What was found
DURING A C-CHECK, NR 4 SLAT WS 405 INTERIOR RIBS AT ACTUATOR ATTACH INBOARD & OUTBOARD CRACKED RIBS. REMOVED NR 4 L/E SLAT IAW B727 M/M 27-81-11. REMOVED DAMAGE RIBS FROM NR 4 SLAT WS 405 INBOARD & OUTBOARD RIBS AT ACTUATOR ATTACH POINT IAW B727 SRM 51-30-2, LOCATED AND DRILLED NEW RIBS INBOARD & OUTBOARD NR 4 SLAT WS 405 P/N 65-17276-9, PO 4175400 AND 65-17276-11, PO 4175400 IAW B727 SRM 51-30-5. TREATED, PRIMED AREA WHERE RIBS ARE TO BE REPLACED IAW B727 SRM 51-10-2. INSTALLED NEW RIBS IAW B727 SRM 51-30-2.