What happened
On March 10, 2020, at approximately 19:30 UTC, a Laister-Kaufmann LK-10A glider, registration PT-PAZ, was performing a local flight near Bauru, São Paulo. The aircraft had been towed to altitude and had successfully disconnected from the tow plane to begin its glide phase.
While flying in level flight at an altitude of approximately 1,350 meters, the crew noticed the right wing was becoming detached. The aircraft entered an uncontrolled right-hand spin. The two occupants successfully deployed parachutes and abandoned the aircraft mid-air. The glider subsequently impacted the ground, resulting in substantial damage to the airframe. Both pilots survived the incident, sustaining only minor injuries upon landing.
The investigation
CENIPA investigators examined the wreckage and the maintenance records of the operator, Aeroclube de Bauru. The investigation focused on the structural integrity of the wing attachment points and the adequacy of the maintenance performed by the operator's certified maintenance organization (OM).
Metallographic analysis conducted by the Department of Aerospace Science and Technology (DCTA) revealed that the fracture in one of the spars occurred due to material loss caused by intergranular corrosion. Investigators found widespread corrosion and cracks in the area containing the wing pins and supports.
Furthermore, the investigation identified discrepancies in the aircraft's documentation. While the maintenance logs indicated recent inspections, the aircraft's airframe logbook had not been updated since May 2018. There were also conflicting records regarding which technical orders guided the most recent annual and 100-hour inspections.
Findings
- Inadequate preventive maintenance: The required inspections for the wing pins, spars, and attachment hardware, as mandated by the technical orders and Brazilian civil aviation regulations, were not properly executed.
- Failure of quality control: The maintenance organization's quality control system failed to ensure the airworthiness of the aircraft, allowing it to be released for flight despite visible corrosion and cracks.
- Inadequate management supervision: Inconsistent record-keeping and failure to follow technical instructions were attributed to poor managerial oversight.
Safety action
CENIPA recommended that the National Civil Aviation Agency (ANAC) intervene with the Aeroclube de Bauru to ensure that the maintenance organization's processes for personnel training, managerial supervision, and quality control meet all applicable regulatory requirements.