What was found
INSP 0513132-11, MOUNT BRACKET WAS FOUND TO BE CRACKED. CRACK RAN VERT THROUGH BRACKET AROUND OUTER RADIUS OF AN960-616 WASHER ON UPPER ENG MOUNT BOLT. INSP WAS DONE DUE TO 2 OTHER KNOWN REPORTS OF CRACKS IN THIS BRACKET ON SAME MODEL OF AC, ONE RESULTED IN A PARTIAL ENG AND FIREWALL SEPARATION FROM AC ON LANDING. MUST LOOK INSIDE STRINGER BEHIND INSTRUMENT PANEL. RECOMMEND THAT SPECIAL ATTENTION BE PAID TO UPPER ENG MOUNT BRACKETS DURING INSP. 0513132-3 AND -4 STRINGER ASSEMBLIES WERE USED ON 175 SN 55001 THRU 17557119, 172 SN 17247747 THRU 17272884P172 SN P17257120 THRU P17257188 F172 SN F17201235 THRU F17201909 FR172 SN FR172-0001 THRU FR17200655R172 SN R1722000 THRU R1723199.