ENG FAILURE AND FORCED LNDG. MINOR ACFT DAMAGE AND MINOR PAX INJURIES.

Narrative

ON DEC/SUN/95 AT APPROX XB30 LCL; WHILE ON A COMPANY FLT PLAN FROM GCN TO 61B; FLYING A DEHAVILLAND DH3T ACFT WITH 10 PAX ON BOARD APPROX 5 MI NE OF ARPT 61B AT AN ALT OF APPROX 3500 FT MSL ON APCH. THE ENG OF THE 135A ACFT ENG HAD CATASTROPHIC FAILURE. WHILE REDUCING PWR TO APPROX 35-30 TORQUE LBS; I HEARD A SOUND (A CLUNK) FOLLOWED BY A GRINDING SOUND; STRONG VIBRATION IN RUDDER PEDALS; FOLLOWED BY EXPLOSION; FIRE; THEN SMOKE. DURING THIS TIME I FEATHERED PROP; CONDITION LEVER OFF; IGNITORS OFF; EMER OIL/FUEL SHUTOFF BROKE OFF IN HAND. FIRE OUT; EXECUTED AN EMER LNDG TO A PWR LINE ACCESS ROAD 3 MI NE OF 61B. CALLED MAYDAY TWICE; SECOND TIME WITH NO RESPONSE. REMEMBER NOTING ALL ENG INSTS NORMAL PRIOR. FUEL ON BOARD AT TIME 3+ HRS; 120 GALLONS. DURING LNDG; ACFT EXPERIENCED MINOR DAMAGE TO R GEAR; R SIDE NACELLE; PROP. PAX WERE EVACED WITH NO MAJOR INJURIES. 1 TREATED FOR MINOR. ALL RELATED COMPANY NOTIFIED. FAA NOTIFIED. NTSB NOTIFIED. NASA NOTIFIED. NOTE: 3 DAYS PRIOR; I NOTED A STRONG VIBRATION IN RUDDER PEDALS. NOTIFIED MAINT. DURING INSPECTION THEY FOUND (MAINT) NOTHING. 2 DAYS PRIOR I NOTED SAME VIBRATION IN RUDDER PEDALS. NOTED IT AT APPROX 20-35 TORQUE LBS; MOMENTARILY. 1 DAY PRIOR NOTED SAME VIBRATION DURING PWR CHANGE ON SECOND LEG OF DAY. ALL ENG INSTS NORMAL. ON DEC/XX/95 TOOK MAINT ON TEST FLT; COULD NOT REPRODUCE VIBRATION. ENG INST NORMAL; XA30 LCL; XB30 LCL ENG FAILURE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: POSTFLT INSPECTION OF ACFT REVEALED FAILURE OF THE 5TH STAGE OF THE MAIN TURBINE BEARING. RPTR HAD WRITTEN THAT HE HAD FELT VIBRATIONS IN THE RUDDER PEDALS 2 PREVIOUS DAYS WHEN FLYING THE SAME ACFT AND RPTED IT TO HIS MAINT FACILITY. MAINT SUSPECTED THE VIBRATIONS WERE CAUSED BY EITHER AN AILERON OR RUDDER TRIM. THE DAY OF THE ENG FAILURE; RPTR TOOK A MECH FOR A FLT; NOT SPECIFICALLY TO CHK THE VIBRATIONS; BUT FOR PLEASURE. RPTR SAYS AT THAT TIME NO VIBRATIONS WERE FELT AT ALL. HOWEVER; JUST A FEW HRS LATER WHEN ON THE SUBJECT FLT THE ENG FAILED CATASTROPHICALLY. HAVING TO MAKE A FORCED LNDG ON A PWR LINE ACCESS ROAD; SOME MINOR ACFT DAMAGE WAS SUSTAINED AS WELL AS MINOR PAX INJURIES. HE NOTIFIED HIS COMPANY HEAD OFFICE WHO IN TURN NOTIFIED THE FAA AND NTSB. THE INVESTIGATION WAS DELAYED; BUT THE NTSB WAS NOT INVOLVED SINCE THE FAA LABELED IT AN INCIDENT.