A BN-2A MK111 TRISLANDER WAS DISPATCHED IN NON COMPLIANCE FROM A PHASE CHK WITH THE TAIL ENG NOT SVCED WITH OIL. ENG FAILED AFTER TKOF.

Narrative

I HAD COMPLETED; OR THOUGHT I HAD; PHASE #8 OF THE ANNUAL ACFT INSPECTION PROC ON A BRITTEN-NORTIAN TRISLANDER; WHICH IS THE 3RD PHASE OF 4 THAT CONSTITUTES A 500-HR INSPECTION. PHASE #6 COVERS L ENG AND WING. PHASE #7 THE R ENG AND WING; AND PHASE #8 THE REAR ENG AND TAIL UNIT. THE ACFT LAYS OVER AT ZZZ ABOUT 9 HRS ON A CARGO CONTRACT BEFORE DEP AT XA15. ANOTHER MECH; WHO WAS NOT AVAILABLE FOR PERSONAL REASONS WHEN THE 500-HR INSPECTION BECAME DUE; USUALLY ASSISTS ME. I ENLISTED THE HELP OF THE PLT TO REMOVE AND INSTALL INSPECTION PLATES AND TO CHANGE THE OIL ON THE ENGS SINCE I KNEW HE WAS FAMILIAR WITH HOW IT WAS TO BE ACCOMPLISHED. ON THE PREVIOUS 2 DAYS; PHASES #6 AND #7 WERE ACCOMPLISHED WITH HIS HELP. AT THE INITIATION OF PHASE #8; THE OIL WAS DRAINED FROM THE REAR ENG AND THE PLT INFORMED ME HE WAS GOING TO USE QUART CONTAINERS OF OIL TO SVC THE REAR ENG INSTEAD OF THE GALLON CONTAINERS THAT HAD BEEN USED ON THE WING ENGS BECAUSE THE FUNNEL USED WITH THE GALLON CONTAINERS WAS TALL AND HARD TO SEE INTO WHEN SVCING THE REAR ENG POS. I TOLD HIM THE QUART CONTAINERS WOULD BE FINE. ABOUT 1 HR BEFORE DEP TIME; WITH ALL INSPECTION PANELS REINSTALLED BUT WITH THE COWLING STILL OFF; I TOLD THE PLT WE SHOULD RUN THE ENG AS WE HAD ON THE PREVIOUS 2 DAYS. (THE 500 HR INSPECTION REQUIRES REMOVAL OF BOTH MAGNETOS AND AN INTERNAL INSPECTION OF POINTS; ETC; AND I LIKE TO CONFIRM THE ENG WILL START AND OPERATE NORMALLY ON EACH MAGNETO WITH A VERY SHORT RUN AT LOW RPM SO THAT IF THERE IS A PROB WE HAVEN'T LOST THE TIME INVOLVED IN COWLING/UNCOWLING THE ENG.) HE RAN THE ENG AND IT STARTED AND RAN NORMALLY AT LOW RPM; A TOTAL OF ABOUT 20 SECONDS. THE ENG COWLING WAS INSTALLED AND A SHORT TIME LATER THE ACFT WAS LOADED WITH OUTBOUND FREIGHT. THE PLT STARTED ALL THE ENGS AND TAXIED OUT FOR RUN-UP AND DEP. I HEARD HIM TAKE OFF AND WITHIN A FEW MINS WAS NOTIFIED THAT HE RADIOED IN THAT HE WAS RETURNING. WHEN HE TAXIED UP; I SAW THAT THE REAR ENG WAS NOT RUNNING AND WAS NOT FEATHERED. THE PLT INFORMED ME THE REAR ENG FAILED ON CLBOUT AND IT WAS DETERMINED THERE WAS NO OIL IN THE ENG AND THAT THE ENG HAD STRUCTURALLY FAILED. THERE WAS A POINT WHEN I CONSIDERED ASKING THE PLT IF HE HAD SVCED THE OIL ON THE REAR ENG (I HAD OBSERVED THE OIL SVCING ON THE PREVIOUS DAYS; NOT ON THIS DAY) BUT WHEN HE RAN THE ENG ON THE INITIAL RUN I THOUGHT HE MUST HAVE SVCED IT OR HE WOULDN'T BE RUNNING IT. THIS WAS AN ERROR OF ASSUMPTION. IT MAY OR MAY NOT HAVE BEEN RUN LONG ENOUGH FOR OIL PRESSURE INDICATION ON THAT RUN SINCE THE OIL FILTER WAS REPLACED AND IT COULD TAKE A FEW MORE SECONDS THAN THAT RUN LENGTH AFFORDED. HE NEVER TOLD ME ONE WAY OR THE OTHER IF HE HAD PRESSURE INDICATION. HE CERTAINLY SHOULD HAVE NOTED LACK OF INDICATION ON START-UP FOR THE FLT AND RUN-UP. I BELIEVE THAT WAS DUE TO FAILURE ON HIS PART TO FOLLOW THE CHKLIST.