Accident Hughes 369D N5108E, Thursday 30 March 1989

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Date:	Thursday 30 March 1989
Time:	19:25 LT
Type:	Hughes 369D
Owner/operator:	Helinet, Inc.
Registration:	N5108E
MSN:	811075D
Year of manufacture:	1981
Total airframe hrs:	1697 hours
Engine model:	Allison C250-C20B
Fatalities:	Fatalities: 0 / Occupants: 2
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Vallejo, CA - United States of America
Phase:	En route
Nature:	Unknown
Departure airport:	Novato, CA (056)
Destination airport:	Concord, CA (KCCR)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
DURING AN AIR TAXI CARGO FLIGHT ENGINE POWER WAS SUDDENLY LOST & THE PILOT AUTOROTATED TO A LANDING ON A WET MARSH. AS THE AIRCRAFT CAME TO REST THE MAIN ROTORS SEVERED THE TAIL BOOM. EXAM OF THE ENGINE REVEALED THAT THE PC TUBE ASSEMBLY, P/N 6848471, HAD FAILED AT THE SCROLL FITTING FERRULE, & THIS BROKEN LINE CONDITION PRODUCED AN IMMEDIATE LOSS OF ENGINE POWER. THE PC TUBE HAD A TOTAL OF 11.8 HOURS OF USE SINCE BEING INSTALLED/MANUFACTURED. A METALLURGICAL FAILURE ANALYSIS REVEALED THAT THE PC TUBE HAD FAILED IN FATIGUE.

Probable Cause: FATIGUE FAILURE OF A DEFECTIVE PC TUBE ASSEMBLY RESULTING IN A LOSS OF ENGINE POWER. A CONTRIBUTING FACTOR WAS THE UNSUITABLE TERRAIN.

Accident investigation: