What happened
On August 10, 1996, a pilot was operating a Let L-13 glider for its initial solo flight. The pilot had received certification for the aircraft on July 24, 1996, and had logged approximately 2.1 hours in the aircraft prior to this flight.
The flight plan involved being towed to traffic pattern altitude, releasing from the tow line, entering the traffic pattern, and landing. The release occurred at an altitude of 1,850 feet, approximately 3 miles southwest of the airport (elevation 269 feet). Witnesses observed that about 5 to 10 seconds after the release, the glider entered a right spin. The aircraft continued to spin until it impacted the ground, resulting in 1 fatality.
The investigation
The investigation focused on the aircraft's weight and balance configuration. To prevent the center of gravity (CG) from exceeding the aft limit, a placard had been placed in the cockpit stating that the minimum solo weight for the front seat was 150 lbs. The pilot weighed between 128 and 135 lbs, and investigators recovered a single 25 lb ballast bag from the wreckage.
While the aircraft's operating manual contained information based on the original weight and balance configuration, the aircraft had undergone modifications, including repainting and the installation of a non-standard tailwheel. Revised weight and balance data, which was maintained in the operator's maintenance shop, indicated that the new minimum front seat solo weight was actually 181 lbs. Based on this updated data, the glider's CG was calculated to be 1.4 inches behind the aft limit. The pilot's personal copy of the operating manual did not include these revised figures, and copies of the manual being provided to renters also lacked the updated information.