What happened
On November 1, 2020, at approximately 17:40 local time, a Bolkow Phoebus “C” glider, registration LV-DHD, was performing a local training flight at the Rauch aerodrome in Buenos Aires, Argentina. The aircraft was being launched via a winch-tow method. During the takeoff roll, at an altitude of approximately one meter above the ground, the aircraft drifted toward the right edge of the runway. The pilot disconnected the tow line, but the aircraft's right wing struck the terrain, causing a sudden loss of control and a sharp turn to the left. The glider subsequently underwent a 360-degree rotation, resulting in the separation of the wings and the central wing box, before finally coming to rest in an inverted position. The pilot was able to exit the aircraft without injuries.
The investigation
The Argentine Transportation Safety Board (JST) examined the wreckage and maintenance records of the Bolkow Phoebus “C”. The investigation focused on the aircraft's flight dynamics during the low-speed phase of takeoff and the airworthiness of the glider. Investigators analyzed the impact pattern, which showed the initial contact on the right wing followed by a series of rotations. The investigation also scrutinized the maintenance history, noting that the aircraft was not being maintained according to the manufacturer's prescribed plan. Furthermore, the investigation looked into the use of non-standard components, such as an improvised reference flask for the variometer, and undocumented structural repairs and modifications, including unrecorded weight-and-balance changes and unauthorized repairs to the fuselage and landing gear anchors.
Findings
- The primary cause of the accident was the ineffectiveness of the flight controls at low airspeed, which prevented the pilot from maintaining the runway centerline.
- A crosswind component contributed to the aircraft drifting toward the right side of the runway.
- Insufficient or delayed corrective actions by the pilot led to the right wingtip striking the ground.
- The aircraft was found to have numerous undocumented repairs and modifications that deviated from manufacturer standards.
- Maintenance oversight deficiencies were identified, as several discrepancies and unauthorized alterations had not been recorded or addressed by the maintenance facility.