What was found
WHILE N67RT SERIAL NUMBER 381 WAS IN FOR ITS 24-MONTH INSPECTION AT DUNCAN AVIATION IN BATTLE CREEK, MAINTENANCE DISCOVERED THE LOWER FORWARD PYLON YOKE MOUNTING BOLT WAS LOOSE ON THE NR 1 & 2 ENGINES. THE LOOSE HARDWARE WAS DISCOVERED DURING THE INSPECTION OF THE ENGINE AND NACELLE. THE MAINTENANCE TEAM VERIFIED THAT THE BOLTS WERE NOT BROKEN AND THAT THE NUT PLATE FLAG WAS INSTALLED IN THE CORRECT ORIENTATION. ALL HARDWARE WAS PRESENT. AFTER DUNCAN DISCOVERED N67RT’S ISSUE, WE INSPECTED THE REST OF OUR FLEET. WE FOUND THAT N89RT, S/N 383, HAD THE SAME ISSUE WITH THE EXACT SAME BOLTS – BOTH ON THE NR 1 & 2 ENGINES. IN THE CASE OF BOTH AIRCRAFT, NEITHER THE ENGINES NOR THE YOKES HAVE BEEN REMOVED. THIS LED US TO BELIEVE THE BOLTS WERE NOT TORQUED PROPERLY DURING THE PRODUCTION OF THE AIRCRAFT. WE HAVE WORKED CLOSELY WITH DASSAULT STRUCTURES AND ENGINEERING TO RESOLVE THE ISSUE WITH BOTH AIRCRAFT. DASSAULT RECOMMENDED VISUALLY INSPECTING BORES AND BOLTS, AND IF AVAILABLE, REPLACING THE BOLTS. NORDAM (WHO MANUFACTURES THE YOKES) RECOMMENDED RETORQUING THE BOLT BY FOLLOWING THE INSTALLATION GUIDELINES AND MONITORING THE HARDWARE FOR LOOSENESS. ALL FOUR BOLTS WERE REMOVED AND REPLACED WITH NEW ONES FOLLOWING THE RECOMMENDED INSPECTIONS. WE WILL CONTINUE TO MONITOR THESE BOLTS FOR TIGHTNESS OVER THE COMING MONTHS.