On August 22, 1996, a Bell 206B (registration N3896V) operated by Idaho Helicopters was involved in an aviation accident near Glenns Ferry, ID. Investigators recorded the probable cause as: fuel contamination, due to improper servicing of the helicopter, which resulted in an intermittent loss of engine power. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 10 related events involving the same aircraft type or operator are linked below.
A helicopter experienced yaw, vibration, and power loss in cruise. After pilot actions including throttle changes and autorotation, it landed hard and rolled over. Investigation found no mechanical failure but discovered contaminated fuel with water and fungi.
Incident Description
While in cruise flight, the helicopter began to yaw and vibrate, and its engine lost power. The pilot closed the throttle and initiated an autorotation. The helicopter then pitched nose-down, and the pilot pulled back on the cyclic. The auto relight warning light illuminated, and the pilot increased the throttle to full power. The yawing resumed, and the pilot again closed the throttle, but the helicopter again pitched nose-down. The pilot increased throttle and raised the collective in an attempt to regain level flight. The helicopter landed hard and rolled over.
Investigation Findings
A post-incident inspection of the engine and airframe revealed no evidence of a mechanical failure or malfunction. Fuel drained from the helicopter was dark gray and contained very fine suspended particulate matter. Inspection of the fuel truck used to service the helicopter showed heavy contamination in its filters and in fuel drained from the sump. Laboratory analysis of fuel from both the helicopter and the fuel truck confirmed the presence of water and fungi.