What was found
AFTER HAVING PROBLEMS WITH ANOTHER 400 SERIES ACFT, INSPECTED AFT ATTACH POINT OF TIP TANKS. DISCOVERED THE MOST AFT WING SKIN CRACKED AND HORIZ RIVETS SHEARED THAT ATTACH THE OTBD AILERON BRACKET ASSY (CESSNA P/N 521001-12) WHICH ARE SAME RIVETS THAT ATTACH TIP TANK AFT SUPPORT BRACKETS (CESSNA P/N 08222600-29 AND -30) TO THE WING. LT SIDE ALSO CRACKED MOST OTBD RIB (CESSNA P/N 0822040-17) AND THE MOST AFT TIP TANK SUPPORT BULKHEAD (CESSNA P/N 0823400-63, SUBASSY OF 823400-109) HAD 2 CRACKS. RIGHT DID NOT REFLECT ANY DAMAGE TO STRINGER (MOST AFT POINT) OF TIP TANK, HOWEVER, LT SIDE HAD STRUCK SOLID OBJECT AT SOME POINT.