EMERGENCY LNDG; ENGINE NACELLE CAME LOOSE.

Narrative

THE ACFT WAS BROUGHT INTO MAINT TO HAVE LEFT ALTERNATOR CHKED. IT WAS A SHORT/HURRIED DAY FOR THE MAINT DEPT WHICH WAS VERY SHORT HANDED. DIRECTOR OF MAINT WORKED ON ALTERNATOR WHILE SUPERVISING OTHER PROJECTS. AS A RESULT WHEN THE UPPER NACELLE WAS ATTACHED 6 OF THE 15 FASTENERS WERE NOT SECURED CORRECTLY. DURING PREFLT INSPECTION THESE FASTENERS APPEARED TO BE CORRECTLY FASTENED. DURING FLT FROM ARB TO YIP (10 NM) NO PROB WAS NOTED. IN THIS PORTION OF FLT THE AIRSPD WAS NO GREATER THAN 150 MPH IAS. DURING THE LEVEL OFF FROM THE CLB OUT OF YIP THE TOP NACELLE CAME LOOSE (AT 180 MPH IAS). THE AREA AROUND THE 2 OUTBOARD NOSE FASTENERS AND 2 OUTBOARD AFT FASTENERS RIPPED AND THE OUTBOARD PORTION OF THE NACELLE BENT BACK. AN IMMEDIATE DECELERATION TO VMC + 10 WAS INITIATED AND CLE CENTER WAS NOTIFIED THAT AN IMMEDIATE RETURN TO ARB (CLOSEST ARPT) WAS NECESSARY. A SUCCESSFUL LNDG WAS MADE AT ARB WITH THE NACELLE STILL ATTACHED TO THE ACFT BY 5 OF THE 15 FASTENERS. MINOR SHEET METAL WORK IS REQUIRED TO FIX THE NACELLE. THIS INCIDENT COULD HAVE BEEN PREVENTED IF: 1) THE MAINT DEPT WAS NOT IN A HURRY AND DOUBLE CHKED THEIR WORK; AND 2) THE PLT CAUGHT THE DISCREPANCY DURING THE PREFLT. THIS WAS DUE TO INACCURATE KNOWLEDGE ON THE APPEARANCE OF THE ENGAGED FASTENER. BOTH ENGAGED AND DISENGAGED FASTENERS CAN HAVE THE SCREW HEAD LYING IN THE HORIZ POS. AS A RESULT OF THIS INCIDENT THE FASTENERS HAVE BEEN MORE CLEARLY MARKED AND THE CORRECT INDICATION HAS BEEN EXPLAINED TO PLTS AND MECHS.