On October 4, 1991, a Bell 47D-1 (registration N3655F) operated by Allied Helicopter Service, Inc was involved in an aviation accident near Clewiston, FL. Investigators recorded the probable cause as: Contact with a guy wire during a spray pass, which led to rotor damage and an uncontrolled inverted descent. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
A helicopter rolled inverted and crashed after its spray boom struck a guy wire during a crop dusting operation, causing uncontrolled descent and ground impact.
What happened
The accident occurred while the helicopter was executing a pull-up maneuver immediately following a crop spraying pass. During this phase of flight, either the left skid or the spray boom made contact with a guy wire. The impact caused the guy wire to break, and the loose cable then struck both the main rotor blades and the tail rotor blades.
This sequence of events resulted in an uncontrolled descent of the aircraft. As the helicopter fell, it rolled into an inverted attitude before impacting the ground. The pilot later stated that there was no pre-impact failure or malfunction of the helicopter's systems prior to the contact with the guy wire.
Findings
The investigation focused on the mechanical integrity of the aircraft and the circumstances of the impact. Key findings included:
Contact with infrastructure: The primary cause of the accident was the physical contact between the helicopter's lower structure (skid or boom) and a guy wire.
Rotor damage: The broken guy wire subsequently struck the main and tail rotors, leading to loss of control.
No mechanical failure: The pilot confirmed that the helicopter operated normally prior to the external contact event.
Probable cause
Contact with a guy wire during a spray pass, which led to rotor damage and an uncontrolled inverted descent.