FORT PIERCE, FL, USA
N6460W
PIPER PA-28-140
WHILE IN CRUISE FLT THE ACFT'S ENG FAILED AND THE ACFT WAS DITCHED IN A RIVER. POST CRASH ENG EXAM REVEALED THE NO. 1 AND NO. 2 CONNECTING RODS SEPARATED FROM THE CRANKSHAFT WHEN BOTH BOLTS FAILED ON THE NO. 1 ROD AND 1 BOLT FAILED ON THE NO. 2 ROD. METALLURGICAL EXAM OF THE BOLTS REVEALED THE ROCKWELL HARDNESS OF THE NO. 1 ROD BOLTS VARIED FROM 26 TO 44 AT VARIOUS POINTS AND THE HARDNESS OF THE FAILED NO. 2 ROD BOLT VARIED FROM 41.6 TO 42.2. MICROSTRUCTURE ANALYSIS OF THE FAILED BOLTS INDICATED THE STRUCTURE VARIED FROM PRIMARILY FERRITE NEAR THE LOW HARDNESS AREAS TO PRIMARILY MARTENSITE NEAR THE HIGHER HARDNESS AREAS. THE CHANGE IN MICROSTRUCTURE INDICATES THAT ALTHOUGH BLOCKAGES WERE NOT OBVIOUS IN THE LUBRICATION SYSTEM, THE BOLTS WERE SUBJECTED TO EXCESSIVE HEAT. THE NO. 1 AND NO. 2 CONNECTING ROD CRANKSHAFT JOURNALS INDICATED EVIDENCE OF SCORING AND DARKENING.
Source: NTSB Aviation Accident Database
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