Incident Overview
On 11 August 2019 at 13:22 local time, a Robin DR 400RP aircraft operated from the GSS Airfield "Żar" (EPZR) departed for a glider towing mission. The pilot, holding a Private Pilot License (PPL(A)), was the sole occupant. The aircraft experienced an oil system anomaly shortly after release of the glider.
Sequence of Events
During the towing operation, at an altitude of approximately 1,200 feet, the pilot initiated the glider release. Immediately afterward, he observed a decrease in oil pressure and irregular engine operation. He decided to land without delay. After landing, the pilot taxied off the runway and shut down the engine.
Findings
Post-flight inspection of the aircraft revealed a fracture in the oil line connecting the oil pump to the oil pressure sensor. The break had caused near-complete loss of engine oil. The engine was removed and sent to a certified maintenance facility for evaluation. Examination disclosed scoring on the crankshaft main bearing shells, limited to the tin alloy layer. The affected bearing shells were replaced with new ones. No other engine components showed damage.
Investigation Outcome
The investigation determined that the accident cause was the cracking of the oil system line. As a preventive measure, the aircraft operator, in consultation with the CAMO and the aircraft manufacturer, replaced the damaged rigid oil line with a flexible hose, as recommended by the manufacturer's Service Bulletin No. 031104R1 from 2011. No safety recommendations were issued by the investigating commission.
The pilot was uninjured, and no other persons were involved.