What happened
On August 13, 2017, a Schempp-Hirth Discus b glider, registration D-1857, was involved in an accident at the "Umberto Mascioni" airfield in Cuvio, Italy. The incident began after the glider had performed an off-field landing at the site due to deteriorating soaring conditions. To recover the aircraft, an experienced instructor decided to perform an aerotow using a Stinson L-5, registration I-AEEA, rather than transporting the glider by ground.
During the takeoff roll, the glider began to yaw heavily to the right. The pilot attempted to correct the deviation using full left rudder and aileron input, but the right wingtip eventually dipped into the grass. This caused the glider to enter a cart-wheel motion, resulting in the aircraft flipping and striking the ground nose-first approximately 120 to 130 meters from the runway threshold. The pilot of the glider sustained minor contusions, while the aircraft suffered substantial damage to its forward section.
The investigation
The ANSV investigation examined the operational decisions, the condition of the airfield, and the aircraft's flight manual requirements. Investigators found that the "Umberto Mascioni" airfield had been closed to all flight activities for four years due to renovation works, a fact that the flight crew had not verified.
Video analysis of the takeoff revealed that the grass height was uneven and the terrain was bumpy. The investigation also focused on the pilot's inability to release the tow cable. The pilot reported that the yellow release handle was trapped beneath his left leg due to his intense effort to apply full left rudder, preventing a timely manual release. The automatic release mechanism eventually triggered as the glider's heading deviated significantly from the tow path.
Findings
- The primary cause of the accident was human error regarding the inadequate management of the takeoff maneuver, which led to a cart-wheel.
- The decision to conduct an aerotow on an airfield that had been officially closed to flight operations for several years contributed to the accident.
- The pilot failed to follow the Discus b Flight Manual instructions, which strictly prohibit aerotow takeoffs from uncut grass fields to avoid such incidents.
- Pre-takeoff checks were insufficient; specifically, the pilot did not verify that all controls and instruments, including the release handle, were accessible and unobstructed.
- The unevenness of the grass and the presence of bumps on the runway surface contributed to the loss of control.