Incident Overview
On 11 December 2021, at Gliwice Airport (EPGL), an instructor and a student pilot were conducting circuit training on a Schweizer 269C helicopter (registration SP-KGO) under the CPL(H) syllabus. During the third turn of a subsequent circuit, the crew noticed vibrations and a tendency for the helicopter to yaw left. Unusual engine noises were heard, followed by a loud bang from the engine. Engine power then decreased, and main rotor rpm began to drop. The crew immediately initiated an autorotation and performed an emergency landing on the airport without further consequences.
Personnel and Equipment
The flight crew held valid qualifications, licenses, and medical certificates. The helicopter was insured with a valid liability policy and possessed all required technical and operational documentation. Meteorological conditions were not a factor in the occurrence.
Findings and Cause
The investigation determined that the incident was caused by a drop in oil pressure due to a leak in the oil line, which resulted in engine seizure during flight. A contributing factor was a fatigue fracture of one of the brackets securing the oil line. This fracture allowed the line to contact a sharp edge of a second oil cooler element. During flight, vibrations and the sharp edge contact caused progressive abrasion, weakening, and eventual rupture of the oil line, leading to a rapid loss of oil pressure.
Preventive Actions
The helicopter operator took several preventive measures. During a safety management system (SMS) meeting, all personnel were briefed on the incident. The importance of inspecting the condition of oil line mounting brackets during pre-flight checks was emphasized. Additionally, the operator introduced a mandatory engine inspection before each training session, focusing on the condition of oil line brackets and related components.
No Safety Recommendations
The investigation concluded without issuing any additional safety recommendations.