19961022038289I

NARRATIVE: ON 10-22-96 AT APPROXIMATELY 0650 PDT, A BRITISH AEROSPACE JETSTREAM 3101 MODEL AIRCRAFT, N421UE, FLIGHT 6761, A SCHEDULED AIR CARRIER OPERATED BY WEST AIR COMMUTER AIRLINES, INC., DEPARTED FRESNO AIR TERMINAL (FAT) ON AN IFR FLIGHT PLAN WITH THREE PASSENGERS AND A FLIGHT CREW OF TWO. DURING TAKEOFF CLIMB, AND JUST AFTER ACCELERATION HEIGHT, THE FLIGHT CREW HEARD A VERY LARGE "THUMP" AND FELT SOMETHING IMPACT THE AIRCRAFT. MINOR VIBRATION HAD DEVELOPED IN THE CONTROL YOKE ACCORDING TO THE PILOT-IN-COMMAND. THE FLIGHT CREW REPORTED TO THE FAT AIR TRAFFIC CONTROL TOWER THAT THEY HAD A POSSIBLE BIRD STRIKE AND INITIATED A RETURN TO FAT. NO EMERGENCY WAS DECLARED BECAUSE NO CONTROL OF THE AIRCRAFT WAS LOST. THE FLIGHT CREW MADE A LEFT TRAFFIC PATTERN AND LANDED WITHOUT INCIDENT ON RUNWAY 29R. AFTER LANDING, AND WHILE TAXIING BACK TO THE GATE, FAT GROUND CONTROL OBSERVED AND REPORTED TO THE FLIGHT CREW THAT A PORTION OF THE RIGHT ENGINE OUTBOARD COWLING WAS MISSING. WHEN THE AIRCRAFT RETURNED TO THE GATE, WESTAIR'S MAINTENANCE CONTROL DISPATCHED MAINTENANCE PERSONNEL TO INVESTIGATE THE DISCREPANCY. UPON INSPECTION OF THE AIRCRAFT BY WESTAIR'S FIRST MECHANIC ON-THE-SCENE, IT WAS DISCOVERED THAT THE RIGHT ENGINE FORWARD OUTBOARD REMOVABLE COWLING, PART NUMBER 1379095H402, HAD COME OFF IN FLIGHT AND WRAPPED ITSELF AROUND THE RIGHT HORIZONTAL STABILIZER LEADING EDGE. FURTHER INSPECTION REVEALED THAT THERE WERE 13 FASTENERS STILL IN THEIR RECEPTACLES ON THE TOP PORTION OF THE COWLING AND THE LOWER 10 WERE MISSING. THE AIRCRAFT WAS THEN TAXIED TO WESTAIR'S MAINTENANCE FACILITY AT FAT. SHORTLY AFTER THE SUBJECT AIRCRAFT ARRIVED AT WESTAIR'S HANGAR, THE REPORTING AVIATION SAFETY INSPECTOR MADE A VISIT TO THE HANGAR TO EXAMINE N421UE. IT WAS NOTED THAT DAMAGE WAS SUSTAINED TO THE FOLLOWING AREAS; RIGHT ENGINE OUTBOARD FORWARD REMOVABLE COWLING, THE RIGHT HORIZONTAL LEADING EDGE, AND THE OUTER PORTION OF THE RIGHT HORIZONTAL STABILIZER UPPER SKIN. IT WAS FURTHER DISCOVERED THAT OUT OF THE 23 TOTAL CAMLOC (QUICK RELEASE) FASTENERS THAT ARE USED TO SECURE THE RIGHT ENGINE OUTBOARD FORWARD REMOVABLE COWLING TO THE ENGINE NACELLE ATTACHMENT BEAMS, ONLY THE UPPER 13 STILL REMAINED IN THEIR RECEPTACLES AND A CIRCULAR PIECE OF METAL FRAGMENT FROM THE COWLING REMAINED ATTACHED TO THE 13 CAMLOC FASTENERS. THIS INDICATES THAT THOSE 13 FASTENERS WERE PROPERLY SECURED AT THE TIME OF COWLING INSTALLATION PRIOR TO FLIGHT. THE REMAINING 10 CAMLOC FASTENERS LOCATED AT THE LOWER PORTION OF THE COWLING WERE ALTOGETHER MISSING FROM THEIR RECEPTACLES AND WERE STILL ATTACHED TO THE SUBJECT COWLING WHICH DENOTES THAT THEY WERE NOT PROPERLY SECURED AT THE TIME OF COWLING INSTALLATION PRIOR TO FLIGHT. IT APPEARS THAT THE AIRSTREAM ON TAKEOFF CLIMB PULLED AWAY THE COWLING WHERE THE 10 CAMLOC FASTENERS WERE NOT SECURED AT THE LOWER SECTION OF THE COWLING, AND EVENTUALLY TORE THE COWLING FROM THE 13 SECURED CAMLOC FASTENERS. UPON EXAMINATION OF THE AIRCRAFT MAINTENANCE RECORDS, IT WAS DETERMINED THAT PRIOR TO FLIGHT 6761, ON THE MORINING OR 10-22-96, A WESTAIR MECHANIC PERFORMED MAINTENANCE ON N421UE WHILE ACCOMPLISHING CORRECTIVE ACTION ON THE FLIGHT LOG DISCREPANCY INVOLVING THE RIGHT ENGINE. THIS PARTICULAR MAINTENANCE TASK REQUIRED THE REMOVAL OF THE RIGHT ENGINE FORWARD OUTBOARD REMOVABLE COWLING. ^PRIVACY DATA OMITTED^ THIS INCIDENT IS CONSIDERED CLOSED.