What was found
DURING HEAVY CHECK, RT HORIZONTAL STABILIZER, RIB 4 RIVETS BACK FROM FWD SPAR AT UPPER SKIN ATTACH POINT RIB 12 IS CRACKED MAINTENANCE R & R RT HORIZONTAL STABILIZER, RIB 4 RIVETS BACK FROM FWD SPAR AT UPPER SKIN ATTACH POINT RIB 12 IAW SRM 51-40-02, 51-41-02. PN 170-62642-004, RIB 12.