On May 19, 1991, a Bell 47G-3B-1 (registration N73903) operated by Cascade Helicopter was involved in an aviation accident near Malott, WA. Investigators recorded the probable cause as: AN UNDETERMINED FAILURE OF THE FUEL PUMP CASING RESULTING IN AN IN FLIGHT FIRE AND LOSS OF ENGINE POWER. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application flight, a helicopter's engine lost power, leading to a collision with trees. Post-crash investigation revealed an in-flight fire and a broken auxiliary fuel pump casing.
Incident Overview
An aerial application flight ended with a helicopter colliding with trees after the engine suddenly lost power. The pilot attempted to maneuver the aircraft to an open area but was unable to avoid the trees.
Post-Crash Findings
Examination after the crash discovered that the helicopter had experienced an in-flight fire. Investigators found that a section of the auxiliary fuel pump casing had broken away in the area where the fuel line fitting screws into the pump. The fire damage was extensive, and it destroyed the useful fracture topography needed to determine the mode of failure of the pump casing.
Investigation Details
The investigation focused on the auxiliary fuel pump casing failure but was unable to establish the precise failure mode due to fire damage. No further details were provided regarding the helicopter's registration, operator, location, or the number of occupants and their condition. The event occurred during an aerial application operation.