As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 3 CTC STARTED HOWLING LOUDLY INFLIGHT, WITH RPM FLUCTUATION. OILY AND SMOKE SMELL IN COCKPIT. CREW WENT TO MANUAL OXYGEN. NR 3 CTC TURNED OFF HOWLING WENT AWAY. SMOKE REMOVAL PROCEDURES CLEANED COCKPIT AIR. *S/D* REPLACED NR 3 CTC, OPS CHECKED GOOD IAW DC8 MM.