On April 26, 2002, a Bell 47G-5A (registration N14838) was involved in an aviation accident near LA Belle, FL. Investigators recorded the probable cause as: Entanglement of the main rotor blades in tree branches during low-level maneuvering for herbicide application. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter suffered main rotor entanglement in tree branches while conducting low-level herbicide swath runs, resulting in a rapid loss of RPM and a fall into a nearby ditch.
What happened
The pilot was conducting agricultural operations, specifically executing herbicide swath runs at an altitude of approximately six feet above the ground. The aircraft was traveling at a speed between 25 and 30 mph during these maneuvers. While navigating to clear a tree located on the bank of a ditch, the helicopter's main rotor blades became entangled in the tree's branches. This incident occurred at an altitude of approximately 25 to 30 feet above the ground.
Upon contact with the vegetation, the helicopter's rotational speed decayed rapidly. The loss of rotor RPM resulted in the aircraft falling into the adjacent ditch. The pilot reported that there were no mechanical problems with the helicopter prior to the incident.
Probable cause
Entanglement of the main rotor blades in tree branches during low-level maneuvering for herbicide application.