As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING AN UNRELATED REPAIR, IT WAS DISCOVERED THAT THE LEFT HORIZONTAL TIP RIB WAS CRACKED. RIB WAS REPAIRED AND ADOUBLER WAS INSTALLED. CRACKS WERE STOP DRILLED AS NECESSARY. DUE TO VIBARATION, THE LEFT REGION OF THE HORIZONTAL STABILIZER ON MOST OF THESE AIRCRAFT, SUSTAIN SIMILAR SIGNS OF FATIGUE THROUGH CRACKING OR RIVITS LOOSENING. PROP BALANCING AND FLIGHT CONTROL BALANCE CHECKS WILL NOW BE PERFORMED ON A MORE FREQUENT BASIS.