What happened
On May 20, 2016, a Grob G103 Twin Astir 1 glider, registration D-3lan3953, and a Socata MS893A Rallye 180, registration F-BPMB, were engaged in a flight training exercise at the Saint-Florentin airfield in France. The flight crew of the glider, consisting of an instructor and a student, requested a "ground return" maneuver (retour au sol) from the tow pilot. This specific technique, which involves flying at low altitude behind the tow plane to simulate an inability to release the cable, had been discouraged by the French Gliding Federation (FFVV) since 2012.
During the final approach of the exercise, the tow pilot slowed the aircraft. To prevent a stall, the glider crew retracted their airbrakes. This action caused the glider to accelerate and catch up to the tow plane, resulting in the tow cable losing tension. The slack cable dragged across a rapeseed field and became snagged on vegetation. The tension from the snagged cable pulled the glider downward, causing it to strike the ground. The tow cable subsequently broke, and the Socata MS893A Rallye 180 experienced a hard landing at the threshold of runway 25R. There were no fatalities or injuries among the two crew members on board the glider.
The investigation
The BEA investigation examined GNSS flight data from both aircraft, which revealed that the tow plane's speed decreased to approximately 90 km/h during the final approach. Ground-based video footage confirmed that the glider caught up to the tow plane, causing the cable to slacken and snag on the field. The investigators also reviewed the training backgrounds of the pilots and the operational procedures of the Saint-Florentin gliding club.
Findings
- The primary cause of the accident was the execution of a training maneuver that was no longer practiced in France, performed without proper coordination between the pilots.
- A lack of a formal pre-flight briefing between the tow pilot and the glider crew led to mismatched expectations regarding the maneuver's execution.
- The language barrier between the Dutch glider crew and the French tow pilot discouraged necessary safety communications during the flight.
- The tow pilot noticed the glider's configuration was not as expected but did not interrupt the exercise due to communication difficulties.
- The glider crew did not request a change in speed or trajectory despite finding the tow plane's path incompatible with the glider's performance.