As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BIS - OUTBOUND FROM BIS, THE CREW EXECUTED AN AIR TURN-BACK AFTER THE RT ENGINE LOST OIL PRESSURE AND WAS SECURED. THE SINGLE ENGINE FLIGHT AND LANDING WERE UNEVENTFUL. MAINTENANCE REPLACED THE ENGINE AND THE TEST FLIGHT WAS SATISFACTORY. FAILURE IS ASSUMED TO BE A NR 4 BEARING FAILURE. A TEAR-DOWN AT PRATT AND WHITNEY IS PENDING.