Incident Overview
On 4 August 2017, approximately 7:15, a student pilot and an instructor were preparing for the first flight of the day at Bielsko-Aleksandrowice airfield (EPBA). The instructor noticed a slight spontaneous movement of the control stick, which settled near the neutral position. Upon checking control deflections, he found that the ailerons moved correctly, but the elevator did not move; the stick moved without noticeable resistance in that axis.
Discovery of Damage
The instructor then moved to the tail of the glider and manually moved the elevator, but this did not cause the control stick to move. He inspected the elevator pushrod connection through inspection window A and found it properly attached. After opening inspection window B, he saw the pushrod hanging loosely with a fractured threaded length adjustment end fitting.
Investigation Findings
The fracture surface exhibited characteristics consistent with fatigue. The event was immediately reported to the Polish State Commission for Aircraft Accident Investigation (PKBWL), the Civil Aviation Authority (ULC), the continuing airworthiness management organization (CAMO), and the type certificate holder (manufacturer).
Contributing Circumstances
Contributing factors identified include intensive use of the glider during training and a slight bend in the adjustment screw, possibly due to improper securing of the elevator during ground transport.
Preventive Actions
The operator grounded all SZD-9 bis Bocian 1E gliders in the Bielsko-Biała Aero Club until the manufacturer issued Service Information Letter SIL-005/ZSJ/2017 and the recommended inspections were completed.
Safety Recommendations
No safety recommendations were formulated by the commission.