Incident Details
On the first flight following the aircraft's annual inspection, which included replacement of all oil lines, a certified flight instructor (CFI) planned to conduct a biennial flight review (BFR) with the aircraft's owner/pilot. Approximately five minutes after takeoff, the crew observed that the oil pressure gauge indicated near zero pounds of pressure. The CFI monitored the oil temperature gauge, which remained within the green arc. The crew alerted air traffic control (ATC) of the situation and received an instrument flight rules (IFR) clearance back to the departure airport.
During the next 14 minutes, the oil pressure needle remained slightly above the red line, while the oil temperature remained stable and within the green arc. The aircraft passed the final approach fix and continued to operate normally. Suddenly, all engine power was lost. The CFI executed a forced landing on a golf course approximately three miles from the airport.
Investigation Findings
Examination of the engine revealed internal heat distress and broken connecting rods. Further inspection disclosed that a 'B' nut on a newly installed oil line had not been securely torqued and had come loose at its engine case attachment fitting. The oil line was found saturated with oil, indicating that oil had been lost through the loose connection, leading to engine failure due to oil starvation.