What was found
(CAN) ON SCHEDULED 100 HR INSPECTION, VISUAL INSPECTION OF TAILBOOM ATTACH FITTINGS. UPPER LT AIRFRAME FITTING FOUND CRACKED. UPON FURTHER INVESTIGATION AFT AIRFRAME BULKHEAD FOUND CRACKED AT UPPER LT LOCATON. SUSPECTED CAUSE LONG IDLE TIMES AT 60 PERCENT N1 AND HEAVY SLING LOADS. MANUFACTURING DEFECTS POSSIBLY A FACTOR ALSO. SHORTEN IDLE TIMES TO ONLY NECESSARY COOL DOWN AND WARM UP TIMES. WHEN IDLING FOR PERIODS OF TIME, USE 70 PERCENT N1.