What happened
On June 11, 2017, an Olympia-Meise glider, registration D-1420, was participating in a vintage glider gathering at the Novi Ligure airport in Italy. During a routine aero-tow operation, the glider was being pulled by a Robin DR400/180R, registration I-ITAR.
At an altitude of approximately 850 meters, the tow aircraft experienced a sudden, sharp pitch-down maneuver. During this sequence, the glider's left wing detached from the fuselage. The glider plummeted into the town of Novi Ligure, striking a railway fence near the station, which resulted in the death of the pilot. The tow aircraft lost approximately 600 meters of altitude before the pilot regained control and landed safely without further incident.
The investigation
The ANSV investigation focused on the structural integrity of the wing attachment points and the sequence of events leading to the separation. Investigators examined the wreckage and found that the glider had suffered high-energy impact damage. Notably, fragments of the aircraft, including the left wing and the tail rudder, were scattered across the town.
Metallurgical analysis of the wing attachment components revealed that one of the two conical pins was broken. The investigation found that this broken pin was made of a different alloy (a high-alloy steel containing chromium and nickel) compared to the intact pin (a low-alloy steel containing chromium and manganese). Furthermore, the broken pin showed evidence of deformation and overload at the fracture surface. The investigation also examined the wing attachment eyelet, which showed signs of ovalization and ductile overload pitting.
While the exact sequence of events remains uncertain, the investigators considered three hypotheses: the glider moving out of the tow plane's wake and experiencing sudden aerodynamic forces; the pilot initiating a release without confirming separation, leading to a sudden pull on the tow plane; or the tow pilot descending rapidly under the mistaken belief that the glider had already released.
Findings
- The primary cause of the accident was the in-flight separation of the left wing due to a sudden increase in aerodynamic loads during the tow.
- The use of a conical pin with a different metallurgical composition than the original part may have contributed to the failure.
- The tow speed was at or slightly above the maximum permitted speed for this vintage glider type.