What aircraft was involved and where did it happen?

The accident on 2021-10-06 involved a SOCATA – TB 20, registration F-GNSD, at instruct, FR.

What was the probable cause of the accident?

The near collision was caused by the air traffic controller's inability to manage conflicting traffic on parallel runways, a difficulty stemming from the loss of routine operational reflexes following an extended period of single-runway operations due to airfield construction.

Near Collision of Two Training Aircraft at Saint-Yan Airport

A near collision occurred between a SOCATA TB 20 and a Beechcraft Be 58 during simultaneous departures from parallel runways, driven by controller fatigue and recent runway construction.

What happened

On 6 October 2021, at Saint-Yan airport, two aircraft engaged in instructional flights experienced a near collision during their initial climbs from parallel runways. The first aircraft, a SOCATA TB 20 registered F-GGNS, was performing an IFR departure from runway 33R. Simultaneously, a Beecraft Be 58 registered F-GNSD was performing a touch-and-go maneuver on runway 33L.

As the F-GGNS began its climb, the tower controller was managing a high volume of traffic following a period of intense airfield construction. The controller instructed the F-GNSD to continue its climb to avoid a conflict with another aircraft, but the relative speed between the two aircraft led to a rapid closing. The F-GNSD eventually overtook the F-GGNS, which was flying approximately 100 feet lower. The pilot of the F-GNSD acquired visual contact with the F-GGNS only during the overtaking maneuver. The collision was avoided because the F-GGNS instructor, having monitored the radio frequency, identified the threat and held the aircraft on the runway axis rather than proceeding with the planned left turn.

The investigation

The BEA investigation examined ATC communications, flight recorder data from the F-GGNS (ApiBox), and the Garmin G500 TXi display from the F-GNSD. The investigation focused on the air traffic controller's management of the parallel runways and the impact of recent airfield maintenance. The investigators also reviewed the operational environment, noting that the airport had been operating with single-runway constraints for several weeks due to repairs to the runways and taxiways.

Findings

The primary contributing factor was the temporary loss of automatic traffic management reflexes in the controller, caused by a long period of airfield work that required operating with only one runway.
The controller was experiencing significant fatigue due to a heavy workload and unpredictable schedule changes regarding runway closures.
The controller lacked sufficient mental resources to manage the complex conflict between the two aircraft during a period of high traffic density.
The pilot of the F-GNSD failed to read back certain clearances, which increased frequency occupancy and workload for the controller.
The pilot of the F-GNSD did not announce visual contact with the F-GGNS after acquiring it, which hindered situational awareness.
The instructor on the F-GGNS prevented the collision by actively monitoring the radio frequency and delaying the planned turn after perceiving the approaching traffic.