What happened
On January 14, 2023, at approximately 18:30 UTC, a Schleicher K6 glider, registration LV-DEW, was performing a local flight at the Rauch aerodrome in Buenos Aires province. The aircraft was being towed by an Aero Boero 180, registration LV-ASB, operated by the Club de Planeadores Alas de Rauch.
During the takeoff roll, the glider experienced longitudinal oscillations and a loss of control. As the tow plane began its climb, the glider's nose pitched up abruptly. This sudden change in attitude placed extreme tension on the tow rope, causing the structural anchor of the tow hook assembly to fail. The glider, now disconnected from the tow plane, continued to climb to an altitude of approximately 48 meters, performed a loop, and subsequently impacted the ground. The accident resulted in one fatality (the pilot) and the total destruction of the Schleicher K6.
The investigation
The investigation analyzed audiovisual records of the takeoff roll and examined the mechanical state of the tow hook assembly. Investigators determined that the glider was unstable even before the tow plane initiated its ascent. The investigation also reviewed the flight instruction manuals from the Argentine Gliding Federation (FAVAV), which mandate that a pilot must immediately release the tow rope if the tow plane is lost from view.
Technical analysis of the tow hook assembly revealed that the structural failure of the anchor was likely triggered by forces exceeding the design limits during the sudden pitch-up maneuver. Furthermore, the investigation looked into cockpit ergonomics, noting that the use of cushions to improve the pilot's field of view was a common practice at the club to compensate for structural blind spots in the K6 model.
Findings
- The glider exhibited unstable flight attitude and oscillations during the takeoff roll.
- The pilot failed to release the tow rope after the glider deviated from its path and lost sight of the tow plane.
- The structural failure of the tow hook anchor caused the separation of the aircraft from the tow plane.
- The glider's control surfaces (ailerons and rudder) were less effective due to the low speed during the critical takeoff phase, and over-controlling may have contributed to the loss of control.
- The release load of the glider's tow hook was found to be lower than the requirements specified in the applicable advisory circular.