What was found
WHILE IN HEAVY CHECK, MAINTENANCE FOUND HEATED DRAIN MAST ANGLES ARE CORRODED AFT OF FR87 BETWEEN STRG.27R AND 28R. MAINTENANCE REMOVED AND REPLACED 2EA HEATED DRAIN MAST INTERCOSTAL CLIPS (ANGLES) AFT OF FR87 BETWEEN STGR 27R-28R REF. EMB SRM 51-40-08. PNS REPLACED ARE 170-87561-001, 170-87563-001, 170-87563-001 AND 170-87560-001. THIS AIRCRAFT REMAINS IN HEAVY CHECK FOR DURATION OF THE CHECK.