What was found
ER/A 635012-14; A220-100 FUSELAGE REAR BARREL SKIN DOUBLER , WASTE ACCESS AND WASTE BOX ASSY / BTW FR75 - FR76, STR 32L - STR 36L / CORROSION. SUBJECT REPAIR REQUIRES FOLLOW-ON ACTION. ACCOMPLISH 635012-14, SECTION II REPETITIVE INSPECTION WITHIN EVERY 1,000 FLIGHT HOURS FROM 14,712 TOTAL AIRCRAFT FLIGHT HOURS AS OF 5JUN26 UNTIL SECTION III IS ACCOMPLISHED. ACCOMPLISH SECTION III PERMANENT REPAIR WITHIN 10,000 FLIGHT HOURS FROM 14,712 TOTAL FLIGHT HOURS AS OF 5JUN26. ADDITIONAL ENGINEERING AUTHORIZATION (ER/A REVISION) IS REQUIRED FOR FLIGHT BEYOND THIS LIMIT. ASSOCIATED ER/A 00-635012 ADDED FOR AC 8137. (LP# 1638194; AIRCRAFT WAS GROUNDED)