What aircraft was involved and where did it happen?

The accident on 2013-05-31 involved a 42-500, 42-300, registration EFY9066, NSE8663, at Rionegro, CO.

What was the probable cause of the accident?

The probable cause was an operational error by the air traffic controller, who authorized the ATR 42 to climb to FL190 without considering that the maneuver would cross the altitude of the Jetstream 41, which was flying in the opposite direction.

Airprox Incident Involves Two Aircraft in Colombian Airspace

A near mid-air collision occurred in the B689 airway when an ATR 42 and a Jetstream 41 converged with only 100 feet of vertical separation.

What happened

On May 31, 2013, at 21:15 UTC, a serious airprox incident occurred in the B689 airway involving two passenger aircraft flying in opposite directions. The first aircraft, an ATR 42-500 operating flight NSE8663, was climbing from 17,000 feet toward 19,000 feet. Simultaneously, a Jetstream 41 operating flight EFY906 6 was climbing through 15,800 feet toward 18,000 feet.

As the aircraft converged, the air traffic controller notified the crew of the ATR 42 of the opposing traffic. The controller subsequently instructed the ATR 42 to increase its rate of climb to maintain separation. However, the pilot reported that the aircraft was unable to increase its climb rate due to encountered icing conditions. Following this exchange, the controller issued a left turn instruction to the Jetstream 41 to resolve the conflict. Shortly thereafter, the crew of the ATR 42 reported initiating a TCAS ascent maneuver. The investigation determined that the two aircraft had converged at a distance of 6.2 nautical miles with a vertical separation of only 100 feet.

The investigation

The GRIAA investigation focused on the air traffic control (ATC) sequence and the performance of both aircraft. The investigation established that while both aircraft were under radar contact, the controller's primary error was authorizing the ATR 42 to climb to 19,000 feet without accounting for the fact that this flight path would cross the 17,000-foot cruise altitude of the Jetstream 41, which was traveling in the opposite direction.

While the controller did provide traffic information, the investigation found that the controller failed to issue proactive separation instructions to resolve the conflict. The controller also failed to inquire about the ATR 42's climb performance after the pilot mentioned icing. The investigation noted that the controller relied on providing traffic advisories rather than utilizing radar surveillance to actively manage and ensure separation between the converging flights.

Findings

Operational error by the air traffic controller, who authorized the ATR 42 to climb to a level that intersected the flight path of the Jetstream 41.
The controller failed to provide instructions to resolve the conflict, instead only providing traffic information.
The crew of the ATR 42 did not promptly notify ATC of the performance limitations caused by icing conditions.
The aircraft were in a state of convergence with a vertical separation of only 100 feet.

Safety action

Satena is recommended to instruct crews to promptly notify air traffic control of any circumstances, such as icing, that affect aircraft performance.
The Colombian Civil Aviation Authority (Aerocivil) is recommended to provide specialized training for air traffic controllers regarding ATS surveillance services, vector guidance, and the application of vertical separation minima.