What happened
On March 14, 2021, at approximately 14:35 UTC, a KW1 glider, registration PT-PKA, was performing a local flight at the Erechim Aerodrome (SSER) in Rio Grande do Sul, Brazil. The aircraft was being operated by Aeroclube de Erechim for private flight training.
Following takeoff, the glider became unexpectedly disconnected from the tow plane, an Aero Boero AB-180 (registration PP-GSD). While the pilot attempted to execute an emergency return to the runway, the glider's flight path was altered twice before it ultimately collided with a building approximately 500 meters before reaching the opposite runway threshold. The impact resulted in substantial damage to the glider, though the pilot emerged uninjured.
The investigation
CENIPA investigators examined the towing system, the tow cable, and the pilot's training records. The investigation confirmed that the aircraft's airworthiness certificate was valid and the aircraft was within weight and balance limits. The tow cable and the mechanical release system on the glider were inspected; despite the damage to the glider's nacelle, the release mechanism showed no signs of mechanical failure, broken components, or looseness. Subsequent testing by a maintenance workshop confirmed the release command and the hook's ability to withstand both aligned and angular tension.
Investigators also noted that ground crew members observed the glider's air brakes were open during the initial takeoff, which likely hindered the aircraft's rate of climb. While the pilot was properly licensed and medically certified, the investigation focused on why the disconnection occurred without a commanded release.
Findings
- The towing system and cable were fully operational and intact.
- The separation between the aircraft occurred via the glider's release system.
- The most probable cause of the premature disconnection was the unintentional activation of the release handle by the pilot inside the nacelle.
- The pilot's limited flight experience, combined with potential errors in command application and pilot judgment, contributed to the unsuccessful emergency return to the runway.