On April 18, 1986, a Bell 47G-3B1 (registration N1371X) was involved in an aviation accident near Lapwai, ID. Investigators recorded the probable cause as: The pilot's failure to see and avoid powerlines during the pre-flight terrain survey, which resulted in the helicopter rotor mast striking the lines at low altitude. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter struck powerlines at low altitude during an aerial application flight because the pilot failed to see them during her pre-flight terrain survey.
What happened
The helicopter rotor mast contacted overhead powerlines while operating at an altitude of 12 feet above ground level (AGL) during an aerial application flight. Following the impact, the aircraft descended and subsequently struck the terrain in a nose-low attitude.
The investigation
During the pre-flight phase, the pilot conducted a survey of the terrain to identify potential hazards. The pilot reported that she inadvertently failed to notice the powerlines during this visual inspection prior to commencing the flight.
Probable cause
The pilot's failure to see and avoid powerlines during the pre-flight terrain survey, which resulted in the helicopter rotor mast striking the lines at low altitude.