What was found
WHILE ENROUTE, THE PILOT EXPERIENCED A FAILURE OF THE STANDARD ELECTRICAL POWER SYSTEM FOLLOWED BY FLUCTUATING AND DECREASING OIL PRESSURE. THE PILOT LANDED WITHOUT INCIDENT. MAINTENANCE PERSONNEL FOUND THAT THE AFT END OF THE ACCESSORY DRIVE OF THE ACCESSORY DRIVE FOR THE EXTERNAL SCAVANGE PUMP HAD SHEARED OFF. THIS FAILURE ALLOWED ENGINE OIL IN THE SCAVANGE PUMP HOUSING TO EXIT BY THE PLAIN SEAL AND VENT OVERBOARD THROUGH THE ALTERNATOR DRIVE PULLEY ASSY DRAIN TUBE. THE LOSS OF OIL PRESSURE. POSSIBLE CAUSE OF FAILURE OF THE SCAVANGE PUMP DRIVE SHAFT IS A TWIST LOAD INDUCED BY EITHER THE ALTERNATOR DRIVE PULLEY BEARINGS OR THE ALTERNATOR BEARINGS. (K)