Cessna Stationair/Turbo Stationair 6
Maintenance Airframe; Maintenance Powerplant
Maintenance Technician 1
Fatigue
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
Aircraft Aircraft Damaged; Flight Crew Inflight Shutdown
Procedure; Aircraft; Company Policy
While employed for this company; I was instructed to meet the aforementioned aircraft at our home base to conduct routine maintenance (an oil change and an AD-required inspection). The aircraft arrived at dusk; and I proceeded to drain the oil; remove and replace the oil filter; add new oil; and complete the AD inspection. Because it was not common company practice to cut open and inspect every oil filter removed from an aircraft; I set the old oil filter aside to drain and did nothing more with it. At this point; I had been on duty for twelve hours and was eager to finish the maintenance and go home.The aircraft departed early the next morning. In the afternoon; the company received word that the aircraft had experienced a catastrophic engine failure and made a forced landing.Some weeks later (I do not remember exactly how much time had passed since the incident); another maintenance technician located and cut open the oil filter [I] removed. Upon inspection; the technician found the filter to be glittering with ferrous and non-ferrous metal; an obvious indication that the engine was not airworthy and required immediate attention. Had I cut open and inspected the filter the evening it was removed; I would never had signed off the aircraft as airworthy and the incident would have been avoided.I believe several factors contributed to this occurrence. As mentioned; a long duty day and consequent fatigue likely inhibited my better judgment to cut and inspect the oil filter. Also; a lack of standard company procedure that included a filter inspection as part of an oil change assuaged my decision to skip this critical step. Pressure from management to keep aircraft in the air regardless of potential maintenance issues further dissuaded me from looking for a reason to ground the aircraft.Since this incident and subsequent findings; I have made several resolutions. First and most obviously; no oil change occurs without also cutting and inspecting the oil filter. Second; safety must always come before company productivity demands. This led me to eventually quit my job with the company in question; as I would rather be alternatively employed than party to another incident or accident. Third; experience should be shared. I have not hesitated to offer this story to other maintenance technicians as a caution against cutting corners; and I share it now with the broader aviation community to likewise contribute to the body of experience that helps make aviation safer. Although this report is being filed [many] months following the incident and no longer offers me any legal benefit; I do so anyway in the hope that others may learn from my experience.
The Reporter stated that the oil filter was loaded with metal and the company he worked for did not have a procedure in place to inspect oil filters and did not send oil out to be analyzed. The aircraft in question was still not in service and the cause of the engine failure still has not been determined.
After servicing the engine the aircraft experienced an engine failure in flight. This happened because the oil filter was not inspected for metal. Further investigation reviled that the oil filter was full of metal.