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Helicopter Loses Power After Takeoff, Strikes Trees; Fuel Contamination Found (N80SD)

Sedro Wooley, WA, US

On April 20, 1998, a Bell 47G-3B-1 (registration N80SD) operated by Helfenberger, Daniel, E. was involved in an aviation accident near Sedro Wooley, WA. Investigators recorded the probable cause as: Fuel contamination and subsequent carburetor fuel flow restriction initiated by the use of an improper material (incorrect fuel hose). A factor was the trees. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

A helicopter lost power during initial climb after takeoff. The pilot attempted to reach a clear area but struck trees. Post-crash examination found no mechanical malfunction, but fuel samples contained a plasticizer compound. The fueling hose, though deemed acceptable by the local distributor, had a manufacturer note against unleaded gas.

Accident Overview

A helicopter experienced a loss of power during initial climb immediately after takeoff. The pilot maneuvered to reach a clear area but struck trees during the descent.

Post-Crash Examination

Post-crash examination revealed no mechanical malfunction with either the engine or carburetor. However, the carburetor had been subjected to a post-crash fire, and its fuel metering orifices could not be bench tested.

Fuel Sample Analysis

Fuel samples were taken from the helicopter's fuel tank prior to the accident, and from the fueling hose of a portable fuel truck. A fuels testing lab examined the samples and found they contained 1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester. The pre-accident aircraft fuel sample contained a submersed glob of clear substance similar to that observed by the pilot seeping from the cut ends of the fueling hose. Testing revealed that the 'soluble gum' consisted of the same compound and that nearly 100% of the gum was soluble in the fuel.

Fueling Hose Information

The operator was advised by the local distributor of the 'Versicon' hose that the hose was acceptable for use with aviation fuels. Specifications provided by the manufacturer, HBD Industries, included a note stating 'Not recommended for the variety of unleaded gas existing presently.'

Fuel exhaustion & starvation

Frequently asked questions

What happened in the 20 Apr 1998 Bell 47G-3B-1 accident near Sedro Wooley, WA?

A helicopter lost power during initial climb after takeoff. The pilot attempted to reach a clear area but struck trees. Post-crash examination found no mechanical malfunction, but fuel samples contained a plasticizer compound. The fueling hose, though deemed acceptable by the local distributor, had a manufacturer…

What aircraft was involved and where did it happen?

The accident on 20 Apr 1998 involved a Bell 47G-3B-1, registration N80SD, operated by Helfenberger, Daniel, E., at Sedro Wooley, WA.

What was the probable cause of the accident?

Fuel contamination and subsequent carburetor fuel flow restriction initiated by the use of an improper material (incorrect fuel hose). A factor was the trees.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X09960. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.