As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE PILOT REPORTED A STEADY LOSS OF RT ENGINE OIL PRESSURE AFTER TAKEOFF. ENGINE SHUTDOWN AND FEATHERED BEFORE OIL PRESSURE REACHED THE RED LINE. DIVERTED BACK TO THE DEPARTURE. DURING MX INSPECTION, A LOOSE B-NUT WAS ALSO FOUND ON THE OIL PRESSURE LINE TO THE WASTE GATE. B-NUT TIGHTENED, AND ACFT RELEASED FOR SERVICE.