What was found
UPON REMOVING THE UPPER ENGINE COMPARTMENT HEAT SHIELD FOR REPLACEMENT, A 4 INCH CRACK WAS DISCOVERED IN THE TOP OF THE ENGINE COMPARTMENT, ALONG THE RIVET LINE, WHERE THE TAIL BOOM STRUCTURE ATTACHES TO THE FIRESHIELD. OUR 2 OTHER M.D. 369E HELICOPTERS WERE INSPECTED AND ALSO HAD SIMILAR CRACKS IN THE SAME AREA. (N5247S, SN 0119E, 6066.0 HRS. 11463 LANDINGS AND N6508U, SN 0084E, 2793.0 HRS. 6816 LANDINGS) THIS AREA IS USUALLY COVERED BY THE HEAT SHIELD BLANKET WHICH IS NOT REMOVED FOR NORMAL INSPECTIONS. RECOMMEND THE MANUFACTURER ISSUE A SB OR AD TO THE INSPECTION CHECKLIST TO INSPECT THIS AREA PERIODICALLY.