What was found
FS 27 LOWER BEAM & LOWER SKINS DAMAGED. REMOVED F27 LOWER BEAM. PREVIOUSLY REPAIRED RT LOWER SKIN SECTION, LT & RT FS27 TO C CHANNEL BRACKETS/CVR BOX MOUNTING STRUCTURE. CUT MIDDLE/LH LOWER SKINS JUST AHEAD OF F28 FLANGE REMOVING FWD ~13" OF BOTH SKINS. FAB'D NEW F27 LOWER BEAM. FAB'D NEW RH LWR SKIN SEC. TO SAME DIMENSIONS, ADDITIONAL OVERLAP ON AFT SIDE JOGGLED TO SIT FLAT. FAB'D NEW LH SEC. 29.25"X15" THICK W/ ADDITIONAL OVERLAP ON AFT SIDE JOGGLED TO SIT FLAT. NEW SKIN LAPS AT F28 ON MIDDLE/LT SKIN HAD ADDITIONAL ROW OF RIVETS ADDED TO MAKE DOUBLE ROW COPYING MANUFACTURERS RIVET PATTERN. ALL NEW COMPONENTS ACID ETCHED/ALODINED/PRIMED W/ EPOXY PRIMER PRIOR TO INSTALL. RH & LH SINK SEC. HAD THEIR OB 2 CHANNELS ON CHINE ANGLE & CARGO DOOR FRAME SUPPORT LAID DOWN WET W B1/2. SKINS/FRAME MEMBER/CVR BOX MOUNTING STRUCTURE/F27 TO C CHANNEL BRACKETS INSTALLED USING MS20470AD, RIVETS. 1 RIVET WAS SUBSTITUTED FOR CR 3213. PINS USED TO ATTACH F27 BRACKETS TO LT & RT C CHANNEL STRUCTURE. MATERIALS USED: RIVET SIZE/SPACING/REPAIR CRITERIA WERE OBTAINED FROM SRM SEC. IV FIG 4-33 ITEM 14, FIG 4-34 ITEM 3, AC43.13 1B SEC. 4 FIG. 4-5 (P4-20), TABLE 4-9 (P4-37) & PAR 4-58G (P4-27) & FROM PREV. ACCOMPLISHED FORM 337 DATED 3/24/22. CONTINUED AIRWORTHINESS MAINTAINED IAW CURRENT INSP. PROGRAM OR AIRCRAFT MANUFACTURERS INSP. PROGRAM.