On June 23, 1994, a Hiller HU-12E (registration N330CW) was involved in an aviation accident near Watertown, SD. Investigators recorded the probable cause as: impact with a transmission wire during aerial application maneuvers. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter struck a transmission wire and terrain while maneuvering during aerial application operations. The pilot was not injured, and no mechanical anomalies were found.
What happened
The helicopter was engaged in aerial application operations when it impacted a transmission wire followed by the terrain. The incident occurred while the aircraft was maneuvering in the area.
The investigation
A subsequent examination of the helicopter revealed no pre-existent mechanical anomalies that would have contributed to the accident. A post-mortem examination of the pilot revealed no physical impairment, and toxicological specimens were negative for screened drugs.
Findings
The impact with the transmission wire during low-level maneuvering was the primary factor in the event. No evidence of mechanical failure or pilot incapacitation was found.
Probable cause
impact with a transmission wire during aerial application maneuvers