As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETAINING RING "SPACER" APPARENTLY BROKE AND AS IT SPUN AROUND, CAUGHT M/R SHAFT CHIP DETECTOR AND BROKE THE END OF IT OFF THUS TURNING ON "CHIP LIGHT" IN COCKPIT. AC TURNED AROUND AND LANDED AT BASE. FOUND CHIP DETECTOR BROKEN, TRANSMISSION APART AND SUBSEQUENTLY FOUND SOURCE OF PROBLEM. (K)