Event Details
On 1 August 2018, training flights were conducted at the Biała Podlaska airstrip (EPBP) using a glider towed by a winch. A 55-year-old glider instructor pilot, holding a valid SPL license with current FI instructor rating and medical certificate, prepared for a training flight with a student pilot. The glider, a SZD-54-2 Perkoz, had the required technical documentation and was airworthy. The crew intended to practice takeoff, traffic pattern, and landing per the glider training syllabus. This was the student's nineteenth training flight for this exercise. At 12:31 LMT, the glider landed on the concrete runway. After the landing roll and exiting the cockpit, the crew observed that the main landing gear wheel and its suspension had retracted into the wheel well in the fuselage. All landings on the day of the event were reported as normal and occurred on the same runway.
Investigation Findings
The glider was transported to a hangar, and the Continuing Airworthiness Management Organization (CAMO) and the Type Certificate Holder (TCH) were notified. After disassembling the landing gear, investigators found that the metal components of both elastomeric shock absorbers in the main landing gear were fractured. Examination indicated the fractures were fatigue-related. The TCH representative performed an inspection that revealed no damage to the composite structure of load-bearing elements (fuselage, wings, tail) or the truss within the main gear bay. The user's commission stated that weather conditions did not affect the event; at the time of landing, wind was along the runway axis at about 2 m/s.
Probable Cause and Contributing Factors
The probable cause of the incident was fatigue fracture of the main landing gear shock absorbers. A contributing circumstance was likely hard landing(s) during previous glider operations, which may have initiated the fracture process.
Preventive Actions
The organization conducting the training reminded personnel during theoretical and practical training to report hard landings, landings with tail strike (without flare), or landings with the wheel brake engaged, in accordance with the mandatory occurrence reporting system within the Approved Training Organization (ATO). The investigation commission issued no safety recommendations.