As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLT/TRI - FLT 873 - AFTER TAKEOFF FROM CLT, THE CREW NOTICED A SMOKE SMELL IN BOTH THE COCKPIT AND THE CABIN. THE SMOKE DETECTOR IN THE AFT LAVATORY ACTIVATED. THE FLIGHT RETURNED TO CLT WITHOUT FURTHER INCIDENT. MAINTENANCE DETERMINED THE SMOKE WAS DUE TO OIL FROM THE APU. THEY REPLACED THE APU. (X)