What was found
WHILE IN HEAVY CHECK, THE SHEAR CLIP AT FRAME 87, STRINGER 21L BELOW AFT PAX DOOR IS CORRODED. MX REMOVED AND REPLACED THE SHEAR CLIP IAW SRM 51-43-01, 51-23-04, 51-23-05, 51-23-06, 51-31-00, ETD 2016-170-051897, SRM 51-41-02, AND 51-43-01. MAJOR REPAIR.