ISLAND AIR CHARTERS INC

Operated by Island Air Charters (per NTSB report)

PILOT REPORTED THAT ON DOWNWIND, IN TRAFFIC PATTERN AT DESTINATION AIRPORT, HEARD A LOUD "POP," AND EXPERIENCED A POWER LOSS ON THE LT ENGINE. ALSO NOTICED OIL AND SMOKE COMING OUT OF LT ENGINE COWL. SHUTDOWN ENGINE AND FEATHERED PROPELLER IAW ENGINE FAILURE CHECKLIST AND LANDED NORMALLY. VISUAL INSPECTION OF THE LT ENGINE REVEALED A QUARTER SIZED HOLE IN THE CASE NEAR THE FORWARD HOIST RING. ON REMOVAL, A CRACK WAS NOTICED ON THE LT ENGINE CASE SECTION IN FRONT OF THE NR 6 CYLINDER. CRACK EXTENDED THROUGH ENTIRE CASE HALF. ONE OF THE COUNTERWEIGHT DAMPER PIN RETAINER PLATES BROKE INTO PIECES RELEASING THE PIN ALLOWING THE COUNTER WEIGHT TO CONTACT CRANKCASE CAUSING IMMEDIATE STOPPAGE OF ENGINE.

PILOT REPORTED THAT ON DOWNWIND IN THE TRAFFIC PATTERN AT THE DESTINATION AIRPORT, HEARD A LOUD "POP", AND AND EXPERIENCED A POWER LOSS ON LT ENGINE. NOTICED OIL AND SMOKE COMING OUT OF LT ENGINE COWL. SHUTDOWN ENGINE AND FEATHERED PROPELLER IAW THE ENGINE FAILURE CHECKLIST AND LANDED NORMALLY. VISUAL INSPECTION OF ENGINE REVEALED A QUARTER SIZED HOLE IN THE LT ENGINE CASE NEAR THE FWD ENGINE HOIST RING.

PILOT NOTED LEFT ALTERNATOR INOPERATIVE LIGHT ON IN ACFT DISCREPANCY LOG. MECHANICAL INSPECTION OF THE ALTERNATOR REVEALED THAT THE LOWER BRUSH LEAD CARRIAGE HELD IN PLACE BY A TERMINAL STUD AND NUT, HAD ROTATED FROM ITS ASSY POSITION TO A POSITION IN WHICH THE EXPOSED WIRES AT THE CARRIAGE ATTACHMENT POINTS OF BOTH BRUSH LEADS WERE IN CONTACT WITH EACH OTHER CREATING A GROUNDED CIRCUIT (AS EXPLAINED BY THE DIRECTOR OF WARRANTY AND SUPPORT OF MFG ENGINE TECHNOLOGIES).

DURING 100 HOUR INSPECTION, 2 MIRRORED AREAS ON THE UPPER SKIN OF EACH WING BETWEEN THE ENGINE NACELLES AND FUSELAGE LATERALLY, AND BETWEEN THE MAIN SPAR AND THE T/E OF THE WING LONGITUDINALLY DISPLAYED DIAGONAL RIPPLING INDICATIVE OF A HARD LANDING.

IN CRUISE FLT, AT 2500 FT AGL & APPROX 15 MILES FROM DESTINATION, PILOT NOTED A SLIGHT VIBRATION ON STARBOARD (RT) ENG FOLLOWED BY A LOUD BANG. IN RESPONSE, PILOT SHUT THE ENG DOWN, AND FEATHERED PROP. AFTER LANDING, THE POST-FLIGHT INSP REVEALED THE NR 3 CYLINDER HEAD PROTRUDING THROUGH THE OTBD MATING JOINT OF THE UPPER AND LOWER ENGINE COWLINGS. WHILE REMOVING LWR COWLING IT BECAME EVIDENT THAT ENTIRE CYLINDER ASSY HAD SEPARATED FROM ENG CASE SHEARING ALL CONNECTING STUDS. NR 3 PISTON CONNECTING ROD END CAP WAS RECOVERED IN THE LWR COWLING WITH BOTH CONNECTING ROD BOLTS INSERTED. OF THE (2) CONNECTING ROD BOLTS (PN LW-13923) ONE (1) WAS INTACT WHILE THE OTHER BOLD HAD BEEN BENT APPROX (90) DEGREES AND SNAPPED IN PROXIMITY TO MATING CONNECTION OF CONNECTING ROD AND END CAP. A CURSORY INSP OF ENG COULD LOCATE THE 2 CONNECTING ROD NUTS (PN LW12186). THREAD DAMAGE TO BOTH BOLTS SUGGESTS BOTH NUTS LOOSENED AND FELL OFF CONNECTING ROD BOLTS AS OPPOSED TO FAILING STRUCTURALLY. NR 3 CONNECTING ROD WAS LOCATED IN THE LWR COWLING AND SUSTAINED DAMAGE FROM STRIKING OPPOSING CYLINDER FLANGE AND ENG CASE (ON ONE END) AND STRIKING THE NR 3 CYLINDER FLANGE (ON THE OTHER END). PISTON WAS RECOVERED IN THE LOWER COWLING. DAMAGE TO PISTON WAS LIMITED TO FAILURE OF BOTH WRIST PIN FITTINGS. BOTH VALVES WERE NORMALLY SEATED AND SHOWED NO EVIDENCE OF STRIKING THE PISTON.

FLT 1275 - BOTH ENGINES EXCEEDED MAXIMUN TORQUE LIMITS AS PRESCRIBED BY THE MANUFACTURER. ISLAND AIR BELIEVES THE CAUSE OF THE INCIDENT WAS OR CAN BE ATTRIBUTED TO THE WIND CONDITIONS THAT WERE PRESENT DURING THE COURSE OF THE FLIGHT.