As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FATIGUE CRACK OCCURRED ON RIGHT HAND VERTICAL FIN SPAR MEMBER APPROXIMATELY .5 INCH FORWARD OF THE 90 DEGREE GEARBOX ATTACH FITTING. THIS CRACK WAS DETECTED DURING COMPLIANCE OF AD. PROBABLE CAUSE: FATIGUE. REMOVED AND REPLACED VERTICAL FIN SPAR ASSEMBLY IAW AD, SHOULD PRECLUDE THE PROBLEM.