NTSB Identification: NYC07LA030.
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Accident occurred Saturday, November 18, 2006 in Manchester, NH
Probable Cause Approval Date: 01/31/2008
Aircraft: Stump Rotorway Exec 90, registration: N169JS
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The amatuer-built helicopter was about 45 minutes into its flight when the pilot heard a "pop," and saw a puff of blue smoke. He also noticed an odor of "burning" oil, and heard "crackling" in the engine compartment on the pilot's side of the helicopter. He selected a forced landing site and entered autorotation as the engine "sputtered" and stopped producing power. The helicopter touched down on an upslope with forward motion, then rolled over on to its side. A split engine oil suppy line was identified at the site, and examination revealed that beneath the torn fire sleeve and damaged outer braiding material, there was longitudinal cracking about 1 inch in length due to fatigue. Positioning of the oil line on the accident helicopter was different than a factory-assembled version that was examined, but because the helicopter was amateur built, there was no standard. Photographs of the oil line installation on the 23 year-old accident helicopter suggested the oil line was curved more tightly than the manufacturer's suggested minimum radius, and showed the oil line in close proximity to a source of high heat; the engine exhaust.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

An improperly installed oil line, which resulted in oil line fatigue failure and a subsequent loss of oil to the engine. A contributing factor was the sloping terrain at the forced landing site.

Full narrative available

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