What was found
***WHILE A/C WAS OUT OF SERVICE FOR HEAVY CHECK*** EXTERNAL CF I, FWD CARGO DOOR LOWER SILL BEAM FOUND CORRODED UNDER FWD FITTING. EXTERNAL CF I, FWD CARGO DOOR LOWER SILL BEAM REPLACED IAW E-170 SRM 51-43-04. A/C REMAINS OUT OF SERVICE FOR HEAVY CHECK COMPLETION.