What happened
On August 25, 2017, an L-13 SE Vivat motor glider, registration OK-8118, was conducting a series of three training flights at Frýdlant nad Ostravicí airport (LKFR). The crew, consisting of an instructor and a student pilot, had completed three successful landings.
While taxiing toward the holding point for runway 26 after the third landing, the main landing gear suddenly collapsed forward. The sudden nose-down movement caused the aircraft to come to an abrupt halt. Following the instructor's commands, the student pilot immediately shut down the engine, cut the fuel, and deactivated the electrical system. The crew exited the aircraft without injury.
Upon inspection, it was discovered that the main landing gear leg had struck the lower part of the fuselage, causing significant damage to the composite skin and the internal bulkhead structure. No propeller strike occurred during the event.
The investigation
The ÚZPLN investigation examined the aircraft's maintenance history, the crew's qualifications, and the physical condition of the landing gear components. The investigation included a technical inspection by a maintenance organization, which identified a torn eyelet on the landing gear locking linkage.
Investigators reviewed the aircraft's maintenance records, noting that the aircraft was properly maintained in accordance with manufacturer requirements and that the last 400-hour inspection had been completed in 2014. The investigation also confirmed that the weather conditions were suitable for flight and that the aircraft's weight and center of gravity were within permissible limits.
Findings
- The primary cause of the accident was a fatigue fracture of the main landing gear deployment strut.
- The fracture occurred at a point where the strut's cross-section changes, a location subject to high stress during both gear extension/retraction and taxiing on uneven surfaces.
- The failure of the locking linkage caused the main gear to collapse forward under the aircraft's weight.
- The aircraft's maintenance, operation, and engine servicing were all performed in compliance with manufacturer requirements.
- There was no evidence of exceeding operational limits during the training flights or during taxiing that could have contributed to the structural failure.