AIRLINE GND PERSONNEL FAILED TO RPT A STRANGE ENG NOISE TO THE FLC.

Narrative

STARTUP OF THE TURBOPROP ENGS ABOARD OUR SMT SEAPLANE WAS UNEVENTFUL. TKOF AND CLB TO CRUISE ALT WAS NORMAL; BUT IT WAS NOTED THAT THE #1 ITT WAS BORDERING THE CAUTIONARY RANGE. PWR WAS ADJUSTED TO AN ECONOMY CRUISE SETTING WHICH KEPT ALL READINGS 'IN THE GREEN.' AFTER LNDG AND DURING WATER TAXI; THE CAPT NOTED AN UNUSUAL SOUND FROM THE #1 ENG; AND UPON LOOKING; NOTED A FUEL STREAM. THE ENGS WERE SHUT DOWN; THE ACFT ANCHORED AND PAX DEPLANED WITHOUT INCIDENT. SUBSEQUENT INSPECTION SHOWED A BLADE FAILURE IN THE COMPRESSOR SECTION OF THE ENG AND A BREAK IN THE FUEL RETURN LINE. INTERVIEWS AT THE ORIGINATING STATION OF RAMP PERSONNEL SHOWED THAT ONE HAD HEARD A STRANGE NOISE FROM #1; YET DIDN'T RADIO OR SIGNAL THE OBSERVATION. NEITHER THE CREW NOR A STATION MGR RIDING AS A PAX HEARD THE UNUSUAL NOISE UNTIL IT BECAME AN EXPENSIVE REPAIR. CLRLY; ALL PERSONS ASSOCIATED WITH AN ACFT'S OP NEED TO MAINTAIN A STEADY 'HEADS UP' VIGILANCE WHEN IT COMES TO IDENTING AND CONVEYING ITEMS OUTSIDE THE NORM.