What happened
On June 10, 2017, a Glasflügel Mosquito glider, registration I-VIUS, was engaged in a recreational VFR flight after being towed from Aosta Airport by a Robin DR 400. After approximately three hours of flight, the aircraft struck a steep mountain slope near Riva Valdobbia at an altitude of approximately 2,400 meters. The impact caused the total destruction of the glider and resulted in one fatality.
The investigation
The ANSV investigation utilized data from an onboard data logger, which recorded the flight's final maneuvers. The data revealed that the pilot had been performing various turns and spirals throughout the flight. In the final moments, the aircraft executed two consecutive "eight" maneuvers followed by a nearly circular turn, a sequence typically used to initiate a climbing spiral to gain altitude.
Analysis of the terrain and meteorological conditions indicated that while visibility was generally good, the presence of mountain rotors or sudden downdrafts could not be ruled out. The investigation also examined the pilot's flight history and the aircraft's maintenance records, finding the glider to be in good operational condition and the maintenance up to date. The investigation also considered the possibility of hypoxia, though the aircraft had been below 3,000 meters for approximately 15 minutes prior to the crash.
Findings
- The primary cause of the impact was a significant loss of altitude during a climbing maneuver, likely triggered by sudden downdrafts caused by mountain rotors.
- The pilot was flying at a relatively low airspeed, specifically below the recommended safety margin of 1.45 times the stall speed, which reduced the margin for error during atmospheric disturbances.
- The aircraft was operating with insufficient clearance from the terrain to allow for a recovery maneuver.
- Decision-making may have been influenced by "get-home-itis," as the pilot likely felt pressure to return to Aosta due to a scheduled work commitment later that afternoon.