As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ANNUAL INSPECTION, FOUND LT WING MAIN SPAR UPPER CAP SEVERELY CORRODED ON FWD FLANGE. ONLY WAY TO DETECT IS WITH A MIRROR THROUGH FWD WHEELWELL INSPECTION PANEL. WING REMOVED AND SPAR REPLACED. SUBMITTER STATED INTERGRANULAR CORROSION IS THE CAUSE.