What happened
On March 17, 1993, a KW-1 Quero-Quero glider, registration PT-PHB, was performing its third flight of the day near the Osório Aerodrome in Rio Grande do Sul, Brazil. The flight, operated by Aeroclube de Planadores Albatroz, began as a standard tow operation. After the glider released from the tow cable at approximately 700 meters, the aircraft entered the downwind leg of the flight pattern. Witnesses observed the glider pitching forward at a 45-degree angle. The aircraft struck the ground in a nose-down attitude, resulting in one fatality.
The investigation
CENIPA investigators examined the wreckage and the maintenance history of the aircraft. The investigation focused on the flight control systems, specifically the control column, the aileron torque tube, and the elevator control components. Technical analysis by the Institute of Aeronautics and Space (IAC/CTA) revealed that the elevator control tube exhibited widespread corrosion. This corrosion had weakened the structural integrity of the component.
Furthermore, the investigation scrutinized the maintenance practices at the aeroclube. It was established that the facility lacked a dedicated maintenance workshop, a maintenance manual, and a proper registry of Airworthiness Directives (ADs). The mechanic in charge was unaware of specific mandatory inspections, including AD 82-12-01, which required a specialized inspection of the elevator control tube using liquid penetrant to check for cracks and weld integrity.
Findings
- The primary cause of the accident was the failure of the elevator control tube due to generalized corrosion, which likely led to the jamming or buckling of the flight controls.
- The maintenance services performed on the aircraft were inadequate and non-compliant with established standards, as the required Airworthiness Directlamative inspections were not performed.
- The pilot had limited flight experience in this specific aircraft type and had been away from flight activities for nearly four months.
- The aeroclube lacked proper administrative supervision regarding aircraft maintenance, failing to maintain records of completed airworthiness directives or the aircraft's maintenance manual.
- The elevator trim was found locked in the "nose-down" position at the time of impact.