, with a horizontal distance of approximately 3.24 nautical miles. The encounter triggered the Traffic Alert and Collision Avoidance System (TCAS) on both aircraft. The flight crews responded immediately by performing evasive maneuvers as instructed by the collision warning system, successfully avoiding a collision.

The investigation

The Swedish Accident Investigation Authority (SHK) examined the actions of the air traffic controller at the Stockholm Air Traffic Control Centre. The investigation focused on why the conflict was not identified by the controller despite the availability of several automated safety tools.

Investigators reviewed the use of the Short Term Conflict Alert (STCA) and the Conflict and Risk Display (CARD). It was established that while the STCA had activated 90 seconds prior to the infringement, the controller did not notice the visual alarm. Furthermore, the controller was actively engaged in managing other flights and preparing for a handover to another sector, which diverted attention away from the primary radar screens.

Findings

  • The air traffic controller was focused on the early handover of flights to a different sector.
  • The controller's mental model of the airspace did not include a conflict between the two aircraft, leading to the clearance of PH-DCI to a flight level that intersected with SE-MDC.
  • Air traffic control aids were unable to break the controller's established mental picture of the sector's traffic.
  • The controller attempted to manually modify the aircraft flight paths during the TCAS alert rather than following standard procedures for Resolution Advisories.
  • Automated tools like the STCA and CARD were either not noticed or not utilized due to high volumes of non-critical alerts or the controller's physical orientation away from the relevant monitors.

Safety action

The Swedish Transport Agency has been recommended to enhance training for Air Traffic Services providers, specifically regarding the procedures for handling TCAS Resolution Advisories (RAs).

Probable cause

The incident was caused by the air traffic controller's preoccupation with flight handovers, which prevented the detection of a conflict, compounded by the fact that automated warning systems failed to alert the controller effectively.

Frequently asked questions

What happened in the 2012-06-20 aircraft accident near Serious incident involving the aircraft PH-DCI and SE-MDC north-east of Jönköping, SE?

Two aircraft narrowly avoided a collision in Swedish airspace after an air traffic controller failed to detect a conflict between a climbing Jetstream and an ATR 72.

What aircraft was involved and where did it happen?

The accident on 2012-06-20 involved a aircraft, registration PH-DCI, at Serious incident involving the aircraft PH-DCI and SE-MDC north-east of Jönköping, SE.

What was the probable cause of the accident?

The incident was caused by the air traffic controller's preoccupation with flight handovers, which prevented the detection of a conflict, compounded by the fact that automated warning systems failed to alert the controller effectively.

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