Serious incident Fairchild SA227-AC Metro III N380PH, Thursday 17 November 1994

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Date:	Thursday 17 November 1994
Time:	08:35 LT
Type:	Fairchild SA227-AC Metro III
Owner/operator:	Horizon Air
Registration:	N380PH
MSN:	AC-582
Year of manufacture:	1984
Total airframe hrs:	23955 hours
Engine model:	GARRETT TPE331-114
Fatalities:	Fatalities: 0 / Occupants: 4
Other fatalities:	0
Aircraft damage:	Minor
Category:	Serious incident
Location:	Missoula, MT - United States of America
Phase:	En route
Nature:	Unknown
Departure airport:	Helena, MT (KHLN)
Destination airport:	Spokane, WA (KGEG)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
WHILE IN CRUISE FLIGHT, THE FIRST STAGE COMPRESSOR IMPELLER OF THE NUMBER TWO ENGINE EXPERIENCED A TOTAL FAILURE. THE CREW THEN ELECTED TO MAKE A PRECAUTIONARY LANDING AT AN ALTERNATE AIRPORT. A METALLURGICAL ANALYSIS REVEALED THAT THE IMPELLER HAD EXPERIENCED A LOW CYCLE FATIGUE FRACTURE.

Probable Cause: THE FATIGUE FAILURE OF THE FIRST STAGE COMPRESSOR IMPELLER.

Accident investigation: