What happened
On 27 July 2016, a Diamond DA42, registered F-HCTA, was conducting an IFR cross-country flight from Muret-Lherm to Melun-Villaroche. The aircraft was accompanied by a pilot and two passengers. Simultaneously, a Rolladen Schneider LS8 glider, registered HB-3284, was performing a local flight near Pont-sur-Yonne.
While the Diamond DA42 was descending through 3,000 feet following instructions from air traffic control, the passenger in the front right seat identified a glider on a conflicting path. The pilot performed immediate evasive maneuvers, disconnecting the autopilot and banking sharply to move behind the glider. At the moment of closest proximity, the two aircraft were separated by approximately 300 meters horizontally and only 15 feet vertically. The glider pilot did not observe the aeroplane during the encounter.
The investigation
The BEA examined the onboard avionics of both aircraft, including the Garmin G1-000 Traffic Advisory System (TAS) on the Diamond DA42 and the FLARM module on the Rolladen Schneider LS8. The investigation also reviewed air traffic control records, meteorological conditions, and the regulatory framework of Class E airspace. Investigators established that the air traffic controller was unaware of the glider's presence, as the glider was not in radio contact with the service.
Findings
Several factors contributed to the near collision:
- The glider pilot had not switched on the transponder to conserve battery power, which prevented the Diamond DA42's TAS from detecting the aircraft.
- The encounter occurred in Class E airspace, where VFR pilots are not required to maintain radio contact with controllers, leaving the controller unable to provide traffic alerts.
- The effectiveness of the "see and avoid" principle was limited by the flight conditions and the difficulty of detecting gliders near cloud layers.
- There is a lack of interoperability between different onboard traffic detection technologies.
Safety action
Following the incident, the glider pilot committed to always activating the aircraft's transponder during flight to improve visibility to other traffic.