What happened
On 28 May 2019, a SCHEMPP HIRTH - DUO DISCUS glider, registration HB-3lar3362, was performing a local flight at Vinon aerodrome. The aircraft was being prepared for a towed takeoff on an unpaved runway. As the takeoff run commenced, a wing runner assisted in keeping the left wing level for the first 10 meters. However, the left wing began to drop toward the ground, and while the pilot attempted corrections, the aircraft remained tilted to the left.
As the glider reached an indicated airspeed of approximately 80 km/h and lifted off, a sudden upward movement of the right wing caused the left wingtip to strike the runway. The pilot activated the tow cable release, but the momentum caused the glider to spin around its left wing and lift into the air before falling back onto the runway. The impact caused the tail to break off, and the aircraft came to rest facing the opposite direction of the takeoff.
The investigation
Investigators examined the aircraft, the runway conditions, and the meteorological data. The site examination revealed that the grass on the runway was significantly taller than recommended, averaging 25 cm and reaching up to 45 cm at the edges of the takeoff strip. The investigation also reviewed the flight manuals and the pilots' training backgrounds.
While the pilot was trained under Swiss procedures—which suggest being ready to pull the release handle without necessarily holding it—the French Gliding Federation (FFVP) had issued a safety directive since 2013 recommending that pilots hold the release handle firmly during the start of the takeoff run to ensure an immediate response to wing-drop incidents.
Findings
- The takeoff was conducted in gusty conditions with a significant crosswind component that likely exceeded the aircraft's maximum demonstrated crosswind limit.
- The pilot's decision to release the cable was made too late to prevent the cartwheel effect once the wingtip had made contact with the ground.
- The presence of tall grass on the runway may have contributed to the destabilization of the glider during the takeoff roll.
- The pilots did not sufficiently account for the possibility of wind gusts exceeding the aircraft's operational limits during the takeoff run.